I gotta say I agree with others who think that bolting the shelf to the rack ends up with transmission of energy from the rack. But the OP is the only one who knows what that looks like. Maybe there is something about the arrangement that mitigates what we see as a problem. However, the points about fastening a "wall shelf" to a weight bearing wall are correct, based on the received wisdom. I do agree that concrete transmits energy, but I can't agree it "rings like a bell". That metaphor calls forth the sound of a bell, metal on metal. Concrete does not "ring" like that in my experience. Also, in my house where I have two completely separate systems, one of which is in our finished basement sitting on an indoor/outdoor carpet over a solid cement foundation flooring and the other of which is in our living room on a suspended floor supported by studs (or whatever you call those wood support beams placed about 12 inches apart) and a steel beam as well, the basement system is far less susceptible to floor-borne feedback. The two turntables in that system produce a very solid image. So, I don't think concrete flooring is to be sneezed at. It's a good start.
The OP says he is using 3 woofers in this system and is planning on adding more. Is this the Audiokinesis woofer system or just an attempt to wring out the lowest possible frequencies? If the latter, that doesn't help with eliminating various forms of feedback.
The OP says he is using 3 woofers in this system and is planning on adding more. Is this the Audiokinesis woofer system or just an attempt to wring out the lowest possible frequencies? If the latter, that doesn't help with eliminating various forms of feedback.