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fperra 22nd January 2013 06:43 PM

I'm thinking of a new ELS/Hybrid Design
My last build was a large, two way, bi-amp'd design what sounds absolutely wonderful and can play down to 50HZ. If you didn't follow the build thread, it can be found here:

The problem I'm having is that they are so large that my subwoofers that I recently built can only fit in the room in out of the way locations and I would to have the subs right next to my main speakers. Here are some pics of the subs:

So I'm planning on building a new line source speaker set using 9 TB W5-704D speakers per side crossed over at about 500 HZ to a 60"X3.5" Electrostatic to cover the rest of the frequency range. This design will be a lot slimmer than by current speakers and will allow the subs to fit beside them.

One question I have for all you experts is that I'm thinking about mounting the ELS's in a closed back cabinet about 12 inches deep and stuffed BAF to absorb the rear waves. Does anyone have any experience or thoughts on this?

Bazukaz 22nd January 2013 09:53 PM


ESLs are very transparent to any box coloration and stuffing may not be a good solution either. Tried square open baffles in the past. "Wings" are sometimes made from a half cut PVC pipe to improve bass response, or some form of flat baffle.
With a closed box in addition to standing waves you will get low output; air compliance inside the box is too high for this kind of transducer to work well.
Your target of 500Hz is easy to achieve with a dipole element having width of ~10 cm or so.
However a wider panel of 20 cm could do down to 200 hz or even lower, especially if you can handle a few db drop in midbass with some form of equalization.That could significantly simplify integration.


geraldfryjr 22nd January 2013 10:10 PM

I have tried to do this with my Little panels and I have found the results to be sub par.
It seemed that they had lost there high end finesse and detail when anything comes too close to the diaphragm by as much even 10".

I was using some very thick fiberglass wall insulation.
I am not sure if it was the reflected back wave that caused cancellations or the added back pressure that overdamped the diaphragm that caused the effect.

It sounded okay as the frequency's were still there but they just sound dull and lifeless and lacking detail,Airyness if you will.

I did find however find that by just increasing the path around the panel (wings) worked well to increased the lower end output a bit without any (or little) degradation of detail.
By doing some simulations I have found that this can be good by as much as 2db to 3db at 300hz and below or so just by doubling or tripling the front to back path length.

I had some pictures of this and documented it in another thread but they had got deleted.
A very large section of that thread had gotten wiped out for some unknown reason?!!!

In my new build I am going to experiment with a electrically segmented stator using the same 3.5" wide diaphragm and a 5" frame width.
It is just 10" high but I do plan on making a 18" and 36" long models to compare as well using the same dimensions.
All I have left to do is glue on the diaphragm only I have been busy with other projects as well.

The taller models will be paired with a single 8" sub or two.
In the simulations it matches well with a 18" version but a taller one may be better for a line source type of driver.

In the end I am looking to make a 6' or 8' model of the system possibly increasing the width to about 6" for more output in the 200Hz to 300Hz range and electrically segmented to give a better horizontal dispersion.
This will also create a nicer load for the amplifier.

The complete details of my new build with Horizontal and vertical dispersion simulations can be found here,

A Segmented Stator Desktop ESL

It will be interesting to find out how close the simulations are.


jer :)

fperra 22nd January 2013 11:47 PM

Weren't Beveridge ELS's closed back? I never heard them but the people I know who did thought they sounded fabulous.

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