Edorr, I have the ultras on carpet. In my case I have 2 Ultra Padz by Symposium under the front feet of my speakers, in order to raise the tweeters to desired level. If you try the Ultras let me know your results. What speakers do you have and do you have a sub? In my case, at first there seemed to be less bass, and that was correct. What was gone was a cabinet resonance around 40 to 60 Hz. What was left was tuneful bass with tempo set by bass. I did have to bring up my subs somewhat to compensate. Besides this the mids and highs improved markedly. PS As far as wood underneath, I would try it if you feel it is needed, but it never hurts to listen and hear for oneself.