[jostber]

I have a pair of Vandersteen speakers with spikes that are set in the Cone/Spike decoupling gliders. I want to isolate the speakers as much as possible from sending sound down through the floor, and might get two slate stands to place them on. Are there any isolation pads or something I can place under the rack feet to eliminate sound transport from the speakers to the floor?

[Herbie]

Hi, jostber. Cone/Spike Decoupling Gliders should isolate speaker vibrations from the floor very well. If not quite adequate, Giant Fat Gliders would surely do the job.

If you're looking for something to keep airborne sound waves from going down through the floor, that's a different matter. Slate stands might be beneficial, I don't know. For one thing, you'll be introducing a twanky slate coloration into the vibrational sonic environment. Decoupling the speakers from the stands with Big Fat Dots or Square Fat Dots would be essential.

For the floor/stand interface, Herbie's Audio Lab has several isolation/decoupling products:

http://herbiesaudiolab.net/spkrfeet.htm

If the stands have spikes, use your Cone/Spike Decoupling Gliders under them. Otherwise, Fat Gliders would be ideal.

Steve
Herbie's Audio Lab

[jostber]

Thanks. I was thinking of having the speakers with the spikes in the cone/spike gliders on the slate rack, and maybe some thin fat dots under the rack feet. Or would the giant fat glider be the best?

[Herbie]

Gliders are usually used on the floor, for mobility of the speakers in addition to the primary purpose of isolation/decoupling.

Herbie's Hush Puckies or Fat Grounding Bases between spikes and stand would be okay. Fat Dots usually provide a superb interface between speaker and stand, though, without spikes. Since you already have the Gliders though, they would be okay to use on the stand, though the speakers might slide off the stand if pushed. With Fat Dots, it would be like having the brakes on--the speakers will not slide on them.

Thin Fat Dots under the rack feet would be okay on a bare floor. On either a bare or carpeted floor, Little Fat Gliders or Giant Fat Gliders would provide more substantial isolation/decoupling plus give you easier mobility of the speakers.

Steve
Herbie's Audio Lab

[jostber]

Would you recommend another type of stand material instead of slate?

[Herbie]

Baltic birch plywood is very good. If your stand is more like a single layer platform or slab, polished granite is very good.

Steve
Herbie's Audio Lab

[jostber]

I actually ended up getting me some Townshend Stella Stands to give extra protections against vibrations to the floor.,
and will put everything on top of those. Will arrive in some weeks. 

[JustinT]

See http://uhfmag.com/Issue63/soundproofing.html

It explains a lot,  in technical, but understandable language.

An important concept is that you do not want to transfer sound energy to the floor, because it will travel (just like the wave the energy is in the form of) as a wave along the floor.

The more contact area between any two objects,  the more sound energy is transferred between them.   If you (theoretically) had an object you could use to separate the speaker from a floor, such that the contact point was only one atom (or even a molecule) in size, then any energy transferred would have to do so serially through that tiny contact point. Needless to say,  it could take decades for the full energy of even a single low frequency sound wave to be passed through that point.

Of course,  you could not have such a tiny point that could still serve to support the speaker,  so you have to settle for the size of the contact point on a cone or a spike.

Now, think of what happens when you use anything the size of the speaker base to connect to the floor.  if the waves are longer than the thickness of that something, you will couple the speaker to the floor for their full amplitude (but if shorter, you have a chance at absorption,depending upon the material).

The same is true of spikes or cones, but the contact area on one end is so small, that so little of the wave's energy can pass through that contact area and so the amplitude of the coupled wave will be virtually nil.

Think of separation, not absorption, for low frequencies.  Effectively absorbing low frequencies could require separation objects that are too massive to be practical.