would appreciate help out there for the following: Contractor installed multiple room speaker cables behind walls/molding of new apartment. Living room has wall mounted monitor audio radius 90 speakers and monitor audio radius 360 subwoofer. Problem is contractor only ran one cable from amp (NAD C352) via Niles SVL-4 speaker selctor controller to subwoofer; should have run pair of cables for right/left input. Not practical to rip our cable and start over. How can I properly connect subwoofer to amp/speaker select controller.