Best vibration isolation for speakers on carpet?

+1 for Townshend speakers bars. I use them under my Harbeth M40.z Anniversary.  More difficult to adjust than the Podiums but sema results.

I have vandersteen quatros which are a big heavy speaker. I had leveling issues and bass control issues. Started out with the gaia with speaker discs. Midrange was magical but bass still to heavy and still hard to level. I called Richard vandersteen and he told me to get some granite surface plates. They're 3 inches thick and 18x24 or so. They weight an absolute ton but when I put them down they flattened the carpet and made it easy to level the speakers. The speakers are still on the Gaia but are now much more functionally isolated from the floor. Sound is amazing. Looks pretty cool too

Use butcher blocks and gaia isoacoustics

 I used the isoacoustics carpet spikes and didn't like them they were a little unstable. My speakers are very stable now and they are about 80lbs each.

I don’t have carpet. But I used to have my Magico A3s on Isoacoustics Gaia I footers. Then I tried the Townshend Seismic Podiums and that was it. The Magicos are staying on the Podiums and the Gaia Is got repurposed onto a pair of standmount speaker stands. Get the Townshend Podiums.