I have an old Sony STR-AV720 receiver and I recently acquired an old Fisher SW6100 powered subwoofer and would like to connect the two. The receiver has speaker connections for surround sound but no subwoofer connection. The powered sub has high level input and output connections that appear to be for speaker wires and low level RCA type inputs. There are crossover dials on the back of the sub as well. What is the recommended configuration for connecting this sub to this receiver ?