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Taming/Damping Electrostat Backwave

In my understanding of the physics of the situation, the signal coming off the back of an electrostat panel is the same signal that comes off the front though in opposite phase. If there are reflections off a back wall, they cannot be a better signal than the one off the front of the panel. It strikes me that in a strict sense, if one could COMPLETELY eliminate the backwave on electrostatic speakers (a giant silent sound vacuum, sucking in the sound off the back of the dipole), this would be, in the words of the once famous and now infamous [:)] Martha Stewart, 'a good thing'. Am I missing something? Is there any argument to support not trying to eliminate the backwave through all means possible?

My Martin Logan SL3s sound reasonably intolerable when too close to the back wall, great when a certain distance away, and in my limited, ad hoc, distinctly non-scientific (not to mention bad WAF) experiments, even better when I put a variety of dampening material between the panel and the back wall (even when the wall is 6ft back).

Does anyone have a view or experience on the "complete backwave elimination" strategy? Do you try to eliminate it entirely? Do you leave some backwave in for 'flavor'? How do you deal with it? Put shag carpeting on the wall? Hire tall sheepdogs to sit on stools calmly for hours on end a la Fay Ray? I would love to know how other people deal with the backwave issue...
t_bone
hififuchs's avatar
hififuchs
16 posts
 

Hi,

I am fully aware that this statement, copied from above, is very old :"Room Lenses work wonders behind 'stats." Despite that I wonder if any of you could share some more specific experience using/positioning room lenses behind/beside electrostatic speakers?

My Speakers are Martin Logan Aerius (not i). Since app. one year I have two DIY Room Lenses standing behind my speakers. My room does not allow placing one room lens in the middle between the speakers.

What are your experiences when it comes to distance behind the panels?

Do you angle (toe in or out) the room lenses?

I read somewhere that some people cover the lenses with foam/cloth to absorb some of the back waves. Any thoughts on that?

Any experience from you are highly appreciated. 

hififuchs's avatar
hififuchs
16 posts
 

No comments to my above tweed concerning DIY Argent Room Lenses 😒 ? 

larryi
4,038 posts
 

Provided you have enough room to place the panels away from the back wall, the backwards radiation is a feature, not a problem with such speakers.  The out of phase signal cancels to the side a bit, given that bass waves wrap around "small" objects like a speaker.  The rest of that back wave bounces off the walls and gives the impression of a bigger soundfield.  Yes, there will be some cancellation and reinforcement from soundwaves interacting, but, that is the case with front-firing speakers too, once the sound starts bouncing off all the various surfaces in a room.  If the panel is at least five feet from the back wall, its reflection off the back wall will be delayed enough that your ear/brain will separate it from the direct sound of the front wave and it will be perceived as a reverberation and will not mess up what you hear from the direct sound.  

Don't bother with trying to supress the back wave.  Make the effort to place the speaker where it will sound its best which might mean trying to delay the reflection back to your listening position for as long as possible (meaning keeping the speaker as far from the wall behind it as possible and perhaps having enough randomness in the surfaces behind the speaker (bookshelves, potted plants, wall hangings, etc.).

mapman's avatar
mapman
22,311 posts
 

@larryi +1

erik_squires
16,142 posts
 

@audiokinesis  is right on about primarily needing diffusion though perhaps combination diffusers/absorbers could be considered.

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