Bose 502c System Controller User Manual

The Bose 502c System Controller is a professional audio control unit designed for managing and optimizing the performance of Bose 502 Series loudspeakers. It features comprehensive equalization, crossover, and system protection controls to tailor the sound for various environments. Below are key sections covering 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 & Cleaning 10. Regulatory Information 11. Troubleshooting

Features at a Glance

Key components: System Controller unit, input/output connectors, control knobs, status indicators.

Feature	Description
Input Level Control	Adjusts input sensitivity for optimal signal matching
3-Band Parametric EQ	Precise frequency, bandwidth, and level adjustment
Crossover Controls	High-pass and low-pass filter settings for system integration
Limiter/Protection Circuit	Prevents amplifier and speaker damage from overload
Bypass Switch	Engages/disengages all processing for A/B comparison
Status LEDs	Indicates signal presence, limiting, and power status
Balanced Input/Output	XLR and 1/4" TRS connectors for professional audio connections
Ground Lift Switch	Eliminates ground loop hum
Rack Mountable	Standard 19-inch rack mount design
Power Requirement	Powered via external AC adapter or rack power supply

Installation

Unpack and inspect contents. Mount in standard 19-inch equipment rack.

Rack Mounting: Secure unit using provided rack ears and screws.
Power Connection: Connect the included AC adapter to the DC input on the rear panel.
Audio Connections: Use balanced XLR or 1/4" TRS cables to connect the controller between your mixer and power amplifier.
Connect to Amplifier: Output from the 502c connects to the input of your power amplifier(s).
Connect to Speakers: Amplifier outputs connect to your Bose 502 Series loudspeakers.

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

First-Time Setup

Power on the system; set initial controls to neutral positions.

Initial Settings: Set all EQ knobs to 12 o'clock (flat), Input Level to minimum, Bypass switch to OUT.
System Check: Send a signal from the mixer; observe the SIGNAL LED illuminates.
Gain Structure: Adjust Input Level until the mixer's nominal output level lights the 502c's SIGNAL LED steadily without activating the LIMIT LED during peaks.
Crossover Setup: Set High-Pass and Low-Pass filters according to your speaker configuration (e.g., 502A/502B).
EQ Adjustment: Make subtle adjustments to the parametric EQ to suit the acoustics of the room.

CAUTION! Always power down amplifiers before making connection changes.

Specifications

Type: Active System Controller with EQ, Crossover, and Limiter.
Frequency Response: 20 Hz - 20 kHz, +/- 0.5 dB (Bypass mode).
Total Harmonic Distortion: < 0.01% @ 1 kHz.
Input Impedance: 20 kΩ balanced.
Output Impedance: 100 Ω balanced.
Maximum Input Level: +20 dBV.
Parametric EQ: 3 bands, variable frequency, bandwidth, and level.
Crossover: Continuously variable high-pass and low-pass filters.
Limiter: Threshold adjustable, fast-attack/slow-release.
Power Supply: External AC adapter (included).
Connectors: XLR and 1/4" TRS balanced input/output.
Dimensions: 19" x 1.75" x 8" (rack width x height x depth).

Controls and Settings

Front Panel: INPUT LEVEL, 3-Band EQ (FREQ, BANDWIDTH/Q, LEVEL), BYPASS switch, POWER switch, STATUS LEDs (POWER, SIGNAL, LIMIT).

Rear Panel: BALANCED INPUT (XLR/TRS), BALANCED OUTPUT (XLR/TRS), HIGH-PASS FREQUENCY, LOW-PASS FREQUENCY, LIMITER THRESHOLD, GROUND LIFT switch, DC POWER input.

EQ: Adjust LOW (e.g., 80 Hz), MID (e.g., 1 kHz), HIGH (e.g., 10 kHz) bands. Crossover: Set points based on speaker models (e.g., 502A: HPF ~100 Hz). Limiter: Adjust threshold to protect amplifiers and speakers. Use Bypass to compare processed vs. unprocessed sound.

Connecting Devices

Mixer to Controller: Use balanced cables from mixer main/monitor outputs to 502c INPUT. Controller to Amplifier: Use balanced cables from 502c OUTPUT to power amplifier inputs.

Turn off all equipment before making connections.
Use high-quality, shielded balanced cables to minimize noise.
If hum is present, engage the GROUND LIFT switch on the rear panel.
Ensure proper polarity (Pin 2 hot) throughout the signal chain.

Tip: Label all cables for easy identification in multi-zone setups.

System Configuration

Optimize settings for your specific Bose 502 speaker array.

Determine Application: Identify if system is for main reinforcement, low-frequency extension, or stage monitoring.
Set Crossover: For 502A full-range, set High-Pass to recommended frequency (e.g., 100 Hz). For subwoofer integration, set Low-Pass on sub channel and High-Pass on main channel.
Tune EQ: Play reference music. Adjust parametric EQ to compensate for room modes or feedback tendencies. Make narrow cuts, broad boosts.
Set Limiter: Play system at maximum intended level. Adjust LIMITER THRESHOLD until the LIMIT LED flickers only on the loudest peaks.
Final Check: Engage/Disengage BYPASS switch to verify the controller is improving system sound and protection.

WARNING! Excessive low-frequency boost can damage speakers. Use high-pass filters appropriately.

Protection Features

Limiter Circuit: Protects against amplifier clipping and speaker overload. Adjustable threshold allows customization for your specific amplifiers and speakers. The LIMIT LED illuminates when the circuit is actively reducing gain.

Care & Cleaning

Unplug from power before cleaning. Use a soft, dry cloth to wipe the exterior. For stubborn marks, lightly dampen the cloth with water. Do not use solvents or abrasive cleaners.

CAUTION! Never allow liquid to enter the unit through vents or connectors. Keep in a dry, dust-free environment.

Regulatory Information

FCC Part 15: Class A digital device. This equipment is intended for use in commercial, professional audio environments. Compliance with local electrical safety standards is required. Copyright and trademarks owned by Bose Corporation. For technical support and product information, visit www.bose.com or contact Bose Professional Division.

Troubleshooting

Symptom	Possible Cause	Corrective Action
No output signal	Power/Bypass/Cables	Check POWER LED; ensure Bypass is OUT; verify all cable connections are secure.
Excessive noise or hum	Ground loop/cable quality	Engage GROUND LIFT switch; use balanced cables throughout; check for damaged cables.
Distorted sound	Input overload/Limiter	Reduce INPUT LEVEL on 502c; check mixer output isn't clipping; adjust Limiter Threshold.
LIMIT LED constantly on	Threshold set too low	Increase LIMITER THRESHOLD control until LED only flashes on extreme peaks.
No effect from EQ controls	Bypass engaged	Ensure the front panel BYPASS switch is in the OUT (disengaged) position.
Incorrect frequency response	Crossover settings	Verify High-Pass and Low-Pass filter settings match your speaker system design.

Reset: To return to a neutral state, set all rotary controls to 12 o'clock (center detent) and switches to OUT/OFF positions.

Service: This unit contains no user-serviceable parts. Refer all internal service to qualified Bose professional audio technicians.