My experience is that they don't make much if any of a difference. I've tried many kinds of isolation devises. None of them made any difference in the sound I heard. It's one of those things that fit into the "I think I heard a difference but it could be in my mind" type of thing. That said, I still use them but I wouldn't expect much of a difference. IMO. I look at them as finishing touches to an already fine system. Of course if you have your CD player on a cardboard box to begin with....:-)

Hope this helps.