Problem with speaker at higher volumes - answers????


My buddy who is "internet deficient" asked me to try and find a solution to a problem he has with one of his speakers (Wharfedale but don't have the model although it would appear to be a generic type problem and I assume not indegenious to that particular manufacturer.) He is experiencing what he says sounds like a "thwap" sound coming from one of his speakers when he is playing it loudly and only on very dynamic passages. At lower volumes all is well and apparently the amp isn't clipping. I defer this problem to those more expert than I who reside here... Any possible answers???
rgd
Jimbo - Bryston website advises that the 3B has a damping factor of "over 500 @ 20Hz, ref. 8 ohms. For that matter the 4B is rated the same but the 7B is "300" as opposed to 500... not sure what this means or whether these are high, low or typical numbers associated with damping???
Thats definitely the voice coil bottoming out as Jimbo stated. Better turn down the volume or destroy the speakers!
Don't get wrapped up about damping factors- the 3B should be enough. If you want to keep the "sound" of the current speakers, the next model up in that series of speakers (if available) might be the answer.

Jim