Need help?Do you have a question about the Harman JBL MA704 and is the answer not in the manual?
The JBL Marine MA704/MA4505 Amplifiers are designed to provide high-performance audio for marine environments, offering robust power and versatile connectivity for various speaker configurations. These amplifiers are built to deliver the sound quality expected from JBL products, ensuring an enhanced listening experience on your boat or vehicle.
The JBL Marine MA704/MA4505 amplifiers serve as the central power unit for your marine audio system, boosting audio signals from your source unit to drive speakers and subwoofers. They feature multiple input and output channels, allowing for flexible system designs, from basic stereo setups to multi-channel systems with dedicated subwoofers.
The amplifiers include a power indicator that illuminates blue when the unit is receiving power and playing, providing a visual confirmation of operation. A protect indicator illuminates red if the amplifier enters protect mode, signaling conditions such as over/under voltage, short circuit, output circuit failure, or excessive heat. This protection mechanism safeguards the amplifier and connected components from potential damage.
Speaker output connectors are provided for connecting your speakers, with clear markings for positive (+) and negative (-) terminals to ensure proper polarity. The MA704 is a 4-channel amplifier, featuring Front L+, L-, R+, and R- terminals, and Rear L+, L-, R+, and R- terminals. The MA4505 is a 5-channel amplifier, adding Sub + and - terminals for subwoofer integration.
Input options include both low-level (RCA) and high-level inputs, accommodating various source units. If your head unit has preamp outputs, you can connect them to the FRONT, REAR, and/or SUB inputs using RCA patch cables. For head units without line-level outputs, supplied bare wire-to-RCA adapters allow connection to the speaker outputs, with set screws for secure wire insertion. The MA704 also includes PRE OUT outputs, enabling connection to a second amplifier.
Crossover filter selectors (X-OVER) allow you to tailor the frequency response for different speaker types. You can choose between Low Pass (LP) for subwoofers or mid-bass speakers, Full Range (FULL) for full-range speakers without a subwoofer, or High Pass (HP) to prevent low bass from reaching midrange or full-range speakers when a subwoofer is in use. Crossover-filter frequency controls (FREQ) allow fine-tuning of the crossover point, adjusting the dials to the left to lower the point and to the right to raise it, based on listener preference.
Input level selectors (GAIN) are crucial for matching the amplifier's input sensitivity to the output level of your source unit, ensuring optimal signal processing without distortion. For the MA4505, a SUB INPUT selector allows you to choose between internal summing (INT) for source units without a subwoofer output or external input (EXT) if your source unit has a dedicated subwoofer output. Phase adjustment (0° or 180°) for the subwoofer output helps optimize bass response, and a Bass Boost feature (0dB to +9dB) allows for further enhancement of low frequencies.
Installation and Wiring: Proper installation is critical for optimal performance and longevity. The manual provides detailed instructions and precautions. It is recommended to choose a safe mounting location that allows for adequate air circulation to prevent overheating. The amplifier should be mounted on a flat surface, away from moisture, fuel lines, and wiring harnesses that could interfere with its operation.
Power input connections require running a power wire from the +12V input to the vehicle's battery, with an appropriate fuse holder and fuse installed within 18 inches (457mm) of the battery. The ground wire should connect from the GND input to the battery's negative terminal, using the same gauge as the power wire. A remote wire connects from the source unit's "Remote Out" lead to the REM input, turning the amplifier on when low-level input signals are used.
Setting Input Levels: To match the amplifier's input sensitivity (gain) to your source unit's output level, a specific procedure is recommended:
For input level selection, if using RCA-level outputs from your radio, set the Input Level switch to "LO." If using high-level outputs, start with the "HI1" position. If the audio signal fails to play when connected to the audio system's speaker outputs, switch to "HI2," which includes a circuit designed to "fool" factory audio systems into detecting a speaker. The "HI2" setting should not be used with aftermarket head unit's line-level outputs.
Setting the Crossover: Properly setting the crossover filter selectors optimizes frequency distribution for efficient speaker operation and sound quality.
Adjusting the Subwoofer (MA4505): If connecting a subwoofer to the MA4505 amplifier and your source unit lacks a subwoofer output, select INT for the SUB INPUT to send a summed audio signal to the subwoofer. If your source unit has a subwoofer output, select EXT to connect to that output.
Subwoofer Phase and Bass Boost: You can choose a subwoofer phase output of 0° or 180°. To check your sub's phase, play music with lots of bass and listen as another person slowly flips the 0/180 degree phase switch back and forth. The correct setting is the one that gives you more bass. The Bass Boost dial can be turned clockwise to increase the bass output from 0dB to +9dB.
Troubleshooting: The manual provides a comprehensive troubleshooting guide to address common issues:
Fuse Replacement: Only replace fuses with those of the same amperage. For the MA704, use 30A fuses. For the MA4505, use 30A fuses.
General Care: Keep the owner's manual and sales receipt in a safe place for future reference and warranty service. If you lack the knowledge or tools for installation, it is strongly recommended to consult an authorized JBL dealer. This ensures proper installation and prevents potential damage to the amplifier or your vehicle's electrical system.
General| Type | Marine Amplifier |
|---|---|
| Channels | 4 |
| RMS Power (4 Ohms) | 70W x 4 |
| RMS Power (2 Ohms) | 100W x 4 |
| Bridged RMS Power (4 Ohms) | 200W x 2 |
| Frequency Response | 20Hz - 20kHz |
| Signal-to-Noise Ratio | >80dB |
| THD at Rated Power | <1% |
| Crossover Slope | 12dB/octave |
To Next Page