isolation platforms not only help eliminate the floor form adding to the sound but also vibration getting back to the speaker, especially with concrete floors. The vibrations have no where to go but back into the speaker.
That comment, especially the bold part, has really helped me see why the "concrete floor" factor is not the end of the story. Thank you! I suppose I figured that the floor was so inert, it wouldn't resonate in sympathy with the speakers -- and indeed it would not. But the vibrations coming from the speaker is the key, and thank you for pointing that out in a way that made sense to me.
@sokogear Thank you for your recommendation. It's hard to believe a platform that inexpensive is out there as a solution. I appreciate it.
@lemonhaze I deeply respect your opinion and experience. I will read the link you provided and seriously consider the platforms. It defies my economic common sense to spend that much but you're making a salient pitch, here.