Speaker vibration isolation

Nothing beats clay ceramic patio stones with 1'' thick fiber pads made for floor polishers available at the Depot for a few bucks more, topped off with a 1/4" rubber mat. A 17X12 fiber scratch pad will take a lot of weight.

Agree on the massive patio slab as a great solution on suspended (wood) floors. I have used 2" thick concrete patio slabs under my previous Infinity RSIIa speakers, the slab up on Tip Toes. The speaker on thin layer of blue tack just to keep it stuck in place. Definitely lowered the 'bass into floor' vibration issue.
Currently, with Magnepan 20.7 and it having a large oval base, I feel no need for i, though I am still on carpeting over a suspended wood floor. (I might try the TipToes under my 20.7s sometime?? See if it tightens up the bass any?)

Clay ceramic is the key to blocking those lower frequencies