Rockford Fosgate P400X4 400W 4-Channel Amplifier

The Rockford Fosgate P400X4 is a four-channel car amplifier designed to add dedicated power to factory-replacement or aftermarket speakers. It provides a practical upgrade path for systems that need more output and control than a head unit’s built-in amplifier can provide. Its four-channel layout supports front and rear speakers, or alternate bridged-channel configurations.

Rated at 50 watts RMS per channel at 4 ohms and 100 watts RMS per channel at 2 ohms, the P400X4 is suited to full-range speaker systems with appropriately matched power handling. It can also bridge its channels to deliver 200 watts RMS x 2 at 4 ohms. This flexibility allows it to serve a conventional four-speaker installation or a system combining stereo speakers with bridged channels.

The P400X4 uses a Class A/B circuit topology for full-range amplification across a 20 Hz to 20 kHz frequency response. Separate front and rear crossover sections let an installer tailor the signal for speakers or subwoofer duties. The onboard Punch EQ provides adjustable bass and treble shaping according to the selected crossover mode.

Its RCA inputs accept high-level speaker signal or low-level RCA signal, helping it integrate with a wide range of source units. When high-level input is used, the amplifier can use its auto turn-on function. RCA pass-through outputs support expansion to additional amplifiers without splitting the incoming signal externally.

Rockford Fosgate includes C.L.E.A.N. clip-indicator setup support to help establish source-unit and amplifier levels during installation. Power, protect, thermal, input-clip, and output-clip indicators provide useful operating feedback. The compact chassis is intended for vehicle mounting with adequate airflow around its heatsink.

Key Features

• Four-Channel Power: Supplies 50 watts RMS x 4 at 4 ohms for speaker-system upgrades.
• 2-Ohm Stability: Delivers 100 watts RMS x 4 into compatible 2-ohm speaker loads.
• Bridgeable Channels: Provides 200 watts RMS x 2 at 4 ohms bridged.
• High- and Low-Level Inputs: Connects to speaker-level or RCA-level source signals.
• Selectable Crossovers: Front and rear HP, LP, and all-pass settings aid system tuning.
• C.L.E.A.N. Setup Indicators: Helps set input and output levels while monitoring clipping.

Design & Installation

The P400X4 combines a cast-aluminum heatsink with convection cooling and a top-mounted control panel. Its captive C-clamp power and speaker terminals provide secured wire connections, while the status LEDs identify power, protection, thermal, and clipping conditions. The amplifier measures 2.38 x 7.76 x 11.03 inches, making it suitable for many trunk, hatch, and amp-rack installations.

Use a 60-amp external fuse on the battery power lead and keep the fuse within 18 inches of the battery connection. The amplifier supports 2-ohm stereo loads or 4-ohm bridged loads; lower impedances are not recommended. Allow at least 1 inch of air space around the heatsink, connect all active RCA inputs, and use the front/rear crossover controls to match the speakers and intended channel assignment.