My father in-law bought a Sherwood Home Theater systems a while back. THe speaker hookup is unusual with the front left and right speaker hookups running through the subwoofer. There is no subwoofer specific connection or wire. Now he decided to upgrade to a brnad new Pioneer receiver but doesnt want to replace the speakers. The question is: how does the sherwood system subwoofer gets its signal? and secondly how do I hook it up with the pioneer system?