why spikes under speakers???

Actually, woofers can move enclosures. Try putting your cell phone on vibrate mode and set it on the counter. Watch what happens when it rings. It doesn't stand still..

thanks guys!

I have achieved substantial improvement in the sound of tower speakers that were already spiked on a carpet, by placing them on a spiked stand on the carpet. I think that having the speaker lifted away from the carpet (even that it was already on spikes) seems to help the sound. I can't even begin to speculate why this is true. I don't think its tweeter height, as I do experiment with seating position height. I've done this with with several pairs of Thiels, Proac 2.5, Spendor FL-9 and now Silverline Sonatina II's. The degree of improvement always surprises me (you'd think I'd learn, but nah... ; - )
Art

Just to add to Goinbroke's correct explanation of what spikes are all about, the decoupling of the speakers will give an impression of less bass but in reality there will be more extesion in the lower region (less boom) and not only that but the overall sound will be cleaner.

I'm going to be lazy right now and not do the actual math, but the length of a low bass signal is about 20 feet or more, if I remember correctly. A space of 1-3 inches doesn't greatly diminish its transmission.

This leads me to another discussion that a friend brought up. If my listening room is 18 feet long by 12 feet wide, is there a practical limit to how low a bass signal I can hear in the room? That is, if the length is shorter than the distance between the low-bass waves, does that stop me from hearing them?