@mitch2 — thanks for those tips. I probably will want to use these for something more than room pads, because like many, I'm not so handy that I will be able to finish these into something long-term good looking.
@tvad Good suggestion. I hadn't thought of subtracting and then adding back in. That would create a mix of diffusion and absorption I don't have there now.
@riley804 I have read about isolation a lot, but, first, my stuff was on a really solid and low coffee table and then I moved it off to the side. I figured I would sort out the room before the isolation. The speaker stands are new and very solid. Perhaps you'd do isolation first?
@slaw Thanks for the reference. I'll check into coverings. I really need to see if my 20hz - 300hz range is dialed in before doing too much more with the upper frequencies (using my OC 703); so that's why I call what I'm doing now just "playing."