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Dipole speakers, subwoofers and that rear wall

I own modern quad dipole speakers (2912s). I’ve heard many stories about speaker position, but never something that rang as fully logical to me. I can imagine 3 choices:

 

1/ dipole pretty much against the wall, maybe slight toe-in. The reflecting sound will come quickly after the straight sound and might cancel out the direct wave

2/ dipole far from corner (I hear quad recommends 1.5m). Reflections will amplify the sound?

Both statements feel like they’re incomplete. Surely the frequency, or frequencieS being played matter a lot if the reflected sound is in phase (amplifies) or in antiphase (attenuates) the direct sound. I can imagine perfecting positioning for one frequency and its modes, but not for 20-20,000 hz full spectrum.

 

3/ Close the rear of the dipole or have sound-absorbing material behind the speaker

The third one seems somewhat more logical, since I can’t imagine a sinewave that’s being attenuated by a reflected wave being accurately-sine-y unless the reflection is exactly in counterphase with the frequency played.

But on the other hand, if I have an actual instrument that is somewhat reminiscent of an actual dipole (e.g. a snare drum pointing upward) will have similar reflections on the rear wall.

 

I guess it "feels" true that you don’t want to stuff a musician in a corner too much but I’m not sure if this will negatively impact his sound?

 

As for the second part, a proper subwoofer moves quite a bit of air, can that air damage a dipole eletrostatic speaker?

puntloos

Showing 4 responses by audition__audio

audition__audio
1,342 posts
 

This is the main problem with dipoles. My suggestion is do everything possible to cancel or diffuse that rear wave. Bring the speakers out into the room as much as possible and then put something behind the speakers to deal with the rear wave. The rear wave is the problem and you cant possibly bring the entire bandwidth of reflected sound into proper phase. 

You dont want your speaker doing anything other than reproducing what it is fed as accurately as possible. So the shape of an instrument should nothing to do with the shape of the transducer reproducing it. This is why I always get irritated when speaker manufacturers talk about making their cabinets out of the same material as instruments.

Dont worry about subwoofers and damage. Just be sure to cross your subwoofers over at the lowest frequency possible. Probably around 40 to 55 hz.

audition__audio
1,342 posts
 

The rear wave is not what these speakers are all about it is just, with most designs, a necessary evil. What you should try to do is minimize the downside to dipoles and then attempt to make them as accurate as possible. Listen to Duke's advice from Audiokinesis. Other than the obvious limitations of my Quads the only downside to this speaker is the rear wave and it must be dealt with. 

audition__audio
1,342 posts
 

I wouldnt dampen I would diffuse. You should be O.K. if you are at least 3 feet from the diffusors.

audition__audio
1,342 posts
 

If you are using a diffusor you must understand that a true diffusor is based on mathematical properties and not random variations in a surface. Not saying that these arent true diffusors but you have to be careful. My diffusors were made by RPG and came from a speaker designer/manufacturer who no longer needed them. 

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