Question concerning electrostatics

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Hello, anyone can give me a advice, if possible my idea or not:

I am work on a procedure, aimed to restore the spatial soundfiled of the recording room physically by wfs-principle. This procedure needs a huge amount of single steered small Loudspeakers, build behind or as the screen wall. See the principle by that animations: field transformation.htm

My Question: For good reason I would need a field of 64x24 single steerable speakers, in summary 1536 pcs., each 2 inch broad and 3 inch high= 3,25x1,82 meters.
Would it like a good idea, to build such speakers wall from electrostats? It must work from 160...10000 Hz. Because of the good air resistance accomodation for the big plane only very small membrane movemennts would need. Would be possible to build a common front layer for all speakers? And such layer able in white reflecting color?

Sorry for the mistakes in english
Mein Gott, Helmut...

What an ambitious project!

I haven't read the whole "synthetic wave" document which may address this, but will you tell us what your budget is for this project, including processors, amplifiers and speakers? 1536 of any type of transducer/amp systems will be very expensive, as you must know.

Anyway, to answer your original question, RtR made some nice electrostatic elements back in the day that were roughly 3" x 6" with a radiating area about 2" x 5". These are the smallest commercial ESLs that I know of. Used in a big enough array with some eq, they probably could get down to your lower frequency limit.

If you ever get this thing built, please let me know---I would love to hear it!

Hello David,

you are right, I would need very rich early adapters for such an huge project. Unfortunately I am not among those, but I work on the topic. I assume, my ideas not far away from a promising attempt to restore the primary sound field physically.
Your answer encouraging my opinion, electrostats would be a possible solution for the transformers. You know what the maximal membran elevation by such electrostats? I am not very familiar by this kind of speakers, but i know it sounds good. It would be able to calculate the maximum SPL for given surface, frequency and and membran elevation.
Calvin wrote,
such a low separation frequency wouldn’t to be gotten with this small panels.

But we never should desert a new approach without a good reason. We must including into the though, all speakers are work together on low frequencies. Likely as on the horn speakers the air hasn’t the possibility, simple to evade to the sides and up and down, if the membrane takes the attempt to shift it in the listener’s direction. That gets a comparable efficiency. Let us ponder about before deserting the idea.

with ESLs there will be several major probs to consider.

If You use a box-kind compartement to deal with the acoustic energy of the panel´s backside it shouldlook different from that what is normally used with a dynamik speaker. Typically this compartement will build large and very deep. Even though You´ll face a problem with high sound pressures from the accompanying bass, that simply blows the diaphragm into the stators. A solution to this will be to use a FR-ESL, but this will lead to other -probabely even more severe- problems.

Using small panels (even in multi-multiples) won´t solve entirely the efficiency and bandwidth problems of too small panels.

A quite interesting idea of Mr. Walker (e.g presented in Ron Wagner´s book about Electrostats) was, to built a FR-ESL of wall to wall dimensions and room heigth. The complete ESL was segmented and each segment should be driven via a delay line. This way the 2 stereo channels could be fed from both sides into the system, generating two tilted wave fronts. Stereo imaging would such be possible at averey point within the listening room.
This system could be built of multitudes of tall and thin ESL-panels instead of one big system. Still though such a system consisting of FR-ESLs would suffer from lowefficiency and all te drawbacks of a FR-ESL.


ps: At least in theory the wave-field theory relys on reflectionless sound recordings. Does this render all life-performance recordings useless? ;-)

nice theory !

If you want to have something comparable, which can be realized with avaiable components - here is my proposal:

1. Place two tall but small ESL-Elements in a baffle as wide as possible
2. Put each baffle directly to the sidewalls and about 1,5 meters away form the frontwall.
3. Split the ESL-width in 9 small segments and drive them by delayed amplifiers.
4. Make the segmentation asymmetrical, means the non-delayed segment is the closest to the side-wall, the delay will increase towards the center of the room.

Whats the result technically ?

-The tall ESL-Element will provide a cylindrical wave down to 80 Hz, avoiding floor and ceiling reflections
- The small width of the Element will avoid interferences off axis
- The wide baffle will assist seperation of front- and backwaves by its physical dimension
- The delayed segments will improve horizontal dispersion
- The asymmetrical segmentation will avoid reflection to the sidewall and will improve radiation to the center of the room.

Whats the result acoustically ?

- You can sit near of far, left or right, sit or stand, the first wave front will be everywhere nearby the same and undisturbed

And whats about low frequency performance ?

- Realize a BPA, means a lot of distributed woofers placed at front and rear wall. Rear woofers will be delayed depending on room length.
The result is a room having "no rearwall" and in consequence having no standing waves.

Hi Calvin

Thanks for the advices; I see in other discussions, you are very familiar with the stuff. I haven’t considered in my thought before, the force which moves the ECL Membranes are very faint. That’s the subwoofer would blow the diagrapms it into the wall is a real problem. I am doesn’t know what’s a FR_ESL? My idea was not to build a separate cabinet for each speaker, only a strongly damped environment on the rear. Possibly small apertures in the front wall, too small for high frequencies, would equalize the pressure differences?
Mr. walkers Idea seems very interesting in my matter, is that the book?:

You must not ditching your records, the wfs has the ability to rendering conventionally produced material with an enlarged sweet spot. But if you want to restore the genuine sound field, you need the MPEG4 recordings.


Your thoughts are very similar those of my proposal. For my solution each speaker must headed by delaying signals. Many problems are solvable in that way by the steerable wave fronts. I have calculated the single membrane movements depending virtual source point for a 16*9 speaker matrix in an xls. Is old working material, includes some errors, but you can see the principle:

You can change coordinates and the virtually starting point of the wave fronts. Unfortunately the applied number of single speakers is too small for correct working concerning high frequencies.
Hello Capacity,

i have seen on your website your tall and beautiful ELS. I can imagine, the sound is much more clearly as from a undirected source, because the directed radiation in the elevation plain avoiding misguiding cues, caused by too early reflected wave fronts on ceyling and bottom. I have depict that problem for conventionally point sources:
Avoid this is one of the goal of my project. The second step is the attempt, to generate the reflection from the ceiling in correct time, frequency response and direction. Should that goal justify the effort?

Your new ELS works, assume on help of a DSP, down to 35 Hz, should that not been possible for my approach?
...but I hope you have not given up selecting the parts. That sounds much better as the degeneration in the industry amps, I know.

You want some links regarding practical build up WFS approaches. Until today all approaches are working by the horizontal loudspeaker rows. Leading Producer is IOSONO:
The plants mounted in some cinemas in Germany, the best known is the "Bavaria Filmstadt 4D- Erlebniskino":
But also by other universities work own produced the speaker rows. The largest on the TU Berlin has 2700 Loudspeakers (but only 832 Canals as far as I know):
A two dimensional Speaker field was build up by the university Tokyo in 1999, but it was consider as too expensive by this time. It was not the approach to recreate larger or smaller recording rooms by early reflections, which it was my idea.
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