A very loooong, long article about a very well understood topic.
Of course we don't want our speakers to vibrate (good speakers hardly do), of course we don't want the vibrations to be transferred to our listening environment if they still DO vibrate.
And of course spikes are not 'mechanically designed' to play a part in this equation (they're 'mechanically designed' to keep speakers from migrating the carpet, and to, instead, transfer possible vibrations to many other types of floors, sometimes with surprising efficiency).
And of course soft, plyable and preferably heavy materials are key in decoupling the speakers mechanically from your concrete, wood, or other enthousiastically resonating rigid structures.
Rubber, and rubber associated materials, immediately come to mind (and have in fact long been used to perform exactly this function quite effectively). Case in point are Genelec's (!!) standard issue rubber feet accompanying their complete range of near field monitors.
There's tons of rubber-like materials you can experiment with, and (if vibration tranmissions are indeed a problem you are dealing with) each will yield a measurable and sometimes audible effect.
I'd say, depending on your hourly rate, a retail price of $ 1.000 - 1.700 gives you quite some time to experiment. Or just get Genelecs for that money, including rubber feet.
This is just a long story, about a rip off for very little audible effect, that you can easily solve otherwise.
Ah, and when you DO experiment (with ten to 25 dollars worth of materials), keep in mind that a combination of massive and foamlike rubbers with different densities works best, because each takes care of a range of frequencies.
Happy listening!
