Blev Medlem: Jun 01, 2005 Inlägg: 6773 Från: Nattmössan
Skrivet: 2011-01-21 17:18 Ämne:
Konstruerad för Sjöfn av en "James Croft" enl. sign."sumadoggie"
på AudioCircle forum . . någon som hört talas om denne J. Croft ? _________________ Sterio . . . krävs dä tvillingar för å lyssna på´t åsså, typ . . . ?
Blev Medlem: Jun 01, 2005 Inlägg: 6773 Från: Nattmössan
Skrivet: 2011-01-21 19:16 Ämne:
Ajsan bajsan . . . religion är strängeligen förbjudet
på forumet, har jag hört . . . _________________ Sterio . . . krävs dä tvillingar för å lyssna på´t åsså, typ . . . ?
Blev Medlem: Jun 29, 2003 Inlägg: 14558 Från: helsefyr
Skrivet: 2011-01-22 08:28 Ämne:
phon skrev:
35 hög, 20 bred och 26 djup, dom har inte alla clues än.
men enligt omdömmen så spelar högtalaren fint ändå, så baffelmåtten kanske är tillräckliga för vad dom vill åstadkomma, men även elementen är ju annorlunda _________________ Fuck off
Blev Medlem: Oct 04, 2003 Inlägg: 15271 Från: Metropolis, men passet är från Moskva
Skrivet: 2011-01-22 18:03 Ämne:
Letar man lite på Nätet så finner man att det finns en person som heter James Croft som varit insyltad i diverse ljud-projekt. _________________ In Cod we trust...
Blev Medlem: Nov 13, 2004 Inlägg: 9867 Från: kopplad
Skrivet: 2011-01-25 22:56 Ämne:
celef skrev:
men enligt omdömmen så spelar högtalaren fint ändå, så baffelmåtten kanske är tillräckliga för vad dom vill åstadkomma, men även elementen är ju annorlunda
Blev Medlem: Aug 09, 2005 Inlägg: 2641 Från: och till
Skrivet: 2011-01-26 01:08 Ämne:
"The price on The Clue, if you are in the market for high-fi equipment, is only worth mentioning because it is so absurdly low compared not only to the performance you get for the price, but also because The Clue beats the pants off both monitors and floor-standers costing 5x, 10x, 20x more. No joke. Nuff said. "
Blev Medlem: Aug 09, 2005 Inlägg: 2641 Från: och till
Skrivet: 2011-01-26 12:48 Ämne:
phon skrev:
Ragnwald skrev:
Vad är det för diskantelement?
Ett Vifa med en egen waveguide tror jag.
"Some basic info on The Clue is that it is essentially a single driver design with proprietary Scanspeak woofer and tweeter. The monitor is room coupled to get bass extension flat down to between 28-32HZ depending on the "stiffness" of the wall to which it's coupled and some basic room treatment. I believe that the driver takes care of frequency response up to about 4kHZ and then there is a kind of "passive crossover" (I might be flubbing that description) which lets the tweeter take over the higher frequencies and fill in off-axis response. The mids and highs are as good as anything at the show. And all this is from a speaker that Sjofn is selling for $999 for the duration of the show."
Skrevs av sumadoggie, Audiocircle i första länken.
"Anyway, I own a pair of the Guru QM10s that Sjofn (Lars Erickson and crew) had been repping for a few years, and The Clue (in my humble opinion) is a quantum leap beyond that monitor which has had great reviews the past couple years. The first comment out of my mouth when I heard The Clue for the first time a couple days ago was simply... CRAZY"
Borde det inte gå att skaka fram ett par i Sverige?
"Yah, the WAF was absolutely taken into consideration when designing these speakers. "the clue" clearly has an aesthetic which will appeal to a large cross section of audiophiles and their spouses"
-Det var ju lite kul. -Med tanke på att de är byggda av den där standardlådan från Parts Express (om det stämmer), som dom då inte har designat... _________________ /Roger Jönsson
Från PE: Dimensions: 14" H x 8" W x 10.5" D
Från Sjofn Hifi: 14" x 8" x 10.5" (http://www.sjofnhifi.com/thecluespecs_v7.pdf)
22,5 graders invinkling ska det tydligen vara också, samt 50-55cm från golvet. _________________
"Jag tycker man bör vara ödmjuk och ha lite självkritik"
"Personligen så tycker jag mig se en motvilja att sätta sig in vad andra säger och istället endast försvara sin åsikt"
Blev Medlem: Sep 03, 2007 Inlägg: 12224 Från: Skåne
Skrivet: 2011-01-26 21:27 Ämne:
Ton skrev:
Fjonkalicious skrev:
Jävligt ful låda enligt mig.
Ja, det tycker jag oxå. Men fruarna gillar den tydligen o så låter den helt fantastiskt. Allt enligt texten ovan
Känns tryggt att det finns några enstaka människor i världen som på ren stortåkänsla vet hur alla fruar vill ha det. _________________ Head of Design - Acoustic Illusion AB
Blev Medlem: Jun 29, 2003 Inlägg: 14558 Från: helsefyr
Skrivet: 2011-01-26 22:29 Ämne:
men vad kan vara anledningen till skapandet av denna högtalaren, vad är det som har hänt, har sjöfn ställt krav på guru om en mer hemmaanpassad högtalare och fått nobben, sjöfn har då blivit sura och börjat gapa å skrika för att sedan kavlat upp skjortarmarna för att skapa sig något eget? _________________ Fuck off
Blev Medlem: Mar 17, 2009 Inlägg: 8862 Från: speedad
Skrivet: 2011-01-26 23:13 Ämne:
celef skrev:
men vad kan vara anledningen till skapandet av denna högtalaren, vad är det som har hänt, har sjöfn ställt krav på guru om en mer hemmaanpassad högtalare och fått nobben, sjöfn har då blivit sura och börjat gapa å skrika för att sedan kavlat upp skjortarmarna för att skapa sig något eget?
I ain't gotta clue. _________________ M O N S T E R ® C A B L E
Blev Medlem: May 16, 2007 Inlägg: 333 Från: Svartbäcken
Skrivet: 2011-01-27 07:06 Ämne:
Vi noterar att det spekuleras om vårt förhållande med Sjöfn. Det kan vara värt att notera att vi inte haft samarbete med dem sedan hösten 2008. De hade oss med på sin hemsida längre än så, men det var inget vi kunde göra något åt. _________________ -----------------------------------
Guru Pro Audio
www.guruproaudio.com
-----------------------------------
Blev Medlem: Jan 31, 2005 Inlägg: 4741 Från: sett det, så mår jag bra. Tack!
Skrivet: 2011-01-27 07:33 Ämne:
nilsviktor skrev:
Vi noterar att det spekuleras om vårt förhållande med Sjöfn. Det kan vara värt att notera att vi inte haft samarbete med dem sedan hösten 2008. De hade oss med på sin hemsida längre än så, men det var inget vi kunde göra något åt.
Kan det vara värt att notera varför också? _________________ Mvh Björn//
Blev Medlem: Oct 29, 2003 Inlägg: 33943 Från: Grå Hamnarna
Skrivet: 2011-01-27 08:13 Ämne:
Welcome Jacro.
If you're able to manage it with through the translator - do make a footer which tells of your commercial involvement - it's a forum rule to have it like that. _________________ Det viktigaste är inte att förstå vad man upplever, utan att inse vad av det man upplever man inte förstår.
Blev Medlem: May 16, 2007 Inlägg: 333 Från: Svartbäcken
Skrivet: 2011-01-27 08:27 Ämne:
screen skrev:
nilsviktor skrev:
Vi noterar att det spekuleras om vårt förhållande med Sjöfn. Det kan vara värt att notera att vi inte haft samarbete med dem sedan hösten 2008. De hade oss med på sin hemsida längre än så, men det var inget vi kunde göra något åt.
Kan det vara värt att notera varför också?
Nej. Vi tyckte olika bara. _________________ -----------------------------------
Guru Pro Audio
www.guruproaudio.com
-----------------------------------
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-01-27 22:14 Ämne: My history with loudspeakers
paa skrev:
Hi Jacro!
Please tell us about your history with loudspeakers.
First, thank you for the warm welcome!
My involvement in music reproduction goes back to childhood, but professionally it started in 1973 when after studying psychoacoustics, acoustics, and power electronics in college, as my final college project I developed a new type of Regenerative Transmission Line (currently produced by Wisdom Audio) similar to what is often referred to as a Tapped Horn.
After college I developed loudspeakers for Audionics of Oregon, the importer of the British Radford electronics at the time.
In 1975 I opened a high-end audio store called Definitive Audio, in Seattle Washington, which continues today with three stores, but I don’t participate much anymore, as I stopped running the store in 1985 and continued as Chairman of the board of directors.
With funding from Definitive Audio, in 1976 I started extensive 9-year research into psychoacoustics, acoustics, electro-acoustics, and power electronics, in an effort to define the remaining issues that keep us from having the effect of a live concert in our homes.
I’m not sure I can remember all the loudspeaker systems I’ve developed since I started professionally in about 1974 but I will list a few of the products I developed that some of you may be familiar with (I’m not sure how many products that were known in the USA were also visible in Sweden).
Audionics of Oregon:
TL-30
M33
Snell: Type One (concept and proof of concept prototypes)
Fulton (FMI) J-Modular Premiere Subwoofer and Supertweeter
Speakerlab Delta-i Hybrid
Satterberg MW2 mid-woofer for the Rogers LS3/5a
Carver Corporation:
The Carver Amazing Loudspeaker
(Planar magnetic line source/Dipole bass 12”x 4)
I have about 30 or 40 patents in the field of audio, mostly loudspeakers, power amplification and signal processing and continue to do consulting for many in the industry such as SJÖFN HiFI, Atlantic Technology, Magnepan and Wisdom Audio.
I hope this is the kind of answer you were looking for. If you wish to have me expand on anything in particular or answer something else, let me know.
Best regards,
James Croft
_________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Skrivet: 2011-01-27 22:50 Ämne: Re: My history with loudspeakers
Jacro skrev:
My involvement in music reproduction goes back to childhood, but professionally it started in 1973 ...
...
Snell: Type One (concept and proof of concept prototypes)
Thanks for the resume.
Did you come up with the concept of the Snell Type One?
What is your comment to that design today? Could that floor bound tweeter solve any of todays reproduction problems, or has evolution found better ways by now?
By the way, this is my attempt at full range floor support, a mini speaker built just for fun, inspired by Stig Carlssons prototypes and patents:
http://user.faktiskt.se/paa/minione_8.jpg
I also believe Stig Carlsson was somewhat inspired by the Type One at that time.
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-01-27 23:46 Ämne: The Clue for Export?
KarlXII skrev:
Impressive resume there, James. Jeez.
Again, Welcome to faktiskt.se.
Any chance we will see these speakers over here?
Thank you. With old age comes long resumes'.
I'm not sure of the President's (Lars Erickson) plans for export. I know he is a big fan of all things Scandinavian, and I would expect that he would like to have a good reason to visit more often. So, eventually, he may introduce The Clue in Sweden or other parts of Europe. As you may know, he is the US importer for Supra Cables.
For now, we are very busy working to build enough for the US market and it appears that will keep us busy for awhile.
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-01-28 00:19 Ämne: Re: My history with loudspeakers
paa skrev:
Jacro skrev:
My involvement in music reproduction goes back to childhood, but professionally it started in 1973 ...
...
Snell: Type One (concept and proof of concept prototypes)
Thanks for the resume.
Did you come up with the concept of the Snell Type One?
What is your comment to that design today? Could that floor bound tweeter solve any of todays reproduction problems, or has evolution found better ways by now?
By the way, this is my attempt at full range floor support, a mini speaker built just for fun, inspired by Stig Carlssons prototypes and patents:
http://user.faktiskt.se/paa/minione_8.jpg
I also believe Stig Carlsson was somewhat inspired by the Type One at that time.
Thank you for the Carlsson pic! I hadn't seen that particular model.
Yes, I came up with the concept for the Snell Type One, but in late 1976, when I did a patent search, I found Snell's original patent (US 3,964,571) had somewhat anticipated the idea, even though he was producing only the Type A at the time. So, I contacted Peter Snell and presented the concept to him, along with sketches of my configuration and test data (Mine was 8" two way, Audax and Peerless, Snell's was 10" two way Audax all around). It wasn't very nice looking, and it wasn't very practical with a 60 cm 'tongue' sticking out for people to trip over, but the performance was rather special. I had adjusted my prototypes to sound almost identical to the QUAD 57's placed on the floor.
Anyhow, I was busy with other projects and didn't want to have a patent dispute, and I was working on making a better version anyhow, as the one problem with my original approach, and the production Type One, was that the image is too low... similar to sitting up in the balcony and looking down at the orchestra. But, it was remarkably uncolored and transparent.
Two or three years later (in about 1979 I believe), Snell came out with the Type One and I offered it for sale at my audio store. Unfortunately, it went out of production after just a couple years. Even so, it was the beginning of something special and I was surprised that they abandoned it so completely. But, also, Peter Snell died around that time, so I think he would have done more with it if he had lived longer.
Yes, the concepts still have much validity today and about 12 years ago, I built prototypes of some of my next generation thinking on the idea, of which I hope to get back to in time.
With all the DIY work that the groups in this forum do, I'm sure it would be a fun project for many here to try. The patent is public domain, so have fun!
Skrivet: 2011-01-28 04:53 Ämne: Re: My history with loudspeakers
Jacro skrev:
Carver Corporation:
The Carver Amazing Loudspeaker
(Planar magnetic line source/Dipole bass 12”x 4)
James Croft
Hi James,
Cool to see that you have been working with line source systems.
Maybe we can have a chat over a beer next time I go to US..?
Best,
//BB _________________ F.d. Audio-Tronic, f.d. Centara. Consulting åt bl.a. Mark Levinson, (Red Rose Music), samt Cello Film & Music Systems. Grundare av Transmission Audio Inc., NJ, USA. http://www.transmissionaudio.com
Skrivet: 2011-01-28 06:26 Ämne: Re: My history with loudspeakers
Jacro skrev:
[Thank you for the Carlsson pic! I hadn't seen that particular model.
...
..., and the production Type One, was that the image is too low... similar to sitting up in the balcony and looking down at the orchestra. But, it was remarkably uncolored and transparent.
Yes, the concepts still have much validity today and about 12 years ago, I built prototypes of some of my next generation thinking on the idea, of which I hope to get back to in time.
With all the DIY work that the groups in this forum do, I'm sure it would be a fun project for many here to try. The patent is public domain, so have fun!
All the best,
- James
James,
With my small speaker the sound stage can at best be quite a bit higher than one would expect, but then sometimes not.
Do you see a possibility to raise the heigth of the sound stage from loudspeakers whith the drivers placed so close to the floor?
Here is an in-depth look into the design of the never finished Carlsson Three Way speaker:
http://www.faktiskt.se/modules.php?name=Forums&file=viewtopic&p=502903
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-01-28 08:28 Ämne: More about The Clue
celef skrev:
välkommen jacro, kul att ha dig här, berätta gärna mer om högtalarna, är det verkligen parts-express-lådor?
jacro welcome, good to have you here, tell me more about the speakers, it's really parts-express-boxes?
Celef,
I’m not sure which aspects of the design you are most interested in, so I will discuss some of the design concepts and please feel free to ask more questions if I don’t provide what you were looking for.
I believe that if the science of audio is well understood by the designer, then high quality sound doesn’t have to have high cost. Ultimately, if the design is truly advanced, the “quality” of sound should be able to be made to equal the state of the art for a modest price. With effective design, only the “quantity” of sound should drive the cost upwards, as one attempts to have the system play much louder and fill larger spaces.
The President of SJÖFN HiFi, Lars Erickson and I have known each other since the late 1970s. He and I always talked about developing a new loudspeaker that would challenge the very best, but could be affordable to those that loved music but didn’t have a lot of money to spend. We had both gone different directions for the last 25 years but we linked back up a couple years ago and immediately started where we left off, both feeling like it was time to build the speaker we had discussed so many years ago.
I had been working for a few years on new room interaction and transducer technologies and had developed a few different approaches, one of which looked like it would meet the requirements for our high value/low cost concept.
I have worked with a number approaches that attempt to ignore the room, and substantially provide direct sound only. While these can be very effective, they are at this stage in their development, rather expensive, and fairly inefficient. I wanted to have a more practical product, but one that still dealt with the “room problem”. So instead of fighting the room, and attempting to ignore it, I went in the other direction and worked to embrace the room, but to decorrelate its affects in a manner that minimized room coloration and provided great leverage to the acoustic power delivered to the listener, allowing for a modest sized system to create the level of dynamics that would be satisfying.
To start with, The Clue is based on an “enhanced” full range driver concept. The 100 mm ‘woofer’ was originally conceived as a full range driver. Full range drivers being seamless, without crossovers, have a certain desirable potential (Peter Walker of Quad was working on a full range dynamic driver as one of his last designs) but, at least in conventional form, even the few that have good on-axis response also have very poor, collapsing power response in the upper octaves, tending towards a rather ‘dark’ sound.
I wanted to have the coherence of a full range device but also with optimum power response. So, we developed the ‘woofer’ to be very smooth and wideband on axis, while using the tweeter in an unconventional manner to contribute primarily increased off-axis energy as the full-range driver dispersion starts to collapse above 2 to 4 kHz. The dispersion driver comes on stronger with increased frequency, filling in more and more of the off-axis energy while they operate together with the woofer still dominating the on axis response up to about 11 kHz wherein above that frequency, the dispersion driver starts to take over both the on and off-axis energy maintaining consistent power response to beyond 30 kHz. (I hope that is a clear enough explanation).
To further enhance the seamless transition, the dust-cap of the woofer utilizes the same silk material as the tweeter diaphragm. All of this provides a very well integrated and low coloration wave front over a consistent angle of dispersion across the entire bandwidth.
The woofer is unusual in that it has both a large linear X-max and smooth, extended upper range capability. We worked hard to get as much large signal capability (quantity) as possible while maintaining a cost effective structure. The woofer is rather expensive, but could not be built for less and still meet our bandwidth and large signal design targets.
The low frequency alignment is based on a Keele Cs = 0.58, step-down tuning, as disclosed in his 1974 AES presentation, but without requiring an active equalizer.
The very narrow use model is that of the sequential engagement of boundary gain and specific left/right speaker spacing to provide mutual coupling gain at the maximum excursion frequency. This is to passively duplicate the gain of a Q of 2 high-pass equalizer down to Fb (but with much greater acoustic power to excursion ratio), and coordinate that with a golden ratio diversification of specular boundary reflections, such that the arrival at the listener is not colored by combing of the amplitude response due to correlated reflections cancelling on-axis energy at odd half wavelengths.
This diversified, half space approach achieves very satisfying sound pressure levels while maintaining useful response to below the tuning frequency without reaching non-linear excursion from about 28 Hz upward, providing approximately a 1/3 octave deeper bass extension than the active version of the Keele alignment.
The near boundary coupling has some aspects in common with the design practice of others, such as Carlsson, Audio-Pro, and Ino-Audio, but also includes novel attributes that allow us to realize our specific target functions.
The all production units are matched within less than ½ dB to The Clue reference standard pair.
These are just a few of the design elements, and they don’t really represent a complete set of attributes that determine the sound quality of The Clue, but hopefully I have provided some useful information.
In terms of the questions about the enclosure, originally we designed a different cabinet structure with optimized internal ratios, and a form fit to the boundary coupling. In keeping with our goal of maximizing sound for cost, we found that if we modified the internal cabinet for controlled wave development and applied efficient bituminous damping to remove any remaining panel resonances, that we could use a cabinet built at the same factory as the Parts Express enclosures and equal or exceed the performance of our original custom cabinet for less than half the cost.
The goal with The Clue is to design from a systems approach, wherein increased money is spent only where it actually provides a sonic improvement and cost is reduced wherever it has no impact on sound quality.
This is achieved by way of a process that I call “Design from Local and Global Variables” using “Impedance Interface Matching”, but that is a much longer story and I have probably already carried on longer than what the questioner was looking for.
I hope this provides some of desired answers. Let me know if there are any more questions.
Cheers,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-01-28 09:23 Ämne: Re: Elevation of image height in floor coupled systems
paa skrev:
Jacro skrev:
[Thank you for the Carlsson pic! I hadn't seen that particular model.
...
..., and the production Type One, was that the image is too low... similar to sitting up in the balcony and looking down at the orchestra. But, it was remarkably uncolored and transparent.
Yes, the concepts still have much validity today and about 12 years ago, I built prototypes of some of my next generation thinking on the idea, of which I hope to get back to in time.
With all the DIY work that the groups in this forum do, I'm sure it would be a fun project for many here to try. The patent is public domain, so have fun!
All the best,
- James
James,
With my small speaker the sound stage can at best be quite a bit higher than one would expect, but then sometimes not.
Do you see a possibility to raise the heigth of the sound stage from loudspeakers whith the drivers placed so close to the floor?
Here is an in-depth look into the design of the never finished Carlsson Three Way speaker:
http://www.faktiskt.se/modules.php?name=Forums&file=viewtopic&p=502903
It IS possible, by a few different methods, to raise the height of the sound stage with the speaker boundary coupled close to the floor. As with many acoustical subjects it is difficult to provide a useful and thorough answer in a few paragraphs in this forum, but I'll mention a few things to hopefully at least stimulate some thinking and discussion on the matter.
The psycho-acoustics of the situation is that we receive most of our information relative to image height from frequencies above 4 kHz, at least when we keep our head perfectly vertical. in actuality, we are always tilting our heads sideways a small amount as we listen to music and this allows our ear/brain system to start to use left/right ear comparison for vertical imaging, which lowers the frequency sensitivity down below 1 kHz for vertical detection.
Even so, one approach is to use the midrange or woofer/midrange driver floor coupled, while placing the tweeter up at ear level, crossing over at about 2 to 3 kHz with precision 8th order slope crossovers to minimize lobing in the vertical polar response at and near the crossover frequency. With this approach the tweeter provides the height information and the boundary driver operates below 3 kHz where it is most important to eliminate correlated reflections (those arriving equally at both ears, such as front wall, floor and ceiling reflections). This approach has a number of things that have to be carefully optimized to work effectively, (such as perfectly matched tweeter/midrange horizontal directivity at the crossover frequency) but it can be made to work reasonably well.
Another approach is to use both the tweeter and midrange drivers boundary coupled to the floor, and use altered frequency response above 4 kHz to mimic the pinna derived frequency changes that normally tell the ear/brain system that an image is elevated. While this can work, it tends to vary in its effectiveness depending on the listener. Additionally, the ripple that one needs to invoke to get this effect is difficult to optimize for a variety of reasons, one being that one wants the ripple to have enough amplitude and bandwidth to stimulate the ear to sense elevation of image, while at the same time not to be so high in amplitude and broad band that it colors the tonal balance.
Again, I must mention that there are many subtle issues that must be dealt with to make these types of approaches work well without side effects causing audible tonal and spatial colorations.
I hope this answers your question.
Best regards,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Skrivet: 2011-01-28 09:28 Ämne: Re: More about The Clue
Jacro skrev:
with the woofer still dominating the on axis response up to about 11 kHz wherein above that frequency, the dispersion driver starts to take
So widely centered around (or mainly below?) 11 KHz you have two drivers several inches apart outputting equal levels? How have you solved the vertical dispersion, without getting deep cancellations only slightly above and below height center? -Or is this a design feature? _________________ /Roger Jönsson
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-01-28 10:16 Ämne: Re: More about The Clue
RogerJoensson skrev:
Jacro skrev:
with the woofer still dominating the on axis response up to about 11 kHz wherein above that frequency, the dispersion driver starts to take
So widely centered around (or mainly below?) 11 KHz you have two drivers several inches apart outputting equal levels? How have you solved the vertical dispersion, without getting deep cancellations only slightly above and below height center? -Or is this a design feature?
Roger,
I can share part of 'what' we are doing in this regard, but 'how' we do it must remain a trade secret.
The way this approach of enhanced power response can be made to work successfully without interference is that the outputs of the two drivers are tailored in a unique manner such that the through the overlap region, the dispersion driver contributes more off-axis energy than on-axis energy, and the full-range driver contributes more on-axis energy and less off-axis energy. The amounts that each contributes to the on or off-axis energy varies with frequency, but at any given frequency, and axis, they are not providing equal energy, so the interference is minimized and good response is maintained above and below the listening axis.
We work hard to maintain smooth response at all angles as we want to have smooth response at the listening axis and also smooth response for most room reflections, to have good first arrival response and also a balanced spectrum for the delayed, room response.
Best regards,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Skrivet: 2011-01-28 11:24 Ämne: Re: More about The Clue
Jacro skrev:
The way this approach of enhanced power response can be made to work successfully without interference is that the outputs of the two drivers are tailored in a unique manner such that the through the overlap region, the dispersion driver contributes more off-axis energy than on-axis energy, and the full-range driver contributes more on-axis energy and less off-axis energy. The amounts that each contributes to the on or off-axis energy varies with frequency, but at any given frequency, and axis, they are not providing equal energy, so the interference is minimized and good response is maintained above and below the listening axis.
So, in short. -The smooth/tailored power response is to heal the off-axis cancellation of the direct radiated/unreflected sound (due distance between drivers)? _________________ /Roger Jönsson
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-01-28 17:02 Ämne:
paa skrev:
James, would it be possible to push this concept with a full range driver and a filler tweeter to ever larger sizes, do you think?
Generally, yes, it is scalable, but to work without compromise, the basic architecture must change with larger devices, particularly if one wishes to maintain the same transition bandwidth and corner frequencies.
For what we wanted to achieve, The Clue is the best size that still allows standard driver constructions to be effective and for the upper frequency transition frequencies to be in the right place while still being able to generate adequate low frequency extension.
