Room Acoustics overkill or worse?


Would acoustically treating the ENTIRE back wall behind the speakers be overkill? This is mainly for aesthetic reasons. What I would like to do is to break up the back wall into 9 4’x3’x3” (WxHxD) modules and treat with Jon Risch’s design but flush with the wall. I have some questions regarding materials:

1. Can one substitute the fiberglass with poly bat entirely
2. Can anyone tell me if it’s a bad idea to use 1”, 40 grade foam sheet or a 1” coir sheet rather than the rockwool panel for the back.
3. Instead of burlap can I use raw silk. (wife’s suggestion)

For now I just have foam in different densities stacked behind the speaker (total thickness about 3”) and it made a huge difference. I also ‘stole’ 4 of my wife’s cushions and stuffed them with poly fill and have those in the corner which improved things even further. I would be happy if I got the same effect from the above design.

Thanks in advance for any comments/suggestions.
keroo1099
That sounds like a very lively room! As to the specific question, I can attest that too much treatment can degrade the sound. I moved my system into an untreated room with absolutely nothing on any wall or window. It was like an echo chamber in there. I purchased a room treatment kit from Auralex and went to work. The kit included more treatment pieces than my room required, as I had some DIY panels, but that didn't stop me from using them.
I would listen as I went along and it did get to a point where I was noticing a degradation in the sound from too much absorption. I removed some treatment until I got it correct, or what I thought sounded best. Some of what I removed was behind the speakers. A totally dead wall does sound like overkill to me but your ears will judge. Good luck and do post your system. I'd be interested to see the outcome.
thanks for the advice. The reason for making it in modular form was to have the option of removing a panel or two if required.

Any suggestions on using the coir vs rockwool?
one last question on this topic before I start on the wall. What frequencies does the rockwool panel control and what frequencies does the fiberglass insulation absorb?

Thanks