For what it's worth, I did a little experiment regarding isolation recently. I needed a single large diameter (IIRC about 4") o-ring for a project and had to source it through McMaster Carr, meaning I had to order 10 of them. So when I was setting up the three sub woofers on the hardwood floor in the home theater I put them each on a couple of the extra o-rings. As I hoped it cut down the energy transmission of the bass into the floor and cleaned things up quite a bit.