This is the Bose Acoustimass 6 series 1 and series 2 in black. It is a passive 5.1 system subwoofer, designed to be used with 5.1 amplifiers rated at 100 watts per channel x 5. Series 1 is designed to be used with Bose Acoustimass classic redline double cube speakers, although can use later type for a more modern appearance. Series 2 is designed to be used with later Bose Acoustimass double cube speakers. Connection on rear is via 5 x standard RCA for inputs from the amplifier speaker outputs, 5 x standard RCA for speaker outputs to the cube speakers.