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-01-28 17:38 Ämne: Re: More about The Clue
RogerJoensson skrev:
Jacro skrev:
The way this approach of enhanced power response can be made to work successfully without interference is that the outputs of the two drivers are tailored in a unique manner such that the through the overlap region, the dispersion driver contributes more off-axis energy than on-axis energy, and the full-range driver contributes more on-axis energy and less off-axis energy. The amounts that each contributes to the on or off-axis energy varies with frequency, but at any given frequency, and axis, they are not providing equal energy, so the interference is minimized and good response is maintained above and below the listening axis.
So, in short. -The smooth/tailored power response is to heal the off-axis cancellation of the direct radiated/unreflected sound (due distance between drivers)?
Well, I would say it a bit differently. The smoother power response of the combined system is to optimize the direct and off-axis responses to combine the most accurate direct arrivals while also keeping the reverberant field well balanced. By having the off axis energy delivered independently from the on axis information, I attempt to have any particular angular vector from the system maintain smooth response, but at that vector, to have the energy dominated by either the dispersion driver or the full range driver, not shared, through the overlap region, so that the interaction is minimized.
As an analogy, think of the comparison being that convention speakers have a crossover between upper and lower frequencies, wherein we are attempting to have a crossover between on-axis and off-axis energy, at least over a certain band of frequencies.
I know it is probably somewhat confusing, but it is a bit difficult to explain more clearly without telling more about how we implement the effect.
I hope this helps at least make it somewhat clearer.
All the best,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
I'm not sure of the President's (Lars Erickson) plans for export. I know he is a big fan of all things Scandinavian, and I would expect that he would like to have a good reason to visit more often. So, eventually, he may introduce The Clue in Sweden or other parts of Europe. As you may know, he is the US importer for Supra Cables.
For now, we are very busy working to build enough for the US market and it appears that will keep us busy for awhile.
Cheers,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Jun 29, 2003 Inlägg: 14558 Från: helsefyr
Skrivet: 2011-01-29 10:02 Ämne:
tack james för ett utförligt svar, jag är väldigt nyfiken på spridningstekniken i diskanten, jag likt många andra sliter hårt för att få ihop denna del i våra hembyggda högtalare, flacka delningsfilter och inte för stora element samt att försöka rikta huvudloben på sådant sätt att man minskar dips i vistelsezonen i rummet är min lösning hitills. vet du om stereophile eller soundstage kommer testa 'the clue', det vore väldigt intressant att se mätningar på dom
translate by google:
thanks james for a detailed answer, I'm very curious as to spread the technology in the treble, I like many others work hard to get together this part of our home-built speakers, flat crossover and not for major elements and to try to target the main beam in such a way as to reduces the dips in the occupied zone in the room is my solution so far. do you know about Stereophile or Soundstage will test 'the clue', it would be very interesting to see measurements on them _________________ Fuck off
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-01-29 17:54 Ämne:
celef skrev:
tack james för ett utförligt svar, jag är väldigt nyfiken på spridningstekniken i diskanten, jag likt många andra sliter hårt för att få ihop denna del i våra hembyggda högtalare, flacka delningsfilter och inte för stora element samt att försöka rikta huvudloben på sådant sätt att man minskar dips i vistelsezonen i rummet är min lösning hitills. vet du om stereophile eller soundstage kommer testa 'the clue', det vore väldigt intressant att se mätningar på dom
translate by google:
thanks james for a detailed answer, I'm very curious as to spread the technology in the treble, I like many others work hard to get together this part of our home-built speakers, flat crossover and not for major elements and to try to target the main beam in such a way as to reduces the dips in the occupied zone in the room is my solution so far. do you know about Stereophile or Soundstage will test 'the clue', it would be very interesting to see measurements on them
Celef,
If I understand the translation properly, you are saying that you attempt to have flat response through the crossover and at the same time target the main beam (forward vertical lobe) to the location of the listener.
I'm not sure what the english translation of; "AND NOT FOR MAJOR ELEMENTS" means.
Did you mean that you try to avoid using large transducers with large center-to-center spacing? If so, I understand.
There are a number of solutions to this problem, only a very few that are effective, most approaches compromise the end result.
As you know, the vertical and horizontal power response, are both critical, but each for different reasons and each having different criteria to achieve the best sonic result.
In terms of sending the clue out for measurement, we may do so later, but right now we are not concerned so much with getting more reviews, because we are getting more orders than we can currently supply.
Our target customer is the discerning music lover who may not have the money to buy expensive loudspeakers, and may not even be very interested in the technology, but is interested in the best musical experience.
Normally, I would not be talking so much about the technical aspects of our design, as the customer that is most interested in good music reproduction isn't always interested in the technical details as much they are interested in listening.
I talked more about the technical aspects of the clue in my posts in this forum, because I know your group understands the technical concepts and likes to know more about the acoustical design elements involved (as well as good sound quality, of course!) so I answered your questions from more of a technical viewpoint.
Best regards,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
James, I'll try to make an alternative translation of parts of that text, originally written by celef, where Google Translations was a bit off:
Citat:
I'm very curious about the technique with the tweeter/treble dispersion, I like many others fight hard to get this thing together in our diy speakers, low order filters and not too large drivers, and trying to aim the main lobe to minimize dips in the place we dwell, is my solution so far.
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-01-30 04:31 Ämne:
paa skrev:
James, I'll try to make an alternative translation of parts of that text, originally written by celef, where Google Translations was a bit off:
Citat:
I'm very curious about the technique with the tweeter/treble dispersion, I like many others fight hard to get this thing together in our diy speakers, low order filters and not too large drivers, and trying to aim the main lobe to minimize dips in the place we dwell, is my solution so far.
Yes, that is easier for me to understand. Thank you.
In general, low order filters are better if the directivity of the drivers isn't well matched at the crossover frequency.
Low order slopes tend to help make the directivity more consistent through the crossover transition frequencies, but at a cost of worse vertical lobing, so one has to steer the axis of the lobing in a manner that creates the best result.
If the directivity of the drivers is well matched, then one can use higher order slopes to minimize interference and vertical lobing, but this also requires more precision.
That is an over simplification, as there are many factors, but generally, both approaches can effective, if the variables are well understood.
Thanks again for the translation help.
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Jun 29, 2003 Inlägg: 14558 Från: helsefyr
Skrivet: 2011-01-31 14:18 Ämne:
translate by google
thanks for the post james! concerning the low frequency alignment and boundary gain, can you elaborate on the mutual coupling, I do not think I've read about the effect before.
and thanks for the translation paa _________________ Fuck off
I have about 30 or 40 patents in the field of audio, mostly loudspeakers, power amplification and signal processing and continue to do consulting for many in the industry such as SJÖFN HiFI, Atlantic Technology, Magnepan and Wisdom Audio.
I have about 30 or 40 patents in the field of audio, mostly loudspeakers, power amplification and signal processing and continue to do consulting for many in the industry such as SJÖFN HiFI, Atlantic Technology, Magnepan and Wisdom Audio.
Respect, welcome to faktiskt.se!
Thank you Glebster, it's good to be here.
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-01-31 22:09 Ämne: Mutual Coupling
celef skrev:
translate by google
thanks for the post james! concerning the low frequency alignment and boundary gain, can you elaborate on the mutual coupling, I do not think I've read about the effect before.
and thanks for the translation paa
Celef,
Mutual coupling is the effect the diaphragm of one transducer has upon another transducer diaphragm when they are closely spaced with respect to the wavelength they are radiating. There are many variables that impact the interaction, such as baffle size and nearby boundaries (front wall, sidewalls, and floor) so the information as put forth here is a simplified representation of the effect, but hopefully, useful in providing an understanding of the concept.
In general, when two transducers are approximately ½ wavelength apart, the mutual coupling starts to cause an increase in radiation resistance, which in turn causes an increased gain in output that reaches a maximum of about +3 dB at the frequency that corresponds to approximately 1/3 wavelength. This is usually considered for two drivers mounted close together in a common enclosure, but relative to the optimization of a bass alignment, we are observing the effect, in this discussion, for two separate loudspeakers and looking at the center-to-center spacing of the left loudspeaker’s woofer in relation to the right loudspeaker’s woofer. We will make the assumption, that for most program material, frequencies below 75 Hz are substantially monophonic and correlated.
As an example, two loudspeakers that are spaced apart, such that the center-to-center distance of their woofers is 2.3M, would have the effect of maximum mutual coupling gain at the frequency corresponding to 1/3 wL, which is 50 Hz (2.3 x 3 = 6.9 M = wL @ 50Hz). Gain would begin to appear at approximately ½ wL, (75Hz) and increase below that frequency until it reached maximum coupling gain at 50 Hz.
Again, if one makes the simplification of operating on an infinite plane/half-space, then one can change the spacing of the two woofers, and set the ½ wL corner frequency and 1/3 wL Maximum Gain frequency to optimize the output for a given loudspeaker and room conditions.
Keep in mind, that in the real world, actual sound rooms are not simple infinite plane/half-space environments and there are many factors that add complexity to the simplified illustration I am providing. One obvious issue is, that as one moves the loudspeakers closer together to raise the frequencies of mutual coupling gain, one is most likely also moving the them farther from the sidewalls and lowering the corner frequency of the boundary gain of the sidewall coupling.
This can be used as a method of maintaining consistent gain as one optimizes loudspeaker spacing for imaging, or it may used to shift the low frequency gain in a favorable manner for better low frequency response.
I hope this is useful.
If any of you are interested in studying subject further, here are two papers from the Journal of the Acoustical Society:
R. L. Pritchard, "Mutual Acoustic Impedance Between Radiators in an Infinite Rigid Plane",
32, 730 (1960).
S. J. Klapman, "Interaction Impedance of a System of Circular Pistons",
11, 289 (1939).
Also, if one wishes to read a more accessible (less mathematical) paper on the subject, try:
“Design Parameters of a Dual Woofer Loudspeaker System” by Edward M. Long, Journal of the Audio Engineering Society, October 1969, v.17, No. 5.
All the best,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
James,
How would you comment on the horn community, with their compression drivers and horns that are designed more for low coloration and/or controlled directivity, than for maximum sensitivity and output. E.g. LeCleach, Kugelwellen, Tractix and Gedlees waveguides?
I believe there is quite a following in the US west coast and thus also Oregon for such things?
Do you see any advantages with any or all of those, compared to normal hifi-drivers for hifi and home theatre?
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-02-01 00:26 Ämne:
paa skrev:
James,
How would you comment on the horn community, with their compression drivers and horns that are designed more for low coloration and/or controlled directivity, than for maximum sensitivity and output. E.g. LeCleach, Kugelwellen, Tractix and Gedlees waveguides?
I believe there is quite a following in the US west coast and thus also Oregon for such things?
Do you see any advantages with any or all of those, compared to normal hifi-drivers for hifi and home theatre?
paa,
I believe this is some of most important work being done right now. The difference between a diffraction "horn" for maximum output, and a "waveguide" applied for the purpose of directivity control and optimized for minimal 'high order modes' is a significant distinction that has taken the high end consumer audio industry too long to recognize. Horns had developed such bad reputation relative to sound quality, that when the modern waveguide began to show promise, the audiophile community continued to reject them, associating them with the horns of the old days.
This area of development has not yet matured to reach its full potential, but as a tool for advancing the state of the art, it is one of the most promising.
LeCleach and Geddes have set good starting points in the formulations for the basic waveguide, but there are next generation architectures that are being developed to address the remaining device and systems issues. There continue to be some problems with many of the axi-symmetric devices and they need to evolve into more appropriate forms to maximize their potential, particularly in the larger devices.
With one of the key attributes of high quality loudspeaker development being that of directivity control, an effectively designed modern waveguide is one of the best tools to reach the most desirable target functions.
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Oct 29, 2003 Inlägg: 33943 Från: Grå Hamnarna
Skrivet: 2011-02-01 07:45 Ämne:
I've begun to wonder if it isn't just the waveguide but the entire speaker that should be machined into some bumpy blob thing to achieve desired radiation patterns... _________________ Det viktigaste är inte att förstå vad man upplever, utan att inse vad av det man upplever man inte förstår.
Blev Medlem: Mar 24, 2003 Inlägg: 25879 Från: Krischansta
Skrivet: 2011-02-01 08:10 Ämne:
Nattlorden skrev:
I've begun to wonder if it isn't just the waveguide but the entire speaker that should be machined into some bumpy blob thing to achieve desired radiation patterns...
Like Genelec? _________________ Audiodesigner åt en del. Larsen, Holographic Audio etc.
CEO och huvudägare i Acoustic Landscape R&D AB.
CTO / R&D Manager och delägare i Acoustic Illusion AB.
thank you for the post, i need to re-read it a few times. i have always thought about the loudspeaker as a mono-source, then interacting with the room or parts of the room, the interaction in a stereo setup is all new to me, i sure would have liked to discuss this in swedish _________________ Fuck off
LeCleach and Geddes have set good starting points in the formulations for the basic waveguide, but there are next generation architectures that are being developed to address the remaining device and systems issues. - James
Could you point to one or two from that next generation?
And would you consider the DXT lens one of those, or how would you categorize that design?
Have you tried or seen other ways to fight HOM than the foam plug that Geddes has patented?
Blev Medlem: Oct 29, 2003 Inlägg: 33943 Från: Grå Hamnarna
Skrivet: 2011-02-01 08:44 Ämne:
Naqref skrev:
Nattlorden skrev:
I've begun to wonder if it isn't just the waveguide but the entire speaker that should be machined into some bumpy blob thing to achieve desired radiation patterns...
Like Genelec?
If that would turn out to be the optimal shape, I'm more thinking about local protubations to incur beneficial difraction where needed, even if the result might look like
_________________ Det viktigaste är inte att förstå vad man upplever, utan att inse vad av det man upplever man inte förstår.
thank you for the post, i need to re-read it a few times. i have always thought about the loudspeaker as a mono-source, then interacting with the room or parts of the room, the interaction in a stereo setup is all new to me, i sure would have liked to discuss this in swedish
Celef,
I'm sorry that I can't deliver the information in Swedish. Maybe someone in the forum can help us with translations.
I think it is important in two-channel loudspeaker design to always consider both loudspeakers to be an integrated system.
In fact, one must consider the pair of loudspeakers, the environment/room, and the listener all as an integrated, inter-dependent system. The loudspeakers are coupled locally (mutual coupling) and also coupled globally (listener and boundaries).
(In a perfect world, the program source and method of recording would be included, but not in today's discussion.)
Mono-source evaluation of a loudspeaker is certainly useful, but it is only the starting point, not a complete characterization.
There are more issues than I can cover in this post, but, as one example, even the interference and resulting frequency response ripple due to cross-talk of the two channels at the listener's head must be considered when balancing the loudspeaker 'system', and this can only be observed when both loudspeakers operating at the same time, and interaction at the listener's body, is considered.
With two-channel reproduction, there is far greater complexity of all the interactive effects, but also more possibilities to improve, not only the spatial aspects, but also the tonal effects.
Then, of course, there is another set of issues relative to loudspeaker design for more than two channels...
Cheers,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-02-01 21:11 Ämne: Commercial Involvement in Footer
Nattlorden skrev:
Welcome Jacro.
If you're able to manage it with through the translator - do make a footer which tells of your commercial involvement - it's a forum rule to have it like that.
Night Lord (Nattlorden)
Thank you for letting me know about the forum protocol.
I believe I have installed the footer information properly.
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Jun 01, 2005 Inlägg: 6773 Från: Nattmössan
Skrivet: 2011-02-03 22:57 Ämne:
Nu när vi har(ytterliggare) en bevisligen professionell
"högtalardesigner" på forumet . . . finns det verkligen
inga fler frågor att ställa till honom . . själv så diys:ar
jag inga egna högisar, men jag gissar/vet ju att flera
av medlemmarna bygger som bara attan. Om jag vore
som ni(diys:are) så skulle jag passa på innan han tröttnar
. . .(pga. ignorans) _________________ Sterio . . . krävs dä tvillingar för å lyssna på´t åsså, typ . . . ?
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-02-03 23:43 Ämne:
paa skrev:
Jacro skrev:
LeCleach and Geddes have set good starting points in the formulations for the basic waveguide, but there are next generation architectures that are being developed to address the remaining device and systems issues. - James
Could you point to one or two from that next generation?
And would you consider the DXT lens one of those, or how would you categorize that design?
Have you tried or seen other ways to fight HOM than the foam plug that Geddes has patented?
Sorry for the delay in answering... I've been busy this week.
As you know, to reduce HOMs one can either;
1) Design the waveguide in a manner that minimizes the generation of high order modes,
or,
2) Apply an absorption means to reduce HOMs that are generated by the waveguide,
or both, of course.
In the first case, if a waveguide is very carefully designed to minimize high order modes then the addition of the absorption foam does not provide a significant audible improvement.
Alternatively, when designing a waveguide, if one can gain an advantage of some desirable parameter (such as improved directivity control) by allowing high order modes to increase, then adding the absorption material can make a significant sonic improvement.
This second approach can be used to improve the DXT type structure, which is very good at directivity control, but due to its directivity control being created by using diffraction steps, it can generate more high order modes than some of the other, low diffraction types, such as Oblate Spheroid, LeCleach, or Iwata types.
A good source for DIY waveguides that are designed for low HOMs (or low Bessel modes) is Auto-Tech in Poland.
I have been working on new waveguide topologies that are based on an elliptical variation of the Oblate Spheroid.
Here is a similar approach, which is a “Quasi-Super Elliptical Oblate Spheroid”.
http://www.diysoundgroup.com/images/large/SEOS-15-9060-N3_1.jpg
It is also available to DIY builders.
This device has two significant advantages over the standard Geddes type axi-symmetric Oblate Spheroid. The waveguide mouth termination is asymmetrical, so it does not exhibit the problems with on-axis high frequency dips in on axis amplitude response. It also allows closer center-to-center spacing with the woofer/mid, so vertical nulls in the response can be separated farther apart and allow a larger usable vertical listening window.
This is a good improvement over the axi-symmetric approach, but doesn’t maintain and ideal Oblate Spheroid form. While it is possibly the best overall design of the current state of the art waveguides, this one is still somewhat compromised compared to an ideal for, so that it can mount flush on a flat frontal cabinet surface.
The waveguides I have been working on follow a more precise rendition of an oblate spheroid formulation converted to elliptical form, which must be shaped in a manner that doesn’t conveniently mount to a flat surface, but offers even a further reduction in modal distortions.
(It is somewhat similar in appearance to the Iwata structures).
In terms of your question about alternatives to foam as a method of reducing HOMs, I am currently exploring different materials than the standard acoustic foam insert, as per Geddes. Ideally, to reduce HOMs more than the fundamental signal output, one would want to have a angular absorption greater than axial absorption, so I am exploring new materials that can have absorption calibrated in an angle dependent manner.
Some of the first work on minimizing this type of horn/waveguide distortion by using foam was pursued by Milton Putnam in 1980, as described in his US patent 4,381,831. In this case, the absorption foam was used mainly at the mouth of the horn and on any diffractive edges within the horn.
I can speak more to this topic if there is specific interest.
Warm regards,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-02-04 04:00 Ämne:
patjoh skrev:
Interesting to have you here James, good reading. Checked out your store to http://www.definitive.com/ and it looks great.
Among all the brands you sell, what is your personal favourite speakers and amplifiers? (if you are not allowed to build them yourself )
Hi patjoh,
I didn't see your post until just now.
Two issues regarding your question;
First, since I am working mostly outside of Definitive Audio, focusing on research and development, I am no longer involved with many of the daily decisions, including which products are chosen to offer for sale.
Secondly, I'm sorry, but I prefer not to recommend or critique products, made by others, that are currently in production. I hope you understand.
I am more than happy to discuss classic products that are no longer being offered for sale.
Also, I am glad to discuss any design principles, psychoacoustics, acoustics, systems, or audio concepts in general and will gladly answer any design related questions anyone in the forum may wish to ask.
Best regards,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-02-04 16:08 Ämne:
paa skrev:
James, would you think the HOM reduction foam also works as an acoustic lens that further smothes the dispersion whithin the desired coverage angle?
Interesting idea.
The current goal of applying foam to a waveguide to reduce HOMs is to be able to maintain consistent absorption such that directivity is not changed from the ideal directivity of the waveguide. Correctly applied, directivity does not change when the foam is applied.
Attempting to use the foam to change directivity does add a degree of complexity that may be difficult to fully characterize. As one changes absorption rates, it must be achieved in a manner that the absorption discontinuities don't increase HOMs, simulating diffractive effects.
That said, the concept of using the foam to alter directivity while reducing HOMs may be a very good idea. The ability to provide an addition variable to control directivity in waveguides may allow one to relax the directivity capability of a waveguide in order to achieve an improvement of some other parameter (such as efficiency, or bandwidth, etc.), and then re-optimize the directivity with a variable density foam insert.
Definitely worth exploring.
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
thank you for the post, i need to re-read it a few times. i have always thought about the loudspeaker as a mono-source, then interacting with the room or parts of the room, the interaction in a stereo setup is all new to me, i sure would have liked to discuss this in swedish
Celef,
I'm sorry that I can't deliver the information in Swedish. Maybe someone in the forum can help us with translations.
I think it is important in two-channel loudspeaker design to always consider both loudspeakers to be an integrated system.
In fact, one must consider the pair of loudspeakers, the environment/room, and the listener all as an integrated, inter-dependent system. The loudspeakers are coupled locally (mutual coupling) and also coupled globally (listener and boundaries).
(In a perfect world, the program source and method of recording would be included, but not in today's discussion.)
Mono-source evaluation of a loudspeaker is certainly useful, but it is only the starting point, not a complete characterization.
There are more issues than I can cover in this post, but, as one example, even the interference and resulting frequency response ripple due to cross-talk of the two channels at the listener's head must be considered when balancing the loudspeaker 'system', and this can only be observed when both loudspeakers operating at the same time, and interaction at the listener's body, is considered.
With two-channel reproduction, there is far greater complexity of all the interactive effects, but also more possibilities to improve, not only the spatial aspects, but also the tonal effects.
Then, of course, there is another set of issues relative to loudspeaker design for more than two channels...
Cheers,
- James
how is this done, if i look at it at different angles i get different results for each angle!? how important is this "compensation" for the average listener? do we all have different sensitivities for errors in this regards? _________________ Fuck off
thank you for the post, i need to re-read it a few times. i have always thought about the loudspeaker as a mono-source, then interacting with the room or parts of the room, the interaction in a stereo setup is all new to me, i sure would have liked to discuss this in swedish
Celef,
I'm sorry that I can't deliver the information in Swedish. Maybe someone in the forum can help us with translations.
I think it is important in two-channel loudspeaker design to always consider both loudspeakers to be an integrated system.
In fact, one must consider the pair of loudspeakers, the environment/room, and the listener all as an integrated, inter-dependent system. The loudspeakers are coupled locally (mutual coupling) and also coupled globally (listener and boundaries).
(In a perfect world, the program source and method of recording would be included, but not in today's discussion.)
Mono-source evaluation of a loudspeaker is certainly useful, but it is only the starting point, not a complete characterization.
There are more issues than I can cover in this post, but, as one example, even the interference and resulting frequency response ripple due to cross-talk of the two channels at the listener's head must be considered when balancing the loudspeaker 'system', and this can only be observed when both loudspeakers operating at the same time, and interaction at the listener's body, is considered.
With two-channel reproduction, there is far greater complexity of all the interactive effects, but also more possibilities to improve, not only the spatial aspects, but also the tonal effects.
Then, of course, there is another set of issues relative to loudspeaker design for more than two channels...
Cheers,
- James
how is this done, if i look at it at different angles i get different results for each angle!? how important is this "compensation" for the average listener? do we all have different sensitivities for errors in this regards?
Celef,
I've put your questions below with answers after...
HOW IS THIS DONE?
There are a number of techniques.
One way is to simply calculate the differential in arrival distance/timing between the left and right channel to one ear. The half-wavelength (and each odd half wavelength) frequency the length differential corresponds to determines the cancellation or dip frequencies from which one can plot the ripple in the response.
Another way is to measure the differential error with a dummy head and in-ear microphones.
Another step is to compare the sound with and without a crosstalk cancelation device, using the crosstalk-cancelled mode as a reference for tonal balance.
Upon establishing the error, it is not necessary to correct all of the resulting measurable ripple. Instead, an gentle spectral correction, on a ½ to 1/3-octave basis, tends to be adequate for this type of error in that the first octave of error has a dip and peak that are a half octave apart. Above the first octave of onset, the comb filtering of the response is closely spaced and has high enough density that it doesn’t require further correction beyond the first octave, or so, of error.
The correction is a delicate one, in that if implemented inappropriately, it can create coloration in the mid-band.
As usual, this is an over simplification, and more is required to deal with the issue effectively, but hopefully this gives you the general idea.
IF I LOOK AT IT AT DIFFERENT ANGLES I GET DIFFERENT RESULTS FOR EACH ANGLE?
Yes, you are correct. The effect is different at each different listening angle.
That is one of the reasons that one must define the listening angle in relation to the loudspeaker pair very precisely.
Most loudspeaker companies only provide general positioning recommendations, hoping to satisfy a wide variety of different placement preferences of a large number of customers. Necessary for high unit volume products.
As an example of an alternative approach, with ( the clue ), we recommend a very limited use model, with precise placement, and listening angle requirements.
While this is not practical for everyone, due to the restricted use model, it allows us to better optimize the performance of the loudspeaker pair in a way that wouldn’t be possible if we recommended generalized placement.
HOW IMPORTANT IS THIS "COMPENSATION" FOR THE AVERAGE LISTENER?
I’m not sure what you mean by the ‘average listener.’
In terms of amplitude errors related to crosstalk cancellation, they tend to fall in the frequency range that the ear is most sensitive, and are also above just noticeable detection thresholds for amplitude errors, so most any listener with healthy hearing, will detect the difference.
But, your question is valid, in that even though most can discern the difference, will it be important to them?
I would expect discerning listeners to find each change of a similar magnitude to this one to be important, but I guess you would have to decide that one for yourself.
DO WE ALL HAVE DIFFERENT SENSITIVITIES FOR ERRORS IN THIS REGARD?
Interesting question.
I find that each listener comes to a listening session with a personal set of system attributes that they tend to prioritize and focus on in their listening experience and judgment.
