Rockford Fosgate PM400X4 4-Channel Marine Amplifier

The Rockford Fosgate PM400X4 is a four-channel marine and motorsports amplifier built to add clean, configurable power where a source unit alone is not enough. It is designed for boats, off-road vehicles, and other installations exposed to demanding environments. Its four-channel layout supports front and rear speakers, component systems, or mixed speaker-and-subwoofer configurations.

Rated at 50 watts RMS per channel at 4 ohms, the PM400X4 provides an appropriate power range for many marine coaxial and component speakers. It can also deliver 100 watts RMS per channel at 2 ohms, or 200 watts RMS to each of two bridged 4-ohm channels. This flexibility lets an installer tailor the amplifier to a straightforward four-speaker system or a three-channel system with speakers and a subwoofer.

The amplifier uses Class A/B circuitry for full-range amplification across a 20 Hz to 20 kHz frequency response. Variable high-pass and low-pass crossover controls allow speakers and subwoofers to be assigned more suitable frequency ranges. A built-in Punch EQ provides adjustable bass enhancement at 45 Hz, with treble adjustment also available for additional tonal tuning.

For marine and powersports use, the PM400X4 combines a cast-aluminum heatsink with a marine-grade two-part epoxy-coated circuit board and stainless-steel hardware. These construction details are intended to help protect the amplifier's electronics and mounting hardware in moisture-prone installations. Short-circuit, over-current, and thermal protection circuits add operational safeguards.

Installation flexibility includes low-level RCA inputs, high-level input capability, and an automatic turn-on circuit for compatible factory-style speaker-level signals. The 2/4-channel input selector can simplify signal routing when the source unit has only one pair of outputs. C.L.E.A.N. setup indicators help with gain adjustment, while RCA pass-through outputs can support expansion with another amplifier.

Key Features

• Four-Channel Class A/B Design: Powers front and rear speakers from one amplifier.
• Flexible RMS Output: Supports 4-ohm, 2-ohm, and bridged system layouts.
• Variable Crossovers: Helps direct appropriate frequencies to speakers or subwoofers.
• Punch EQ: Adds adjustable bass and treble tuning capability.
• Marine-Grade Construction: Uses epoxy-coated circuitry and stainless-steel hardware.
• High-Level Input Capability: Works with compatible speaker-level source signals.

Design & Installation

The PM400X4 uses a cast-aluminum heatsink, a stealth top-mounted control panel, marine-grade stainless-steel hardware, and a two-part epoxy coating on its circuit board. Its compact amplifier chassis measures 2.38 by 7.76 by 11.03 inches. Convection cooling and protection circuitry are integrated for normal operating use.

Mount the amplifier in a secure location with ventilation and protection from direct water exposure. Use 4 AWG or 8 AWG power wire, install the required external 60-amp fuse, and match speaker wiring to loads no lower than 2 ohms per channel or 4 ohms when bridged. The variable 50-250 Hz crossover, input selector, and C.L.E.A.N. indicators should be set during installation to suit the connected speakers, subwoofers, and source unit.