Turnable Rack Vibration

Just my opinion of course, but if you have a suspended floor, it is going to be awfully difficult for you to obtain the performance you were achieving with the wall mount, so my suggestion is, unless it is impossible, go back to it.

Secondly, my experience is that with a suspended table you want light and rigid for the shelf material. With non-suspended tables massive like the granite may be ok, but granite rings like crazy so it should be damped if used at all. Personally I don't like what it does to the sound, especially without damping.

If you want to create a shelf for your rack, given the suspended table, I would look at having a shelf cut from 5/8" extruded acrylic. If it can be placed directly on the rack (replacing the existing glass or mdf shelf) you could try that. Alternatively you could try the vibrapod sandwich, with vibrapods under the acrylic shelf on the top shelf of the rack but that would be my second choice (third actually, as going back to the wall mount-with a custom acrylic shelf for it-makes the most sense.)

I went with a Target wall shelf for the same reasons but found that my sound was no longer lively. I also found that the new Target Pro shelf that I bought would actually flex under load. I wrote Target but no response.

Your answer may be a Finite wall shelf: http://www.finite-elemente.de/en/racks/pagode_signature_wall

However, this is an expensive solution compared to the Target. I've decided to take a leap of faith and build a "Flexi-Rack" made from Maple and Brass. I have a current thread going about this here: http://forum.audiogon.com/cgi-bin/fr.pl?htech&1262360875&openmine&zzKennythekey&4&5, but there's even more information over here: http://forum.audiogon.com/cgi-bin/fr.pl?htech&1158841915&openmine&zzJdoris&4&5

I'll be done with it pretty soon if you have some time. You see, I have a similar foot-fall situation. If the rack handles the foot-fall problem and also sounds real good then perhaps there's a way to get off the wall.

Anyway, I'll be continuing my thread and post my findings.

Good Luck.

A couple of comments:

When I think of Target wall shelves, I'm thinking of their original design with the angled side braces. This "triangulated" design is a structurally braced shape, deriving its strength from its geometry.

The current Target design(s) use a "box" frame which is only as good as the welded connections, the shear strength of the weld itself, and the metal tubing's ability to resist bending. If I had to buy the current model, I'd take it to a welding shop and have some angle bracing installed on each side. Just look at Billy Bags designs -- every damn thing (except their little 2020 amp stand) has diagonal bracing.

Steel is the ONLY material for the BEST structural rigidity. Titanium and magnesium are better in the strength vs. weight department -- not an issue in audio (usually ;--)

A truly rigid connection between dissimilar materials is impossible because it will be mechanical, not monolithic like a weld. Further, mechanical connections almost always involve a third material like glue, or screws. This eventually leads to loosening of the joint, due to movement, structural stresses, thermal expansion, and variations in humidity. Anyone who thinks they can make truly RIGID structures out of any material that can't be welded is just nuts IMO; they are depending on intuition without knowing anything about physics and math. Intuition is useless, even when you get a lucky break, because you can't go back and figure out why it worked! (Simply PLACING a wood, corian, acrylic, granite, etc. shelf on some kind of rigid steel frame is not what I'm discussing here.)

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Acoustic isolation of a TT or other object from airborne sound (pressure waves) is another fantasy. Oh yes, sonic pressure waves do indeed exist, but they exist in a gas (air) which means they propagate in all directions -- unless you are literally on top of the source. And they exert the same pressure on all surfaces of an object, if that object is fully inside the space where the sound occurs. Floors and walls are a different story. When they vibrate, it's because the pressure on the other side is different; usually lower.

So if a TT is "dancing to the music" it's because the structure that it rests upon, (along with everything ELSE one has contrived to stick under it,) is all already resting on a moving platform: the floor!
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Having faced this issue countless times, the only technique that consistently works is to fasten a 90 degree shelf bracket (which you can buy or fabricate yourself) to the top shelf at the back and to the wall. This will cure 95% of the problem.

Failing that, even wedging something between the wall and the back or the rack/shelf can help a bit, until it falls. :)

A vertically suspended turntable such as a Linn on the top shelf that is susceptible to footfalls is actually having to contend with some horizontal movement, which it cannot handle.