Well. I've a little sony ht. It has a 100w subwoofer. It has been working fine for about 1 year. Then one day the sub stop working. It turns on sometimes but when a low frequency comes at moderate volume it turns off and a click noise is heard. I think these subwoofers has an auto disconnection function to prevent some damage when the volume is too high or something like that, but it happens at low or moderate volume. Sometimes the sub never turns on or sometimes it works perfectly. But almost always it only works at low volume, and if a high volume low frecuency comes it disconnects and then you hear the click noise. 2 or 3 seconds later you hear again the click noise and it sounds again... What could it be.. Sorry about my bad english but I'm from Mexico.. lol..