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Old 26th November 2007, 05:38 AM   #1
jerko is offline jerko  United States
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Default An idea for a wide dispersion ESL

I'm new to ESLs, so I'm not sure if someone has done this before, but I have an idea for an ESL that would have good dispersion characteristics.

The wavelength of a 20 kHz sound wave at sea level is about 1.7 cm, so the idea is to have the stator broken up into multiple rings which are each about that half that wide (or whatever gives the desired dispersion pattern). The signal sent to each ring would be delayed by the time it takes sound from the center of the panel to get to that ring (digitally delayed, before it is ever amplified) and then sent to separate amplifiers (one for each ring).

I know the Quad ESL had something like this (except without separate amps), but my understanding is that the delays and the rings were spaced too far apart to give good dispersion at high frequencies.

I know it could work, but I am not sure about the various factors that would possibly need to be worked out (and I would like to hear if anyone has tried to). For instance, each ring needs an amp, so for a reasonably sized panel this could get expensive quickly, and each ring needing its own transformer just compounds the problem. Is it possible to make a class-D amp that would put out the voltage necessary for an ESL without having to use a transformer?

Another problem is what to make the stators out of. Printed circuit boards seem to be almost ideal, but getting a large one made is prohibitively expensive. I'm really at a loss on this question.

I'm sure there are plenty of other things I am not thinking of, so please let me know what those are too.
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Old 26th November 2007, 06:02 AM   #2
wrl is offline wrl  United States
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Just a random question. I've seen a lot of these posts now about creating ESLs with wider dispersion patterns. I'm wondering if achieving greater dispersion can be accomplished without losing some of the imaging or intangible qualities of ESLs in the sweet spot.

From my experience, martin logans and such don't sound quite as dynamic in the sweet spot as planer ESLs. A wide dispersion ESL to me sounds good in theory, but I feel like there has to be a compromise in something in order to achieve this.

-Wes
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Old 26th November 2007, 06:39 AM   #3
jerko is offline jerko  United States
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The reason why I want dispersion (and the only reason I can think of to want it) is to have a larger sweet spot.

The original idea was to make an array of small electrodes on the stator with lots of pre-processing before the amps (one amp for each little electrode) so that the speaker could reproduce each source of sound between the far left and far right with a spherical pattern. Such a speaker would be wall sized and expensive beyond belief, but would, when coupled with an appropriate sub, be essentially ideal and have a huge sweet spot.

Since almost all recordings are stereo, I decided it would be good enough to try to reproduce two point sources rather than hundreds.
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Old 26th November 2007, 07:58 AM   #4
Calvin is offline Calvin  Germany
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Hi,

as wrl pointed out, optimizing one parameter will effect another parameter in the quite opposite direction. Unsegmented panels sound more dynamic in the mid-highs than segmented ones. Curved panels and planar panels (only unsegmented ones!) sound basically the same, since the claimed wider dispersion doesnīt really happen in praxis.
The problem with small rings or strips is, that they represent a very high impedance, which has to be transformed with much larger transformation factors. Everybody skilled in building transformers knows that high transformation factors always(!) cost on bandwidth and dynamics. Unsegmented designs can work with factors down to 1:50 (often 1:75), segmented panels maybe down to 80 (often 1:100)
The older Quads worked with up to 1:270. Besides the problems of getting Your hands on such a transformer, itīll be no doubt worse than a simpler tranny with a small transformation factor.
Besides the highimpedance prob such small rings or strips will suffer in efficiency. Think of reduced effective membrane area or increased and wasted capacitance (beneath the spacers).

I can only recommend -especially those newbies in ESL- to closely watch what the great names did....to understand why they did it the way they did and no other way. This alone will take You considerable time and maybe lead to the lesson, that those designs not only have their merits but can hardly be topped.
I still have to listen to a Quad I could like and I think that the concept has major flaws, but the engineering behind is straightforward and marvellous. Same is with MLs. Those are much more than some pieces of sheet metal and a film diaphragm.

jauu
Calvin

ps: hereīs a little task for You if You like: ;-)
The point source!
Is it the one and only distribution character?
Is it the best distribution character in my living room?
Can a different dispersion character be superior?
If so under which circumstances?
Which distribution character could that be?
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Old 26th November 2007, 10:16 AM   #5
el`Ol is offline el`Ol  Germany
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Thyratrons are cheap and can drive an ESL transformerless, but are too slow for Class D and too non-linear for other amps. KOON3876 works on a concept of array speakers where the single drivers are Class D driven, but not with full resolution, so only the array as a whole gives the full signal. You could ask him about his progress.
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Old 26th November 2007, 02:06 PM   #6
oshifis is offline oshifis  Hungary
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Does a curved panel give wider dispersion? If it does, the solution is simple. Quad, ML and others use this approach, I think.
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Old 26th November 2007, 05:17 PM   #7
jerko is offline jerko  United States
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First, no, curved panels don't have a wider dispersion. Or at least what I have heard says that they do not have a significantly higher dispersion.


Calvin,

I think I might not have been as clear as I would have liked. I did not mean that the diaphragm would be segmented. The stator electrodes are the only thing that would be rings. I don't think that your points hold when the diaphragm is large but the stator electrodes are in segments (the stator itself (the thing the electrodes are attached to) would not be segmented). I agree that all of your points hold true for the design you thought I was talking about though.
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Old 26th November 2007, 05:33 PM   #8
el`Ol is offline el`Ol  Germany
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What do you think about that?
http://www.freepatentsonline.com/20070242844.html
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Old 26th November 2007, 06:25 PM   #9
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Quote:
Originally posted by el`Ol
What do you think about that?
http://www.freepatentsonline.com/20070242844.html

Hi,

I remember that audiostatic had made a hybrid esl with the esl being dome-shaped. They discontinued its production. I have been told that this was because of production problems, no official source, so maybe because of another reason.
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Old 26th November 2007, 11:09 PM   #10
jerko is offline jerko  United States
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Yeah, that looks absolutely impossible to produce.
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