Getting granite tomorrow.

Doug, that is a very nice explanation of the various steps and results. I had a different experience with my unsuspended turntable. I did put a Vibraplane pre-loaded with 136 lbs of steel plate ballast under my unsuspended turntable. Interestingly, I found that the noise floor was lowered AND dynamics and bass response improved.

It just goes to show, as you wrote, that everyone's TT is different and thus solutions may work in some situations and not in others. I will shortly be trying out a suspended TT on the Vibraplane, and I may find the added isolation is not needed and perhaps even detrimental to the sonics.

Agree with Doug about speakers. I put one expandable column directly under each speaker in the basement below my listening room. I bought these at Home Depot for about $30 each. My speakers aren't spiked because I have very soft, very old wide pine floor boards in my listening room. The speakers are, however, on hard round cones and as each speaker weights 200 lbs, they don't move. As Doug says, one wants all of the speaker's energy directed at the forward/backward movement of the cone drivers. The cabinet should not move at all.

I also placed two columns under my equipment rack to support it's massive weight, but also to reduce the floor bounce. I've found the solution to be quite effective.

I'm in the process of building a new rack. I considered two distinct approaches. One is to have massive shelves to which the components are coupled, but the shelves need to be isolated from the rack structure and from floor born vibrations. The other approach is to have a very rigid, heavy rack coupled to a solid floor but have the components isolated from the shelves. I've chosen the latter approach and have the components on a Vibraplane and Townshend Seismic sinks for isolation all on a very rigid and massive rack/frame system. I guess I'll find out if it is effective once I finish building it.