Small but mighty! Fosi Audio M04 is a 100w mono-channel class D subwoofer amplifier, with a SUB/PBTL switch you can select a subwoofer bass amplifier or full frequency mono amp, can be connected to an active/passive subwoofer and passive speaker. The power switch was integrated into volume control, we made it small but supply an in-wall or stand-alone subwoofer the power it needed so you can experience room-shaking low-frequency impact (bass) on movies and music soundtracks. Input Interface: RCA input Output Interface: speaker’s output THD: ≤ 0.02% (1KHz, 1W) Output: passive subwoofer/speaker Input Voltage Range: DC 12V - 24V SNR: ≥ 102dB Terminating Impedance: 2Ω - 8Ω Max Power Output: 100watt @3Ω Input Sensitivity: 600MV Net weight: 175g Dimensions (H * W * D): 103 x 57 x 43MM (4.06 x 2.24 x 1.69’’) includes knobs Frequency Response Range: 20Hz-20KHz(±3db) Bass Frequency Range: 20Hz-200Hz