Memphis MJP800.4 4-Channel Car Amplifier

The Memphis MJP800.4 is a four-channel car amplifier designed to add substantial, controllable power to a vehicle speaker system. It delivers 125 watts RMS to each of four channels at 4 ohms or 200 watts RMS per channel at 2 ohms. This makes it a practical choice for powering front and rear speakers, component systems, or other full-range speaker arrangements.

For systems that need higher output from fewer channels, the MJP800.4 can be bridged to provide 400 watts RMS x 2 at 4 ohms. Its stereo channels are stable down to 2 ohms, while bridged operation requires a 4-ohm or higher load. This flexibility lets installers configure the amplifier around compatible speakers and the system's power goals.

The amplifier uses variable high-pass and low-pass crossovers to help direct appropriate frequencies to connected speakers. Each crossover adjusts from 50Hz to 250Hz with a 12dB-per-octave Butterworth slope. Independent front and rear crossover controls support different setup needs across the vehicle.

A selectable three-position EQ boost provides 0dB, +6dB, or +12dB settings for tonal adjustment. The amplifier's 10Hz to 25kHz frequency response supports full-range audio use, while its rated THD is below 1%. Gain controls help match the amplifier to the output level of the connected source unit.

The MJP800.4 accepts both low-level and high-level source signals, making it suitable for many aftermarket and factory-radio integration projects. Its compact extruded-aluminum heatsink chassis is intended for installations where ventilation and efficient use of space matter. It fits naturally into a speaker-focused upgrade path when more output and crossover control are needed than a head unit can provide.

Key Features

• Four-Channel Output: Powers four speakers with up to 200 watts RMS per channel at 2 ohms.
• Bridged Capability: Combines channel pairs for 400 watts RMS x 2 at 4 ohms.
• Variable Crossovers: High-pass and low-pass filters help tailor speaker frequency ranges.
• 12dB Butterworth Slopes: Provides controlled frequency rolloff for speaker protection and system tuning.
• Selectable EQ Boost: Offers 0dB, +6dB, and +12dB adjustment positions.
• High- and Low-Level Inputs: Supports aftermarket RCA signals and compatible speaker-level integration.

Design & Installation

The MJP800.4 is built on an extruded aluminum heatsink chassis with exposed aluminum details and an orange accent strip. Its listed dimensions are 7.5 x 2 x 8.7 inches, supporting placement in many trunk, hatch, behind-seat, or side-panel installations. The heatsink design is intended to help manage operating heat when the amplifier is mounted with adequate airflow.

Use a 4-gauge amplifier wiring kit as recommended by Memphis, with the power fuse installed near the battery. Mount the amplifier securely in a ventilated location and avoid mounting it with the fins facing downward. Verify speaker impedance before wiring: use 2 to 8 ohms per stereo channel, or 4 to 8 ohms for each bridged channel pair.