Wayner:
I don't understand about killing the bass. If you put some bass traps in the corners, the bass will increase in depth, definition, and punch. I know that the idea of low frequency absorption increasing bass response seems bizarre, but the "bad bass", the standing waves, resonance, echo, reflection, etc., of low frequencies in an untreated room actually interferes with the listener's ability to hear the "good" bass. (That is my layman's way of describing the result.)
In general, I suspect, a combination of absorption and diffusion is preferable. However, room size and location of listening positions probably contributes to the effectiveness of diffusion. In my small room and single listening position, I have relied solely on absorption. I have (4) bass traps and (14) acoustic panels. The bass traps are in the corners, and the acoustic panels are behind the speakers, behind the listening position, on the first and second reflection points on the side walls, on and between the first reflection points on the ceiling, and on the ceiling between and slightly forward of the speakers.
The treatments in my room have made a tremendous improvement in numerous ways. Bass response is improved. The soundstage is wider, deeper, and higher than before. The placement of vocals and instruments is precise. I can crank the music louder without fatigue, if I desire. The reflections, echos, resonances, etc., have been reduced. Additionally, despite my room's smallness, I would experiment with diffusion, but I don't have too much wall space left.
When I initially received my Insight gear, I thought my speakers were deficient (which they were, but for different reasons). I thought that vocals were "breaking up" because they couldn't reproduce the source (which they couldn't, but not in a "breaking up" way), but the vocal's "cracking" was because of reflections, and a few acoustic panels cured the problem immediately. I think that if you were to stand a suitable thickness of mineral wool or OC 703, in just two locations at a time for symmetry, in the corners, behind the speakers, behind the listening position, and against the first reflection points on the walls, you would here a enormous difference in the sound with the absorption material at any of these locations.
I don't know how much the cork costs, but mineral wool and/or OC 703 panels are not very expensive. With your exceptional fabrication skills, you could easily build some very nice flat panel or cylindrical bass traps and flat acoustic panels. There is a good thread on the acoustic forum that follows Bob in St. Louis' journey.
BTW, Wayner, your system looks great, and the AR table looks fantastic.
