Sorbathane under granite slabs for speaker bases?

how much is the TMC ?

If I read your proposed installation correctly, the unusual variable I doubt any of us has worked with is the "hollow five inch high tile shelf" that your speakers will be placed on. Your speakers are fairly heavy (75 lbs. or so) and it has been my experience that heavier speakers can do fine on granite, lighter weight speakers perform better coupled to wood platforms. That's just my experience, there are always outliers and ears that hear things differently. I would try both the spikes and the glider feet that your speakers came with, the spikes might not necessarily sound better. You might find that using Herbies products under both the granite plinths and the speakers would prove optimal with that hollow tile shelf. I've never tried sorbothane products for isolation, mainly because I've never known anyone to have anything positive to say about the material for this type of application. 

jl35
how much is the TMC ?

My guess is $5K new from factory. On their web site TMC makes the following statements. I know, it sounds like there's an echo in here, right?

"Granite Tops
Granite surfaces are standard with 64 Series tabletop platforms. They are available on special order with other isolation systems. The advantages of a granite top are its relatively high mass and stiffness and the potential for being lapped to a precise surface flatness. Granite’s non-magnetic nature is useful in some applications.

For small tops, granite is an inexpensive, moderate performance material. In larger sizes, however, granite is more expensive than standard TMC top plates, sacrifices damping, and does not have other desirable features."

Thank so again for the replies everyone,

Does anyone know what Herbie’s soft fat and thin dots are made of? It seems there is a lot of advice here to avoid sorbathane but use his products. Wouldn’t they have a similar effect? I don’t mind supporting him at all I just want to make sure I take the best path. My KEFs did come with the spikes and the brass gold feet. I’ll try both the spikes and just the gold feet on granite to see what works best. I’m still wondering what/if anything I put between the granite and tile. I wish I didn’t have to hollow tile shelf but at this time I have to work with it.

If you go over to "Audiocircle" that website has a group discussion devoted to Herbie's products best uses/applications. As far as similarities between Herbie's products and sorbothane, I suppose they are similar in that they are both viscoelastic materials. However, Herbie's products are mixtures of different silicones and fillers and have physical properties that differ from sorbothane.