Question: Sound Treatment behind the Listener?

That youtube vid posted earlier is excellent. I'm thinking about ordering  2D / GIK polys to put next to (new and larger) GIK 242 panels on my side walls. 

I just need to take a smidge of treble energy out of the room - not much but some - well quite a bit for some recordings but none to very little on others. Resisting buying an EQ.

Well, I submitted the form to GIK. Before being able to submit the form, I must say the constant need for showing that I am not a robot is annoying. Especially so for the GIK website. Why is that necessary?

ozzy

I ended up going with GIK 6A Alpha diffusor/absorbers to go behind my listening position. Granted, my room constraints necessitated something that would work relatively nearfield which these do. Highly recommend these.

There is a rule-of-thumb (a formula in acoustical engineering terms) for how far one must be from the wall behind the listening position when using diffusion rather than absorption. I didn’t bother to memorize it, as it told me I couldn’t use diffusion on that wall, my currently situation requiring me to sit too close to be able to do so. I'll bet a Google search will lead one to the answer.

With approximately 8' behind you to the wall, the sound level is only attenuating 3.52dB, plus whatever the absorption coefficient of the building materials (ie CD cases are which is probably very low), and another 3.52dB attenuation on the reflection. I do not believe that is near enough. I would be shooting for no less than 10dB if not 15dB. The only options are increasing the distance (which is probably not an option), or adding sound absorption material0, which can achieve that.