Sony XMZZR3301 Class D Mono Subwoofer Amplifier (Grey) (Discontinued by Manufacturer) Rated Power: 600W RMS (50Hz 1.0% THD+N, 2 Ohms) Rated Power: 330W RMS (20Hz-200Hz 1.0% THD+N, 4 Ohms) High Level Sensing Power On Subsonic Filter: 6-70Hz, OFF, -12dB/Oct Low Pass Filter: 50-300Hz, -12dB/Oct