The Mystery MBS-204A is an active compact subwoofer designed to enhance the low-frequency audio output in a car audio system. It integrates an amplifier and a speaker into a single unit, making it a convenient and space-saving solution for adding bass.
Function Description
The MBS-204A serves as a dedicated low-frequency reproducer, taking audio signals from a source unit (like a car stereo or CD player) and amplifying them to drive its internal speaker, producing deep bass. It features both low-level (RCA) and high-level (speaker wire) inputs, offering flexibility in connecting to various car audio systems. The device includes controls for adjusting key audio parameters such as gain, phase, and crossover frequency, allowing users to fine-tune the bass output to match their vehicle's acoustics and personal preferences. A remote controller is also provided for convenient volume adjustment from the driver's seat.
Important Technical Specifications
- Model: MBB-204A
- RMS Power @ 13.8VDC:
- 4 Ohm stereo: 60W x 1
- 2 Ohm stereo: 90W x 1
- Sub-woofer @ 4 Ohms: 200W x 1
- Speaker Impedance: 4 Ohm
- THD Distortion: <0.08%
- IMD Distortion: <0.08%
- Frequency Response: 50Hz~160Hz
- Input Sensitivity:
- Low Level Input: 200mV~2V
- High Level Input: 2V~20V
- Input Impedance: 15K
- Signal-to-Noise Ratio: 85dB
- Remote Gain Control: 0.2V~+6V
- Crossover Network:
- Sub-woofer Filter: 40Hz~160Hz
- Bass Boost: 0dB~+12dB
- Indication LED: Green (Power) / Red (Protection)
- Protection: Short circuit, Temperature
- Size (L x W x H): 350 x 232 x 70mm
Usage Features
The MBS-204A offers several features for user control and system integration:
- Low Level Input (RCA): These inputs (Left and Right channels) are designed for connecting to pre-amplifier outputs of a source unit (head unit, CD player, DAT, etc.) or an external electronic crossover. This provides a clean, low-noise signal path for optimal audio quality.
- High Level Input: This terminal allows connection directly to the speaker outputs of a CD player or other source unit. It is particularly useful for systems that lack dedicated RCA pre-outs. It's important not to use both low-level and high-level inputs simultaneously.
- Gain Control: A knob for adjusting the overall volume level of the subwoofer. This allows users to balance the subwoofer's output with the rest of the car's audio system.
- Phase Adjustment: A switch that allows adjusting the phase from 0 to 180 degrees. This helps to ensure that the subwoofer's output is in phase with the main speakers, preventing cancellation and improving overall bass impact and clarity.
- Crossover Frequency Adjustment: A knob to set the low-pass filter frequency, ranging from 50Hz to 160Hz. This control determines the upper frequency limit that the subwoofer will reproduce, allowing for seamless integration with the main speakers and preventing the subwoofer from playing frequencies that should be handled by other speakers.
- Power/Protection LED: A dual-color LED indicator. It illuminates green when the unit is powered on and operating normally, and red if the amplifier enters protection mode due to a fault (e.g., short circuit, overheating).
- Remote Controller Outlet: A port for connecting the included remote controller.
- Remote Controller: A separate volume level knob that allows for convenient adjustment of the subwoofer's gain from the driver's seat. For optimal use, the main gain knob on the amplifier should be set to maximum before using the remote.
- Power Connections:
- +12V: Connects to the anode (positive terminal) of the car battery, ideally with an appropriate fuse value.
- REM (Remote Turn-On): Connects to the remote turn-on lead from the source unit. This terminal controls the amplifier's switching on and off, ensuring it only operates when the car's audio system is active. The applied voltage must be between 7 and 15 VDC.
- GND (Ground): Connects to the car chassis. It is crucial to keep the length of the ground cable to a minimum to ensure a stable and low-resistance connection.
Maintenance Features
The manual provides a "Trouble Shooting Guide" to assist users in diagnosing and resolving common issues, which can be considered a form of user-level maintenance.
- No Sound:
- Power LED not illuminated: Check amplifier fuses, ensure turn-on lead is connected, check signal leads, gain control, tuner/deck volume, and clean fuse holder contacts.
- Diagnosis LED illuminated: Check for speaker short or amplifier overheating.
- No power to power wire: Repair power wire or connections.
- No power to remote wire with receiver on: Check connections to radio.
- Fuse broken: Check and replace the fuse.
- No Sound in One Channel:
- Check Speaker Leads: Inspect for short circuit or an open connection.
- Check Audio Leads: Reverse Left and Right RCA inputs to determine if the issue is with the amplifier or the source.
- Amp Turning Off Medium/High Volume:
- Check speaker load impedance: Ensure proper speaker load impedance recommendations are observed. Note that DC resistance (measured with an ohmmeter) may differ from AC impedance.
- Temperature shutdown: Turn radio down to reduce heat.
- Protection LED On (Red):
- Speaker wires short circuit: Separate speaker wires and insulate them.
General Warnings and Installation Guidelines:
- Pre-installation Inspection: Thoroughly investigate the car's layout before drilling or cutting, paying attention to gas lines, brake lines, hydraulic lines, and electrical wiring.
- Mounting: Do not mount the system in a way that exposes wire connections to pinching or damage from nearby objects.
- Fusing: The +12V DC power wire must be fused at the battery's positive terminal connection.
- Power Connections: Always disconnect the +12V wire at the battery end before making or breaking power connections to the system.
- Source Unit Off: Confirm that the radio/cassette player and other equipment are turned off while connecting input jacks and speaker terminals.
- Fuse Replacement: If a fuse needs replacement, use only a fuse identical to the one supplied with the system. Using a different type or rating may void the warranty and damage the system.
The MBS-204A is designed for ease of installation and use, providing robust bass performance within a compact form factor, making it suitable for various vehicle types.
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