Best vibration isolation for speakers on carpet?

Townshend podiums. I would say they were the purchase the surprised me the most with how much improvement I got.

edit:  btw, podiums are the opposite of spikes.  spikes anchor the speakers to the floor to deaden the vibrations of the cabinet.  Podiums isolate the speaker from the floor and let it vibrate at the excitation frequency.

+1 for the IsoAcoustics Gaia footers with Gaia carpet discs.  Have used them on a couple different speakers with excellent results.  The carpet discs have spikes that secure to the floor.  The isolator feet sit on the discs and provide vibration control.  

Well if you feel ambitious  but a plank of very dense hardwood. You can find two inch thick purple heart quite easily.  Drill and tap three holes in it one in the front and two in the back. Put inserts into the holes and build some ready rod spikes with nuts on the to so you can level the speakers from the top. Measure in the stands you have built and level them your spikes that come with the speakers or I use disc's that cam with my speaker stand place them two at the front  on at the rear measure  the speakers on the stands. Then check out the level  on the speakers and from side to side the angle on each the toe in compared to each other etc. You have a system  that cam be adjusted  easily  that will anchor the speakers to the floor everything will be wonderful.  

Regards

I’m really happy with the Isoacoustics Gaia’s. I believe your speakers would use the Gaia 3’s and their carpet spikes, or you can do what I did and put everything on some granite slabs. 
 

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