Wayne Parham Messages: 18786 Registered: January 2001
Illuminati (33rd Degree)
Rubber decouples the speaker cabinet from the surface it is sitting on. You're right that it does transfer some energy, but it is damped. I expect fabric cushions like your socks would even do a better job but that's inconvenient 'cause it's too loosey-goosey.
I put rubber feet under my speakers when they're on stands. It helps them stay in place while still providing some isolation.