BUT, I also find that often in a casual, uncontrolled listening session, listeners will often miss subtle system errors, but if I put that same person in a controlled, blind listening situation, I can almost always teach them to recognize the sonic error, such that after the training, they can then notice the same error in the general listening session.
Again, in the cases of crosstalk cancellation amplitude errors, they appear in the portion of the midrange that the ear is most sensitive to so they will tend to be audible to most listeners.
I hope this all makes sense.
All the best,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Jun 29, 2003 Inlägg: 14558 Från: helsefyr
Skrivet: 2011-02-06 00:00 Ämne:
Jacro skrev:
Celef,
I've put your questions below with answers after...
HOW IS THIS DONE?
There are a number of techniques.
One way is to simply calculate the differential in arrival distance/timing between the left and right channel to one ear. The half-wavelength (and each odd half wavelength) frequency the length differential corresponds to determines the cancellation or dip frequencies from which one can plot the ripple in the response.
Another way is to measure the differential error with a dummy head and in-ear microphones.
Another step is to compare the sound with and without a crosstalk cancelation device, using the crosstalk-cancelled mode as a reference for tonal balance.
Upon establishing the error, it is not necessary to correct all of the resulting measurable ripple. Instead, an gentle spectral correction, on a ½ to 1/3-octave basis, tends to be adequate for this type of error in that the first octave of error has a dip and peak that are a half octave apart. Above the first octave of onset, the comb filtering of the response is closely spaced and has high enough density that it doesn’t require further correction beyond the first octave, or so, of error.
The correction is a delicate one, in that if implemented inappropriately, it can create coloration in the mid-band.
As usual, this is an over simplification, and more is required to deal with the issue effectively, but hopefully this gives you the general idea.
i'm not sure if i understand this, but i sounds close to recent topics about the "bbc-dip" and "fundamental flaw in stereo" we have had at this forum, i couldn't figure out then how this correction should look like, and how to achieve a frequency response that changed dramatically att smal offaxis angles
Citat:
IF I LOOK AT IT AT DIFFERENT ANGLES I GET DIFFERENT RESULTS FOR EACH ANGLE?
Yes, you are correct. The effect is different at each different listening angle.
That is one of the reasons that one must define the listening angle in relation to the loudspeaker pair very precisely.
Most loudspeaker companies only provide general positioning recommendations, hoping to satisfy a wide variety of different placement preferences of a large number of customers. Necessary for high unit volume products.
As an example of an alternative approach, with ( the clue ), we recommend a very limited use model, with precise placement, and listening angle requirements.
While this is not practical for everyone, due to the restricted use model, it allows us to better optimize the performance of the loudspeaker pair in a way that wouldn’t be possible if we recommended generalized placement.
this is very interesting, how much of the room should be treated as part of the loudspeaker and when starts the room to be just the room? for my own speakers i sometimes use a simple model by roy allison to compensate for boundary gain, even though it calculates this in a simplistic way the compensation often sounds overcompensated
Citat:
HOW IMPORTANT IS THIS "COMPENSATION" FOR THE AVERAGE LISTENER?
I’m not sure what you mean by the ‘average listener.’
In terms of amplitude errors related to crosstalk cancellation, they tend to fall in the frequency range that the ear is most sensitive, and are also above just noticeable detection thresholds for amplitude errors, so most any listener with healthy hearing, will detect the difference.
But, your question is valid, in that even though most can discern the difference, will it be important to them?
I would expect discerning listeners to find each change of a similar magnitude to this one to be important, but I guess you would have to decide that one for yourself.
DO WE ALL HAVE DIFFERENT SENSITIVITIES FOR ERRORS IN THIS REGARD?
Interesting question.
I find that each listener comes to a listening session with a personal set of system attributes that they tend to prioritize and focus on in their listening experience and judgment.
BUT, I also find that often in a casual, uncontrolled listening session, listeners will often miss subtle system errors, but if I put that same person in a controlled, blind listening situation, I can almost always teach them to recognize the sonic error, such that after the training, they can then notice the same error in the general listening session.
Again, in the cases of crosstalk cancellation amplitude errors, they appear in the portion of the midrange that the ear is most sensitive to so they will tend to be audible to most listeners.
I hope this all makes sense.
All the best,
- James
when looking at measurements of varios loudspeakers at sources like stereophile or soundstage there is hard to detect if they have been compensated for any errors, or at least i have not find any, is this due to the measurement technic they are using or is this compensation rare? _________________ Fuck off
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-02-06 08:27 Ämne:
celef skrev:
Jacro skrev:
Celef,
I've put your questions below with answers after...
HOW IS THIS DONE?
There are a number of techniques.
One way is to simply calculate the differential in arrival distance/timing between the left and right channel to one ear. The half-wavelength (and each odd half wavelength) frequency the length differential corresponds to determines the cancellation or dip frequencies from which one can plot the ripple in the response.
Another way is to measure the differential error with a dummy head and in-ear microphones.
Another step is to compare the sound with and without a crosstalk cancelation device, using the crosstalk-cancelled mode as a reference for tonal balance.
Upon establishing the error, it is not necessary to correct all of the resulting measurable ripple. Instead, an gentle spectral correction, on a ½ to 1/3-octave basis, tends to be adequate for this type of error in that the first octave of error has a dip and peak that are a half octave apart. Above the first octave of onset, the comb filtering of the response is closely spaced and has high enough density that it doesn’t require further correction beyond the first octave, or so, of error.
The correction is a delicate one, in that if implemented inappropriately, it can create coloration in the mid-band.
As usual, this is an over simplification, and more is required to deal with the issue effectively, but hopefully this gives you the general idea.
i'm not sure if i understand this, but i sounds close to recent topics about the "bbc-dip" and "fundamental flaw in stereo" we have had at this forum, i couldn't figure out then how this correction should look like, and how to achieve a frequency response that changed dramatically att smal offaxis angles
Citat:
IF I LOOK AT IT AT DIFFERENT ANGLES I GET DIFFERENT RESULTS FOR EACH ANGLE?
Yes, you are correct. The effect is different at each different listening angle.
That is one of the reasons that one must define the listening angle in relation to the loudspeaker pair very precisely.
Most loudspeaker companies only provide general positioning recommendations, hoping to satisfy a wide variety of different placement preferences of a large number of customers. Necessary for high unit volume products.
As an example of an alternative approach, with ( the clue ), we recommend a very limited use model, with precise placement, and listening angle requirements.
While this is not practical for everyone, due to the restricted use model, it allows us to better optimize the performance of the loudspeaker pair in a way that wouldn’t be possible if we recommended generalized placement.
this is very interesting, how much of the room should be treated as part of the loudspeaker and when starts the room to be just the room? for my own speakers i sometimes use a simple model by roy allison to compensate for boundary gain, even though it calculates this in a simplistic way the compensation often sounds overcompensated
Citat:
HOW IMPORTANT IS THIS "COMPENSATION" FOR THE AVERAGE LISTENER?
I’m not sure what you mean by the ‘average listener.’
In terms of amplitude errors related to crosstalk cancellation, they tend to fall in the frequency range that the ear is most sensitive, and are also above just noticeable detection thresholds for amplitude errors, so most any listener with healthy hearing, will detect the difference.
But, your question is valid, in that even though most can discern the difference, will it be important to them?
I would expect discerning listeners to find each change of a similar magnitude to this one to be important, but I guess you would have to decide that one for yourself.
DO WE ALL HAVE DIFFERENT SENSITIVITIES FOR ERRORS IN THIS REGARD?
Interesting question.
I find that each listener comes to a listening session with a personal set of system attributes that they tend to prioritize and focus on in their listening experience and judgment.
BUT, I also find that often in a casual, uncontrolled listening session, listeners will often miss subtle system errors, but if I put that same person in a controlled, blind listening situation, I can almost always teach them to recognize the sonic error, such that after the training, they can then notice the same error in the general listening session.
Again, in the cases of crosstalk cancellation amplitude errors, they appear in the portion of the midrange that the ear is most sensitive to so they will tend to be audible to most listeners.
I hope this all makes sense.
All the best,
- James
when looking at measurements of varios loudspeakers at sources like stereophile or soundstage there is hard to detect if they have been compensated for any errors, or at least i have not find any, is this due to the measurement technic they are using or is this compensation rare?
Celef,
Answer to question #1:
I think that the BBC, or “Gundree”, dip is invoked to address audible coloration and inadvertently addresses the crosstalk cancellation errors. If one doesn’t analyze the source of the problem, but instead attempts to correct what is experienced as a tonal error, then one might apply a BBC type dip as a partial fix and hear a sonic preference in the result.
But, if one shapes the response correction to more closely follow the shape of the crosstalk error (not simply a dip), the tonal correction will sound more “life-like”. The BBC dip takes away the “peak” portion of the error, and softens the coloration, but also takes a bit of the “aliveness” out of the midrange.
All of this is fairly subtle, but significant in the totality of the sonic presentation.
Answer to question #2:
If I understand what you are asking, I think of the boundaries that have reflective path lengths within 10 milliseconds, and greater than -10 dB of the direct sound, to be “the loudspeaker”, and the rest to be “the room”.
***
Allison’s work was significant, in that he got people thinking about the importance of considering the effects of the first three boundaries, but it is amazing to me how few loudspeaker companies incorporate Allison’s notions into their loudspeaker design. Roy was also surprised that he had such a small influence on loudspeaker design in the industry.
I’m working on a new paper that I hope to present at AES next year that honors Allison, but shows that his basic thesis that acoustic impedance of the boundary and the change in acoustic impedance due to the distance to each boundary from acoustic matching function dominated the spectral errors. I have found that the issue is not dominated by the acoustical impedance of the boundary, but instead is based on a “specular” reflection differential relationship to the direct sound and this new way of viewing the problem provides a more accurate analysis and correction factor.
Answer to question #3:
I think this type of compensation is rare.
I am not aware of any other loudspeaker manufacturer that claims to use compensation for crosstalk amplitude errors in their loudspeakers. Some may, but I am not aware of it.
As stated above, the most similar approach may be the use of a simple BBC type dip.
Without establishing a very specific listening angle between the loudspeaker and the listener, this approach is difficult to calibrate for correct results and most loudspeaker companies don’t provide strict and specific angular use instructions.
Also, I’m not aware that very many companies design their loudspeakers with any specific design elements that optimize for two-channel usage. Most test and optimize in monophonic mode. Surprisingly, even Floyd Toole and Sean Olive’s “advanced” Harman International loudspeaker test and evaluation center uses only single loudspeaker, monophonic testing and comparative listening sessions. I’ve discussed this with them and, in private, they admit it is a shortcoming that they don’t have a solution for.
For the correction is best to use what I call a “soft correction”, which is a gentle alteration to the frequency response, which may not be easy to interpret from standard measurements. Many loudspeakers have response ripple errors that are as large as the correction, so, if they were applying this type of correction, it could be hard to see the correction hidden within their response errors in the measurements that you have observed.
All the best,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Answer to question #1:
I think that the BBC, or “Gundree”, dip is invoked to address audible coloration and inadvertently addresses the crosstalk cancellation errors. If one doesn’t analyze the source of the problem, but instead attempts to correct what is experienced as a tonal error, then one might apply a BBC type dip as a partial fix and hear a sonic preference in the result.
But, if one shapes the response correction to more closely follow the shape of the crosstalk error (not simply a dip), the tonal correction will sound more “life-like”. The BBC dip takes away the “peak” portion of the error, and softens the coloration, but also takes a bit of the “aliveness” out of the midrange.
All of this is fairly subtle, but significant in the totality of the sonic presentation.
All the best,
- James
13.I've heard mention of 'the BBC dip' or 'the Gundry dip'. What does that mean?
There is much myth, folklore and misunderstanding about this subject.
The 'BBC dip' is (was) a shallow shelf-down in the acoustic output of some BBC-designed speaker system of the 1960s-1980s in the 1kHz to 4kHz region. The LS3/5a does not have this effect, neither in the 15 ohm nor 11 ohm, both of which are in fact slightly lifted in that region.
According to Harbeth's founder, who worked at the BBC during the time that this psychoacoustic effect was being explored, the primary benefit this little dip gave was in masking of defects in the early plastic cone drive units available in the 1960's. A spin-off benefit was that it appeared to move the sound stage backwards away from the studio manager who was sitting rather closer to the speakers in the cramped control room than he would ideally wish for. (See also Designer's Notebook Chapter 7). The depth of this depression was set by 'over-equalisation' in the crossover by about 3dB or so, which is an extreme amount for general home listening. We have never applied this selective dip but have taken care to carefully contour the response right across the frequency spectrum for a correctly balanced sound. Although as numbers, 1kHz and 4kHz sound almost adjacent in an audio spectrum of 20Hz to 20kHz, the way we perceive energy changes at 1kHz or 4kHz has a very different psychoacoustic effect: lifting the 1kHz region adds presence (this is used to good effect in the LS3/5a) to the sound, but the 4kHz region adds 'bite' - a cutting incisiveness which if over-done is very unpleasant and irritating.
You can explore this effect for yourselves by routing your audio signal through a graphic equaliser and applying a mild cut in the approx. 1kHz to 4kHz region and a gradual return to flat either side of that.
Enligt detta var BBC-dipen ursprungligen en åtgärd för att hantera egenskaper hos de högtalarelement som användes. Givetvis har den trots det en psykoakustisk inverkan.
Blev Medlem: Mar 17, 2009 Inlägg: 8862 Från: speedad
Skrivet: 2011-02-06 23:07 Ämne:
Hi James, welcome to the forum, what do You think is the secret about tubes and that they almost always sounding more pleasant and true to the ears? And do we really need all that watts, low powered amps seems to gain in transparent sound, may be construction simplicity or cost effectiveness? Why do I think carbon sounds more real than metal as a conductor? Any clue? _________________ M O N S T E R ® C A B L E
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-02-07 04:13 Ämne:
paa skrev:
Jacro skrev:
Answer to question #1:
I think that the BBC, or “Gundry”, dip is invoked to address audible coloration and inadvertently addresses the crosstalk cancellation errors. If one doesn’t analyze the source of the problem, but instead attempts to correct what is experienced as a tonal error, then one might apply a BBC type dip as a partial fix and hear a sonic preference in the result.
But, if one shapes the response correction to more closely follow the shape of the crosstalk error (not simply a dip), the tonal correction will sound more “life-like”. The BBC dip takes away the “peak” portion of the error, and softens the coloration, but also takes a bit of the “aliveness” out of the midrange.
All of this is fairly subtle, but significant in the totality of the sonic presentation.
All the best,
- James
Thank you for the link to your BBC dip discussions. It seems that almost every topic in audio has been discussed in your forum.
I always find enjoyable reading here.
I had some great discussions with Alan Shaw at Harbeth a few years ago. He is a wealth of information regarding the truth about the LS3/5a and BBC loudspeaker research.
It would seem that the LS3/5a is a combination of accuracy and sonic trickery. Odd for a studio monitor to be optimized for sensationalism rather than neutrality. It is a wonderfully entertaining and fun loudspeaker to listen to, but I’m not sure it qualifies as a neutral, professional monitor.
I’ve owned 8 different pairs of LS 3/5a, 15 ohm, 11 ohm, Rogers and Spendors, and still have a couple pair that I enjoy. I had to do a very extensive analysis of the LS 3/5a when I developed the Satterberg Mid-Woofer for them back in the 1980’s. It was very difficult to get a seamless match through the crossover and retain all the sonic attributes of original loudspeaker when used with the Satterbergs.
It was a fun and challenging project, in that we had to develop an unusual approach to subwoofer matching to get it to work properly.
In terms of the BBC/Gundry dip, while it was originally developed to minimize the colorations in the early generations of Bextrene cones, it has been used for many other purposes.
If I remember correctly, I believe the Spendor BC1 and BBC LS3/6 incorporated a Gundry type dip in the upper midrange.
These days this reduction of energy in the upper midrange is most often used to minimize tweeter “flare” or excess off-axis tweeter energy at the crossover frequency.
One of the things that also must be considered, when applying BBC dip type response changes in the midrange, is that they don’t just alter the perception of the tonal character, but they also impact imaging, as the amplitude changes correspond to changes in source angle, as observed in head related transfer functions.
Cheers,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Jun 29, 2003 Inlägg: 14558 Från: helsefyr
Skrivet: 2011-02-07 17:58 Ämne:
james,
thanks for your post, i need some time to think it throu. i have much to ask but one thing comes to mind; this might be against your policy but, what do you think about technologies like www.embracingsound.com
Blev Medlem: Jan 21, 2008 Inlägg: 2942 Från: Göteborg
Skrivet: 2011-02-07 20:15 Ämne:
Det här är ju jätteintressant!
Citat:
"Although as numbers, 1kHz and 4kHz sound almost adjacent in an audio spectrum of 20Hz to 20kHz, the way we perceive energy changes at 1kHz or 4kHz has a very different psychoacoustic effect: lifting the 1kHz region adds presence (this is used to good effect in the LS3/5a) to the sound, but the 4kHz region adds 'bite' - a cutting incisiveness which if over-done is very unpleasant and irritating."
Så det som jag brukar kalla för överdiven kontrast, eller en analogi till en LCD-skärm med för kraftig skärpeinställning kan vara en höjning i 4kHz området? Vidare skulle en höjning av 1kHz ge en ökad närvarokänsla.
Rörsteg??????
Citat: "A spin-off benefit was that it appeared to move the sound stage backwards away from the studio manager who was sitting rather closer to the speakers in the cramped control room than he would ideally wish for."
Den falska förskjutningen av ljudbilden bakåt! Rymden i ljudbilden?
QLN Signature!
Rörsteg?????
Eller kombinationen av vissa steg med vissa högtalare som ger ett konstlat djup i ljudbilden. Är det så enkelt? _________________ Plinius åt folket!
Blev Medlem: Jul 17, 2003 Inlägg: 2549 Från: Hlewanger
Skrivet: 2011-02-07 20:34 Ämne:
DanNorman skrev:
Detta är alltså den raka motsatsen till pip (och guru qm10)?
Ingvar hade problem att hitta en tillräckligt högspridande diskant till pip, medan här väljer man att stoppa den i en waveguide. Intressant.
Kanske att wave guiden ifråga sprider ljudet annorlunda än förväntat?
Bara en tanke... Hursomhelst en intressant tråd detta.
/G _________________ "och allt är bara en test av synapserna"
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-02-08 00:58 Ämne:
Objektivisten skrev:
Hi James, welcome to the forum, what do You think is the secret about tubes and that they almost always sounding more pleasant and true to the ears? And do we really need all that watts, low powered amps seems to gain in transparent sound, may be construction simplicity or cost effectiveness? Why do I think carbon sounds more real than metal as a conductor? Any clue?
Objektivisten;
First, thank you for the friendly welcome. Everyone has been very friendly.
These are big subjects, and often difficult to explore effectively in a short post, but I will start the discussion.
Lately, I tend to avoid answering these types of questions in that I find that many people have already made up their minds and aren’t interested in hearing an answer that contradicts their beliefs.
I have been involved in extensive research in this area, both independently in the early 1980’s and again in the 1990’s when I ran the R&D department at Carver Corporation.
In this post I’ll start with some well-verified, general principles, and if there is further interest I can go into deeper specifics.
One thing that is important to understood is that to find truths about such matters is a complex process and not at all fun if done properly.
Hard work.
It takes a lot more effort and rigor than most audiophiles are willing to endure. For many, audio is a joyful endeavor, and it should be.
It is fun to do casual listening tests and derive and proclaim judgments about many aspects of audio, in terms of what is good, what is bad, all from a casual environment without establishing careful controls and repeating hundreds of tests, over and over again to be sure that one is not fooling themselves.
It is not easy or fun, and I find that there are not many that are willing to put forth the great effort it takes and be open to challenging ones most cherished beliefs.
To me listening to music through an audio system is one of the most fun hobbies one can have. Doing the research to find out which things really sound different, or better, and what really makes a difference, is a completely different kind of, serious, rigorous, activity.
Many seem to confuse the two.
I’m sorry to start by preaching, but I think it is important to establish how careful one has to be to really answer these types of questions with a degree of certainty.
So, I’ll tell you what, after great efforts, I have found to be true.
I’m not saying you should believe me, and I suggest you don’t just believe what anyone says, but test carefully and thoroughly and always find out for yourself. But, be sure to be thorough and rigorous in your testing. Question your most fundamental beliefs as you work through your tests.
Because the subject is so involved, I’ll start with your last question for this first post, and work back to the first question in subsequent posts.
These cannot be complete answers in a single post, but hopefully they will provide a starting point for thought and discussion…and entertainment.
Your Question:
1) WHY DO I THINK CARBON SOUNDS MORE REAL THAN METAL AS A CONDUCTOR?
First, I’m not sure why you think that, as I don’t know how you have tested your hypothesis to arrive at your conclusion.
So maybe the question is not, "Why do you think carbon sounds better than metal?", but maybe your real question is, "Is it true that carbon sounds more real than metal?"
If my answer about whether it is true or not, doesn't satisfy, then we can explore the psychology and process of "Why do YOU think it is true?"
I have found that one must not make judgments about any component out of the context of the system that it is used in. It has almost no meaning to discuss component types outside of the circuit that they operate in, because the quality of their performance is dominated by the relational impedance interface within the system.
You might say, I have found this system (amp, pre-amp, loudspeaker, etc.) that when I use resister “A”, it sounds better to me that when I use resister “B”. You may even say, that I have found this pattern in a number of systems.
I would tend to ask first, what is it about these systems that they react in an unfavorable manner when used with resister “B”? Is the circuit interface compatible with resistors that are of type “B”? Is resistor type “B” being used in the manner that it is best suited?
While it might seem more obvious to question the component “resistor type B”, it turns out, that unless one has a component that is fundamentally defective, or is functioning outside a standard deviation of some important parameter, it is more likely that what you are experiencing as a sonic difference, is the system mismatch, not the inferiority of the component in isolation.
Sometimes one will find that in a certain component category, such as a capacitor, the one that is the “audiophile favorite” is not necessarily the best to use in a particular circuit.
At a recent show, people kept asking me what kind of capacitors I used in the crossover of ( the clue ) loudspeaker. I would have to say, that I cannot give a simple answer to the question.
I have a number of networks designed that all sound the same. Each network has different components from different vendors.
The reason I had to design different networks is that I have certain components that I cannot second source, so if they become unavailable, I have to substitute another component from another vendor.
But, in some cases, another component will not work perfectly, just substituted in, even if it has the same specified values. The transfer function will have changed a little. So, when I have to change one component, such as a capacitor from a one brand name to one of another, I may have to change the components that interface the input and/or the output of that capacitor to maintain the same dynamic transfer function, and sound quality. One cap wasn’t better than the other, but the system that it was operating within, was better matched to achieve my ideal input to output function.
So, to be able to use alternative components in certain places in the crossover network, I designed different networks to best work with different component set combinations while maintaining the same dynamic transfer function.
When I first substituted the replacement part, and found the system to perform worse, I could have blamed the quality of the part and decided not to use it, and call it “a bad part”. But, it wasn’t “a bad part”, it was a part that the system was not matched to. Once properly re-matched with new associated components, one could not hear any difference.
It can easily happen that substituting the most expensive component will actually disturb the transfer function of the total system. Sometimes it will sound different, when put in the circuit, and listeners will assume the difference means “better” because they think it is a better, more expensive component, that has a good reputation, but it doesn’t always work that way.
Good audio is predominately a systems design approach, not an individual component selection approach. The components have to be appropriate within a standard deviation, but beyond that, it is all based on the impedance interfacing of the system.
Some designers operate from a systems approach, and some try to use all the most expensive components and hope for the best result.
Whether one has an unlimited budget or is designing for lowest cost, the systems approach will provide a better result and will tend to be less wasteful. But, it takes longer and requires more careful assessment.
Cheers,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Im a little bit more interested in the waveguide. I see you use a very small WG, so small that some people (like geedle) dont even call it a waveguide.
However I think reasonably sized WGs are more interesting and also would have more relevance in home-audio (as its more "design-driven").
Ive been looking at JBL* and what they call "elliptical oblate spheroidal waveguide" and by the looks of it it seem to be only 5x8cm or something like that. Thats very small when it comes to waveguides but they (JBL) seem happy with the directivity control, or matching, they get.
Looking at the site you linked to, small waveguides seem rare.
Do you fell that the WG have to be big to be effective? If one assumes a 2kHz crossover, is a size like JBL WG enough or is it just for show?
The DXT-lens is a diffraction lens and maybe not a true WG, but it is very effective att directivity control down to 2Khz. But being a diffraction-device there should be alot of HOM being created. Seeing the "rave" that this lens have got (like in the speakers from Acoustic Energy) it would seem that HOMs arent that bad?
In what way are you using the WG in your speaker and isnt it very short and of a "simple" profile to be effective as a WG? (no disrespect intended of course)
Heres the link to JBLs Linear Spatial Reference Studio Monitor System
*http://www.jblpro.com/catalog/general/Product.aspx?PId=26&MId=5 _________________ Vackra ord är inte sanna, Sanna ord är inte vackra. / Tao Te Ching
Blev Medlem: Jun 01, 2005 Inlägg: 6773 Från: Nattmössan
Skrivet: 2011-02-08 11:09 Ämne:
Jacro skrev:
. . . . . .
Good audio is predominately a systems design approach, not an individual component selection approach. The components have to be appropriate within a standard deviation, but beyond that, it is all based on the impedance interfacing of the system.
Some designers operate from a systems approach, and some try to use all the most expensive components and hope for the best result.
Whether one has an unlimited budget or is designing for lowest cost, the systems approach will provide a better result and will tend to be less wasteful. But, it takes longer and requires more careful assessment.
Cheers,
- James
James, welcome to the forum !
Like poetry in my ears(eyes) . . . . wounderful words. _________________ Sterio . . . krävs dä tvillingar för å lyssna på´t åsså, typ . . . ?
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-02-08 21:21 Ämne: Stereo Dipoles
celef skrev:
james,
thanks for your post, i need some time to think it throu. i have much to ask but one thing comes to mind; this might be against your policy but, what do you think about technologies like www.embracingsound.com
best regards
Celef,
I look forward to your next questions.
