You don't wall sound directly behind you bouncing back at your head. Directly behind I use absorption and then to the L and R I use 3D diffusors, maybe try either of these:
https://auralex.com/tfusor-3d-sound-diffusor/
or
Question: Sound Treatment behind the Listener?
I have treated the 1st and 2nd reflection points and I have sound panels between my speakers. I also have tube traps in all 4 corners, but I am not sure what (if any) should be done with the wall behind the listener.
That wall presently has a DIY rack system that holds about 5000-6000 cd’s. I believe it helps scatter the sound. But I’m not sure if that is the right approach.
So, what are you guys using on that wall? Diffusion, Absorbtion, Reflection? Anything else?
I would appreciate your thoughts.
ozzy
