natural fibers are generally more absorptive than synthetic. you should not need a pad with an area rug except for the type that keeps it from sliding on the wood. to give you some personal experience on this: my listening room has wall-to-wall synthetic carpet; i have a thick wool chinese rug ( approx. 5'x8') in front of my speakers, which makes my system sound perceptively better than without it. plus, its quite handsome and ties together the whole listening space.