In terms of the Embracing Sound System, I think it is a very promising technology.
The basic principle of an crosstalk cancellation systems have has been attempted and explored since the mid 1960’s.
In 1963, Schroeder and Atal out-lined a method for generating a phantom source. These ideas were elaborated by Damaske in 1971 and were followed in the mid-1970’s by Iwahara in Japan, with the JVC’s Bi-Phonic processor. As the pure theory suggests, all were made for use with Binaural recordings. In 1979 Robert Carver created a modified version of the JVC unit and offered a processor recalibrated for stereo recordings called Sonic Holography.
All were attempts to fix some of the fundamental spatial and tonal flaws of 2-channel stereo. Theoretically, under ideal conditions, it can be a superior approach, but is much more critical to optimize than conventional stereo. While potentially better than stereo, if it isn’t perfectly calibrated it can sound much worse than stereo. Ultimately, it is best suited for reproducing a binaural based recording.
These types of systems were always problematic with widely spaced loudspeakers, because the cancellation signals were very difficult to match, as they had to include the frequency response effects of the sound rapping around the face, to the opposite ear.
Around the same time (about 1980-1) we built a crosstalk isolation wall/barrier with a loudspeaker on each side of the barrier, with the wall projecting from the loudspeakers to the face of the listener. The spatial effects were quite impressive, and formed a reference sound field for further development work but the structure was not practical for consumer use. (Don Keele wrote an AES paper on this technique in 1986) With this structure as a reference, we worked on the processor approach and found that if we placed the loudspeakers close together that the correction for face-related-transfer-functions were much easier to apply and retain neutral tonal balance, and the spaciousness was even more impressive.
Unfortunately, due to the new movement towards multi-channel Surround Sound becoming popular, our two-channel project was halted and 5-speaker surround sound was where development efforts were redirected.
In 1995 new work began by Kirkeby, Takeuchi and Hamada, (University of Southhampton and Tokyo Denki University) as filed in British Patent App. # 9,603,236.2 “Stereo Dipole”. This closely spaced cross talk canceller was found to have lower coloration and greater stability of image with head movements. The same group wrote a series of very interesting papers on the subject of Stereo Dipoles, provide thorough analysis and synthesis information that was much more advanced than the work we did in the 1980’s.
It appears that the Embracing Sound Systems are based on the work of Kirkeby, Takeuchi, and Hamada (I don’t think their patent was ever granted) and if properly implemented, should be very good.
It has always been a system with great potential, particularly with binaural recordings. While it can provide an impressive demo with standard stereo recordings, it doesn’t reproduce an ideal transfer from stereo recordings, at least not as an accurate representation of the source, but it is a lot of fun to experiment with.
Now if we could get all the recording companies to offer a binaural alternative to every stereo recording, life would be great, but I don’t think that is going to happen anytime soon.
So, in the meantime, those of us that design reproduction systems, must work blind to the recording process, never knowing what kind of microphone technique is going to be used. Ultimately, an impossible task, but we persevere, searching for the best ways to create a believable facsimile of the original sound from an imperfect model.
All the best,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-02-09 04:30 Ämne: Waveguide Size
Kraniet skrev:
Im a little bit more interested in the waveguide. I see you use a very small WG, so small that some people (like geedle) dont even call it a waveguide.
However I think reasonably sized WGs are more interesting and also would have more relevance in home-audio (as its more "design-driven").
Ive been looking at JBL* and what they call "elliptical oblate spheroidal waveguide" and by the looks of it it seem to be only 5x8cm or something like that. Thats very small when it comes to waveguides but they (JBL) seem happy with the directivity control, or matching, they get.
Looking at the site you linked to, small waveguides seem rare.
Do you fell that the WG have to be big to be effective? If one assumes a 2kHz crossover, is a size like JBL WG enough or is it just for show?
The DXT-lens is a diffraction lens and maybe not a true WG, but it is very effective att directivity control down to 2Khz. But being a diffraction-device there should be alot of HOM being created. Seeing the "rave" that this lens have got (like in the speakers from Acoustic Energy) it would seem that HOMs arent that bad?
In what way are you using the WG in your speaker and isnt it very short and of a "simple" profile to be effective as a WG? (no disrespect intended of course)
Heres the link to JBLs Linear Spatial Reference Studio Monitor System
Thou shalt not judge a man by the size of his waveguide
- Anonymous Swedish philosopher
A waveguide doesn’t always have to be big to be effective. Generally, the purpose of a waveguide is to increase the directivity of the tweeter to more closely match the directivity of the woofer for frequencies that are at, and near, the crossover. To achieve that purpose, the waveguide should be comparable in dimension to the active radiating portion of the woofer.
Also, generally, one wishes to maintain the smallest center-to-center distance between the woofer and the tweeter, to avoid interference nulls in the vertical response.
So, if one had a 160mm woofer, with a tweeter attached to a 300mm waveguide, the overly large size of the waveguide would be problematic in at least two different ways:
- The tweeter/waveguide would have significantly more directivity at the crossover frequency than the woofer, causing a mismatch and very poor off-axis frequency response
- The center-to-center spacing between the woofer and the tweeter would be quite large (at least 230mm) causing a very narrow vertical listening window between the vertical nulls in the polar response
An additional point is that is significant, is that it is difficult to determine the radiating size of a given woofer just by measuring the size of the diaphragm. Some woofers and midranges will have a smaller source size with increase in frequency, due to the outer portion of the cone breaking up and decoupling from the center portion of the cone. So the waveguide may need to be a bit smaller than the cone diameter to have matched directivities at a given frequency.
Big woofers = Big waveguides.
Small woofers or midranges = Small waveguides.
With the JBL link that you provided, the crossover to the tweeter/waveguide is stated as 2.2 kHz. The waveguide appears a little small but again, it may be size-matched to the characteristics of the midrange. JBL considers off axis frequency response, and directivity matching, to be one significant parameters, so one can assume they chose their waveguide size very carefully.
The DXT waveguide does have diffraction steps but they are fairly shallow and hopefully don’t develop significant amounts of high order modes, but I am not certain what amount of HOMs are created in the DXT waveguide.
I would expect that the very good directivity control of the DXT waveguide when combined with a high quality transducer will produce good results.
It would be interesting to add a foam insert to absorb the high order modes and find out if eliminating the HOMs significantly improved the sound quality.
After extensive testing, the form and size of the waveguide in ( the clue ) was chosen to achieve the desired effect in matching the interaction with the cone driver over the transition frequencies. If we can make the system perform better by making the waveguide larger, or of a more complex form, we would do so, but so far, we have found the current waveguide to be the best match.
(No disrespect taken )
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Thats reassuring to hear. Listening to Geddes one get the feeling that everything goes as long as its by his defenition..
You mentioned Revel and JBL earlier and their work on evaluating meaningful speaker attributes. I think some of it we could all agree to, like a reasonably flat on-axis and a even and slowly falling off-axis for higher frequencies. But their testing method seem limited to "voicing" and percieved sonic balance. The issues with the stereo flaw doesnt seem to enter the picture.
Why is that do you think? Is it a little to "subjective" of a thing for them to be able to "double blind" it? As you say they seem aware of their limitations.
But isnt it also a good way to go, establishing the "true objective" attributes of speakers like frequency/power response, low distortion etc? I mean looking at the industry at a whole there seem to be a lack of an "even ground" for how a speaker should reasonably work for it to have a chance of being a true reproducer och the source material. Lacking those attributes it seems useless to optimize for stereo imaging. Or? _________________ Vackra ord är inte sanna, Sanna ord är inte vackra. / Tao Te Ching
The work of Dr. Choueiri is very impressive, and encouraging, in its thoroughness.
He has taken the cross-talk cancellation process beyond Local simplicity and has included the Global issues, such as listener body related transfer functions and the room issues. His use of the power of digital signal processing to address the secondary effects of XTC is what makes his system more encouraging than the work that has been attempted by others.
There is still the issue that post processing of this type is only “correct” for binaural recordings, but as he suggests, it will also work reasonably well for any stereo recording that has attempted to preserve the original inter-aural time and level differences.
Choueiri is one of the few that has suggested, and required, directivity control in the loudspeakers used with his system. He addresses how the room effects distort the correction signals and he has developed a very sophisticated filter system to address the tonal coloration found in all the prior art systems of this type.
His custom filter calibration to listener location and attributes is also a step forward.
I have been following his work since he first made it public, and I have not yet measured or heard one of his systems. But the fact that he is not just talking about the difficulty of secondary problems, and instead is actually addressing them is very encouraging.
Theoretically, he appears to be on the right track in many ways.
Cheers,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
seems limited to one person listening though. he speaks of it being viable for TV but I cant see how it would work in a normal living room with 4-6 people getting the full experience. _________________ Vackra ord är inte sanna, Sanna ord är inte vackra. / Tao Te Ching
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-02-09 19:12 Ämne:
Kraniet skrev:
seems limited to one person listening though. he speaks of it being viable for TV but I cant see how it would work in a normal living room with 4-6 people getting the full experience.
Yes, your observation and concerns are correct.
If one moves their head, even though the Stereo Dipole is more robust than other XTC systems, it still tends to be limited to an ideal listening region of less than half a meter square...Not enough for more than one listener.
Currently, the best 2-channel approach for multiple listeners is to use a conventional stereo system, incorporating time/intensity trading, with the most intense axis of the loudspeakers crossing in front of the listener, as originally proposed by Ben Bauer in the 1960s and Mark Davis at DBX in 1983 (US 4,503,553).
Modern versions of this approach use waveguides for directivity control and cross fire the loudspeakers in front of the listeners.
As a general rule though, the potential of the accuracy of an audio signal at the listening seat is inversely proportional to the size of the listening region around the head.
So, the best sound is always in the center, but the best cross axis solutions can make the sound quality remain quite satisfying a few people sitting together.
Best regards,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-02-09 19:28 Ämne:
paa skrev:
Jacro skrev:
I have been working on new waveguide topologies that are based on an elliptical variation of the Oblate Spheroid.
- James
Seems like Procella has gone towards that direction too (and it's smaller than it looks in the picture):
Yes, a number of groups are starting to work with this form of waveguide, as it is found to be quite effective in regards to consistent directivity control, low linear/diffractive distortions, and allows reduced center-to-center spacing compared to axi-symmetric waveguides.
Some, such as Geddes, point out that it doesn't match the directivity of the midrange/woofer in the vertical axis as well as an axi-symmetric waveguide and they believe that the center-to-center spacing advantage is not as important as directivity matching.
The counter argument is that while the local directivity of an axi-symmetric waveguide and woofer, of approximately the same size, DO match better at the crossover frequency, the Global, combined vertical directivity of the two symmetrical units causes a significant directivity change at the crossover frequency.
And the pro- axi-symmetric group claims they can control that effect in the crossover... and... and...
Proper system design can result in great performance from either approach, with one offering some advantage over the other depending on all the system variables.
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-02-09 21:56 Ämne: Tube Amplifiers and Power Levels
Objektivisten skrev:
Hi James, welcome to the forum, what do You think is the secret about tubes and that they almost always sounding more pleasant and true to the ears? And do we really need all that watts, low powered amps seems to gain in transparent sound, may be construction simplicity or cost effectiveness?
Hi Objektivisten,
I still owe you an answer on your Tube amp and Power requirement questions.
I’m still not sure how to address such vast topics adequately in a single post.
So, to start, I’ll provide you with some information that you may find interesting from earlier research that we did, and I will spread the discussion over a few posts.
Part One (A partial review of Large Signal/Overload Issues):
1) WE FOUND THAT PARTIAL CLIPPING OF AN AMPLIFIER IS NORMAL USAGE FOR MANY LISTENERS.
- We monitored the systems of 92 different audiophiles over a 2-year period by monitoring their amplifiers in their homes and collecting data on how often their amplifiers were clipped.
When using high quality program material, we found that over 70-percent of the test subjects used their systems in a manner that regularly caused the onset of overload, or mild clipping, even though most of them would not be considered to listen at inappropriately loud levels.
(We eliminated the data of the subjects that obviously drove their systems beyond their capability and into hard clipping.)
(The average rated wattage of their amplifiers was 45 watts per channel, with the lowest being 9 watts and the highest being 350 watts per channel. Average rated loudspeaker sensitivity was 88dB/1 watt.)
2) WE FOUND THAT SOME AMPLIFIERS HAVE EUPHONIC CLIPPING CHARACTERISTICS THAT CAN ACTUALLY ENHANCE SOUND QUALITY DURING MILD CLIPPING LEVELS.
- We found that there is a wide variety of overload parameters and associated audible artifacts that are derived from those overload parameters.
• Harmonic distortion: Depending on whether the amplifier generated predominately low order*, even harmonics*, or high order**, odd harmonics** determined whether the clipping sounded “enhanced*” or “irritating**”.
Many tube amplifiers generate low order, even harmonics during overload, due to their asymmetrical clipping characteristics.
Most solid-state amplifiers produce primarily odd-order harmonics due to their symmetrical clipping characteristics.
• Other characteristics that can provide either ‘euphonic’ or ‘irritating’ sound quality during overload;
Overload In-phase or out-of-phase cross talk:
(Out-of-phase cross-talk can cause enhanced spatial effects. Some tube amplifiers exhibit this characteristic during mild overload)
Overload recovery time:
(Can prolong either positive or negative overload effects, unless recovery is extended due to “sticking” wherein an amp will stay “stuck” to one power supply rail is itself a malady of the design)
Overload output impedance increase:
(Can cause under-damping of loudspeaker during overload. High feedback amplifiers can have a greater delta between linear and overloaded output impedance, which may cause a more disturbing sonic result.)
3) SOME HIGHER POWERED AMPLIFIERS ARE CRITICIZED FOR POORER SOUND QUALITY WHEN COMPARED TO LOW POWERED AMPLIFIERS:
- It turned out, that in nearly every case, the higher-powered amplifier was not inherently worse sounding, but because it had more unclipped power, it was found that it could more easily over-drive the loudspeakers into greater non-linearity, causing the loudspeaker (not the amplifier) to have worse sound.
But since the amplifier was the only element changed in the system when comparing the sound, the higher-powered amplifier was most often unfairly blamed for the decreased sound quality.
4) In later studies we have found that many class-D amplifiers have an even more severe problem in that they start to have significantly increased distortion effects as they approach clipping, but have not yet overloaded. Because of this, they may not be able to be used in a manner that fully utilizes their full power capabilities without sonic changes.
So, in conclusion:
A - Hard clipping is very irritating in any amplifier, but mild onset clipping can provide a wide variety of sonic effects, some of which can actually be experienced as “more enjoyable” than unclipped. Many tube amplifiers exhibit similar overload characteristics that may be experienced as “euphonic”.
This effect of mild overload, being sometimes experienced as favorable, is partially due to the fact that program peaks tend to be very brief and the ear’s ability to accurately analyze the quality of the peak energy is greatly reduced and more easily fooled as compared to the ear’s ability to evaluate long-term average levels.
B – Larger amplifiers can easily be blamed for poorer sound quality if they are used with loudspeakers that change sound quality when driven to the greater peak levels of the larger amplifier, even when the average levels are held to the same as comparable low powered amplifier.
Some loudspeakers have such low levels of linear capability that merely changing from a 10-watt to a 35-watt amplifier may cause this confusing effect of the larger amplifier being the cause of the sonic deterioration.
Again, this is a very limited discussion of the topic, but it may possibly explain experiences that some of you have had with differences between power amplifiers.
If there is further interest, I’ll try to follow up soon with a bit more information on the topic, including a few small signal issues with power amplifiers.
I originally interrupted your discussion here just to answer a few loudspeaker questions, and I don’t want to hi-jack your forum, so let me know if I am inappropriately dominating your discussions.
I would be curious to see what everyone else’s thoughts are on some of these subjects, and/or what everyone considers to be the largest remaining questions and areas of concern with their audio systems.
Best regards,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-02-09 22:21 Ämne:
Laila skrev:
Jacro skrev:
. . . . . .
Good audio is predominately a systems design approach, not an individual component selection approach. The components have to be appropriate within a standard deviation, but beyond that, it is all based on the impedance interfacing of the system.
Some designers operate from a systems approach, and some try to use all the most expensive components and hope for the best result.
Whether one has an unlimited budget or is designing for lowest cost, the systems approach will provide a better result and will tend to be less wasteful. But, it takes longer and requires more careful assessment.
Cheers,
- James
James, welcome to the forum !
Like poetry in my ears (eyes) . . . . wonderful words.
“A waveguide by any other name would sound as sweet”
Hmmm… Maybe it is best that I not pursue a career as an audio poet, and just stay focused on the technical discussions -- But thank you for your kind words.
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Mar 30, 2004 Inlägg: 848 Från: Karlstad
Skrivet: 2011-02-09 22:21 Ämne:
Hi, and Welcome Jacro!
Very interesting ta read about your study of amplifiers/loudspeakers!
I am interested to hear what you think about Siegfried Linkwitz approach to loudspeaker design, dynamic dipoles.
I myself have found them to solve a great deal of the problems in the speaker/room area in my listening room. The uniform powerresponse may be part of the answer here i guess.
What are your experiences or oppinions regarding this?
Blev Medlem: Jun 01, 2005 Inlägg: 6773 Från: Nattmössan
Skrivet: 2011-02-10 12:21 Ämne: Re: Tube Amplifiers and Power Levels
Jacro skrev:
If there is further interest, I’ll try to follow up soon with a bit more information on the topic, including a few small signal issues with power amplifiers.
Please do that. . .
Jacro skrev:
I originally interrupted your discussion here just to answer a few loudspeaker questions, and I don’t want to hi-jack your forum, so let me know if I am inappropriately dominating your discussions.
Not a chance(I think ) ! _________________ Sterio . . . krävs dä tvillingar för å lyssna på´t åsså, typ . . . ?
Blev Medlem: Oct 29, 2003 Inlägg: 33943 Från: Grå Hamnarna
Skrivet: 2011-02-10 13:15 Ämne:
Jacro - almost no thread here ends on the same note as they begin, so that's completely natural. And feel free to comment/contribute in other threads than this one - I think I speak for everyone here when I say we're delighted to have yet another professional designer on the forum.
It's interesting when you all agree and equally so when you don't.... _________________ Det viktigaste är inte att förstå vad man upplever, utan att inse vad av det man upplever man inte förstår.
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-02-10 19:07 Ämne:
Stereotypen skrev:
Hi, and Welcome Jacro!
Very interesting ta read about your study of amplifiers/loudspeakers!
I am interested to hear what you think about Siegfried Linkwitz approach to loudspeaker design, dynamic dipoles.
I myself have found them to solve a great deal of the problems in the speaker/room area in my listening room. The uniform powerresponse may be part of the answer here i guess.
What are your experiences or oppinions regarding this?
Hi Stereotypen,
I have great respect for the work that Linkwitz does and the generosity he has come to exhibit by sharing so fully on his website. (He was much more guarded with information in his younger days.)
You are correct in assuming the importance of uniform, or at least carefully tailored, power response.
My general recommendation is that once one has established an effective direct sound, with minimum interference from early correlated reflections, then the ideal is to have the best full range balance possible on all secondary room sounds, preferably with the appropriate delay between the direct sound and correlated reflections.
To achieve this, I believe the loudspeaker should either be operated as a boundary coupled half-space device, or as an omni or full range dipole well out into the room.
(These out-in-the room, symmetrical dipole, systems work best in larger rooms, so as to be able to be well removed from the front wall, and sidewalls. Small rooms do not accommodate them very well, particularly the more omni-directional devices. Dipoles can be oriented to aim the dipole nulls at the sidewall and front wall first reflection points to minimize early reflections to help work better in a smaller room, but that is still a compromise.)
Unfortunately, most loudspeakers operate in the awkward middle ground between these two approaches. Most (cone in a box) loudspeakers are operated a short distance away from the front wall, but they have omni-directional response at all lower frequencies, and more directional sound in the upper frequencies, with “uneven” power response creating an unbalanced “room sound”. The “rear 180-degree wave angles” tend to exhibit very uneven, frequency response and drive the room to an unnatural secondary sound field.
While I feel the half-space, boundary-coupled approach is the more universally consistent way to achieve the best effect, the Linkwitz approach can also provide a very good result, particularly if the room size is compatible. The equal front/back response at least drives the room in a manner that is consistent with the direct sound, but there are some questionable side effects, such as artificial reflections off the front wall behind the loudspeakers, often creating interference with the direct sound, and also creating “false depth”.
False depth can be an enjoyable effect, but it does not represent an accurate mapping of the original event into your room.
Only recently has Linkwitz finally arrived at making sure that the dipole response is equal on the front AND backside of the loudspeaker. Previously, he only operated dipole up to approximately 2kHz, but now he has adopted full symmetry.
If one is putting a loudspeaker out into the room, it must be either very symmetrical, preferably with constant directivity vs. frequency, and even better, constant “high” directivity with frequency, or it must be power response tailored in a very careful manner.
A few loudspeakers that don’t follow the guideline (of symmetry or half-space), can be made to perform well, but must be tailored very carefully to be successful (Quad ESL 57).
Otherwise, to work well, they should be used in the near field, eliminating room sound as much as possible (Harbeth HL-P3, LS3/5a).
Again, all of this is an over simplification, but as a guideline, but hopefully, it at least points to some of the issues that must be dealt with.
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-02-10 22:47 Ämne:
paa skrev:
Jacro skrev:
...While I feel the half-space, boundary-coupled approach is the more universally consistent way to achieve the best effect,-
...
James
You really sound like the Carlsson-followers here. Have you studied Stig Carlssons loudspeakers to any extent?
I suppose I do sound somewhat like the Carlsson followers.
And, yes, I looked at his speakers, paper, and patents quite a few years ago. I believe that at least part of his concept that he developed in later years was valid and useful.
Carlsson, Snell, and Allison had all gotten part of the puzzle solved.
I'm not saying one can't get enjoyable sound with a non-boundary coupled loudspeaker, but it is much more difficult to create an accurate representation of the original event if one stimulates early, correlated front wall reflections, and do so with a spectrally distorted wavefront from the back and sides of the loudspeaker.
Boundary coupling makes things easier by creating a simpler wave-launch architecture and taking care of a number of issues that are normally rather difficult to deal with.
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Ive been thinking in terms of wall-close speakers but its not all that easy. The shallow, flat box arent always that easy to position along the wall with the wall-sockets and what have you. So its either relatively small boxes hung on the wall or more conventional florstanders made for a close placement against the wall.
Older Carlsson-speakers suffer alot by the fact that they are spreading the sound everywhere. Makes it all very diffuse and an artificial "soundstage". I call it painting with a wide (to wide) brush. The later madels work better but need a substantial dampening on the wall to not get that diffuse soundstage.
I get the same feeling with dipoles. But i guess some well placed damping and diffusion can work miracels with a dipole. _________________ Vackra ord är inte sanna, Sanna ord är inte vackra. / Tao Te Ching
Blev Medlem: Mar 30, 2004 Inlägg: 848 Från: Karlstad
Skrivet: 2011-02-11 11:50 Ämne:
Thank you Jacro for answering my question and sharing your thoughts.
I hope you will find this a pleasent forum and decide to drop in here every now and then.
James, when you try to get a rectangular box like The Clue as coupled as possible to the wall, how much absorbtion would you prefer behind it? What size and thickness would you consider minimum and optimum?
I had previously read about the Bremen loudspeakers on Faktiskt, but I do not remember seeing a 3-speaker version discussed.
The 2-speaker version of the use-model concept seems to be very much the same as the Harold Beveridge line source electrostatic from the 1970's, wherein Mr. Beveridge boundary coupled his loudspeakers to the side-walls, about 1/3 of the distance along the side-wall, facing each other. They were linesource, and electrostic, but the general sound field presentation seems the same.
The perceived sound field from this type of presentation is quite impressive, spacious and deep, and fun, but some other aspects are questionable.
Also, it is difficult to find the correct room for them, that has the optimum length to width ratio.
They were the most expensive loudspeakers when they were first available. I've always thought it would be fun to have a low cost conventional-driver version that would create the same sensationalized sound field. I built prototypes years ago of planar magnetic line sources arranged in this manner and it worked quite well. Very entertaining.
It would seem that the Bremen speaker arrangement may provide this effect very well, and in a cost effective manner, but I have not had the opportunity to hear them.
Kraniet skrev:
Ive been thinking in terms of wall-close speakers but its not all that easy. The shallow, flat box arent always that easy to position along the wall with the wall-sockets and what have you. So its either relatively small boxes hung on the wall or more conventional florstanders made for a close placement against the wall.
Yes, if a loudspeaker is specified for "wall-close" or corner placement, or any specific placement, then, unfortunately, there are always a significant number of people that don't have that kind of space available in their homes. That is the problem with specified placement, but the advantages of designing to a specific placement are so compelling, that I believe that I must choose that path, even if a majority of potential customers choose to avoid the product because they don't have a proper place for it.
There are plenty of other options for those particular customers and hopefully they can find a loudspeaker that makes them happy, in placement, appearance, and sound quality.
Kraniet skrev:
Older Carlsson-speakers suffer alot by the fact that they are spreading the sound everywhere. Makes it all very diffuse and an artificial "soundstage". I call it painting with a wide (to wide) brush. The later madels work better but need a substantial dampening on the wall to not get that diffuse soundstage.
I get the same feeling with dipoles. But i guess some well placed damping and diffusion can work miracels with a dipole.
Ultimately, to get the best performance from each system type, one needs to be able to provide best placement and the associated room treatment that supports that particular system type.
The only system architecture that I have found to substantially transcend those requirements is to build a highly directional loudspeaker that inherently "ignores" the room for all early reflections. This type of hyper-directivity is very difficult to achieve in a practical manner, over a wide bandwidth, but the net result can be very impressive and transportable to a wide variety of acoustic environments.
I developed these types of systems from about 1994 to 2008, with some of the systems using ultrasonic to audio conversion (a parametric loudspeaker), and while they were not particularly practical, they could be very impressive in their ability to eliminate what I call the "Second Venue Problem", allowing one to hear the original, or "First Venue", where the original performance was recorded in a very convincing manner.
