I realize I am on a Polk site (and I do own polks), this question has to do with an Infinity BU-120 sub. I tried their site - it's not very good.
Yesterday we used our Onkyo system to play a CD at normal levels. No problems, worked fine. Later in the afternoon with the audio system OFF, the sub started to pop and rapid fire - almost sounding like a machine gun. The only way to stop it is to pull the power plug. I tried it again today with the audio system OFF and the same thing is happening.
Is this the amp? The circuit board?
BTW, the sub is about 5 years old and not subjected to abuse (IMHO). This is the second time this happened. The first time it was covered under warranty (and I don't remember what was wrong).
Any help would be greatly appreciated. Thanks.