The G4000.5D is a 5-channel car amplifier from the DS18 G series, built as a Class D design. It delivers 2 x 420 watts RMS at 4 ohms, 900 watts RMS at 1 ohms, 600 watts RMS at 2 ohms and 300 watts RMS at 4 ohms. The channels are bridgeable, so you can combine them to drive a subwoofer or a pair of higher-power speakers from the same amplifier. Total harmonic distortion is rated at 0.01% with a signal-to-noise ratio of greater than 90 dB. A selectable HPF/LPF crossover covers HPF:10-250Hz / LPF:50-250Hz, so you can send each channel only the frequencies it should reproduce. Bass boost is adjustable from 0-12dB centered between Fixed @ 45Hz. Match the amplifier to the RMS rating of your speakers or subwoofers and set the gain to that rating for clean, reliable output. | Ds18 Audio | | GEN-X 5-Channel Class D Car Amplifier | Black | Best Buy