All the best,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-02-13 06:52 Ämne:
paa skrev:
James, when you try to get a rectangular box like The Clue as coupled as possible to the wall, how much absorption would you prefer behind it? What size and thickness would you consider minimum and optimum?
As a minimum I recommend 75mm thick acoustic foam that is arranged on the wall, inward from the right loudspeaker (going towards the left loudspeaker), starting at the inside corner of the cabinet that is closest to the wall, and also starting at the bottom edge of the cabinet.
The panel should be about 60 x 60cm, extending about 25cm above the top of the cabinet.
Ideally, additional amounts and placement would be adapted to the needs of a particular environment.
For a more complete/optimal arrangement, as a general rule, I would suggest a 75mm thick, 150cm x 150cm square piece centered horizontally behind the cabinet, and starting at the floor.
Also, place 100mm thick acoustic foam outward from the speaker, (to the right of the right loudspeaker) over to the corner, and from the corner extend 1/3 the length of the sidewall, OR, a piece 1-meter wide centered on the point where the first specular reflection bounces off the sidewall to the listener.
Again, each room has it’s own issues to deal with, but these are the general guidelines for minimum and optimal absorption.
Let me know if I need to provide further explanation.
Cheers,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-02-13 07:13 Ämne:
Objektivisten skrev:
Hi James, welcome to the forum, what do You think is the secret about tubes and that they almost always sounding more pleasant and true to the ears? And do we really need all that watts, low powered amps seems to gain in transparent sound, may be construction simplicity or cost effectiveness? Why do I think carbon sounds more real than metal as a conductor? Any clue?
Objektivisten,
I was just curious... I have not seen any comment or feedback from you on the answers I provided so far to your questions.
It is a rather complex topic, so I thought I should check to see if my starting answers were useful for you, such that you would like me to continue, or not?
Best regards,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Mar 17, 2009 Inlägg: 8862 Från: speedad
Skrivet: 2011-02-13 14:34 Ämne:
Jacro skrev:
Objektivisten skrev:
Hi James, welcome to the forum, what do You think is the secret about tubes and that they almost always sounding more pleasant and true to the ears? And do we really need all that watts, low powered amps seems to gain in transparent sound, may be construction simplicity or cost effectiveness? Why do I think carbon sounds more real than metal as a conductor? Any clue?
Objektivisten,
I was just curious... I have not seen any comment or feedback from you on the answers I provided so far to your questions.
It is a rather complex topic, so I thought I should check to see if my starting answers were useful for you, such that you would like me to continue, or not?
Best regards,
- James
Thanks for a very interesting an thoughtfull answer James. I have wait in silence and hope for the other topics, and I have read all your inputs in this thread and understand You have a had a lot to do. Please welcome. _________________ M O N S T E R ® C A B L E
The Bremen "Egg" is supposedly able to work with just thw two speakers, but as I understand a third, "center", speaker is being developed.
It would be interesting to hear your opinion on the multi-channel audio. There is a few people saying that the best way to get "true stereo" is by using three speakers, thus bypassing the "stereoflaw". There are a few processors doing multichannel from stereo, like dolby PL och Harmans Logic 7. Do you think its a good idea trying to recode stereo into multichannel? True multichannel recording might be better but were seeing some pretty stupid example of instruments panned hard to the rear sides etc.
Mr Steindl have is own "black box". Are the existing systems not good, and why (in your opinion).
regarding the placement of speakers its true like you say. But the best thing for a loudspeaker developer would be to make speakers that fit most persons/rooms. Your Clue for instance seems a better choice than say a Snell type A.
In my case its was only when I tried to position my 45cm wide speakers that I realized they werent as placement-friendly as I thought. With the type A´s it seems youd have to modify the room after the speakers to be able to position them correctly.
Making the speaker more like your Clue seems a better choice i that case.
Did you consider an even more "wall-integrated" desing like the Carlsson OA51 or Larsen speakers? http://www.larsenhifi.com/larsen8.htm _________________ Vackra ord är inte sanna, Sanna ord är inte vackra. / Tao Te Ching
Jacro - almost no thread here ends on the same note as they begin, so that's completely natural. And feel free to comment/contribute in other threads than this one - I think I speak for everyone here when I say we're delighted to have yet another professional designer on the forum.
It's interesting when you all agree and equally so when you don't....
Well stated, agree 100%!
Welcome Jacro. Even if this is my first response in the thread, you should know that I enjoyed immensely your contribution to the forum.
I know many other people that read a lot more than post...
On this forum we just LOVE discussing technical details, especially based on own experience and studies.
Theory and calculations are interesting subjects in itself but nothing beats personal experience imho.
I'm going to respond to a few of your posts later on.
To be continued as they say...
To achieve this, I believe the loudspeaker should either be operated as a boundary coupled half-space device, or as an omni or full range dipole well out into the room.
I agree on pretty much everything in this post and have a Q regarding this quote - please list a few of your favorite speakers during the years
Yes I read about your reluctance commenting on existing products so list discontinued speakers then.
(even if I consider giving positive feedback about a competing product something that gives cred )
The 2-speaker version of the use-model concept seems to be very much the same as the Harold Beveridge line source electrostatic from the 1970's, wherein Mr. Beveridge boundary coupled his loudspeakers to the side-walls, about 1/3 of the distance along the side-wall, facing each other. They were linesource, and electrostic, but the general sound field presentation seems the same.
The perceived sound field from this type of presentation is quite impressive, spacious and deep, and fun, but some other aspects are questionable.Also, it is difficult to find the correct room for them, that has the optimum length to width ratio.
Most (if not all) speakers are compromises so please elaborate about the not so great aspects please.
What is according to you the best length to width ratio?
Is that ratio different depending of speakers used?
[s a minimum I recommend 75mm thick acoustic foam that is arranged on the wall, inward from the right loudspeaker (going towards the left loudspeaker), starting at the inside corner of the cabinet that is closest to the wall, and also starting at the bottom edge of the cabinet.
The panel should be about 60 x 60cm, extending about 25cm above the top of the cabinet.
Ideally, additional amounts and placement would be adapted to the needs of a particular environment.
For a more complete/optimal arrangement, as a general rule, I would suggest a 75mm thick, 150cm x 150cm square piece centered horizontally behind the cabinet, and starting at the floor.
Also, place 100mm thick acoustic foam outward from the speaker, (to the right of the right loudspeaker) over to the corner, and from the corner extend 1/3 the length of the sidewall, OR, a piece 1-meter wide centered on the point where the first specular reflection bounces off the sidewall to the listener.
Again, each room has it’s own issues to deal with, but these are the general guidelines for minimum and optimal absorption.
Let me know if I need to provide further explanation.
Great info,thanks!!!
What are your thoughts about acoustic treatment on the back wall, floor and ceiling?
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-02-16 23:39 Ämne:
Objektivisten skrev:
Jacro skrev:
Objektivisten skrev:
Hi James, welcome to the forum, what do You think is the secret about tubes and that they almost always sounding more pleasant and true to the ears? And do we really need all that watts, low powered amps seems to gain in transparent sound, may be construction simplicity or cost effectiveness? Why do I think carbon sounds more real than metal as a conductor? Any clue?
Objektivisten,
I was just curious... I have not seen any comment or feedback from you on the answers I provided so far to your questions.
It is a rather complex topic, so I thought I should check to see if my starting answers were useful for you, such that you would like me to continue, or not?
Best regards,
- James
Thanks for a very interesting an thoughtfull answer James. I have wait in silence and hope for the other topics, and I have read all your inputs in this thread and understand You have a had a lot to do. Please welcome.
Very good.
Thank you,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-02-16 23:55 Ämne:
sportbilsentusiasten skrev:
Jacro skrev:
[s a minimum I recommend 75mm thick acoustic foam that is arranged on the wall, inward from the right loudspeaker (going towards the left loudspeaker), starting at the inside corner of the cabinet that is closest to the wall, and also starting at the bottom edge of the cabinet.
The panel should be about 60 x 60cm, extending about 25cm above the top of the cabinet.
Ideally, additional amounts and placement would be adapted to the needs of a particular environment.
For a more complete/optimal arrangement, as a general rule, I would suggest a 75mm thick, 150cm x 150cm square piece centered horizontally behind the cabinet, and starting at the floor.
Also, place 100mm thick acoustic foam outward from the speaker, (to the right of the right loudspeaker) over to the corner, and from the corner extend 1/3 the length of the sidewall, OR, a piece 1-meter wide centered on the point where the first specular reflection bounces off the sidewall to the listener.
Again, each room has it’s own issues to deal with, but these are the general guidelines for minimum and optimal absorption.
Let me know if I need to provide further explanation.
Great info,thanks!!!
What are your thoughts about acoustic treatment on the back wall, floor and ceiling?
Room treatments should be environment specific, but generally, I would recommend diffusion on the back-wall, and most everywhere else after the first specular reflections are absorbed.
At least first specular front-wall, floor, and ceiling reflections should be eliminated as much as possible, as they tend to be correlated and can cause the greatest sonic coloration and spatial compression distortion. After that, is good to keep the later reflections substantially live, but diffused to best attempt to simulate a larger, first venue type environment.
This is an over simplification on many counts. Bandwidth of the absorption is important as it is important not to just create a partially absorbed, spectrally imbalanced reflection contributing to the room sound.
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-02-17 22:33 Ämne:
sportbilsentusiasten skrev:
Jacro skrev:
To achieve this, I believe the loudspeaker should either be operated as a boundary coupled half-space device, or as an omni or full range dipole well out into the room.
I agree on pretty much everything in this post and have a Q regarding this quote - please list a few of your favorite speakers during the years
Yes I read about your reluctance commenting on existing products so list discontinued speakers then.
(even if I consider giving positive feedback about a competing product something that gives cred )
Okay, here are a number of classic loudspeakers that I have either enjoyed and/or believe that they have contributed to advancing the state of the art. Most were very good performers with a few flaws, a few had significant flaws, but introduced important new capabilities or architectures to the field of loudspeaker development.
(I have not included any systems that I designed)
They are listed generally in chronological order of when they were produced.
Quad ESL 57
BBC LS3/6 – Spendor BC1
Hegeman H1 (Re-equalized)
Dayton Wright XG-8
Beveridge Model 2
Fulton FMI-80
BBC - Rogers LS3/5a (First build – Near-field or quasi-anechoic use)
Fulton J-Modular
Quad ESL-63 (modified and reoriented for optimized directivity)
AR-9
Snell Type ‘A’
Allison Model Three
Magneplanar Tympani 1D and Tympani IV
Acoustat 1+1
Snell Type One
Sound Labs A-1
3D Acoustics 3D6/10 (First version w/dust cap damping)
Carlsson OA Series
Gradient 1.3
Harbeth Monitor 40 (semi-near field)
AR-303
Here are a few currently available loudspeakers that, in my opinion, have promising characteristics.
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-02-17 22:54 Ämne:
2-ch skrev:
Very interesting reading, i havent seen this thread earlier. I wonder how a guy from Seattle Washington found this place on the net?
Anyway, your are most welcome to faktiskt.se
I have written audio industry patent reviews for a loudspeaker engineering journal called "Voice Coil" for about 15 years. A few years ago, I was looking up some references on boundary coupled loudspeakers, for an article in the journal, and found Faktiskt.se for the first time when searching for additional information on Carlsson OA series and Audio Pro A4-14 loudspeakers.
I've always found it interesting to observe audio discussions from outside of the USA, and have particularly enjoyed Faktiskt.
I had not submitted any comments until just recently when a friend of mine told me that they noticed ( the clue ) loudspeaker being mentioned here. Since there appeared to be some questions and interest, as designer of the loudspeaker, I thought I should make myself available for discussion as long as there was an interest in my doing so.
I thank you, and everyone here, for warmly welcoming me into the clubhouse.
Cheers,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Feb 18, 2007 Inlägg: 19636 Från: Himlafiket
Skrivet: 2011-02-17 23:03 Ämne:
Google translate is really a fantastic tool.
Jacro, have you listened to Carlsson and Ino yourself?
The Clue has really made people interested over here! Are there any plans to extend the series with e.g. a center speaker, surrounds or perhaps a big brother up front? _________________ T H E. G O O S E B U M P. F A C T O R
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-02-18 22:48 Ämne:
KarlXII skrev:
Google translate is really a fantastic tool.
Jacro, have you listened to Carlsson and Ino yourself?
The Clue has really made people interested over here! Are there any plans to extend the series with e.g. a center speaker, surrounds or perhaps a big brother up front?
I hope that the Google translator doesn't provide too many embarrassing mistakes. I often translate from English to Swedish, and then translate the Swedish back to English again, to see what it says, and the errors can be quite entertaining.
Yes, I have heard the Carlsson and Ino loudspeakers. Sonab and Carlsson many years ago, and the larger Ino Audio loudspeakers more recently.
I have always been lucky enough to have customers and friends that have traveled all over the world, wanting to show me their latest loudspeaker discoveries that they bring back home to America.
I'm glad to hear that The Clue has generated interest here. I hope we can build enough to fill the U.S. orders so that eventually SJÖFN Hi-Fi can offer them in Europe. My understanding is that there have been orders from Europe but I don't know if they have been fulfilled.
In terms of future product plans for SJÖFN Hi-Fi, we will be focusing on support for The Clue and will be making some associated products to enhance the performance of The Clue.
As we announce any new products, I’ll post the announcement in Faktiskt.
Cheers,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
James, I have just been reading a little of what Roy Allison have to say, and he apparently tries to get "maximum and equal dispersion
from the lowest to the highest audible frequencies" (in half space).
A tractrix or kugelwellenhorn and/or a small midrange with very wide dispersion, sounds like a possible way to achieve this in the upper range, but I cannot see how this goal could be compatible with using directivety control waveguides having the standard 60 to 90 degrees coverage angles?
Do you agree with Roy Allison that full half space is the optimum dispersion for the entire sound spectrum?
Blev Medlem: Jun 01, 2005 Inlägg: 6773 Från: Nattmössan
Skrivet: 2011-02-18 23:49 Ämne:
Kanske att man skall respektera vad Jacro tidigare
har skrivit, nämligen att han helst inte vill uttala sig om
typ "prylar" som nuvarande är i produktion, ity han
själv är i "branschen" . . . _________________ Sterio . . . krävs dä tvillingar för å lyssna på´t åsså, typ . . . ?
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-02-19 00:45 Ämne:
paa skrev:
James, I have just been reading a little of what Roy Allison have to say, and he apparently tries to get "maximum and equal dispersion
from the lowest to the highest audible frequencies" (in half space).
A tractrix or kugelwellenhorn and/or a small midrange with very wide dispersion, sounds like a possible way to achieve this in the upper range, but I cannot see how this goal could be compatible with using directivety control waveguides having the standard 60 to 90 degrees coverage angles?
Do you agree with Roy Allison that full half space is the optimum dispersion for the entire sound spectrum?
paa,
It depends on the type of system architecture, boundary characteristics, and distance relationships among the closest four boundaries.
I tend to not agree with Allison, relative to the 180-degree radiation pattern being optimal, except for specialized applications, such as the Beveridge electrostatic or Bremen Egg when mounted on the sidewalls.
If I were NOT designing a dipole, I would generally prefer one of two approaches to the radiation pattern;
Either,
1) Limit a forward, monopole radiator to a maximum of 90-degrees over the full bandwidth (cross-firing in front of the listener), [[One of the ways this is accomplished through the use of a constant directivity, 90-degree waveguide combined with a proprietary type of gradient low frequency architecture]]
OR,
2) Arrange for the first four boundary distances to be cross-relational such that they are distributed and/or cross-cancelling. In the second case, the system would ideally, have a smooth, but complex transitional power response that is calibrated to match the predetermined boundary interaction.
Both are rather complex to develop, and the second approach is the basis for the operation of The Clue.
In terms of Allison’s systems, most all of them were 180-degree/half space horizontal radiators, and while they had a smooth balance and generous spaciousness, they were rather poor at focusing images, making the placement of each instrument more spatially vague than what the recording has to offer. Allison liked this type of spaciousness and vague imaging but it was not well received in America.
The exception was the less well-known Allison Model Three, which was meant to operate into a limited, 90-degree angle over the entire spectrum, and when properly set up with local absorption and an optimal room, was by far his best sounding product and an exceptional performer under ideal conditions.
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Apr 18, 2007 Inlägg: 21231 Från: Saltsjö-Boo
Skrivet: 2011-02-19 00:49 Ämne:
Laila skrev:
Kanske att man skall respektera vad Jacro tidigare
har skrivit, nämligen att han helst inte vill uttala sig om
typ "prylar" som nuvarande är i produktion, ity han
själv är i "branschen" . . .
Det existerar ingen INO högtalare. Det finns ingen INOhögtalare i produktion , eller?
Allt är ju på hobbybasis och i så fall existerar ingen produktion. Eller har jag förstått något felaktigt? Det är som jag ser det en fullkomlig omöjlighet att både ha en produktion och ha en produktion på hobbybasis.
MvH
Peter _________________ VD Bremen Production AB; Grundare av Ljudbutiken AB; Fd importverksamhet av hifi; Konstruktör av LICENCE No1 D/A, Bremen No1 D/A, Forsell D/A, SMS FrameSound, Bremen ägghögtalare m.fl.
... combined with a proprietary type of gradient low frequency architecture
...
- James
Thanks James for your interest in this forum and all the well written answers.
This proprietary gradient low frequency solution, is this something you have already used in any of your speaker designs?
Would it look something like this effort by Naqref on this forum:
The exception was the less well-known Allison Model Three, which was meant to operate into a limited, 90-degree angle over the entire spectrum, and when properly set up with local absorption and an optimal room, was by far his best sounding product and an exceptional performer under ideal conditions.
- James
But that is a speaker designed for corner placement, isn't it?
Then we have problems with driving all room modes to the max, and maybe a "hole in the middle", don't we?
How much wall absorbents would you put around corner speakers like these?
Blev Medlem: Dec 19, 2007 Inlägg: 3593 Från: Skövde
Skrivet: 2011-02-19 19:00 Ämne:
James,
You wrote in an earlier post that you have worked with Magnepan. May I ask what kind of input you provided and which model(s) you worked on? _________________ Fd kabelforskare & professor på KTH
Konsult åt andra
Innehar ej F-skattsedel
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-02-20 03:23 Ämne:
JanBanan skrev:
James,
You wrote in an earlier post that you have worked with Magnepan. May I ask what kind of input you provided and which model(s) you worked on?
Hi JanBanan,
My most recent work has been related to development of a new crossover topology that has been applied to the 1.7 and 3.7 models that were just introduced over the last 12 months or so.
I am basically a technical consultant that Magnepan brings into their development process to solve technical problems or provide training when their internal engineering group can’t find a solution or are having trouble optimizing particular design.
I am currently working on a new type of low frequency system.
They are very nice people and have been good friends since the mid-1970’s.
Best regards,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-02-20 05:17 Ämne: Di-Cardioid type gradient loudspeaker
paa skrev:
Jacro skrev:
... combined with a proprietary type of gradient low frequency architecture
...
- James
Thanks James for your interest in this forum and all the well written answers.
This proprietary gradient low frequency solution, is this something you have already used in any of your speaker designs?
Would it look something like this effort by Naqref on this forum:
No, the design that Naqref built is not the form of gradient loudspeaker that I was referring to, but I have developed the Naqref type a number of times, since the mid-1980’s (I refer to this special form of gradient as a “Di-Cardioid” [[Hybrid of Dipole and Cardioid]]) and was granted a patent (US 7,551,062) on a number of new variations of the concept.
(I also received a trademark on it: “SoundVector™”.)
I have used it in wide bandwidth loudspeakers I have experimented with over a couple decades, but about 5 years ago I developed a narrow-band, directional backup alarm for trucks, tractors, etc. for ECCO Safety Group, using this same basic architecture. If you are interested, here are a couple links on the project;
This structure can be very effective, even more so if one makes an active version with two monopole transducers instead of one passive dipole.
I thought I was the first to invent it back in 1985, but it turns out that Bobby Beaver at Altec Lansing had developed products based on the concept at least 10 years earlier with the Model 814A “Extenda-Voice” and was granted a patent (US 3,722,616).
Later work was done in 1982 by POLAR-PRO in Finland (WO8401681) and Skip Cross in America (US 4,437,541), and also in 2001 by Noselli in Italy, EP1137318A2.
Most recently, the technique can be seen in the Gradient Helsinki 1.5 loudspeaker, used as the midrange baffle:
http://www.gradient.fi/helsinki15/
When perfectly optimized, it can provide the best combination of efficiency, and angular cancellation of any first or second order gradient arrangement, clearly outperforming a simple cardioid (but not as effective as an end-fired array).
The gradient arrangement I referred to in my previous post is a unique arrangement that I have not seen used by anyone to date and accomplishes a null-zone in a novel manner that allows a better directivity match between a 90-degree waveguide and low frequency system crossing over to the waveguide. It is an approach that was created as a reference during the development of The Clue and was used in prototyping The Clue to create a tweeter gradient that cancels the tweeter energy on axis, so that it only adds off-axis energy to the larger woofer/midrange, or full range driver (up to a desired transition frequency).
I apologize if this is more information that desired, but this type of design has great potential that has not yet been realized in commercial products, so I thought that some in your group may enjoy seeing the reference materials for the architecture that Naqref (and Ingvar?) were experimenting with.
(By the way, the post of Naqref’s stopped after only 2 pages… Was there further work and measurements reported on the experimental devices?)
Best regards,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-02-20 05:43 Ämne: Allison Model Three
paa skrev:
Jacro skrev:
The exception was the less well-known Allison Model Three, which was meant to operate into a limited, 90-degree angle over the entire spectrum, and when properly set up with local absorption and an optimal room, was by far his best sounding product and an exceptional performer under ideal conditions.
- James
But that is a speaker designed for corner placement, isn't it?
Then we have problems with driving all room modes to the max, and maybe a "hole in the middle", don't we?
How much wall absorbents would you put around corner speakers like these?
Yes, the Allison Model Three is designed for corner placement.
You are correct that the corner placement will activate all the low frequency room modes. It is best used with at least two additional subwoofers with diversity placement to smooth the room response in the modal frequency range. Then the bass response is both strong and smooth.
(Room modes are fine if driven properly from at least 3 diverse locations).
Also, as you surmise, the “hole in the middle” problem can come into play if the room is too wide relative to the listening distance. That is a problem with corner placement… It only works in rooms that have the correct form factor that allows optimal listener/loudspeaker relationship.
With the correct room width-to-listener distance, there is no hole in the middle and the seating position, left to right, is less critical than with most systems.
The problematic reflections are very close the loudspeaker in this case, so damping material only needs to extend from the loudspeaker about a half-meter along the front and side walls.
I redesigned the Allison Three to have the midrange and tweeter placed rearward, much more closely coupled in the corner (the speaker face was about 35 cm wide at the bottom, and less than 10 cm wide at the top, near the tweeter), with a Snell type One ramps from the tweeter edge to the front and side walls.
With this arrangement one could operate with minimal damping material because of the absence of early reflections.
Very effective, if you have the ideal room layout.
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Curious... I'm not sure of what the significance of this statement is.
All the best,
- James
If we assume it's correctly spelled, the swedish expression "hell" means "hail", although that word is not yet included in google translations.
Thanks for your answers again, by the way.
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-02-21 02:34 Ämne: Re: ?
paa skrev:
Jacro skrev:
Objektivisten skrev:
Hell James
Objektivisten,
Curious... I'm not sure of what the significance of this statement is.
All the best,
- James
If we assume it's correctly spelled, the swedish expression "hell" means "hail", although that word is not yet included in google translations.
Thanks for your answers again, by the way.
paa,
Hell = Hail... That is good to know.
Thank you.
And, you are very welcome on the answers. I hope they are useful.
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Mar 17, 2009 Inlägg: 8862 Från: speedad
Skrivet: 2011-02-21 08:52 Ämne:
Holy macaroni, the significance of my 'statement' is zero (maybe below) James. Can we please go back to the real substance in this thread, your eminent inputs and answers. Regards _________________ M O N S T E R ® C A B L E
Blev Medlem: Dec 19, 2007 Inlägg: 3593 Från: Skövde
Skrivet: 2011-02-21 09:05 Ämne:
Jacro skrev:
I am currently working on a new type of low frequency system.
Hell James,
This sounds exciting! Is this something you can elaborate on? _________________ Fd kabelforskare & professor på KTH
Konsult åt andra
Innehar ej F-skattsedel
Blev Medlem: Feb 18, 2007 Inlägg: 19636 Från: Himlafiket
Skrivet: 2011-02-21 09:40 Ämne:
JanBanan, sometimes your particular sense of humour in combination with that avatar (which probably is a display of it) makes for a very ambiguous context. _________________ T H E. G O O S E B U M P. F A C T O R
Blev Medlem: Mar 30, 2004 Inlägg: 848 Från: Karlstad
Skrivet: 2011-02-21 12:29 Ämne:
Jacro:
It would be very interesting for me to hear what you think about the Audio Artistry Beethoven system. This is the speaker that I use myself. Here in Sweden there is a very limited amount of people that own this speaker but I guess that in the US they are more common. Have you heard them? What is your impression/oppinion of them? What is your oppinion of dipole bass in general?
The speakers are not manufactured any more so I guess it would be ok for you to comment on them.
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-02-24 08:12 Ämne: Audio Artistry Beethoven and Dipole Woofer Systems
Stereotypen skrev:
Jacro:
It would be very interesting for me to hear what you think about the Audio Artistry Beethoven system. This is the speaker that I use myself. Here in Sweden there is a very limited amount of people that own this speaker but I guess that in the US they are more common. Have you heard them? What is your impression/oppinion of them? What is your oppinion of dipole bass in general?
The speakers are not manufactured any more so I guess it would be ok for you to comment on them.
My apologies to everyone that has asked questions that I have not yet answered. I am particularly busy this week but will try to get back with more follow up next week.
