I am struggling to see how granite resonance properties enter into turntable isolation when used as a platform for a TT with its own suspension system but as previously noted my ears of clay probably cannot hear such things anymore. I tend to focus on optimizing the overall suspension/isolation properties of the system, which is pretty complicated when multiple spring systems are involved.
Corian is a great idea IMO.
MrAcoustat, the Krell amp stands look awesome, but this thread is about turntable isolation...
Don,
As far as I understand it, the thread is not about turntable isolation, it is a general thread about platforms that make a turntable sound good.
Now for the technicalities. Although we have many types of granite, in general if you tap a thin granite slab it will resonate - unfortunately my current kitchen countertops and tables are all made from Corian, much more silent that the previous one in black granite - otherwise I could measure it. Considering that most turntable suspensions are not optimized in these frequencies, and also that many turntables must drain energy in the platform, we can easily understand why the platform material can be of great importance. Do you remember the Goldmund mechanical diode theories? Sometimes a material must dissipate the incoming energy in itself, not reflect it back in a delayed way.
I had a great experience with Corian some decades ago. Although I already referred it in WBF I will repeat it. In the 90's a good friend became Dynaudio distributor and imported the great Dynaudio kits. Using the factory supplied plans we built two Gemmini's (D'Appolito" configuration) pairs of monitors - one in MDF, the other in Corian, as the Wilson speakers of that period. They sounded very different. But there was no clear preference between listeners - although the Corian one was cleaner and had better definition, some found the Corian excessively alive and bright sounding. Only many years later, reading about the Wilson Audio Watt speakers I learned that Dave Wilson damped the Corian of his speakers with lead to eliminate the Corian intrinsic resonances. Do you remember the Dukas
The sorcerer's apprentice? Fortunately in audio, apprentices are not spanked ...