If the speaker has enough weight they work great on carpet if its not too thick, even better on hardwood floor. If there are any spike inserts should remove them so the entire base rests on the Svelte so it can absorb the energy from the cabinet. I have used them on Proacs 55lbs, Spendors 100lbs and Sonatinas 65lbs with great results. Drains the resonance energy away from the speaker much better than spikes when used under the right conditions. Peter at Symposium is a good guy, check with him.
Symposium Svelte's under speaker's...who has them?
I helped a friend place a pair under his Quatro's today and it was a small PIA(I had to since it was my idea and I'm sure they're better than the MDF shelves he was using).