I'll provide some short answers to a few questions and follow up later with more info.
Stereotypen,
Yes, I heard the Beethoven a few times back in 1998.
I thought that they could be made to perform quite well if they were in a large venue.
With the Linkwitz designs there are still some of the issues associated with center-symmetrical dipoles when they are constructed with point source drivers. This arrangement usually causes a significant dip in the midrange combined with some comb filtering ripple above the first dip frequency which is associated with the symmetrical 1-wavelength acoustical back-to-front path. This issue has been minimized with careful crossover work, but it is difficult to eliminate completely.
With dipoles, it is most often better to either use a full-baffle-sized diaphragm, such as with electrostatics or Magneplanars, OR, horizontally offset the transducer on the mounting baffle, to create diversity paths for the back-to-front output.
In terms of dipole bass, I believe it can be a very effective, at least when used above the lowest modal frequencies. Below the modal range, to maximize room gain, closed-form enclosures tend to be superior.
I've done quite a bit of work in this regard, in that I developed the first effective commercially viable cone based dipole woofer system, for use in the Carver Amazing Loudspeaker (with a Large Area Full Range Ribbon we developed for use above 100 Hz) in the early 1980's. Even though we were told it couldn't be done, we were able to achieve -3dB at 19 Hz by incorporating novel 12" woofers with 1.5" peak-to-peak linear excursion capability and a Qts of 3.4, mounted on a variable width baffle.
If anyone is interested, here is a picture of the system I developed...
The folded version of a dipole woofer, such as used in the Beethovan subwoofer, can perform the bass function quite well, but there are some anomalies above the pass band that can make for more difficult crossover transitions to the upper range system than a simple flat/open dipole woofer system, but if miniaturization of the dipole is important, the folded type can reduce the apparent size effectively.
I don't mean to sound overly critical of the Beethoven. It is a system that has a lot of potential and I would very much like to see it developed further to reach that potential.
More later...
Cheers,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
2) Arrange for the first four boundary distances to be cross-relational such that they are distributed and/or cross-cancelling. In the second case, the system would ideally, have a smooth, but complex transitional power response that is calibrated to match the predetermined boundary interaction.
Both are rather complex to develop, and the second approach is the basis for the operation of The Clue.
...
- James
How can this be made to work for different room sizes, and different listening distances, things that also would demand different distances between the speakers?
Could this cross-relational and cross-cancelling function be simulated in some known software?
Blev Medlem: Mar 24, 2003 Inlägg: 25879 Från: Krischansta
Skrivet: 2011-02-25 13:41 Ämne: Re: Di-Cardioid type gradient loudspeaker
Jacro skrev:
(By the way, the post of Naqref’s stopped after only 2 pages… Was there further work and measurements reported on the experimental devices?)
Hello James,
Finally I had som time (and focus) to read the whole thread and I'm very impressed as many others.
Regarding My little sweetheart it's scrapped but I'll think I have some measurement of it somewhere in one of my computers. Perhaps I'll find it and then I'll post some information here (and in the original thread).
The first ambience-module with the principle was made around 1995. A couple of years later I built the one on the pictures. I was still a poor student at the time so there was actually no money to develop the principle then. And then I found other things more promising.
I found your patent:
http://www.freepatentsonline.com/7551062.pdf
Impressive. I'll think the right way to go ist to use multiple active units just as you say. Passive damping of the sound from the back of the unit is to test intensive to get right.
I am like you intrested in what I call wall integrated speakers. It should perhaps be altered to external wall integrated speakers (EWI) or something like that to avoid beeing misstaken for in-wall-speakers. But anyhow. I'm the designer of Larsen speakers (it's a follow up of Carlsson). Two major problems with ewi-speakers is the perception of depth and excitment of roomresonances I'll think. The problem with depth is that the mind has problems to project auditory sources beyond the visual boundaries. The eye's override of other senses is making it harder to imagine a sound stage beyond the front wall. Do you think this is a big problem and if so what else is there to do about it other than removal of visual clues or to give additional visual clues to aid the sound stage?
The second problem (actually it's really a problem with almost every type of speaker), what is your preffered method of dealing with that? Acoustical lf-absorbers, parametrical eq or perhaps using multiple sound sources to counter act the resonanses?
Send my regards to Lars Erickson. _________________ Audiodesigner åt en del. Larsen, Holographic Audio etc.
CEO och huvudägare i Acoustic Landscape R&D AB.
CTO / R&D Manager och delägare i Acoustic Illusion AB.
I found the Bremen egg spekers to present a somewhat larger soundstage depthwise than sidewise when they were displayed at the Stockholm High End Show a couple of weeks ago. (With front speaker and proprietary matrix center decoding.)
Perhaps that was because they were placed on the sidewalls, positioned a bit back from the front wall, and the room was longer than wide, could that have been mainly a visible illusion too?
Blev Medlem: Apr 18, 2007 Inlägg: 21231 Från: Saltsjö-Boo
Skrivet: 2011-02-25 15:00 Ämne:
paa skrev:
I found the Bremen egg spekers to present a somewhat larger soundstage depthwise than sidewise when they were displayed at the Stockholm High End Show a couple of weeks ago. (With front speaker and proprietary matrix center decoding.)
Perhaps that was because they were placed on the sidewalls, positioned a bit back from the front wall, and the room was longer than wide, could that have been mainly a visible illusion too?
That has primarily to do with the angle difference between the center and the side speakers. If I play the loudspeakers shifted so that the center is on the long wall and the Bremen eggspeakers on the short side walls, then it would have been different.
That was the way in which I originally intended to demonstrate my loudspeakers, but at the end just before moving into the room they said at Sheraton that the desk in the rooms could not be taken out and the desk is rather big, so I decided to do the demonstration as I did.
But the visual information is also important.
Best Regards
Peter Steindl _________________ VD Bremen Production AB; Grundare av Ljudbutiken AB; Fd importverksamhet av hifi; Konstruktör av LICENCE No1 D/A, Bremen No1 D/A, Forsell D/A, SMS FrameSound, Bremen ägghögtalare m.fl.
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-02-28 00:00 Ämne: Part 2 answer to Objectivisten
Objektivisten skrev:
Hi James, welcome to the forum, what do You think is the secret about tubes and that they almost always sounding more pleasant and true to the ears? And do we really need all that watts, low powered amps seems to gain in transparent sound, may be construction simplicity or cost effectiveness?
Objektivisten skrev:
Holy macaroni, the significance of my 'statement' is zero (maybe below) James. Can we please go back to the real substance in this thread, your eminent inputs and answers. Regards
I agree.
In terms of our previous discussion on the causes of sonic differences between power amplifiers, in “Part One” discussed a few of the issues relating to the significance of overload characteristics during normal use of power amplifiers.
As a point of interest, these portions of the total research program that started in the 1970’s and were repeated in the early 1990’s as part of the development program for a new line of amplifiers that were produced in the mid and late 1990’s.
PART TWO: (A brief overview of the impact of wide band output impedance)
Next, in our research on this topic, we uncovered the effects of power amplifier output impedance and the interface with the loudspeaker load.
Output impedance is often referred to as damping factor relative to an 8-ohm load, but as we know, there are is not a single loudspeaker on the market that actually exhibits an 8-ohm, zero phase angle, load over the useful frequency range of the loudspeaker.
Also, damping factor is most often referred to as a low frequency phenomenon, with most amplifier specifications using 100 Hz as a reference frequency, when, in actuality, it is at least as important at high frequencies as it is at low frequencies. Unfortunately, most power amplifiers do not specify their high frequency damping factors… for the reason that most of them are substantially worse than they are at low frequencies.
(NOTE: There can also be dynamic, or non-linear output impedances in power amplifiers, and dynamic, non-linear input impedances in loudspeakers, but for this discussion, we will limit our observations to linear, small signal damping factor/output impedances and input impedances.)
Essentially, as one raises the output impedance (or lowers the damping factor) in a power amplifier, the amplitude error due to the impedance interface can cause the frequency response to take on the shape of the impedance curve more and more as the output impedance is higher.
Nearly all power amplifiers incorporate reactive components between the output stage and the output terminals. Most power amplifiers vary the amount of negative feedback vs. frequency, such that the output impedance increases with frequency due to the reduced feedback and output inductance.
After completing our studies in amplifier overload characteristics, we used the amplifiers in a manner that guaranteed that they operated below overload, and also kept them below the levels that would drive the loudspeaker in test, into nonlinearity, so as to eliminate those two variables in the device under test, as we moved on to isolate remaining parameters that affected sound quality in power amplifiers.
Even though we were operating both the power amplifiers and loudspeakers below and known nonlinear audible thresholds we were still detecting coloration differences between power amplifiers, with greater differences being exposed with some loudspeakers more than with other loudspeakers.
A first causal parameter, that we were able to isolate, was linear amplitude distortion due to the interaction of the amplifier and the loudspeaker impedances.
While there were audible errors in the lower and middle frequencies in certain tube amplifiers and a few specialized, low feedback solid-state amplifiers, (due to higher output impedances - poor damping factor - at low frequencies), this was not too surprising, as this issue had been reported previously, at least anecdotally, if not by way of rigorous controlled testing.
What was more interesting, were the number of amplifier loudspeaker combinations that generated high frequency coloration, due to the amplifier output impedance, at high frequencies, causing high frequency amplitude errors.
Many amplifiers have substantially worse damping factors at the highest frequencies, relative to the lower frequencies (below 1 kHz) and due to phase angle and impedance variations, exhibited in the loudspeaker, substantial response errors were observed. While most varied less than 1.2 dB, in some cases we found high-frequency response variations, between 5 kHz and 20 kHz, of over 2.5 dB!
As one can imagine, these levels of amplitude error, while in many cases subtle, are clearly audible, and repeatable with double blind testing.
It is interesting that there are still no industry standards for minimum impedance and phase angle. (THX and a few private parties have their own guidelines, but that is not recognized or enforced in most realms of audio).
It is easy for loudspeaker designers to be abusive in terms of impedance curves, as it can often serve their purposes to allow the impedance to fall to very low levels in exchange for some other advantage in performance, such as amplitude response.
Recently I was evaluating a new loudspeaker for a company, and I noticed that the impedance curve dipped to well below 2 Ohms at 285 Hz. They had done this because they had a dip in the amplitude response at 300 Hz and the only way to boost the response to flat in the passive-crossover, was to create an under-damped alignment in the high pass filter. The power spectrum in music program tends to be divided approximately equally above and below 270 Hz, and so the greater power demands are right were this loudspeaker had it’s lowest impedance, creating unusual current demands from the power amplifier.
They get the response they wanted and passed the impedance interface problem onto the amplifier designer.
Another popular loudspeaker, from the 1980’s, had a 0.9Ω impedance (and a large phase angle) at about 3.7 kHz. This caused a myriad of problems with amplifier interactions.
Amplifiers with any significant output impedance relative to the input impedance of the loudspeaker don’t operate any longer as an ideal voltage source, and can easily exhibit sonic errors because of this issue.
Depending on the set of conditions, audible problems can be caused by current limiting or by linear amplitude errors, or both.
As an aside, there is a story about our test procedure you may find interesting;
To isolate the audible effects during our testing process we used a number of approaches, such as straight wire bypass tests and double blind testing.
Some folks believe that results derived from blind testing is not valid, particularly when there is a null result.
During the time of our research, and still today, many audiophiles reject double blind testing as a procedure that causes stress that “interferes” with their psychological ability to make accurate assessments.
During our research project, we decided to test this notion. We had two amplifiers that both performed very well, but one sold for seven times more than the other one and was known as a very prestigious amplifier, having received rave reviews. We had two groups of audiophiles that claimed that they could always easily hear the difference between the two amplifiers, speaking rather critically of the lower cost unit, and glowingly of the higher cost amp.
During out double blind tests, each of them failed to consistently pick their favorite amplifier. So, we told them to take the two amplifiers, and listen to them under whatever test conditions they felt they were most comfortable, and to keep notes on what they perceived and which they preferred. We had approximately 20 people in two separate groups involved, all of them diehard audiophiles and critical of DBX testing.
Before we gave them the two amplifiers, we made one change. We exchanged the internal circuitry, so that the “cheap” amplifier was in the “expensive” chassis, and the “expensive” amp was in the “cheap” amp chassis.
We gave them the amplifiers and after they all had a chance to test them in the manner they were most comfortable, we retrieved the amplifiers and their written test results.
It may or may not be a surprise to you, that every one of them chose the amplifier in the expensive amplifier’s chassis as the one that sounded best, and had pages and pages of notes expressing their preference, and also expressing how easy it was to hear the difference and how the difference was quite large.
I learned two things from this experiment: 1) uncontrolled tests, that are not double blind, will produce random or erroneous results, and 2) even when shown this kind of evidence, it is not convincing for most of those that have already made up their mind that double blind testing doesn’t work.
So, I don’t think I made any converts, but it was an illuminating experiment.
Just to be clear, I am not saying that one cannot detect real differences between devices under test without a double blind test. I am only saying that it is important to verify any differences by way of double blind testing.
Actually, we have often been able to identify actual differences with double blind testing that are often not noticed in casual testing… but more on that another time.
Anyhow, so far we have covered two of the elements that can be of significance in explaining audible differences in power amplifiers, both of which are often overlooked;
- Audible clipping characteristics due to partial overload, and
- Wideband damping factor (Output Impedance) interface and interaction with the loudspeaker load
While there are some other issues that can affect amplifier sound quality, we can explain much of your original question with these two forms of distortion.
I can discuss further the specifics of these two forms and how they related to your original inquiry, and we can discuss other issues relative to power amplifiers in the future, if you wish, but I am delinquent on quite a few loudspeaker questions that I should answer first.
All the best,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Dec 25, 2008 Inlägg: 1760 Från: Kristianstad
Skrivet: 2011-02-28 01:13 Ämne:
I have been reading this thread from the begining and want to say thanks to James for all the time he puts into giving us some great information. Especially the last answer about damping factor and amplifier research was great.
Well since I have got the opportunity I might as well ask you a question James.
Whats your view on vintage-hifi? I often get the feeling that there haven´t been much significant development since the golden days in the late 70s early 80s. If their is one thing that has changed its perhaps that there is more badly constructed equipment on the market today.
Some of my audiophile friends doesn´t agree, they´re basicly the ones who don´t believe in blind tests either.
Have you ever come across some of the old Denon totl equipment like poa3000,poa1500 and pma790? I think their great and some of the best amps I ever heard.
Best Regards Carl _________________ Officiell talesman för Guldöronklubben (GÖK) på Faktiskt.
The pi60 is a very organic and well integrated device with many good qualities.
But what impresses me most about the pi60, is not just its ability to perform well with excellent program material, but the unique capability to also extract a surprisingly lifelike presentation from many rather mediocre recordings.
That is not a trivial accomplishment.
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-02-28 07:09 Ämne:
Vinylcalle skrev:
I have been reading this thread from the begining and want to say thanks to James for all the time he puts into giving us some great information. Especially the last answer about damping factor and amplifier research was great.
Well since I have got the opportunity I might as well ask you a question James.
Whats your view on vintage-hifi? I often get the feeling that there haven´t been much significant development since the golden days in the late 70s early 80s. If their is one thing that has changed its perhaps that there is more badly constructed equipment on the market today.
Some of my audiophile friends doesn´t agree, they´re basicly the ones who don´t believe in blind tests either.
Have you ever come across some of the old Denon totl equipment like poa3000,poa1500 and pma790? I think their great and some of the best amps I ever heard.
Best Regards Carl
Hi Vinylcalle,
I am fond of many of the vintage units. The Denon POA-3000 was one of the better implementations of the Dynamic Class-A circuits that were being developed at that time (around 1979), and it was a beautiful package.
The PMA-790 Integrated utilized a variation on the Quad Current Dumping Architecture, that also worked quite well. I never had a chance to try the POA-1500.
I used to put on a vintage demonstration in Seattle every 5 years to show how well a pre-1970 system can be made to perform.
A double or triple set of Quad ESL's, with Marantz 9 power amplifiers, Marantz 7c pre-amp, and playing Master Tapes as source material was always good for illustrating how little progress has been made over the years.
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Hello James,
Earl Geddes seems to say this is as good sound distribution as you need;
Could those curves be close to any goal you would want to reach?
Is it ok to have that much wider dispersion below 1 kHz than above?
Maybe the bass couples to the boundries and thus tends to narrow its dispersion a bit more than higher frequencies does?
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-02-28 23:50 Ämne: Re: Di-Cardioid type gradient loudspeaker
Naqref skrev:
Jacro skrev:
(By the way, the post of Naqref’s stopped after only 2 pages… Was there further work and measurements reported on the experimental devices?)
Hello James,
Finally I had som time (and focus) to read the whole thread and I'm very impressed as many others.
Regarding My little sweetheart it's scrapped but I'll think I have some measurement of it somewhere in one of my computers. Perhaps I'll find it and then I'll post some information here (and in the original thread).
The first ambience-module with the principle was made around 1995. A couple of years later I built the one on the pictures. I was still a poor student at the time so there was actually no money to develop the principle then. And then I found other things more promising.
I found your patent:
http://www.freepatentsonline.com/7551062.pdf
Impressive. I'll think the right way to go ist to use multiple active units just as you say. Passive damping of the sound from the back of the unit is to test intensive to get right.
I am like you intrested in what I call wall integrated speakers. It should perhaps be altered to external wall integrated speakers (EWI) or something like that to avoid beeing misstaken for in-wall-speakers. But anyhow. I'm the designer of Larsen speakers (it's a follow up of Carlsson). Two major problems with ewi-speakers is the perception of depth and excitment of roomresonances I'll think. The problem with depth is that the mind has problems to project auditory sources beyond the visual boundaries. The eye's override of other senses is making it harder to imagine a sound stage beyond the front wall. Do you think this is a big problem and if so what else is there to do about it other than removal of visual clues or to give additional visual clues to aid the sound stage?
The second problem (actually it's really a problem with almost every type of speaker), what is your preffered method of dealing with that? Acoustical lf-absorbers, parametrical eq or perhaps using multiple sound sources to counter act the resonanses?
Send my regards to Lars Erickson.
Hi Naqref,
Good to hear from you.
You mention two issues related to “EWI” loudspeakers:
(Over here we differentiate from "In-Wall" by calling them either; "On-Wall" or "Boundary Coupled"):
1) Perception of depth
2) Excitement of Room Resonances
I'm not clear on what you are referring to with #2. I think you are referring to reflections off the near boundary, but that is not actually a "resonance" per say. So, to discuss number 2, it would be good if you can clarify for me.
So, in terms of depth perception, in one way it is a problem (difficulty in imagining depth through a wall) and in another way, it is an improvement, in that it doesn't create "false depth" due to reflections off of the wall, spaced some distance behind the loudspeaker.
Loudspeakers spaced away from the front wall tend to create some degree of a false sense of depth depending on the ratio of the direct energy vs. the intensity of the energy reflected back to the listener.
So, in this regard, the boundary coupled systems are more faithful to reproducing the actual depth captured on the recording. (This is an over simplification, due to there being many additional variables determining perceived depth).
Your other observation, of the visual wall blocking our ability to imagine depth behind the wall, can be a significant limitation with some listeners. It is not a universal problem, but certainly a problem for many. Initially, I found it to be problematic for myself.
Sometimes I listen with my eyes closed, when listening to reproduced sound through loudspeakers, and also when I am at a live concert. In both cases, I find that the visual aspects alter my perception of the aural event, so closing my eyes creates a more equivalent situation for comparing live vs. reproduced sound.
If I have my eyes open at a live concert, I perceive the individual instruments as being more focused in a specific location in space than if my eyes are closed. Also, with eyes open, I "visualize" more depth of field, commensurate with the actual stage depth. If I close my eyes at a live concert, then the location of instruments is more vague, less focused, and the perception of depth of field is less.
So, if we are attempting to transport the actual focus, and scale of the sound sources to our listening room, without the actual musicians being visually present, the boundary coupled system is actually a more “accurate” facsimile of the spatial dimension of the original event.
(In a smaller second venue, boundary coupled loudspeakers and loudspeakers out in the room both distort the image compared to the original, but the loudspeakers that are out in the room (unless highly directional) will add more artificiality to the reproduced sound.
To minimize the visual barrier (for some customers that find it bothersome), but still have a boundary-coupled relationship for the loudspeakers, I have developed an alternative use-model.
Let’s see if I can explain it without a drawing.
Instead of facing the front wall of the room, the listener faces into a corner of the room. As an example, the listener might sit 3-meter’s straight out from the corner, and the left loudspeaker is coupled to the wall that extends to the left of the corner, and the other loudspeaker is coupled to the wall that extends to the right of the corner. The distance between the two loudspeakers and the distance from the loudspeakers to the listener are the same as they normally would be, and the loudspeakers are angled, or aimed, in relation to the listener, as they normally would be.
Visually, the corner extends back behind the loudspeakers, but the loudspeakers are effectively boundary coupled to each wall as they normally would be on the front wall.
I usually put extra absorption/diffusion in the corner, such as a quarter round of a half-meter radius, covered with 100 mm of foam, and I use a larger piece of absorption on the wall where the loudspeaker is coupled.
With an angled configuration, such as the Larsen 4, 6, or 8, the right loudspeaker may work better on the left side, and visa versa.
Make sense?
If properly set up, this has a few advantages, two of which are; it provides a visual expansion of depth, and it can leverage a more effective boundary coupling (less than a half-space) which allows a small loudspeaker to better power a larger room.
I use this approach for listeners that find the wall boundary mounting to be problematic for imagining depth, and/or for listeners who have rooms that are larger than what the loudspeaker is normally capable of filling.
This is a rather unorganized, non-technical discussion of the issue that you raised, but hopefully it is still somewhat useful.
I’ll address the rest later.
Best regards,
- James
PS – I’ll be sure to say hello to Lars for you. _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-03-01 00:15 Ämne:
paa skrev:
Hello James,
Earl Geddes seems to say this is as good sound distribution as you need;
Could those curves be close to any goal you would want to reach?
Is it ok to have that much wider dispersion below 1 kHz than above?
Maybe the bass couples to the boundries and thus tends to narrow its dispersion a bit more than higher frequencies does?
paa,
I have to run to a meeting, so a short answer for now.
While I believe that Geddes radiation pattern of constant directivity above 1 kHz is a big improvement over most free-standing loudspeakers, I disagree with Geddes suggesting that it is not important to maintain the constant radiation pattern below 1 kHz. A 12 dB transition below 1.5 kHz still impacts the “room sound”.
Geddes admits that he is not sure that it is important to improve it further, but states that, “even if it is important, it is not practical to do so”.
I humbly disagree.
But, I must also say, that Geddes has done some excellent work, his approach being superior to 99% of the loudspeakers available today, and he is one of the few actually advancing the art.
So, I agree that his configuration is an improvement over most of the other approaches, I merely feel that he has stopped short of what can be achieved on an ideal basis… definitely with his actual device, and possibly with his belief.
He is on the right track… he just needs to take it a bit further.
More later…
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Thanks James for your answer about directivety below 1kHz.
Now imagine that I manage to make loudspeakers that maintain directivety down to say 80Hz, and want to add some subwoofers to them:
If I place two subs in the front corners, they will be boundry coupled in their frequency range and have 90+90 degrees of dispersion which should be fine. But probably we play the subs in mono so now we have 180 degrees bass dispersion which is quite a bit more more than the theoretically perfect main speakers, how do we sort this out? And if we want one or two more subs to improve on room modes, how would all that effect frequency response vs power response in such a system?
Blev Medlem: Jun 19, 2005 Inlägg: 1830 Från: Örebro
Skrivet: 2011-03-02 07:58 Ämne:
Jacro skrev:
I hope that the Google translator doesn't provide too many embarrassing mistakes. I often translate from English to Swedish, and then translate the Swedish back to English again, to see what it says, and the errors can be quite entertaining.
It helps that these errors is mostly one-way, i.e. when you're reading swedish threads. I'd say that 75% (just a guess) around here have no problems using english as primary language on a forum, and half of those should have no problem with quite advanced technical english.
Not a single lecture in my university education, in sweden, were in swedish. It was all in english. That helps. I guess this goes for most of the other people here with any form of higher technical education aswell. For me it's not the language barrier that sometimes keeps me from understanding threads like these, it's lack of physics knowledge.
My beleif is that this kind of participation from you could be alot more difficult in some other languages. (Like... well... french for instance. That would be very difficult for the majority of us swedes aswell, for the same reason.) _________________ Skulle du vilja se ut dummare än vad du är, eller vara dummare än du ser ut?
Blev Medlem: Mar 24, 2003 Inlägg: 25879 Från: Krischansta
Skrivet: 2011-03-02 10:19 Ämne: Re: Di-Cardioid type gradient loudspeaker
Jacro skrev:
Naqref skrev:
Jacro skrev:
(By the way, the post of Naqref’s stopped after only 2 pages… Was there further work and measurements reported on the experimental devices?)
Hello James,
Finally I had som time (and focus) to read the whole thread and I'm very impressed as many others.
Regarding My little sweetheart it's scrapped but I'll think I have some measurement of it somewhere in one of my computers. Perhaps I'll find it and then I'll post some information here (and in the original thread).
The first ambience-module with the principle was made around 1995. A couple of years later I built the one on the pictures. I was still a poor student at the time so there was actually no money to develop the principle then. And then I found other things more promising.
I found your patent:
http://www.freepatentsonline.com/7551062.pdf
Impressive. I'll think the right way to go ist to use multiple active units just as you say. Passive damping of the sound from the back of the unit is to test intensive to get right.
I am like you intrested in what I call wall integrated speakers. It should perhaps be altered to external wall integrated speakers (EWI) or something like that to avoid beeing misstaken for in-wall-speakers. But anyhow. I'm the designer of Larsen speakers (it's a follow up of Carlsson). Two major problems with ewi-speakers is the perception of depth and excitment of roomresonances I'll think. The problem with depth is that the mind has problems to project auditory sources beyond the visual boundaries. The eye's override of other senses is making it harder to imagine a sound stage beyond the front wall. Do you think this is a big problem and if so what else is there to do about it other than removal of visual clues or to give additional visual clues to aid the sound stage?
