I would try something like the Star Sound threaded feet under the speakers. I sell these so I know they are good but there are others. Are you trying to couple the speakers to the floor or decouple the speakers from the floor? If you are trying to ground the speakers so cabinet vibrations would be quickly dissipated I would not use anything under the spikes but here , as always, experiment is best.
What should be under my speakers?
I have Sonus Faber Grand Piano Home speakers in a 20' x 17' room with wood floors. The speakers have spike feet, and each one is sitting on a 1 inch thick, 12" x 12" slab of granite. Each piece of granite has a square piece of carpeting under it, as a further buffer. I know I probably could figure this out with a lot of experimentation, but what impact is the carpet likely having on sound quality? Would it be better (Subjective, I know) to have the granite slabs sitting directly on the wood floors? How would the sound change if I ditched BOTH the carpet and the granite? I would like to maximize bass impact, because these speakers are a bit thin in that regard. Thanks.