I have a 2 mos. old subwoofer but recently I figured out that it is producing a crackling sound especially on loud volumes while watching movies. The volume level of the sub is just set to 11 o'clock, what is that crackling sound. - What's wrong with my subwoofer? - is my subwoofer already damaged? - Do I have to return it to the store? - Is it not yet breaked-in?, how long does it take to break-in a subwoofer? Any suggestions?