The second problem (actually it's really a problem with almost every type of speaker), what is your preffered method of dealing with that? Acoustical lf-absorbers, parametrical eq or perhaps using multiple sound sources to counter act the resonanses?
Send my regards to Lars Erickson.
Hi Naqref,
Good to hear from you.
You mention two issues related to “EWI” loudspeakers:
(Over here we differentiate from "In-Wall" by calling them either; "On-Wall" or "Boundary Coupled"):
1) Perception of depth
2) Excitement of Room Resonances
I'm not clear on what you are referring to with #2. I think you are referring to reflections off the near boundary, but that is not actually a "resonance" per say. So, to discuss number 2, it would be good if you can clarify for me.
So, in terms of depth perception, in one way it is a problem (difficulty in imagining depth through a wall) and in another way, it is an improvement, in that it doesn't create "false depth" due to reflections off of the wall, spaced some distance behind the loudspeaker.
Loudspeakers spaced away from the front wall tend to create some degree of a false sense of depth depending on the ratio of the direct energy vs. the intensity of the energy reflected back to the listener.
So, in this regard, the boundary coupled systems are more faithful to reproducing the actual depth captured on the recording. (This is an over simplification, due to there being many additional variables determining perceived depth).
Your other observation, of the visual wall blocking our ability to imagine depth behind the wall, can be a significant limitation with some listeners. It is not a universal problem, but certainly a problem for many. Initially, I found it to be problematic for myself.
Sometimes I listen with my eyes closed, when listening to reproduced sound through loudspeakers, and also when I am at a live concert. In both cases, I find that the visual aspects alter my perception of the aural event, so closing my eyes creates a more equivalent situation for comparing live vs. reproduced sound.
If I have my eyes open at a live concert, I perceive the individual instruments as being more focused in a specific location in space than if my eyes are closed. Also, with eyes open, I "visualize" more depth of field, commensurate with the actual stage depth. If I close my eyes at a live concert, then the location of instruments is more vague, less focused, and the perception of depth of field is less.
So, if we are attempting to transport the actual focus, and scale of the sound sources to our listening room, without the actual musicians being visually present, the boundary coupled system is actually a more “accurate” facsimile of the spatial dimension of the original event.
(In a smaller second venue, boundary coupled loudspeakers and loudspeakers out in the room both distort the image compared to the original, but the loudspeakers that are out in the room (unless highly directional) will add more artificiality to the reproduced sound.
To minimize the visual barrier (for some customers that find it bothersome), but still have a boundary-coupled relationship for the loudspeakers, I have developed an alternative use-model.
Let’s see if I can explain it without a drawing.
Instead of facing the front wall of the room, the listener faces into a corner of the room. As an example, the listener might sit 3-meter’s straight out from the corner, and the left loudspeaker is coupled to the wall that extends to the left of the corner, and the other loudspeaker is coupled to the wall that extends to the right of the corner. The distance between the two loudspeakers and the distance from the loudspeakers to the listener are the same as they normally would be, and the loudspeakers are angled, or aimed, in relation to the listener, as they normally would be.
Visually, the corner extends back behind the loudspeakers, but the loudspeakers are effectively boundary coupled to each wall as they normally would be on the front wall.
I usually put extra absorption/diffusion in the corner, such as a quarter round of a half-meter radius, covered with 100 mm of foam, and I use a larger piece of absorption on the wall where the loudspeaker is coupled.
With an angled configuration, such as the Larsen 4, 6, or 8, the right loudspeaker may work better on the left side, and visa versa.
Make sense?
If properly set up, this has a few advantages, two of which are; it provides a visual expansion of depth, and it can leverage a more effective boundary coupling (less than a half-space) which allows a small loudspeaker to better power a larger room.
I use this approach for listeners that find the wall boundary mounting to be problematic for imagining depth, and/or for listeners who have rooms that are larger than what the loudspeaker is normally capable of filling.
This is a rather unorganized, non-technical discussion of the issue that you raised, but hopefully it is still somewhat useful.
I’ll address the rest later.
Best regards,
- James
PS – I’ll be sure to say hello to Lars for you.
What you say makes a lot of sense. I hade tried to convince people of using the adjacent walls in a corner and shift right and left speaker in some cases but the look at me like they think; "Are you crazy or something" Perhaps I should work on my way of convincing people more to adress this problem.
Anyhow I think the problem is non existing when you have a picture of some sort between the boundary coupled (better word than mine at least in English) speakers. Like a TV or a projector screen.
Perhaps using mirrors (with some parts of the surface that are opaque) could do the trick?
My second question was about the normal resonances you have in a rectangular room (where you always have pressure nodes and velocity antinodes in the corners). A boundary coupled (just because it's places close to the walls) excite or trigger thes resonances more than free-standing speakers. At higher frequencys as you know the resonances have a modal density that is so high that single resonanses can't be heard. But at low frequencys (below 100 Hz or so) they can be quite problematic. As I see it there are (at least) three methods that can be used against these resonanses;
1. Using absorbtion (helmholtz, mass surface absorbers or large normal sound absorbers).
2. Using multiple or distributed sound sources. If you place a single sound source at in a place in the room where there is a pressure node for a certain frequency then it will trigger that corresponding resonance. But if you place a second correlated sound source at another pressure node for that frequency then that resonance can't be triggered. One way to use this technique is to use several subwoofers for the range of 0-100Hz and place them in a pattern that supresses these resonances.
3. Using a parametric eq.
Does my explanation makes my question more clear?
Reagards
Anders Eriksson _________________ Audiodesigner åt en del. Larsen, Holographic Audio etc.
CEO och huvudägare i Acoustic Landscape R&D AB.
CTO / R&D Manager och delägare i Acoustic Illusion AB.
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-03-03 02:05 Ämne:
paa skrev:
Thanks James for your answer about directivety below 1kHz.
Now imagine that I manage to make loudspeakers that maintain directivety down to say 80Hz, and want to add some subwoofers to them:
If I place two subs in the front corners, they will be boundry coupled in their frequency range and have 90+90 degrees of dispersion which should be fine. But probably we play the subs in mono so now we have 180 degrees bass dispersion which is quite a bit more more than the theoretically perfect main speakers, how do we sort this out? And if we want one or two more subs to improve on room modes, how would all that effect frequency response vs power response in such a system?
paa,
My computer is in for repair for a few days, so I will have to wait to address this question more completely as soon as my computer is returned to me.
You ask a good question. Part of the answer is that it is most important to maintain the directivity down to the Schroeder frequency. Below the Schroeder frequency things change and to some degree, the sound source becomes the room modes themselves, as opposed to the loudspeaker, but that is a concept that needs some further explanation.
I hope to get back to you with more on this topic in a few days.
All the best,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-03-03 02:27 Ämne: Re: Di-Cardioid type gradient loudspeaker
Naqref skrev:
Jacro skrev:
Naqref skrev:
Jacro skrev:
(By the way, the post of Naqref’s stopped after only 2 pages… Was there further work and measurements reported on the experimental devices?)
Hello James,
Finally I had som time (and focus) to read the whole thread and I'm very impressed as many others.
Regarding My little sweetheart it's scrapped but I'll think I have some measurement of it somewhere in one of my computers. Perhaps I'll find it and then I'll post some information here (and in the original thread).
The first ambience-module with the principle was made around 1995. A couple of years later I built the one on the pictures. I was still a poor student at the time so there was actually no money to develop the principle then. And then I found other things more promising.
I found your patent:
http://www.freepatentsonline.com/7551062.pdf
Impressive. I'll think the right way to go ist to use multiple active units just as you say. Passive damping of the sound from the back of the unit is to test intensive to get right.
I am like you intrested in what I call wall integrated speakers. It should perhaps be altered to external wall integrated speakers (EWI) or something like that to avoid beeing misstaken for in-wall-speakers. But anyhow. I'm the designer of Larsen speakers (it's a follow up of Carlsson). Two major problems with ewi-speakers is the perception of depth and excitment of roomresonances I'll think. The problem with depth is that the mind has problems to project auditory sources beyond the visual boundaries. The eye's override of other senses is making it harder to imagine a sound stage beyond the front wall. Do you think this is a big problem and if so what else is there to do about it other than removal of visual clues or to give additional visual clues to aid the sound stage?
The second problem (actually it's really a problem with almost every type of speaker), what is your preffered method of dealing with that? Acoustical lf-absorbers, parametrical eq or perhaps using multiple sound sources to counter act the resonanses?
Send my regards to Lars Erickson.
Hi Naqref,
Good to hear from you.
You mention two issues related to “EWI” loudspeakers:
(Over here we differentiate from "In-Wall" by calling them either; "On-Wall" or "Boundary Coupled"):
1) Perception of depth
2) Excitement of Room Resonances
I'm not clear on what you are referring to with #2. I think you are referring to reflections off the near boundary, but that is not actually a "resonance" per say. So, to discuss number 2, it would be good if you can clarify for me.
So, in terms of depth perception, in one way it is a problem (difficulty in imagining depth through a wall) and in another way, it is an improvement, in that it doesn't create "false depth" due to reflections off of the wall, spaced some distance behind the loudspeaker.
Loudspeakers spaced away from the front wall tend to create some degree of a false sense of depth depending on the ratio of the direct energy vs. the intensity of the energy reflected back to the listener.
So, in this regard, the boundary coupled systems are more faithful to reproducing the actual depth captured on the recording. (This is an over simplification, due to there being many additional variables determining perceived depth).
Your other observation, of the visual wall blocking our ability to imagine depth behind the wall, can be a significant limitation with some listeners. It is not a universal problem, but certainly a problem for many. Initially, I found it to be problematic for myself.
Sometimes I listen with my eyes closed, when listening to reproduced sound through loudspeakers, and also when I am at a live concert. In both cases, I find that the visual aspects alter my perception of the aural event, so closing my eyes creates a more equivalent situation for comparing live vs. reproduced sound.
If I have my eyes open at a live concert, I perceive the individual instruments as being more focused in a specific location in space than if my eyes are closed. Also, with eyes open, I "visualize" more depth of field, commensurate with the actual stage depth. If I close my eyes at a live concert, then the location of instruments is more vague, less focused, and the perception of depth of field is less.
So, if we are attempting to transport the actual focus, and scale of the sound sources to our listening room, without the actual musicians being visually present, the boundary coupled system is actually a more “accurate” facsimile of the spatial dimension of the original event.
(In a smaller second venue, boundary coupled loudspeakers and loudspeakers out in the room both distort the image compared to the original, but the loudspeakers that are out in the room (unless highly directional) will add more artificiality to the reproduced sound.
To minimize the visual barrier (for some customers that find it bothersome), but still have a boundary-coupled relationship for the loudspeakers, I have developed an alternative use-model.
Let’s see if I can explain it without a drawing.
Instead of facing the front wall of the room, the listener faces into a corner of the room. As an example, the listener might sit 3-meter’s straight out from the corner, and the left loudspeaker is coupled to the wall that extends to the left of the corner, and the other loudspeaker is coupled to the wall that extends to the right of the corner. The distance between the two loudspeakers and the distance from the loudspeakers to the listener are the same as they normally would be, and the loudspeakers are angled, or aimed, in relation to the listener, as they normally would be.
Visually, the corner extends back behind the loudspeakers, but the loudspeakers are effectively boundary coupled to each wall as they normally would be on the front wall.
I usually put extra absorption/diffusion in the corner, such as a quarter round of a half-meter radius, covered with 100 mm of foam, and I use a larger piece of absorption on the wall where the loudspeaker is coupled.
With an angled configuration, such as the Larsen 4, 6, or 8, the right loudspeaker may work better on the left side, and visa versa.
Make sense?
If properly set up, this has a few advantages, two of which are; it provides a visual expansion of depth, and it can leverage a more effective boundary coupling (less than a half-space) which allows a small loudspeaker to better power a larger room.
I use this approach for listeners that find the wall boundary mounting to be problematic for imagining depth, and/or for listeners who have rooms that are larger than what the loudspeaker is normally capable of filling.
This is a rather unorganized, non-technical discussion of the issue that you raised, but hopefully it is still somewhat useful.
I’ll address the rest later.
Best regards,
- James
PS – I’ll be sure to say hello to Lars for you.
What you say makes a lot of sense. I hade tried to convince people of using the adjacent walls in a corner and shift right and left speaker in some cases but the look at me like they think; "Are you crazy or something" Perhaps I should work on my way of convincing people more to adress this problem.
Anyhow I think the problem is non existing when you have a picture of some sort between the boundary coupled (better word than mine at least in English) speakers. Like a TV or a projector screen.
Perhaps using mirrors (with some parts of the surface that are opaque) could do the trick?
My second question was about the normal resonances you have in a rectangular room (where you always have pressure nodes and velocity antinodes in the corners). A boundary coupled (just because it's places close to the walls) excite or trigger thes resonances more than free-standing speakers. At higher frequencys as you know the resonances have a modal density that is so high that single resonanses can't be heard. But at low frequencys (below 100 Hz or so) they can be quite problematic. As I see it there are (at least) three methods that can be used against these resonanses;
1. Using absorbtion (helmholtz, mass surface absorbers or large normal sound absorbers).
2. Using multiple or distributed sound sources. If you place a single sound source at in a place in the room where there is a pressure node for a certain frequency then it will trigger that corresponding resonance. But if you place a second correlated sound source at another pressure node for that frequency then that resonance can't be triggered. One way to use this technique is to use several subwoofers for the range of 0-100Hz and place them in a pattern that supresses these resonances.
3. Using a parametric eq.
Does my explanation makes my question more clear?
Reagards
Anders Eriksson
Anders,
As I mentioned in the last post, I am without my computer this week, so I will have to get back to you with a complete answer in a few days.
Yes, I do understand your question now... thank you for clarifying.
There are a number of issues around the topic that you have raised.
The solutions that you mention, or variations on them, tend to be some of the best we have available today.
To make a couple statements until I can get back with complete answers, I would say that I am generally an advocate of "Global", preemptive, solutions (such as modifying the room, loudspeaker configuration and location, and using multiple woofer systems), as opposed to "local", post-corrective solutions (such as digital room correction).
There are a number of ways to implement multiple woofers. I have a new couple of new ways that I have found that exhibit interesting results when compared to some of the current conventional approaches of Welti and Geddes. I'll speak more about them when I get back to complete my answers.
More later...
Best regards,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-03-14 01:58 Ämne:
sportbilsentusiasten skrev:
What is according to you the best length to width ratio?
Is that ratio different depending of speakers used?
Hi sportbilsentusiasten,
My computer is repaired and I am back online. I apologize for the delay.
I have many questions to respond to here.
Relative to your question, the most effective, angle and length-to-width ratio depends on system type and program material. While there are a numerous optimal angles, due to the wide variety of system configurations, I will just list three useful angles that tend to maximize the performance of many of the most common program sources and loudspeaker types.
1) Standard Stereo:
For a simple two-channel system with standard stereo program material, plus and minus 21 degree angles for the left and right loudspeakers tend to work best.
This is not so much due to recording type, which may vary quite a bit based on microphone usage. Instead, the angle is defined placement that provides the least amount of inter-aural crosstalk. This form of “passive” crosstalk cancellation partially mimics binaural or crosstalk cancellation systems. By doing so, it can recreate the perception of the most effective three-dimensional sound field, with “balanced” depth and spatial characteristics.
2) Three Channel:
For systems with a center channel loudspeaker, the purpose is to anchor the centermost information, with low coloration and spatial correctness in multiple listening seats (unfortunately it often introduces a problem of monophonic scale on center channel signals) but with this approach there are some spatial errors that force a different placement for the left and right loudspeaker if one wishes to maintain the full dimensionality of the sound field. One of the reasons is that a hard left signal is normally heard as placed at the left loudspeaker, in a two-channel arrangement. But, with a center channel system, the hard left signal will be placed between the center and left loudspeaker as a phantom image. If the left and right loudspeakers are kept at the same 21-degree angles, the stage width will be limited to about +/- 10.5 degrees.
So, with the center channel addition, we need to change the angular staging of the left and right channel loudspeakers. It turns out that an angle of approximately +/- 67.5-degrees is required to sustain the full stage width when using a center channel device. This wide of an optimal angle is due to a number of issues, including the fact the image spread now being limited by the phantom source width limit, and, also because the speakers can no longer be positioned at the 21-degree inter-aural cancellation angle and therefore they loose the ability enhance spaciousness due to a lack of optimal IAC.
3)Two channel program material that is Cross talk cancellation processed:
As a third angular specification, is that of optimizing for recordings that have been programmed with spatial enhancing crosstalk cancellation or are being post processed with a crosstalk cancellation system. For these recordings it is recommended that the loudspeakers place with angles that are less than plus/minus 15 degrees, and preferably on the order of plus/minus 5 degrees. This is implemented partially to minimize the variation of crosstalk cancellation and head related amplitude response vs. frequency.
What this means is that ideally, one moves their loudspeakers to have different angles relative to the listener depending on the nature of the program source.
As with most all of the issues that we are discussing, this discussion is not at all comprehensive due to both the wide range of program material, channel count and type, and also the myriad of other factors (frequency response, room interaction, etc.) that are altered as one changes the relationship of the two loudspeakers to each other and the listener.
****
To everyone:
I have lost track of which issues remain unanswered. If there are any questions that someone has submitted for me to answer that I have not responded to, or if there any that I have not answered completely of which there is still interest in further discussion, please let me know.
All the best,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
I have lost track of which issues remain unanswered. If there are any questions that someone has submitted for me to answer that I have not responded to, or if there any that I have not answered completely of which there is still interest in further discussion, please let me know.?
I believe this is long lost:
paa skrev:
Jacro skrev:
...
OR,
2) Arrange for the first four boundary distances to be cross-relational such that they are distributed and/or cross-cancelling. In the second case, the system would ideally, have a smooth, but complex transitional power response that is calibrated to match the predetermined boundary interaction.
Both are rather complex to develop, and the second approach is the basis for the operation of The Clue.
...
- James
How can this be made to work for different room sizes, and different listening distances, things that also would demand different distances between the speakers?
Could this cross-relational and cross-cancelling function be simulated in some known software?
Then there was the discussion about power response with multiple subwoofers, where you said you had something more coming.
Skrivet: 2011-03-14 09:18 Ämne: Re: Di-Cardioid type gradient loudspeaker
Jacro skrev:
To make a couple statements until I can get back with complete answers, I would say that I am generally an advocate of "Global", preemptive, solutions (such as modifying the room, loudspeaker configuration and location, and using multiple woofer systems), as opposed to "local", post-corrective solutions (such as digital room correction).
There are a number of ways to implement multiple woofers. I have a new couple of new ways that I have found that exhibit interesting results when compared to some of the current conventional approaches of Welti and Geddes. I'll speak more about them when I get back to complete my answers.
More later...
Best regards,
- James
Jacro,
I have followed the thread with great interest and you are really a good asset to have here.
I have made some test with multiple subwoofers and active digital crossovers (BSS FDS-366T) and I have found rather huge aural differences when using the time delay function. Do you recommend using multiple subbs without delay adjustments? From my small test with multiple subbs using Smaart I found that adjusting the delay for a rather straight frequency response will give a better transient response overall compared to rather straight frequency response using the peq. Are my observations correlated to using an active digital crossover which has an already built-in delay of at least 2ms? Could it be the case that just using an analog active crossover and using several subbs will "cure" all timing problems?
Unfortunately I have not the possibility to test multiple subbs with analog crossover except at home where I just have 2 Paradigm Servo-15 directly placed under the midrange and treble speakers. There I have compared an analogue JBL553 with the BSS and if I sit just a bit off center I could never prefer the analogue time uncompensated filter. In the middle of the sweet spot the difference is less but a dentist chair is preferable.
What is the risk of getting a rather straight frequency response using multiple subbs and losing some transient response due to have the subbs playing a bit in and out of phase with each other and the rest of the system?
I have looked into jevans111 small movies at youtube
http://www.youtube.com/results?search_query=subwoofer+alignment&aq=f about subwoofer alignment and I'm curious how to find out when the setup is fully optimized. What tool would you recommend or is it even a correct approach for home environments.
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-03-15 21:37 Ämne:
avr7000 skrev:
Hello Jacro
Is there a possibly somewhere for me to listen to, and maybe buy, the clue speakers in either:
New York
Grand Rapids
Richmond
-and maybe Chicago.
Regards
Stefan
Hi Stefan,
We have distribution that is ready to be set up in New York as soon as we are fully able to supply our other distributors, hopefully in the next two to three months.
We have nothing available in Grand Rapids or Richmond at this time.
Currently, we DO have an outlet in Chicago. The contact is Paul Lawless ( paul@sjofnhifi.com )
I hope this can work for you. If not, let me know and I'll alert you when we activate our distribution in New York.
Best regards,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-03-19 03:27 Ämne:
paa skrev:
Jacro skrev:
I have lost track of which issues remain unanswered. If there are any questions that someone has submitted for me to answer that I have not responded to, or if there any that I have not answered completely of which there is still interest in further discussion, please let me know.?
I believe this is long lost:
paa skrev:
Jacro skrev:
...
OR,
2) Arrange for the first four boundary distances to be cross-relational such that they are distributed and/or cross-cancelling. In the second case, the system would ideally, have a smooth, but complex transitional power response that is calibrated to match the predetermined boundary interaction.
Both are rather complex to develop, and the second approach is the basis for the operation of The Clue.
...
- James
How can this be made to work for different room sizes, and different listening distances, things that also would demand different distances between the speakers?
Could this cross-relational and cross-cancelling function be simulated in some known software?
Then there was the discussion about power response with multiple subwoofers, where you said you had something more coming.
paa,
I can’t go into all the subtleties and complexity of applying the cross-relational techniques without applying at least ten pages of writing, but I’ll state a few useful starting points to allow one to engage the general concept and get somewhat of a feel for variation relating to room dimension differences.
If the loudspeaker low frequency system is calibrated to the appropriate alignment with the correct high pass slope, and the placement of transducers and cabinet dimensions are properly integrated with the total scheme, then the desirable impact of the upper-most sensitive boundary frequencies (less than 0.75 wL) will be dominated from correct distances being established to the floor and front wall. The secondary relationships will be the sidewalls, ceiling and mutual coupling interactions. This relationship has implications for both the low frequency extension, AND, the smoothness of the response due to direct and the multiple reflected sounds being coordinated for diverse, distributed relationships. Without resorting to the optimal complexity, one approach that can work well is to apply “golden rule” relationships (1.618 x) between each of the specular sources.
The secondary sources have the greatest impacts below the Schroeder frequency, in the modal region. While the optimization of these dimensions are important (and may be interchangeable or reordered, if one of them must change outside an optimum range) have a certain amount of inherent flexibility due to modal dominance.
Yes, the optimization can be simulated and arrived at by way of software, and is currently the subject of a patent application.
There is much more to these relationships, but I would add that a two-loudspeaker system, in most cases, will not provide smooth response in the modal region. The application of multiple diversity woofers will most often be required to optimize the room/system response.
These are complex subjects, the room relationship of the loudspeaker, and also the application of multiple subwoofers.
There are a number of complex, simulation and measurement-based calibration of multiple subwoofers, but a few years ago I developed a simplified system for my customers to effectively apply multiple subwoofers to achieve excellent results with minimal analysis.
It is based on the use of a subwoofer on each of the four walls, with the relationship of each woofer being that of an increasing 1.618 relationship of each woofer to a corner. The first woofer is placed at a distance from a first corner that is based on a specific value relating to a constant relative to room dimensions. The second woofer is placed 1.618 times that distance from the second corner. Third woofer placed, relative to the third corner, 1.618 times the distance of the second woofer, and the fourth, 1.618 of the third. The phase of woofers 2, 3, and 4 are tested individually with reversed phase (usually woofer 2 or 3 work best with phase reversed)
This simple approach produces surprisingly consistent results.
Okay, back to work… I will try to write more later on system power response issues above and below the Schroeder frequency.
Cheers,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Hi James,
Once again, thanks for your patience with all our questions.
However much I await more about these things I have a follow up question here.
Jacro skrev:
...
It is based on the use of a subwoofer on each of the four walls, with the relationship of each woofer being that of an increasing 1.618 relationship of each woofer to a corner. The first woofer is placed at a distance from a first corner that is based on a specific value relating to a constant relative to room dimensions. The second woofer is placed 1.618 times that distance from the second corner. Third woofer placed, relative to the third corner, 1.618 times the distance of the second woofer, and the fourth, 1.618 of the third. The phase of woofers 2, 3, and 4 are tested individually with reversed phase (usually woofer 2 or 3 work best with phase reversed)
This simple approach produces surprisingly consistent results.
...
Cheers,
- James
Are there no problems when every subwoofer stand at different distances from the listener? How much difference can be tolerated?
Toole also argues against* placing bass around the room. One in every corner och one in the middle of every wall are some of the tips. Arguing that more bass speaker are better but above four is hitting diminish return.
Ingvar Öhman argues that the bass should preferably come from the front. That this would bring whats a more "pshycoacoustical correct wavefront".
Any comment in regard to this?
edit: sorry meant to say against not "for" _________________ Vackra ord är inte sanna, Sanna ord är inte vackra. / Tao Te Ching
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-03-21 00:06 Ämne:
Kraniet skrev:
Toole also argues against* placing bass around the room. One in every corner och one in the middle of every wall are some of the tips. Arguing that more bass speaker are better but above four is hitting diminish return.
Ingvar Öhman argues that the bass should preferably come from the front. That this would bring whats a more "pshycoacoustical correct wavefront".
Any comment in regard to this?
edit: sorry meant to say against not "for"
Hi Kraniet,
I believe that these two viewpoints, of Toole and Öhman, are both valid, each within a limited, optimized context.
The importance of maintaining a frontal derived wavefront is dependent on a number of parameters. One parameter set is the low pass corner frequency and/or low pass slope.
It works best if the low pass corner frequency is reduced and/or the low pass slope is increased, progressively for each woofer as the placement of the woofers is moved from front to beside the listener and then behind the listener. Also, the woofers are progressively reduced in level as they are place farther from the frontal launch region.
