room treatment

Just wondering if anyone has used these or heard them in use. Actively absorb sound 20-150hz to prevent or reduce uneven bass response. http://www.psiaudio.com/en/our-products/avaa-c20/ http://www.soundonsound.com/reviews/psi-audio-avaa-c20...

I haven't finished reading the journal article yet but this thread started by Scott Wilkinson over at AVS caught my eye: http://www.avsforum.com/forum/91-audio-theory-setup-chat/2876001-metasurface-schroeder-diffuser-10-times-thinner-than-usual.html Essentially a method of using modified...