Support table or shelf for turntable

Whoa! Hey, leave me out of your petty disputes. Note to self - A biology major thinks I’m weird. That’s weird in itself.

I agree about the Sorbothane. Even though it seems like SUCH a good idea. Even though it appears to be the right material for audio applications it just doesn’t sound good. At least I never found a place it sounded good. I found plenty of places it sounded bad. There are other similar looking materials out there, usually billed as "viscoelastic" that DO work, so don’t give up yet.

Right, cement floors actually don't buy you that much since the entire structure of the house or whatever is moving right along with the surface of the Earth. And since the Earth's surface is moving like a wave on the ocean there are six count em! directions that vibration can travel. 

Actually, slate or marble or granite, assuming it’s not too thin, provides significant isolation against rotational forces attempting to bend the plate or slab, by virtue of its mass and stiffness. I am a big fan of bluestone, the gray blue stone usually used for paving, for its low cost and high mass and stiffness. Thus, the effectiveness of these heavy thick stone slabs with springs.

"Taut and rigid" seems like a good approach but actually this approach allows structural vibration to be transmitted *more easily* than "flexible and wobbly." This was the idea behind the Flexy Rack of yore. It’s also the idea behind isolation (decoupling) per se since the best isolation is obtained when the object being isolated is *free to move* in the directions of interest. I would like to see the object be able to undulate and wobbly slowly up and down and back and forth when manually pushed a little bit. Thus, roller bearings and springs ALLOW motion rather than CONSTRAIN it. Marble and granite are good materials as top plates for isolation stands due to their stiffness and mass. The quick fix the set up at hand would be to place low profile compression springs under the components on the table. The required spring rate of the springs and number of springs are not difficult to calculate. Problem solved!