DB Technologies MarkII Sub-12

DB Technologies MarkII Sub-12 ... the ports are rear-mounted and feature a flared design, air turbulence at high listening levels is minimized for the cleanest sound. The amplifier features high and low level inputs, filtered high and low level outputs, phase switch, volume control, auto on/off (activated by an input signal) and a variable 12dB/octave electronic low pass filter. This subwoofer reproduces serious low-frequency bass that will rival the performance of much more expensive subwoofers."