carpeting

The acoustic properties of wool are superior to any other fabric or synthetic material. However, any type of carpeting will be better than bare wood floors. Without carpeting of some kind you will have substantial reflections off the floor. I had wall-to-wall carpet installed (covering hard wood floors) and then bought Persian carpets (wool) to cover the area of the living room floor between the couch (listening position) and the speakers. The results are well worth the effort and expense.

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.