Best type of metal for turntable platform?

Townsend is the clear winner. I’ve been saying this for almost 2 years now.

I have a vpi classic 3. It’s extremely heavy. The plinth is made out of steel. I would find out what type because even if you tap hard on the player there is no skipping. You can even tap it hard with your hand. Truly amazing. It weighs 65lbs. 

@deanshias,

As others have said , Townsend knows what he talks about. But, let me if I can expound upon what he said. If you view Figure 7 of this Fundamentals of Vibration (newport.com) , when your designing a vibration isolator, the resonant frequency needs to be less than the Hz you are trying to isolate. At resonance (and all vibration isolators have one), any vibration is amplified and this is called the transmissibility. The damping factor reduces the transmissibility peak, but reduces how quickly (the slope) the vibration is reduced after the resonant frequency. So when Townsend say a damping factor of 0.16 - that is near optimum. Townsend may very well have a curve that looks like Figure 7; and each design is limited to a range of supported weights.

Because of the low frequency (foot fall) you are trying to isolate, which has a lot energy associated with it you have an engineering problem that the number of solutions is pretty limited. You can dismiss as you wish; and spend all the $$$ you wish; but your up against some very hard truths. Good Luck.

Antinn gave you good advice. Constrained layer damping is an important element in most plinth designs - it’s often absent and that’s always obvious.

If you want an easy solution, I use Delignit panzerholz B25, which costs about $1000 a sheet. In my plinth, constrained layer is partly in the plies of beech wood in the panzerholz, and partly from a top layer of carbon composite.

Rigidifying your floor is even more important. My floor is concrete - it’s great - and as others have suggested, try to make your floor as much like concrete as possible.

Good luck!

If you're dead set on using an aluminum plate for a plinth, then the alloy makes a big difference. Alloy 2024 is recommended by some who have experimented, and the temper does not seem to matter much; all tempers seem to have about the same loss modulus, which is a lot better than alloy 6061.