Vibration Isolation for equipment using granite?

@cooperdude6: Lots of great comments here, and a link by @ditusa to an excellent article. Here are my thoughts on the subject:

- First, replace the aluminum cones with springs. Cones do NOT isolate, they couple. Sets of four springs from Douk Audio are cheap.

- As many have already said, constrained layer damping works great. But first you want to at least get rid of the MDF shelves, which suck. MDF is nothing more than wood pulp mixed with glue, not at all stiff. I put a 50lb. turntable on the top shelf of my Solid Steel rack, the MDF resting on four corner cones. The MDF remained supported at only the corners, the shelf bending all the way down to the rack’s metal frame in between.

- Replace the MDF shelves with pieces of Baltic Birch plywood. 3/4" thick, 19 layers of cross-laminated Birch. VERY stiff for a wood product. A layer of Baltic Birch plywood with a second of another dissimilar stiff material (sure, granite if you wish) and a sheet of a constrained layer material (check out WallDamp from Acoustic Sciences Corporation) between them makes a great shelf. And at a relatively reasonable price.

Because it is readily available locally, I use Sydney sandstone which comes in 600-foot thick deposits throughout the Sydney basin.

It is about 4% porous, so it has internal damping properties.  It does not ring when tapped!

Under my Garrard 301 turntable I have two layers of 2" sandstone separated by constrained layer damping, sitting on a 2" MDF platform.  The inner plinth sits on three IsoAccoustics OREA Bordeau pucks.  The inner plinth is made of three layers of 1-1/4" MDF with more constrained layer damping.  MDF is widely used in speaker cabinets because of its stability and internal damping properties.

One day I might replace the motor-board with manufactured stone, also known as acrylic containing stone chips, eg Corian.  Manufactured stone has just been banned in Australia because of lung disease issues, though.  At least one high-end turntable uses two layers with constrained layer damping in between.

I personally believe you usually benefit from adding both mass and damping, but Linn owners are cautioned to follow Linn's advice!

@cooperdude6 

It’s funny,  using granite under my KEF Reference 5’s made a huge difference. I have tongue and groove oak floors with pad and carpet and I never got them to sound clean and clear. A friend who redid his kitchen gave me a bunch of granite.  I cut it down to a few inches wider than the KEF’s footprint and gave it a try with amazing results.  Later I added some Isoacoustics Gaia 1’s and they made even more of an improvement.  I have since bought some Sonus Farber speakers and while there is an improvement using the granite, it isn’t anywhere near as noticeable as it was with the KEF’s. 
I also tried putting granite under my electronics and if it made a difference, neither my wife nor I could tell. 
 

All the best.

Place your speaker on large blocks of granite. As heavy as possible. So that any vibrations from your speakers are immediately killed by the mass of the granite. Place your turntable on springs. So that vibrations in the room do not reach your pick-up cartrigde and stylus. Place all rest of your equipment on spikes. So that maybe possible external vibrations of the surface under your equipment are minimized.

for the readers that mention putting loudspeakers on top of granite, or similar bases: I have noticed that several high end speaker manufacturers have now incorporated that into their current design of floor standing speakers, especially ones with a down firing woofer driver. It can be tuned to that base instead of firing into a variable flooring of cement, tile, hardwood or carpet. Of course those models are pricey!