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.

So Doug, what are you using under the speakers? Since I moved a couple of years ago from a nice concrete floor to a suspended wooden floor (albeit decently solid), I've come to realize (despite my best efforts) that some type of decoupling is going to be needed at the speaker/floor interface since too much mid bass energy is being directed into the substructure. And, it probably isn't going to be cheap. I've tried the Herbie devices and they were abysmal in my application. The next step is something like Stillpoint Ultras or the Track Audio decoupling spikes, but now we're talking quite a bit of cash for eight feet. I'd be curious as to your approach. Cheers.

Granite Rings....not a good idea

Peter,
That's really interesting that a Vibraplane beneath your TT improved both noise floor and dynamics. I don't know how they function but I've heard good things from many people. We haven't gotten around to trying one ourselves... so many vibrations, so little time!

Richard,
We've had the shaky floor thing going from when we first got speakers big enough to go below 40Hz. I once tried isolating the floor from them by placing the speakers on butcher block boards, with the boards just sitting on the carpet. When Paul saw this setup he asked what I was doing.

"The speakers excite vibrations in the floor and that's undoubtedly getting to the components in the rack. I thought I'd try isolating them from the floor."

He gave me the pained look scientists reserve for children and idiots (I've seen it before, and since).

Well, we were both right. The isolation worked and the floor got quieter, woo-hoo. However, Paul's scepticism was justified because it sounded like crap.

Think about it. Isolating/decoupling requires allowing a component to move, and let's recall Newton's laws of motion. If a speaker cabinet is free to move then some portion of the energy from each cone excursion, which ought to be 100% dedicated to displacing air forward, will instead displace the cabinet backward. Result? Slurred transients, reduced dynamics, dopplered waveforms and general sonic muck. Decoupling is disastrous for speakers.

Stillpoints do decouple so I'd expect them to be a net negative beneath speakers. OTOH, those Track Audio speaker spikes look similar to the (very effective) Audiopoints spikes we now use. But it's an error to say they de-couple. Spikes couple, that is their purpose. A solid coupling improves speaker performance but as a side-effect the floor will shake more, not less. That problem must be addressed elsewhere, not at the speakers.

Recommendations:
Spike, bolt or glue your speakers to the floor as rigidly as possible. Perfect rigidity, if we could achieve it, would result in 100% of each cone excursion moving air and 0% moving the speaker cabinet. That's the goal.

If a floor's excitable then two approaches suggest themselves:
1. reinforce the floor to resist/dampen/absorb energies
2. isolate sensitive gear from the floor

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.