I use Herbie's gliders under my Wilson MAXX speakers to be able to move them on a hardwood floor. The use of the gliders did not change the sound at all. If I place my hand on the bottom of the speaker when played loud, I don't feel any vibration whatsoever due to the cabinet material and their weight, so that may be the reason they did not change sound. I really like them and recommend you give them a try; my guess is you won't send them back.
Herbies Pucks floor spike protectors...
My very heavy speakers came with 3 spikes per speaker....the floor is travertine tiles. Use or not use? (not for floor protection, but for sound improvement)