So I purchased a used 15" subwoofer on ebay (locally). It is a Paradigm Servo 15a. It is about 15 years old but was originally a $1,500 dollar subwoofer so I am thinking this thing will be pretty nice.\n\nWith music it sounds great, no problem. But at moderately loud movie volumes it sometimes bottoms out with a POP sound during loud booming parts. I am thinking that it may be very low frequencies? Obviously I am not too happy. \n\nThe strange thing is that the subwoofer it is replacing (a Paradigm PDR-10, about the same age) is much smaller and cheaper and does not have this problem. It may not play as many of the low frequencies, but it doesn't bottom out at least!\n\nAny suggestions? I am wondering if something may be wrong with electronics? Maybe it is not pulling itself back as it should?\n\nThank you for your help!\n\nEdited to add: It is sealed instead of ported. I don't' know if that makes a difference.