Thiel 3.6 and 'grounding' / insulating

Congrat's on your house. Sometimes, with speakers that possess prodigious bass output like the 3.6's, it can be disadvantageous to postively couple the speakers to a more resonant suspended wood floor, especially if no carpet is laid, but it all depends on the particular situation. I would first experiment with setting them up the way you have been to see if there might be a problem at all. If there is, it is entirely possible that a combination of mass-loading the speaker base and distributing the load over more of the floor area as you propose could help out. The last resort for a severe problem would be damping/decoupling using some sort of compliant material underneath - such as carpet. (Or, if the floor in question is a ground level, you can look into ways to reinforce the floor from below - especially directly underneath the speaker positions - providing a more solid connection to the foundation.)

Thank you for your response. I will do some in-depth (no pun intended) testing of the bass performance with spikes on quarters. I just needed confirmation of my idea that, by adding a couple of massive slabs of granite, the bass-coupling to the floor would be diminished. I could always move the carper over to the speakers and put the slabs on the carpet, then the speakers with spikes on the slabs. Looks like I'll be shoving heavy boxes around again for a few days, hehe.
Thanks again.

Thiel 3.6's tend to have plumy bass on most any music except classical. I have found by using the brass Audiopoints from Star Sound the bass becomes more articulate with much better speed. Added benefit of cleaning up the bass is you now have a better defined midrange and more focused and quieter soundstage. If you have hardwood floors you will also need the brass coupling discs. A friend of mine was astounded by the substitution of the Audiopoints for the steel ones supplied by Thiel.