Foam Packing will deaden a ring that occurs when striking metal.
Particle Fillers are a design to control amplitude transferal, each Particle needs to take on amplitude and transfer this energy across all Particles. The physics is that the energy is becoming a conversion to heat rather than a amplitude being efficiently transferred.
A additional Footer under the Stands does also work wonders. The amplitude ftom ambient amplitude is reduced, hence, the Speaker Stands are not being directly impacted on.
My experience is Suspension Footers work great, and there are now available 3D Printer suspension footers, that are inexpensive and may prove ideal for long term use. The iitems will certainly supply a god impression of what a much more expensive option can deliver.

