HK Audio LINEAR 9 118 SUB BA 1100-Watt Active Sub Stereo I/O DSP Out EQ Network - 2x18"The LINEAR 9 118 Sub BA is a powerful 18" dual vented bandpass subwoofer. The generous size of the cabinet allows for an exceptionally high sound pressure level with a low cut off frequency at the same time. This makes this subwoofer not only a perfect partner for powerful full range speakers, but also an ideal sub low extension for the direct radiating LINEAR 9 118 Sub A. Thanks to the integrated presets, cardioid setups can be implemented quickly