In my opinion (i think most will agree) that after the original source (instrument, amp, ect..) the room that the instrument is being tracked in is the first stage of EQ. Given that idea I believe you want a general multi-purpose tracking room to have a tight bottom end and bright highs. I'm aware that this is subjective and a matter of taste, application and of course room dimensions. Example: 1. If you have too much high frequency absorption, the instruments you track in that room will most likely sound lifeless in the high's, due to the lack of good high frequency reflections. 2. If you don't have enough low end absorption, the room will probably be "boomy" and "boxy". I think it's really easy to overdo high frequency absorption, which leads me to trying to come up with different ways to make thick absorption panels reflective/scattering in the highs yet still absorbing the lower frequency. I've noticed allot of thick absorption panels in higher end studio's have very thin 1/16 inch wood panels with holes drilled in them. My question is.. What are different simple ways of going about making absorption panels/walls/ ceilings that scatter highs and absorb the lower frequency's?