I think the Ballistic Ceramic (compression wrapped in Kevlar) of my Cerious speakers is an ideal material - it is rigid yet lossy, and requires no internal damping materials. Wrapping ones knuckles on the cabinet is fascinating - the impact from your hand is completely absorbed.
There is a quite a bit of information on their site about the materials used - and the cost is quite reasonable as well.
There is a quite a bit of information on their site about the materials used - and the cost is quite reasonable as well.