Dipole speaker wall treatment (for Quad, Magnepan, Martin-Logan, etc)
Next year I will relocate and create a dedicated listening room, and want to get the design right.
I have read two books on acoustics, scoured online forums and articles, and checked several websites of manufacturers (RPG, Real Traps, A/V Room Service, etc) finding mountains of information on acoustical treatment for conventional box speakers. But I have not found one bit of information regarding how to treat the wall BEHIND dipole ESL's.
The manual for my Quad 2905's merely suggests setting the units at least two feet away from that wall, with 5~20 degrees of toe-in.
Quad-hifi.UK informed me only that their engineers treat their test room front wall with the same egg-shaped foam used in their box speakers (!) - but did not suggest that for everyday listening - and steered me to yet another acoustical engineering book. (I suppose I could purchase a bunch of Quad box speakers and rip out the foam, but that solution seems a bit, ah, over-refined.)
Understanding that much of dipole spaciousness results from the the out-of-phase back-wave reflecting from the wall, I would not want to deaden that reflection too much. Nor would I expect wall treatment to improve imaging, but I don't want to further blur it. (Current setup is three feet from a brittle plaster wall built in 1913, and imaging is vague.)
I'm hoping some of you dipole owners can share results from experimentation with various wall treatments that absorb, reflect or diffuse that back-wave.
Thanks for any input.