this is not a simple question with simple answers. absorption alone is not as pleasing as a combination of absorption, deflection and diffusion. the best sound room i've ever experienced is at goodwin's highend in waltham, mass. you can view it on thier website: goodwinshighend.com. the site also has some useful information for diy'ers (tho its not intended for this purpose). i'd suggest you take a peak. BTW, i have absolutely no connection to goodwins. i simply visted the store on a trip to boston/providence last month, was treated exceedingly graciously, and learned some important lessons from mr. goodwin and his staff.
Room Treatment
We have all talked about the best amp, best pre-amp and the best audio components to buy at a certain price. I would like to find out what material is the best room treatment available. Is is a hard material like a styrofoam product or an absobtive product like rubber or sponge? What has worked for you and why? Do you use fabric to hide these treatments or have you found something better? Room treatment has very little discussion. I would like to find a DIY project that can improve the overall dynamics of a very difficult room. Let me hear your comments.....