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Old 16th October 2011, 12:29 PM   #1
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Default ESL in a transmission line?

I have read up on transmission lines and was wondering if its possible to use an electrostatic panel in a transmission line?
I tried to google it but didnt find any information on this.
I was thinking of a design like this:
It will be roughly 30x30x140cm, placed on my desk 50cm away from my head.
The ESL panel will be 20x20cm
What are your opinions on this design?
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Alternatively:
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Last edited by andrelim; 16th October 2011 at 12:45 PM.
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Old 17th October 2011, 06:36 AM   #2
Calvin is offline Calvin  Germany
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Hi,

itīs just one of the advantages of ESLs.....it dosenīt need a casing to pimp its performance to acceptable quality. Still though a ESL is no good bass in first place. Too many problems with decreasing frequency and increasing excursion demand.
If put into a casing the same physics apply to ESL panels as applys to dynamic drivers. Results are increasing Fs and increasing Qt. Especially the first will rise way too high. A transmissionline, in its true technical sense, not the resonator-style line as usually appears in praxis, could be of use. But this would mean a very large and deep casing, similar to what B&W showed in their Nautilus prototype. And You wouldnīt want reflecting surfaces behind the membrane as in the TL-sketches of Yours, since the ESL membrane is acoustically transparent.

>I have read up on transmission lines and was wondering if its possible to use an electrostatic panel in a transmission line?<
A: Yes, possible in principle and praxis, but it means just a lot of effort without appropriate yield.

>What are your opinions on this design?<
A: Lots of effort for inferior output compared to an openbaffle ESL.

jauu
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Old 17th October 2011, 07:40 AM   #3
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I was thinking of using a transmission line because I don't have much space, so my speaker will be right up against a wall.
Are there any other methods to have an ESL near a wall without the out of phase signal being reflected?
And is this any better?
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Old 17th October 2011, 08:20 AM   #4
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An ESL membrane has only a very small pk-pk excursion, so they are normally used in large panel sizes. Simply using a small ESL to replace the drive unit in a transmission line would not provide any advantages. The limited excursion would simply mean that your LF output would be very low.
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Old 17th October 2011, 12:10 PM   #5
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Ok, thanks for your reply.
Is there any way to have an ESL placed near a wall without the out of phase signals being reflected?
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Old 17th October 2011, 01:10 PM   #6
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Quote:
Originally Posted by andrelim View Post
Ok, thanks for your reply.
Is there any way to have an ESL placed near a wall without the out of phase signals being reflected?
The worst situation would be a parallel wall behind the speaker bouncing the backwaves back into the diaphragm. Another bad situation would be having a speaker in a corner where the backwaves do bank shots off the sidewall and backwall, sending early reflections to the listener. I'm thinking it's OK to have the speaker close to a wall provided the angle doesn't bounce sound back to the diaphragm and there are no adjacent walls close enough to bounce any early reflections to the listener. It's the early reflections that create phasing problems and muddle imaging; whereas, the brain tends to ignore the later arriving reflections.

I've also read that placing a curved reflector behind the speaker to disperse the backwaves can be effective in neutralizing the effects of too-close walls-- if it's positioned and angled just right.

I use a beam splitter behind my panels, which allows me to place the speakers very close to the back wall.. Still, I wouldn't place my speakers in a corner, for the reasons explained above.

Last edited by CharlieM; 17th October 2011 at 01:26 PM.
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Old 17th October 2011, 02:38 PM   #7
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Darn, my speakers will be placed in this recessed portion of my room. Roughly 1.8m wide and 25cm deep. The reflections will probably wreck havoc with the sound. And i don't have anywhere else to place them either.
So should i try making electrostatic headphones instead?
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Old 17th October 2011, 03:23 PM   #8
Calvin is offline Calvin  Germany
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Hi,

ESL-headphones are sure a fine thing ;-)
As CharlieM already said it is important to treat the backside soundwaves right. You need to avoid, that reflected backwaves arrive at the ear too early after the directly send waves. Instead highly diffused scattered backwaves with rather long delay are demanded. Reflectors, guides and damping may help. See Charlieīs beam splitter, which is basically of a simply V-style crossection. You may use other crossectional shapes like a half-cylinder or similar instead....just prevent direct reflections back through the membrane.

jauuu
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Old 17th October 2011, 03:26 PM   #9
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You can try treating the wall behind them for high frequency absorbtion and refelctions this will help.
Maybe with some with egg crate style foam or other suitable materials.
This worked well when I had my Apogee Duette's setup.

jer
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Old 17th October 2011, 03:37 PM   #10
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Quote:
Originally Posted by CharlieM View Post
I use a beam splitter behind my panels, which allows me to place the speakers very close to the back wall.. Still, I wouldn't place my speakers in a corner, for the reasons explained above.
Actually I have positioned my Acoustat 0ne plus 0nes directly int the room corners as tightly as the base would allow. It might seem counter intuitive but when you fire the panel into a corner there is no reflection back into the panel as it rear wave loads into the corner and shoots out along the side walls.
With the panel parallel to a flat wall yes lots of cancelation problems but not into a corner. Best regards Moray James.
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