prof, you need to listen to just your sub without the speakers playing. Use the online tone generator to see if the sub is producing sound at midrange frequencies. If it is, something is probably wrong with it or the setup. In my opinion it's illogical to fuss around with sub setup and dissatisfaction with the sound without measuring the room. If you've got a big hump somewhere that could be your problem. I recently got my old Behringer ultracurve out, hooked it up to the sub and measured the room. The room had some big bumps in the deep bass that definitely made it sound thick and slow in certain spots. I cut the two bump frequencies by 3 and 4 db and it sounds great now. I didn't come anywhere near equalizing it completely flat but I cut enough to get rid of the overloaded room sound. In the past I eq'd my system completely flat using huge cuts and it doesn't sound right. A little bit of moderate eq can be a definite improvement, though.
onlinetonegenerator.com/
onlinetonegenerator.com/