Each additional woofer is utilized mainly to provide a sequentially smaller and smaller correction to the modal reform. If this is done properly, there will be no audible difference in the perception of the appropriate psycho-acoustical wavefront direction.
All the parameters must be included before determining the ideal low pass frequencies, but in one example of an optimized room, the frontal woofers were crossed in at 122 Hz, the side woofers were crossed at 83 Hz and the rear woofers were crossed at 61 Hz. There were some additional optimized attributes but the system was carefully tested for tonal and spatial distortions relative to the addition of the side and rear woofers and was found to be transparent in this regard. Of course, the room parameters must support this type of low frequency architecture.
My more universal preference is to utilize a multiple woofer set that has all the individual woofers placed in the frontal hemisphere forward of the listening position, more inline with Mr. Öhman’s preference, but with a few additional enhancements.
My goal with the front hemisphere woofer arrangement, is to still address the most significant modal characteristics of the room, and this can be accomplished in the frontal portion of the room, but one must think three dimensionally.
This requires placing woofers in an arrangement that is not only horizontal, x-axis, but also to diversify in the y and z-axis, with at least one woofer above the half-height point of the room. With this approach, one can substantially accomplish the modal control of woofers placed on each of the four walls, while still maintaining 100% frontal wavelaunch.
In all of these approaches, one or more of the woofer units may contribute most effectively when operated with altered or reversed phase.
If one uses substantially full range (deep bass) left and right channel loudspeakers, then they can be included as one or two of the multi-sub elements.
I prefer to step down the gain of the left and right loudspeakers by 3 to 6 dB below the approximate frequency of the highest subwoofer crossover, and operate in a power-sharing manner below this frequency, both smoothing room modes AND increasing system maximum output capability.
Hopefully this provides at least a partial answer to your question.
Best regards,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Thanks James for your answer about directivety below 1kHz.
Now imagine that I manage to make loudspeakers that maintain directivety down to say 80Hz, and want to add some subwoofers to them:
If I place two subs in the front corners, they will be boundry coupled in their frequency range and have 90+90 degrees of dispersion which should be fine. But probably we play the subs in mono so now we have 180 degrees bass dispersion which is quite a bit more more than the theoretically perfect main speakers, how do we sort this out? And if we want one or two more subs to improve on room modes, how would all that effect frequency response vs power response in such a system?
paa,
My computer is in for repair for a few days, so I will have to wait to address this question more completely as soon as my computer is returned to me.
You ask a good question. Part of the answer is that it is most important to maintain the directivity down to the Schroeder frequency. Below the Schroeder frequency things change and to some degree, the sound source becomes the room modes themselves, as opposed to the loudspeaker, but that is a concept that needs some further explanation.
I hope to get back to you with more on this topic in a few days.
All the best,
- James
Hello James,
Do you have any more information about the Schroeder frequency, and its importance in small rooms?
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-04-04 04:59 Ämne:
paa skrev:
Hi James,
Once again, thanks for your patience with all our questions.
However much I await more about these things I have a follow up question here.
Are there no problems when every subwoofer stand at different distances from the listener? How much difference can be tolerated?
paa skrev:
Hello James,
Do you have any more information about the Schroeder frequency, and its importance in small rooms?
Hi paa,
The nature of sound sources when operating in the modal frequency region seems to be an issue of great confusion. It is fundamentally different than how systems operate, and what parameters are important, above the Schroeder frequency.
In the modal range, it may be more appropriate to think of the dominant source of the sound reaching your ears as being that of the modal output of the room, not the loudspeaker.
In most cases, the woofer drives the room and the modal nature of the room is what delivers the sound to your ears.
Our hearing requires a couple of cycles before it can determine a sound's timbre and when operating below the Schröeder frequency, reflections become an integral part of the sound almost instantly because the wavelengths are comparable to, or greater than, the room's dimensions.
So what we hear is no longer dominated by the loudspeaker but instead is created by the room boundaries and the sense of a perceived transient response is dominated by the amplitude smoothness and harmonics of the bass fundamentals.
There are at least two arrangements that can substantially override this characteristic of the modal frequency range;
1) a woofer system that maintains high directivity at modal frequencies (a rarity, but we have built, tested, and characterized these types of systems to determine their effectiveness)
2) using a near field woofer close to the listening seat, such that the dominant arrival is the direct arrival from the woofer itself (this is a superior technique not commonly used in the industry as of yet. I believe this approach is ahead of its time and will become a standard in another 5 to 10 years. We have developed systems using this approach that consistently outperform all other approaches)
In terms of differential distances between different woofers and the listener, this is not an audible issue from a phase/transient standpoint. If there are phase/timing errors, it is the amplitude response change due to phase differentials that is audible, not the phase difference itself. In fact, when distributing multiple subwoofers around the room, one of the useful techniques to create maximum smoothness in the frequency response, is to alter the phase of at least one of the woofers to adjust the modal development and amplitude summation among the woofers as they drive the room modes.
When setting up distributed woofer systems I tend to use lower frequency low-pass filters for woofers placed behind and/or farther from the listener than the frontal woofers, attempting to maintain less than a quarter wavelength differential between all woofers when measuring their distances to the listener.
As usual, this is a very limited explanation relative to all of the acoustic and psycho-acoustics effects in play, but hopefully this at least gives you some useful information on the topic.
Cheers,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Oct 29, 2003 Inlägg: 33943 Från: Grå Hamnarna
Skrivet: 2011-04-04 06:52 Ämne:
Jacro skrev:
My goal with the front hemisphere woofer arrangement, is to still address the most significant modal characteristics of the room, and this can be accomplished in the frontal portion of the room, but one must think three dimensionally.
This requires placing woofers in an arrangement that is not only horizontal, x-axis, but also to diversify in the y and z-axis, with at least one woofer above the half-height point of the room. With this approach, one can substantially accomplish the modal control of woofers placed on each of the four walls, while still maintaining 100% frontal wavelaunch.
I'm stacking my woofers in the front coners - floor to ceiling. Does this conform, or would you also say I'd need some inbetween?
And what's your view about stereo vs. mono for (sub)woofers, say crossed at 80Hz?
And also something completely different - as I take it you've been around a lot over the years - have you crossed paths with Albert Von Schweikert and if so, have you any stories or such to tell about it? _________________ Det viktigaste är inte att förstå vad man upplever, utan att inse vad av det man upplever man inte förstår.
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-04-04 15:38 Ämne:
Nattlorden skrev:
Jacro skrev:
My goal with the front hemisphere woofer arrangement, is to still address the most significant modal characteristics of the room, and this can be accomplished in the frontal portion of the room, but one must think three dimensionally.
This requires placing woofers in an arrangement that is not only horizontal, x-axis, but also to diversify in the y and z-axis, with at least one woofer above the half-height point of the room. With this approach, one can substantially accomplish the modal control of woofers placed on each of the four walls, while still maintaining 100% frontal wavelaunch.
I'm stacking my woofers in the front coners - floor to ceiling. Does this conform, or would you also say I'd need some inbetween?
And what's your view about stereo vs. mono for (sub)woofers, say crossed at 80Hz?
And also something completely different - as I take it you've been around a lot over the years - have you crossed paths with Albert Von Schweikert and if so, have you any stories or such to tell about it?
Hello Night Lord,
Your arrangement of creating a line source of woofers in the front corners is an excellent approach that can work very well in many types of rooms. It is one of the best at providing both smooth response, due to a diversity line wave room interface, AND, great large signal capability due to corner re-enforcement.
It is unlikely, but if for some reason the shape, dimensions or rigidity of your room still results in non-uniform amplitude response, you may try adding one more woofer, placed midway on the front wall or midway on a sidewall, to further smooth the response, but in most rooms this would not be necessary with your configuration.
As an alternative, the Welti approach of placing 4 woofers on the floor, centered on each of the walls, can be transposed to the front wall, with a woofer centered on the floor, the sidewalls, and the ceiling, all pressed against the front wall.
In terms of maintaining stereo signals in the woofer systems operating below 80 Hz, it depends on room size, modal conditions, and program characteristics.
It is rare that recordings will contain audible separation below 80 Hz but one can generate “artificial” signals that may exhibit slight audibility under controlled conditions in very large rooms, but this does not translate to meaningful differences in the modal range in standard living rooms/studios because the modal nature of the room is to cause the reflected signals to act as a left/right channel-summing network.
My preferred system is to use full range main left and right channel loudspeakers (down to at least 50 Hz, preferably down to below 40 Hz) and have them maintain the separate, stereo, signals, while further incorporating a monophonic, multiple woofer system architecture as a shared bass system below 100 Hz.
Relative to Albert Von Schweikert, I only have a vague memory of him calling a number of years ago to ask me for advise about some patent issues and questions about planar magnetic/ribbon transducers. I have never met him, so I apologize for not having something more intriguing to convey.
All the best,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-04-04 19:09 Ämne:
paa skrev:
James, how do you manage to have all these different crossover frequencies and shared frequency ranges to sum at something close to phase coherence?
paa,
I believe I already addressed this in my previous answers, but maybe I wasn’t clear enough.
To summarize, first arrival phase is relevant to the extent it has summation effects on amplitude (either amplitude interaction with the main L/R loudspeaker and/or amplitude summation of the multiple woofers and modal interactions), but (assuming standard room size and crossover frequency well below the Schröeder frequency) the direct audibility of the phase of the direct sound from the woofer is not significant.
As I suggested, our hearing requires a couple of cycles before it can determine a sound's timbre and when operating below the Schröeder frequency and reflections are nearly instantaneous in becoming an integral part of the sound because the wavelengths are comparable to, or greater than, the room's dimensions.
It is difficult to understand intuitively, but the source of audible low frequency arrivals is dominated by the room itself, not the loudspeaker.
A useful analogy may be that of a bass reflex loudspeaker operating at the tuning frequency; the woofer has a direct output to the listener, but the sound heard by the listener is dominated by vent output due to the Helmholtz resonance transferring energy from the rear-side of the woofer diaphragm coupling through the resonant mode of the enclosure. The phase of these two sources is not ideal from the standpoint of the first arrival from the front side of the woofer diaphragm, but the vent dominates in a manner that overrides the direct sound of the woofer, making the phase relationship insignificant.
Similarly, below the Schröeder frequency the woofer output drives the modes of the room and the modal output of the room is the dominant arrival perceived by the ear-brain.
Again, the phase plays a role in this case, but the significance of the phase is its affect on amplitude. If you hear any anomaly related to the phase relationships not being ideal, in the normal sense, that anomaly is an amplitude error caused by the phase relationship, not the audibility of the phase error itself.
The above is not a perfect analogy, but possibly it provides a useful example of another system that has a dominant source that has an ‘indirect’ relationship to the woofer output reaching the listener.
All of this is why I started my first answer with this statement:
“The nature of sound sources when operating in the modal frequency region seems to be an issue of great confusion. It is fundamentally different than how systems operate, and what parameters are important, above the Schroeder frequency.”
The rules we are used to applying above the Schröeder frequency are not necessarily valid below the Schröeder frequency. It takes a lot of effort to sort these things out, partially because the belief systems we have established from rules that we apply to certain aspects of audio and therefore assume that we can intuitively transfer those rules to all other aspects of the system.
Also, as I stated previously, if one ‘decouples’ the woofers from the modal conditions of the room, such as using high directivity or near-field woofers, then the rules that apply above the Schroeder frequency can still have validity, but these two approaches are not usually applied.
Any clearer?
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Such low crossover frequency as 40-50hz puts large demands on the main to be able to move substantial amount of air.
Don´t you see the advantage of having the larger woofers operate up to 80-100hz as that definetly makes things easier for the mains who can concentrate on upper bass and above? Why put that extra stress on them? _________________
Naqref skrev:
Gör man det dessutom för att torpedera tråden kommer vi hem en mörk natt och installerar Windows ME på alla dina datorer.
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-04-04 22:14 Ämne:
MagnusÖstberg skrev:
Hi James!
Such low crossover frequency as 40-50hz puts large demands on the main to be able to move substantial amount of air.
Don´t you see the advantage of having the larger woofers operate up to 80-100hz as that definetly makes things easier for the mains who can concentrate on upper bass and above? Why put that extra stress on them?
Hi MagnusÖstberg,
I agree with you.
What I had stated it previously, but I forgot to mention again in the last post, is that I always "shelf down" my mains by approximately 6 to 12 dB to reduce the load on the main loudspeakers, but keep them active at that reduced level from 80 or 100 Hz down to their lower limit, to provide a more effective integration with the subwoofers and to create a greater number of diverse sources of bass in the room for further improvements in smoothness.
The greater the number of subwoofers that are added, the greater the amount of LF amplitude reduction can be applied to the mains, reducing their output requirements.
Make sense?
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Oct 29, 2003 Inlägg: 33943 Från: Grå Hamnarna
Skrivet: 2011-04-05 13:34 Ämne:
James, thank you very much your reply. _________________ Det viktigaste är inte att förstå vad man upplever, utan att inse vad av det man upplever man inte förstår.
Such low crossover frequency as 40-50hz puts large demands on the main to be able to move substantial amount of air.
Don´t you see the advantage of having the larger woofers operate up to 80-100hz as that definetly makes things easier for the mains who can concentrate on upper bass and above? Why put that extra stress on them?
Hi MagnusÖstberg,
I agree with you.
What I had stated it previously, but I forgot to mention again in the last post, is that I always "shelf down" my mains by approximately 6 to 12 dB to reduce the load on the main loudspeakers, but keep them active at that reduced level from 80 or 100 Hz down to their lower limit, to provide a more effective integration with the subwoofers and to create a greater number of diverse sources of bass in the room for further improvements in smoothness.
The greater the number of subwoofers that are added, the greater the amount of LF amplitude reduction can be applied to the mains, reducing their output requirements.
Make sense?
- James
Hi!
I must admit I don´t fully understand the meaning of extending the mains further down than 70-100hz, as they still will give some output down to around 50-70hz, even using a 5th order acoustic roll-off. This still means that the bassmodules can be placed fairly free from the mains because of the long wavelenght without compromissing.
I would say that the greater numbers of subwoofers used we will get greater LF amplitude reduction in the subwoofer range, thus increased headroom in the bass range. And ofcourse the acoustic advantage one can achive using multiple woofers spread out. But there will be no reduction in stress for the mains using my way, that is true.
However, I like the idea of letting more stress off the mains. This will however, as I see it, result in special demands om both filter and woofers. Let us play with the thought of gradually reduce the main output under 300hz with 6db/octav down to 75hz where they start rolling-off with 30dB/octav. This would mean that the woofers would have to be able to play up to +600hz - and placement would be more critical.
All in all, I think this route is too complex and will not give bennefit in comparison with the eefort put in. Better to make sure the main can handle all the output you need as long as they are cut crossed over acustically with 5th order around 70-90hz.
What is your thoughts around this?
Best regads
Magnus _________________
Naqref skrev:
Gör man det dessutom för att torpedera tråden kommer vi hem en mörk natt och installerar Windows ME på alla dina datorer.
Blev Medlem: Jun 29, 2003 Inlägg: 14558 Från: helsefyr
Skrivet: 2011-04-05 18:40 Ämne:
jacro skrev:
2) using a near field woofer close to the listening seat, such that the dominant arrival is the direct arrival from the woofer itself (this is a superior technique not commonly used in the industry as of yet. I believe this approach is ahead of its time and will become a standard in another 5 to 10 years. We have developed systems using this approach that consistently outperform all other approaches)
i'm surprised none haven't commented the above, i'm not sure i understand the meaning of it but it sounds to me like the subwoofer placement in early home cinema setups, like coffee table subwoofers, i'm sure this is not what you're saying? _________________ Fuck off
Blev Medlem: Oct 29, 2003 Inlägg: 33943 Från: Grå Hamnarna
Skrivet: 2011-04-05 18:50 Ämne:
I did think that was what he was saying.... but envisioned element facing listeners, not down as in most of those coffee-table subwoofers.
( And I've begun thinking if this placement wouldn't work fine for a couple of subs for my home theater setup (note for James - not the system described above, the tv/home theater room is a much smaller one upstairs) ) _________________ Det viktigaste är inte att förstå vad man upplever, utan att inse vad av det man upplever man inte förstår.
I wonder if this concept is similar to the products called "basstöd" by ino?
paa,
I am not familiar with "basstöd".
Can you explain the concept?
Thank you,
- James
Basstöd may be translated to: "Bass Support".
It's a subwoofer connected with a special crossover together with the main speaker, and it may also have a more powerful driver than the main speaker bass driver.
However, I do not know all the details, maybe someone who know more can fill in the gaps.
2) using a near field woofer close to the listening seat, such that the dominant arrival is the direct arrival from the woofer itself (this is a superior technique not commonly used in the industry as of yet. I believe this approach is ahead of its time and will become a standard in another 5 to 10 years. We have developed systems using this approach that consistently outperform all other approaches)
i'm surprised none haven't commented the above, i'm not sure i understand the meaning of it but it sounds to me like the subwoofer placement in early home cinema setups, like coffee table subwoofers, i'm sure this is not what you're saying?
I'm wondering if a listener moving relative to the closely placed subwoofer would upset the balance of the percieved frequency response.
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-04-05 19:41 Ämne: It was great chatting with all of you...
Okay Gentlemen,
It appears that there are no more questions.
I just wanted to say that I enjoyed interacting with you.
If there is anything more that you wish to discuss or if you feel there is another area in the forum that you would like me to participate in, please let me know.
All the best,
- James
PS - Also, if I missed anyone's question, I apologize. If there is something remaining unanswered, please let me know and I'll do my best to provide an answer. _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Senast ändrad av Jacro den 2011-04-23 23:55, ändrad totalt 1 gång.
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-04-05 20:26 Ämne:
paa skrev:
celef skrev:
jacro skrev:
2) using a near field woofer close to the listening seat, such that the dominant arrival is the direct arrival from the woofer itself (this is a superior technique not commonly used in the industry as of yet. I believe this approach is ahead of its time and will become a standard in another 5 to 10 years. We have developed systems using this approach that consistently outperform all other approaches)
i'm surprised none haven't commented the above, i'm not sure i understand the meaning of it but it sounds to me like the subwoofer placement in early home cinema setups, like coffee table subwoofers, i'm sure this is not what you're saying?
I'm wondering if a listener moving relative to the closely placed subwoofer would upset the balance of the percieved frequency response.
paa,
That is a very good observation.
This one of the aspects that must be properly coordinated with the specific system conditions. It is rather complex to generalize in short discussion, but if one mounts the woofer close enough to the listener that it is within the theoretical "near-field" condition, then inverse-square-law does not apply and the system is not particularly sensitive to movement of the listener's head.
If one places the woofer somewhat farther away, just outside of the theoretical "near-field", then the head movement will not approach a great enough change in distance to significantly alter level, even when inverse-square-law is in effect, due to the ratio of head movement to total distance being quite small.
[[As you may know, “near field” is used as a general term in audio, meaning listening close to a sound source, such that the direct sound to reflected sound ratio is substantially elevated to the point that the environmental effects are minimal. This general version of ‘near field’ should actually have a different name, such as ‘close field’ or ‘direct field’ listening.
“Near-field” is actually a specifically defined acoustical term that is based the precise relationship of the dimensions of the emission source and frequency/wavelength. In the true “near-field”, the sound field maintains greater directivity and more consistent output vs. distance, than it does in the “far-field”.]]
When properly set up, this change in head movement will have an insignificant effect, but the advantages relative to elimination of modal effects will be quite impressive. Many consider the sonic effect on their systems to be quite transformational while substantially obviating the need for multiple subwoofers.
Of course, this approach is less satisfying for listening while wandering around the room, but for specified seated listening for up to 3 or 4 people, it can be quite effective.
Cheers,
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-04-11 19:50 Ämne:
MagnusÖstberg skrev:
Jacro skrev:
MagnusÖstberg skrev:
Hi James!
Such low crossover frequency as 40-50hz puts large demands on the main to be able to move substantial amount of air.
Don´t you see the advantage of having the larger woofers operate up to 80-100hz as that definetly makes things easier for the mains who can concentrate on upper bass and above? Why put that extra stress on them?
Hi MagnusÖstberg,
I agree with you.
What I had stated it previously, but I forgot to mention again in the last post, is that I always "shelf down" my mains by approximately 6 to 12 dB to reduce the load on the main loudspeakers, but keep them active at that reduced level from 80 or 100 Hz down to their lower limit, to provide a more effective integration with the subwoofers and to create a greater number of diverse sources of bass in the room for further improvements in smoothness.
The greater the number of subwoofers that are added, the greater the amount of LF amplitude reduction can be applied to the mains, reducing their output requirements.
Make sense?
- James
Hi!
I must admit I don´t fully understand the meaning of extending the mains further down than 70-100hz, as they still will give some output down to around 50-70hz, even using a 5th order acoustic roll-off. This still means that the bassmodules can be placed fairly free from the mains because of the long wavelenght without compromissing.
I would say that the greater numbers of subwoofers used we will get greater LF amplitude reduction in the subwoofer range, thus increased headroom in the bass range. And ofcourse the acoustic advantage one can achive using multiple woofers spread out. But there will be no reduction in stress for the mains using my way, that is true.
However, I like the idea of letting more stress off the mains. This will however, as I see it, result in special demands om both filter and woofers. Let us play with the thought of gradually reduce the main output under 300hz with 6db/octav down to 75hz where they start rolling-off with 30dB/octav. This would mean that the woofers would have to be able to play up to +600hz - and placement would be more critical.
All in all, I think this route is too complex and will not give bennefit in comparison with the eefort put in. Better to make sure the main can handle all the output you need as long as they are cut crossed over acustically with 5th order around 70-90hz.
What is your thoughts around this?
Best regads
Magnus
Magnus,
I agree, that IF your main left/right loudspeakers cannot handle low frequencies without distortion, then the approach I am suggesting will not work properly. In the case of weak main loudspeakers I would recommend a few other approaches.
But, if your main loudspeakers are capable of full system output with low distortion down to 40 or 50 Hz (with frequencies below 100 Hz shelved down by at least 6 dB) then the room modes can be smoothed by using only one or two subwoofers and the sound quality will be very good.
If the main loudspeakers are weak at low frequencies and must be high passed at higher frequencies then 4 subwoofers carefully placed will usually be necessary.
Each approach has tradeoffs, but I prefer to have my trade-off be one of "quantity", not "quality". I can always improve "quantity" of output by incorporating mains or subwoofers that have higher output capability, but improving the sound "quality" of the final result is more difficult and requires specialized efforts.
I believe the complexity is reasonable, particularly since the improvement in quality is significant.
I hope this makes sense.
Let me know if I am still not addressing your question in the manner you are looking for.
- James _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
James, would you think the HOM reduction foam also works as an acoustic lens that further smothes the dispersion whithin the desired coverage angle?
Interesting idea.
The current goal of applying foam to a waveguide to reduce HOMs is to be able to maintain consistent absorption such that directivity is not changed from the ideal directivity of the waveguide. Correctly applied, directivity does not change when the foam is applied.
Attempting to use the foam to change directivity does add a degree of complexity that may be difficult to fully characterize. As one changes absorption rates, it must be achieved in a manner that the absorption discontinuities don't increase HOMs, simulating diffractive effects.
That said, the concept of using the foam to alter directivity while reducing HOMs may be a very good idea. The ability to provide an addition variable to control directivity in waveguides may allow one to relax the directivity capability of a waveguide in order to achieve an improvement of some other parameter (such as efficiency, or bandwidth, etc.), and then re-optimize the directivity with a variable density foam insert.
Definitely worth exploring.
- James
I believe that acoustical transparent foam (now often called "filter foam") was claimed to behave like an acoustical lens, expanding the directivety of narrow beaming tweeters, when it was introduced in the seventies. To what extent that really worked I have no idea.
Blev Medlem: Aug 16, 2009 Inlägg: 99 Från: Seattle, Washington USA
Skrivet: 2011-04-24 00:01 Ämne: It was great chatting with you...
Okay Gentlemen,
It appears that there are no more questions.
I just wanted to say that I enjoyed interacting with you.
If there is anything more that you wish to discuss or if you feel there is another area in the forum that you would like me to participate in, please let me know.
All the best,
- James
PS - Also, if I missed anyone's question, I apologize. If there is something remaining unanswered, please let me know and I'll do my best to provide an answer. _________________ Founder/Director Definitive Audio
Developer of ( the clue ) for SJÖFN Hi-Fi
Owner Croft Acoustical
Hello James, I hope you still visit faktiskt every now and then.
I´ve been living with (the clue) now for about a month and I just want to say a few words about them. They are not good or very good but utterly brilliant!
I bought them unheard and now I can´t stop listening to them.
thanks!!
Blev Medlem: Jun 29, 2003 Inlägg: 14558 Från: helsefyr
Skrivet: 2011-08-07 19:14 Ämne:
jeppe, berätta gärna hur du gjorde för att komma över ett par! och vad fick dig att köpa olyssnat? beställde fredrik ett par oxå? _________________ Fuck off
Blev Medlem: Jun 29, 2003 Inlägg: 14558 Från: helsefyr
Skrivet: 2011-08-07 20:22 Ämne:
tack för svar! nyfiken som jag är: köpte du högtalarna på grund av skriverierna här eller skriverier någon annanstans, typ i hifimagasin eller andra internetforum? _________________ Fuck off
hmm, ja olika forum och recensioner stärkte köpbeslutet sen var det mycket hur konstruktören kan förklara varje aspekt av konstruktionen och tänket bakom lösningarna.
Blev Medlem: Oct 29, 2003 Inlägg: 33943 Från: Grå Hamnarna
Skrivet: 2011-08-08 06:09 Ämne:
jeppe skrev:
hmm, ja olika forum och recensioner stärkte köpbeslutet sen var det mycket hur konstruktören kan förklara varje aspekt av konstruktionen och tänket bakom lösningarna.
_________________ Det viktigaste är inte att förstå vad man upplever, utan att inse vad av det man upplever man inte förstår.
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