I have always gone with: if the floor is solid underneath the speaker, concert slab etc, couple the speaker with spikes or something similar. If you are on a suspended floor (basement or another floor or crawl space underneath), decouple the speaker and don't use spikes. I have had good luck with Herbies gliders, but I do not use them with spikes like Bill does, just the big fat dot in a glider on the bottom of the speaker. You can also use some heavy duty felt as a decoupling device, it is not as good as some commercial products but works very well and is cheap and easy to do.