While solid objects are often couplers, it’s a matter of at what frequency. Cones, spikes, and Sorbothane type rubber products provide isolation above a certain frequency---around 10Hz, it is said, not nearly low enough. Springs can provide isolation down to a lower frequency, as can air bladders. They act as a mechanical low-pass filter (behaving just like an electronic filter), attenuating vibrations above a corner frequency (and at a certain slope rate), and allowing them to pass through above that frequency (also at a certain rate). The lower the corner frequency the better, of course. The lower the frequency, the better the isolation. And the more expensive the price ;-) . Some make the claim that couplers (cones and spikes) allow vibrations to be drained out of whatever is placed on them, others dispute that claim. AS MG suggests, try it for your self---they are relatively cheap. I, like Geoff, suggest the DH Golden Sound Ceramic Cones. F brass---it's too soft.