if your speakers have a response lower then 35hz, forget that sub, polks 8" sub cannot go lower then that and normally you dont need a response lower then that unless your listening to pipe organs. not to mention its always a bad idea to use a smaller bass driver then the mid-bass driver in your speakers. im sure that 8" sub has to push HARD to keep up with the mains and its never going to sound right. 8" subs, most of them anyways, are good for picking up the low end on smaller bookshelfs with 80hz, give or take a few hz, responses, they are no match for huge floorstanding speakers. what model are your speakers?