Bose 402C Controller Manual

The Bose 402C Controller is a professional sound system controller designed for use with Bose 402 Series loudspeakers. It provides precise control over audio parameters including equalization, crossover settings, input sensitivity, and system protection. Below are key sections for safety, features, installation, setup, operation, and troubleshooting.

1. Features at a Glance 2. Installation 3. First-Time Setup 4. Specifications 5. Controls and Settings 6. Connecting Devices 7. System Configuration 8. Protection Features 9. Care & Maintenance 10. Regulatory Information 11. Troubleshooting

Features at a Glance

Key components: Main control unit with rotary knobs and switches, input/output connectors, power supply, and status indicators.

Feature	Description
Input Sensitivity Control	Adjusts input level for optimal signal-to-noise ratio
3-Band Equalizer	Provides precise control over low, mid, and high frequencies
Crossover Network	Built-in crossover for proper frequency distribution to speakers
System Protection	Thermal and overload protection circuits
Status Indicators	LEDs for power, signal, and protection status
Balanced Inputs	XLR and 1/4" TRS connectors for professional audio sources
Output Connectors	Speakon and binding post outputs for speaker connections
Power Switch	Main power control with standby mode
Ground Lift Switch	Eliminates ground loop hum
Rack Mountable	Standard 19-inch rack mount design

Installation

Unpack and inspect contents. Mount in standard 19-inch rack or place on stable surface.

Rack mounting: Use provided rack ears and screws to secure in rack.
Connect audio sources: Use balanced XLR or 1/4" TRS cables from mixer to controller inputs.
Connect speakers: Use appropriate speaker cables from controller outputs to Bose 402 speakers.
Connect power: Plug into appropriate AC power source.

WARNING! Ensure proper ventilation; do not block cooling vents. Use appropriate gauge speaker wire.

First-Time Setup

Power on controller; verify status indicators.

Set input sensitivity: Adjust input level control until signal LED illuminates with normal program material.
Configure equalization: Set EQ controls to flat position (12 o'clock) initially.
Set crossover frequency: Adjust based on speaker configuration and application.
Test system: Play audio through system and make fine adjustments as needed.

CAUTION! Always power down system before making connections. Ensure proper grounding.

Specifications

Inputs: Balanced XLR and 1/4" TRS, 20k ohm impedance.
Outputs: Speakon and binding posts, compatible with 4-8 ohm loads.
Frequency Response: 20Hz - 20kHz, ±1dB.
Total Harmonic Distortion: <0.05% at rated output.
Signal-to-Noise Ratio: >100dB, unweighted.
Crossover Frequencies: Adjustable 80Hz - 3kHz.
Equalization: 3-band with ±12dB adjustment range.
Power Requirements: 100-240V AC, 50/60Hz.
Dimensions: 19" x 1.75" x 10" (rack mount).
Weight: 8.5 lbs (3.9 kg).

Controls and Settings

Front Panel: POWER switch, INPUT LEVEL control, 3-BAND EQ controls (LOW, MID, HIGH), CROSSOVER FREQUENCY control, STATUS LEDs.

Rear Panel: INPUT connectors (XLR, 1/4" TRS), OUTPUT connectors (Speakon, binding posts), GROUND LIFT switch, AC POWER connector, FUSE holder.

Input Level: Adjusts sensitivity from -20dB to +20dB. Equalization: LOW (40Hz-400Hz), MID (400Hz-4kHz), HIGH (4kHz-20kHz). Crossover: Continuously adjustable 80Hz-3kHz. Protection: Automatic thermal and overload protection with status indication.

Connecting Devices

Audio Sources: Balanced connections from mixer or preamp. Speakers: Properly rated cables to Bose 402 speakers.

Turn off all equipment before making connections.
Connect audio source to INPUT connectors using balanced cables.
Connect speakers to OUTPUT connectors observing proper polarity.
If hum is present, engage GROUND LIFT switch.

Tip: Use high-quality, shielded cables for best performance. Keep power cables separated from audio cables.

System Configuration

Optimize settings for your specific application.

Speech reinforcement: Slight reduction in low frequencies, emphasis on mid-range clarity.
Music playback: Flat EQ initially, adjust to room acoustics.
Live sound: Set crossover based on speaker complement and venue size.
Monitor use: Adjust EQ to reduce feedback potential.
System tuning: Use real-time analyzer for precise room correction.

WARNING! Do not drive system into clipping. Monitor output levels to prevent speaker damage.

Protection Features

Thermal Protection: Automatically reduces output if temperature exceeds safe limits. Overload Protection: Limits output current to prevent amplifier and speaker damage. Status Indicators: LEDs show normal operation, signal present, and protection active.

Care & Maintenance

Unplug before cleaning. Use soft, dry cloth only; avoid liquids and chemical cleaners.

CAUTION! Do not operate in extreme temperatures or humidity. Keep ventilation openings clear.

Regulatory Information

FCC Part 15: Class A digital device; complies with interference limits for commercial use. CE certified for European markets. Copyright © Bose Corporation. All trademarks are property of Bose Corporation. For support, visit www.bose.com or contact Bose Professional Division.

Troubleshooting

Symptom	Possible Cause	Corrective Action
No output	Power/connections	Check power connection; verify input source is active; check all cable connections.
Distorted sound	Overload/clipping	Reduce input level; check for damaged cables; ensure proper speaker impedance.
Hum or buzz	Ground loop	Engage ground lift switch; ensure all equipment is properly grounded.
Protection LED on	Overload/overheat	Allow unit to cool; reduce output level; check speaker impedance.
Intermittent operation	Loose connections	Check all cable connections; inspect connectors for damage.

Reset: Power cycle unit if abnormal operation occurs.

Service: Contact Bose Professional support or authorized service center.