I have an old SOny Surround Sound receiver. I bought Pioneer surround sound speakers - I have 2 speakers, 2 surround sound speakers, a center channel speaker and a sub woofer. The Sony receiver has labels for connecting all of the speakers except the sub woofer - although there is a place to connect two additional impedance speakers. Can I connect this subwoofer tot he existing SOny receiver or do I have to buy a new receiver that has a specific connection in the back labelled for a subwoofer?