JL Audio MediaMaster MM55-HR Hidden Marine Source Unit, NMEA 2000 MFD Control, 10-16V DC, 25W x 4 @ 4 Ohm

Overview

The JL Audio 010-03372-00 is a hidden marine source unit that brings Bluetooth, radio, and USB audio into a three-zone boat system, with control handled through NMEA 2000. It runs on 12 V negative-ground power (10 V to 16 V input), includes a built-in 4-channel amplifier rated 25 W x 4 at 4 ohms, and uses a 15 A fuse.

This is meant to mount out of sight in a console or behind a panel, then get operated from a compatible NMEA 2000 control option at the helm and around the boat. The chassis measures 7.68 in x 2.28 in x 4.96 in (195 mm x 58 mm x 126 mm), which helps when you are planning a protected mounting spot with room for cabling and airflow.

Key features

• Hideaway receiver format for installs where you want the stereo brain tucked away and the dash kept for navigation and switches.
• NMEA 2000 connectivity with Micro-C connector and LEN 1 for integration on a vessel backbone.
• Three audio zones (Z1, Z2, Z3) with separate line-level outputs for left, right, and subwoofer per zone.
• Built-in 4-channel amplifier (25 W x 4 at 4 ohms) with 2 ohm minimum per channel support.
• Speaker-level outputs for Zone 1 and Zone 2, plus dedicated RCA outputs for all zones for systems that mix internal power and external amplifiers.
• Preamp output voltage up to 4 V RMS, with fixed output options selectable at 4 V, 2 V, or 1 V RMS.
• Bluetooth audio streaming supports SBC and Qualcomm aptX, with connection range up to 35 ft (11 m) in open space.
• AM and FM tuner with RDS, plus DAB+ tuning support and up to 18 presets across tuners.
• USB 2.0 input plays MP3, MP4, WAV, AAC, M4A, M4B files and provides up to 1 A device charging.
• Water-resistant construction for typical marine exposure; avoid submersion and high-pressure spray.

Compatibility and control

The unit needs a compatible NMEA 2000 control option to operate. Full functionality is available through a network controller, or through a compatible multifunction display when used with the appropriate MFD data interface. NMEA 2000 control compatibility depends on the entertainment PGNs supported by the display and may require software updates on the helm side.

Electrical and network integration

Power is for 12 V negative-ground systems only. Plan for a clean 10 V to 16 V DC supply, protect the circuit with a 15 A fuse, and keep grounding solid to avoid noise in the audio system. If your boat is 24 V, use a proper DC-DC converter that can handle peak current demand.

On the network side, the Micro-C NMEA 2000 connection drops onto your backbone like any other device, so you will want an open T-connector and correct termination in place. The three-zone layout is a practical fit for boats with separate listening areas such as cockpit, cabin, and bow seating, where each zone needs its own level and tone control.

Installation notes

Choose a dry, well-ventilated location and mount it securely so vibration and pounding do not stress the connectors. If the boat sees frequent washdowns, keep the unit away from direct spray and leave a drip loop on wiring where possible. When routing power, speaker, and RCA runs, keep them away from ignition wiring and high-current conductors, and use grommets and loom anywhere the harness passes through fiberglass or metal.

Who it suits on board

This setup fits boats where you want the head unit out of sight and you already have, or plan to add, networked control at the helm and around the vessel. It also makes sense for multi-zone systems that use internal amplification for a couple of areas while feeding external amps for larger zones.

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