Hi, I have a (not all that old) Mordaunt Short Alumni 9 sub that I would like to use in my setup (when I get all the pieces together!). The only problem is we stopped using it as it started randomly making a loud rumbling noise, even when the amp was off, sounds like rolls of thunder (thought it was at first when it woke me one night!). Other than when it's doing that it works fine, punches hard and sounds great.

Any idea what could be causing it and if it could be or is worth fixing??

Thanks