SONY XM-SD51X Class D Mono Subwoofer Amplifier Mono car subwoofer amplifier 250 watts RMS x 1 at 4 ohms (500 watts x 1 at 2 ohms) Bass boost (0-10 dB at 40 Hz); variable low-pass filter (50-300 Hz at 12 dB per octave) Preamp- and speaker-level inputs; pream outputs Wired remote control for bass boost and low-pass filter