The Original Poster, JBonner, wrote:
My Logic DM101 platter, while substantial, rings like a Tibetan singing bowl, even though it has felt bonding on the upper surface. The addition of an extra felt mat does little to help. I'm quite interested in getting an old AudioRef Le Mat or some such but have been considering other damping options.
If you have ever played with a singing bowl you would know that a mat has almost zero influence on its ringing. I would imagine that the influence of a mat is on the record not the platter unless it is heavy, bonded and lossy, and covers the sides also, especially if the platter is in any way bell shaped, (ie has a rim )
Latex is elastic, rubbery, not ideal.
JBonner : if you actually have a singing bowl, play with that - use blue tak -see where the resonance is attenuated and where it is not.
Position your deck sensibly to reduce airborne vibration. Reduce motor vibration, Reduce structure-borne vibration. In other words, generally, reduce the effects, then deal with the residue.
Hardwoods in general, and softwoods, especially spruce, are good for making musical instruments. The corollary of that is if you want your hifi to be a musical instrument, use wood. Metals make good musical instruments too. Unfortunately they are also good for making things. All sad but true.
Plywood makes poor musical instruments. Plastics and composites even worse.
So, perhaps the moral is: make your hifi from plastics, (then make it look acceptable.... )
Don't use lead, unless you have no children and approve of lead in paint and lead in your plumbing.. The Romans used lead plumbing - they gave us the symbol for it - but look at what's become of Italy today...