The subwoofer has its own audio channel (aka LFE). Also, the SWS is paired (uses same pass-thru connectors) with either the 4.1 or 5.1 subwoofer using the included cables.
5.1 Subwoofer: 11.25" H x 11.875" W x 15" D
SWS Subwoofer: ??????? i can't find it either