Been getting an increasing rumbling sound from my 10 year old sub as its level turned up (not even a third of the way). Came across a 2010forum post of mine in which I had a noise problem with this sub. Opened the back and found some wires dangling. Taped them up and the noise was gone. Figured that I was having the same problem now. Opened the sub and found the tape was unwound and lying on top of the speaker. Retaped the wires, but now still getting the rumbling sound. Is this repairable? And if it is (I naively suspect that the problem is with the speaker cone?), how do I get to work on the speaker as I can't figure how to get to it. Specifically, the grill screen doesn't come off and opening in the back is rather smallish.