Kicker 51LX5004 4-Channel Car Audio Amplifier Class D Amp LX500.4

The LX500.4 is a four-channel Class-D amplifier for running a full set of speakers in a car, truck, or SUV. It makes 125W RMS per channel at 4-Ohm, 225W per channel at 2-Ohm, and 450W x 2 bridged, so the same amp can handle front and rear pairs, a front stage with a bridged pair of coaxials, or an active three-way setup. Class-D output keeps current draw and heat low, which helps in tight under-seat and behind-panel mounting spots.

FIT+ technology accepts low-level signals from 125mV to 5V and speaker-level signals up to 40V, so the amp ties into a factory radio or an aftermarket source without an added line-out converter. Full differential inputs reject alternator whine and other noise picked up along the signal path, and gain-match LEDs show when input level is set correctly. Each channel pair has its own 24dB/octave Linkwitz-Riley crossover that can be set to off, high-pass from 20Hz to 5kHz, low-pass from 40Hz to 5kHz, or band-pass, with selectable 12, 18, or 24dB/octave Butterworth and 12 or 24dB/octave Linkwitz-Riley slopes.

The included LX Control Center handles the fine work from the cabin: gain trim, left-channel time delay for centering the stage at the seat, and crossover type, slope, and frequency, plus live readouts for battery voltage, amplifier temperature, output clipping, and protection status. Selectable turn-on modes and thermal, circuit, and voltage protection cover the install. A reversible center panel and a choice of 11 RGB accent colors let the amp match the rest of the build, whether it sits on display in a trunk rack or hides under a seat.