It has often been recommended that if the loudspeakers are going to sit on a carpeted concrete floor, then spikes are the answer. I went along with this for a while, not really understanding the reasoning (if there was any). When I eventually did reason it out, I decided to place a 25mm thick veneered mdf board between the spiked floor standers and the carpeted floor. Sound quality improved, especially the bass, which tended to be a bit soggy, even for vented jobbies.
For those interested, the reasoning goes something like this. The drive units push (and pull) the cabinets, which tend to wobble a bit. Spikes provide a firm enough base (sic) but don't allow the vibrations to enter the concrete floor, quantitatively. Placing the floor standers on the veneered mdf helped, allowing, at least, semi-quantitative transfer of vibrations, with the carpet adding some damping to the mdf, which has very little.
