Marble or Granite shelfs in a hifi rack?

Excellent post Redkiwi. Non-resonant material is critical, I think. Maybe more important than absorbing vibrations.

Resonance is the natural frequency of a material. I'm thinking when music hits this frequency it will sound very unnatural. Or worse, this resonant frequency could be in the music all the time making strange tonality etc.
Resonances are much greater in intensity than vibrations coming through the floor etc. which are not at the resonant frequency of the base / component / etc.. So I'm thinking this is the first problem that needs to be fixed. Isolation is secondary.

While air bladders and sorbothane may absorb vibrations they are not a rigid mounting base and I'm guessing could create resonances or bad vibrations at some other frequency.

Noting Redkiwi's caution with Maple, maple seems pretty non-resonant and it is hard (compared to rubber or air bladders). So my next experiment will be setting the CDP directly onto 2) 2-3" wide x 1- 1 1/2" thick hardwood like maple.

Why bother with footers which just cost money and could add resonances of their own? I think direct coupling the CDP to the wood would be better. Large contact area / direct transfer. Also mass load the CDP with brass on top or brass sitting on wood sitting on CDP.

Also Redkiwi's post seems to say the ceramic foot polishing stones in the beauty section of Wal-Mart are the perfect footer solution.

I commend Redkiwi on his efforts to form a consistent analysis of vibration and its effects, based on years of experimentation with different materials and theories. I don't disagree with his anaylsis but would add an important caveat - that you test your own equipment on the types and kinds of platforms before going wholesale for one approach or another.

I own a Spectral system, with mostly MIT a/c treatment and cables, including isolation transformers on each of the 3 front end components (transport,dac, preamp). I use Zoethecus equipment stands (hard maple; heavy, layered, damped shelves of several grades;some shot fill in the legs) that I acquired 10 years ago when I first got into Spectral, and sold routinely by most U.S. Spectral dealers. I don't know whether Spectral is 'voiced' on Zoethecus or not. I also own several Symposium ultra's (heavy, damped), several Neuance shelves (light rigid), and any number of cones, shelves, and hats, and have played extensively with combinations of all of the above, plus other stands, over numerous years.

Spectral/MIT is a solid state system designed as very wide band and very detailed. My current system, using Symposium ultras as amp stands and basically Zoethecus equipment racks, has simply outstanding PRAT. It is also very musical, relaxed and non-edgy for solid state.

I find that there are any number of ways to drive the system into being far too analytic, and this almost always means the intensification of high frequencies to the point of non-listenability. Cones, the wrong stands (in my experience, Grand Prix for example), the wrong choice of rack material under individual components can kill the system sound. This is one reason why I think many people post about systems like Spectral sounding too analytic in some dealerships. Retail dealerships don't have the time to fuss with refining the system sound to the nth degree.

Unfortunately, products like Neuance shelves, which are broadband and not peaky in themselves, still have the effect of intensifying high frequencies, presumably by eliminating far more vibration than shelves like the denser Zoethecus shelves do. (Neuance in this case is used as a supplementary shelf sitting on top of upturned cones atop any of the Zoethecus regular shelves, or in place of Zoethecus shelves altogether, or sitting on the floor on top of cones. It is also a general result pertaining to use of Neuance with the preamp, power supplies, and a/c treatment (the places where it has the most effect.)

I am not posting this in order to criticize Neuance, which I have found very useful with, for example, less exemplary players than Spectral, or to imply that detailed solid state gear has too many high frequencies as part of the signature that need to be 'smeared away' with vibration. (Although isolation transformers produce some inherent high frequencies of their own, which may be part of the problem.) The point is to say, again, do characterize your own equipment and its properties regarding vibration, prat, musicality etc. This is also part of the fun in understanding audio equipment.

Flex, if you're saying that the Neuance shelves don't work for you, that's the same results I had. Placed under my Io (all tube) phono stage, the system went completely lifeless.

What does work is the custom aluminum stand I had constructed, with stainless steel spikes to my slate floor. On top of the four post stand is four mod squad soft shoes (EAR group manufactured). On the squad feet sit a 2" slab of granite. On the granite is 12 of the smaller ISO Bearings, and on the ISO Bearings sits my phono stage. On top of the phono stage sits a 6 pound plastic box filled with lead shot and wrapped with layers of black cloth tape.

This combination has wonderful dynamics, is immune to foot falls and the sonic attack of my large speakers, which sit less than twelve feet in front of the stand.

My opinion is that every room and every type of equipment is different in the personality it presents when matched to various materials. The granite used here for instance, when substituted with maple butcher block, looses dynamics. When the granite is removed and the phono stage is coupled directly to the stand with mod squad feet, Walker cones or other direct coupling methods, the isolation is not near as good.

I am not advocating that everyone follow my set up. I am saying that there is not a universal truth as to what will work with every piece of equipment in every room. Best that each takes a bit from the forums and experiments to find what works.

Well, then there's always my approach: I invested about 1K in my Salamander Synergy Twin 40 solely for the reasons of convenience in having adjustable shelf heights, enough space for all my components, and the ease of system reconfiguring that comes with having gotten the Saturn caster option. The shelves are all MDF, the rack itself is fairly flexible and resonant by high end standards (though much better than some more makeshift solutions or mass-market stuff, and heavy as a bear), and way too tall for high rigidity anyway, and of course it isn't positively coupled to the floor, though the fact that the casters employ rubber treads does provide a little isolation.

Frankly, in my circa-$15K system, I've never heard enough differences from various support strategies with most components to place a higher emphasis on this subject. I do own some cones and isolation footers, finding the Iso-Bearings and such mildly useful with certain gear, and don't use the cones. I keep my TT on an original Symposium shelf, which in conjunction with sorbothane pucks underneath, does a very nice job of isolation from energy transmitted through the rack. But I'll tell you what, I'm lovin' life these days with all my gear on one rack and total accesss from all sides (no doors, sides, or rear panel installed) - I probably roll the rack out and make changes (most temporary) around back a few times a week on average, now that this is so quickly and painlessly accomplished. I have decided to replace all the regular corner shelf support brackets with the heavy-duty ones, which employ steel struts that runs front to back between the vertical pillars, for the addtional reinforcing effect they will have on the overall rigidity, but aside from that, I've experienced no objectionable problems in use so far, and I think I'm done with this aspect.

Could it sound better? What do I care - it sounds good enough for me to just relax and enjoy the music, and the ease of use I get with being able to raise or lower shelves and move the whole thing around at will. I personally doubt that any incremental sonic improvements I might get from compulsively obsessing over a more audiophile-approved and tweaked-out arrangement would be worth the candle to me in terms of livability lost. (Oh, and I also don't believe in the concept of "mechanical diodes", self-vibration being more of an issue than acoustically-induced vibration, or the existence of "PRAT", but those are probably issues best left for other threads! :-)