JW – nice set up. I like how you put the panels lower to the floor with your DIY frames. That way you can get those monster 945’s in your room. Yeah, I was thinking that too much dampening with sand/shot may not be a good thing. I think that I’m just going to pour some viscoelastic vibration damping compound (paint) into the vertical tubes to coat the inside walls of the steel tubing and then shove a “noodle” in each tube.
Ernestov – I’ve attached a hand drawn diagram of my clamping idea for clamping my panels to my metal frames.