Bose 901 VI Equalizer Manual

The Bose 901 VI Active Equalizer is a critical component designed specifically for use with the Bose 901 Series VI Direct/Reflecting® speaker system. It provides precise electronic equalization to compensate for the speakers' unique acoustic characteristics, ensuring accurate frequency response and optimal sound reproduction. The equalizer connects between your preamplifier and power amplifier, featuring input/output connections, level controls, and defeat switches. Below are key sections covering features, installation, setup, operation, specifications, and troubleshooting.

1. Features at a Glance 2. Installation 3. First-Time Setup 4. Specifications 5. Controls and Settings 6. Connecting to Audio System 7. Operation and Adjustment 8. Equalization Theory 9. Care & Maintenance 10. Regulatory Information 11. Troubleshooting

Features at a Glance

Key components: Active equalization circuit, Input/Output RCA jacks, Level controls, Defeat switch, Power supply.

Feature	Description
Active Equalization	Precisely shapes frequency response for Bose 901 VI speakers
Input/Output RCA Jacks	Standard audio connections for integration into stereo system
Level Controls	Adjusts output level to match system gain
Equalizer Defeat Switch	Bypasses equalization for A/B comparison with/without EQ
Power Supply	External AC adapter (included) for active circuitry
Compact Enclosure	Designed for easy placement in audio rack
Direct/Reflecting® Optimization	Tailored for 901 Series VI acoustic design
LED Power Indicator	Shows when unit is powered on
High-Quality Components	Designed for minimal noise and distortion
System Integration	Works with most stereo preamp/power amp combinations

Installation

Unpack and inspect contents. Place equalizer near other audio components.

Connect to audio system: Locate PREAMP OUT and POWER AMP IN connections on your receiver or preamplifier.
Connect equalizer input: Use RCA cable from PREAMP OUT to equalizer INPUT.
Connect equalizer output: Use RCA cable from equalizer OUTPUT to POWER AMP IN.
Connect power: Plug AC adapter into wall outlet and DC plug into equalizer.
Ensure all connections are secure before powering on.

WARNING! Always turn off all audio components before making connections to prevent damage or shock.

First-Time Setup

Power on equalizer and audio system; follow setup procedure.

Initial connection: Verify all RCA connections are correct and secure.
Power sequence: Turn on equalizer first, then preamplifier, then power amplifier.
Level adjustment: Play music at normal listening level and adjust equalizer LEVEL control for balanced sound.
Defeat switch test: Engage and disengage DEFEAT switch to hear difference with/without equalization.
Final positioning: Place equalizer in well-ventilated area away from heat sources.

CAUTION! Do not place equalizer directly on top of power amplifier or other heat-generating components.

Specifications

Model: Bose 901 VI Active Equalizer.
Compatibility: Designed exclusively for Bose 901 Series VI speakers.
Frequency Response: 20Hz - 20kHz (±0.5dB with equalization engaged).
Total Harmonic Distortion: Less than 0.1% at rated output.
Signal-to-Noise Ratio: Greater than 90dB (A-weighted).
Input Impedance: 47k ohms.
Output Impedance: 1k ohm.
Maximum Input Level: 2V RMS.
Power Requirements: 12V DC, 500mA (AC adapter included).
Dimensions: 17" W × 2.75" H × 8.5" D (43 × 7 × 21.5 cm).
Weight: 5.5 lbs (2.5 kg).

Controls and Settings

Front Panel: POWER switch, LEVEL control, DEFEAT switch, POWER indicator LED.

Rear Panel: INPUT RCA jacks (left/right), OUTPUT RCA jacks (left/right), DC POWER input.

Level Control: Adjusts output level to match system gain. Start at 12 o'clock position and adjust while playing music at normal listening level. Defeat Switch: Engages/disengages equalization circuit. Use for comparison or if equalizer needs servicing. Power Indicator: Green LED shows when unit is receiving power.

Connecting to Audio System

Standard connection: Between preamplifier and power amplifier.

Turn off all audio components before connecting.
Identify PREAMP OUT and POWER AMP IN jacks on your receiver or separate components.
Connect equalizer INPUT to PREAMP OUT using RCA cables.
Connect equalizer OUTPUT to POWER AMP IN using RCA cables.
Connect AC adapter to equalizer and wall outlet.
Turn on components in proper sequence: equalizer first, then preamp, then power amp.

Tip: Use high-quality RCA cables for best performance and minimal signal degradation.

Operation and Adjustment

Proper operation ensures optimal performance with Bose 901 VI speakers.

Power on: Switch equalizer POWER to ON position (LED illuminates).
Level setting: Play familiar music at normal listening volume. Adjust LEVEL control until sound is balanced (not too loud or soft compared to source).
Defeat function: Press DEFEAT switch to bypass equalization. Compare sound with equalization engaged and disengaged.
Normal operation: Keep DEFEAT switch in OUT position for normal use with equalization active.
Volume adjustment: Use your preamplifier's volume control for normal volume adjustments.
Shutdown: Turn off power amplifier first, then preamplifier, then equalizer.

WARNING! Never adjust LEVEL control while system is at very high volume to prevent speaker damage.

Equalization Theory

The Bose 901 VI speakers use a unique Direct/Reflecting® design that requires specific equalization to achieve flat frequency response. The equalizer compensates for the speakers' acoustic characteristics by boosting certain frequencies and attenuating others. This electronic correction allows the 901 VI to reproduce music accurately across the entire audible spectrum. The equalization curve is precisely tailored to the speaker's design and should not be modified or used with other speaker models.

Care & Maintenance

Unplug before cleaning. Use soft, dry cloth only; no liquids or chemical cleaners.

Keep equalizer in well-ventilated area. Ensure ventilation openings are not blocked. Periodically check all connections for tightness. Store AC adapter properly when not in use for extended periods.

CAUTION! Do not open enclosure; no user-serviceable parts inside. Refer servicing to qualified personnel.

Regulatory Information

FCC Part 15: Class B digital device; complies with interference limits for residential use. Copyright © Bose Corporation. All rights reserved. Bose and Direct/Reflecting are registered trademarks of Bose Corporation. For support, visit www.bose.com or contact Bose Customer Service. This product complies with applicable regulations in the country of purchase.

Troubleshooting

Symptom	Possible Cause	Corrective Action
No sound from speakers	Incorrect connections or power	Check all RCA connections; verify power adapter is plugged in; ensure POWER switch is ON.
Distorted sound	Level set too high	Reduce equalizer LEVEL control; check source material quality.
Hum or noise	Ground loop or poor connections	Ensure all connections are secure; try different power outlet; check cable quality.
No difference with defeat switch	Switch malfunction or incorrect operation	Cycle switch several times; if no change, unit may need service.
LED not illuminated	No power	Check wall outlet; verify AC adapter connections; try different outlet.
Intermittent operation	Loose connections	Check all RCA and power connections; inspect cables for damage.

Service: Do not attempt to repair equalizer yourself. Contact Bose authorized service center for repairs.

Support: 1-800-999-2673; www.bose.com