Bose 901 IV Manual

The Bose 901 Series IV is a legendary direct/reflecting speaker system renowned for its unique acoustic design, utilizing nine full-range drivers (eight facing rearward, one forward) and an active electronic equalizer to achieve a spacious, lifelike soundstage. This manual covers setup, operation, equalizer calibration, specifications, and maintenance for optimal performance. Below are key sections for features, installation, equalizer setup, specifications, operation, care, and troubleshooting.

Features at a Glance

Key components: Two 901 Series IV speaker cabinets, Active Electronic Equalizer, Grilles, Spikes/Rubber feet, Connection cables.

Feature	Description
Direct/Reflecting Design	8 rear-facing, 1 front-facing drivers for spacious sound
Active Electronic Equalizer	Required for frequency response correction and system protection
Full-Range Drivers	Nine 4.5-inch drivers per cabinet
Acoustic Matrix Enclosure	Sealed, non-ported design for precise bass
Equalizer Bypass Switch	For A/B comparison with and without equalization
Input/Output Connections	Tape Monitor loop integration
Level Controls	Individual level adjustment for each channel
Placement Flexibility	Works best placed on stands or shelves against walls
Grille Design	Removable acoustically transparent fabric grille
Spikes/Rubber Feet	Included for stability and decoupling

Installation & Placement

Unpack and inspect contents. Choose optimal listening room placement.

1. Position speakers: Place on stands or shelves 1-3 feet from rear wall, 6-10 feet apart, angled slightly inward.
2. Attach feet/spikes: Install supplied spikes (for carpets) or rubber feet (for hard floors) to bottom of cabinets.
3. Connect equalizer: Route cables from receiver/amp tape monitor OUT to equalizer IN, and equalizer OUT to tape monitor IN.
4. Connect speakers: Use high-quality speaker wire from equalizer speaker outputs to each 901 cabinet.

WARNING! Speakers are heavy; lift with care using legs, not back. Ensure stable placement to prevent tipping.

Equalizer Setup & Calibration

The active equalizer is essential for proper sound. Power on system; follow calibration steps.

1. Integrate into tape monitor loop: Connect as described in Installation.
2. Set receiver/amp: Select TAPE MONITOR or AUX input (varies by model).
3. Adjust level controls: Set equalizer channel levels to match overall system volume.
4. Perform listening test: Play familiar music, toggle BYPASS switch to hear equalized vs. unequalized sound.
5. Fine-tune placement: Small adjustments to speaker distance from wall can dramatically affect bass response.

CAUTION! Never connect speakers directly to amplifier without equalizer. This can damage speakers and produce poor sound.

Specifications

• System Type: Direct/Reflecting® loudspeaker system with active equalizer.
• Drivers: Nine 4.5-inch full-range drivers per enclosure (8 rear, 1 front).
• Frequency Response: 35 Hz - 18 kHz (±3 dB) with equalizer.
• Nominal Impedance: 8 ohms (with equalizer in circuit).
• Recommended Amplifier Power: 10-250 watts per channel.
• Equalizer: Active, required for operation. Includes level controls, bypass switch.
• Dimensions (each cabinet): Approx. 25.5" H x 13.5" W x 12.75" D.
• Weight (each cabinet): Approx. 48 lbs.
• Finish: Walnut, Black, or White oiled oak veneer.

Controls and Connections

Active Equalizer Front Panel: POWER switch, BYPASS switch (in/out), CHANNEL 1 & 2 LEVEL knobs.

Rear Panel: INPUT (from tape monitor OUT), OUTPUT (to tape monitor IN), LEFT & RIGHT SPEAKER outputs, AC power cord.

Operation: With BYPASS switched OUT, equalization is active. Switch IN to bypass equalizer for comparison. Use LEVEL knobs to balance channels if needed. Always power on amplifier/receiver last, and power it off first to prevent turn-on/thump noises.

Connecting to Your System

Integration via tape monitor loop is standard. Alternative connections may be possible depending on equipment.

1. Turn off and unplug all components before connecting.
2. Identify tape monitor loop on receiver/amp: TAPE OUT (play) and TAPE IN (record) jacks.
3. Connect equalizer: Cable from TAPE OUT to EQ INPUT. Cable from EQ OUTPUT to TAPE IN.
4. Connect speakers: Wire from EQ LEFT/SPEAKER to left cabinet, RIGHT to right cabinet. Observe polarity (+/-).
5. Power sequence: Plug in equalizer, then receiver/amp. Select TAPE MONITOR function on receiver.

Tip: Use high-quality, shielded RCA cables for equalizer connections and 16-gauge or thicker speaker wire.

Optimal Listening Setup

The 901's sound is highly dependent on room interaction.

1. Room position: Place speakers on long wall, away from corners, with rear drivers facing wall.
2. Listening distance: Sit 8-12 feet from speakers, forming an equilateral triangle.
3. Toe-in: Angle cabinets so the front driver points just behind the listener's head.
4. Surface: Stable, rigid stands or shelves are mandatory. Do not place directly on floor.
5. Break-in: Allow 20-30 hours of play at moderate volume for drivers to fully loosen.
6. Experiment: Small changes in distance from wall (inch by inch) will tune bass response.

WARNING! Do not block rear-facing drivers. Allow at least 1 foot of clearance behind speaker for reflected sound.

Care & Maintenance

Unplug system before cleaning. Use soft, dry cloth for cabinets. For grilles, use vacuum with brush attachment gently.

CAUTION! Do not use liquids, solvents, or abrasive cleaners on wood finishes or grille fabric. Keep equalizer and speakers away from heat sources and moisture.

Regulatory & Warranty Information

Complies with applicable FCC regulations for home audio equipment. The Bose 901 Series IV loudspeaker system is covered by a limited warranty. For warranty details, service, or parts, contact Bose Corporation. Macrovision notice not applicable. For support, visit www.bose.com or contact Bose Customer Service.

Troubleshooting

Symptom	Possible Cause	Corrective Action
No sound from one/both speakers	Equalizer bypassed/off, loose wires	Ensure EQ is powered ON and BYPASS is OUT. Check all cable and wire connections.
Weak or thin bass	Incorrect placement, EQ not active	Move speakers closer to rear wall (in increments). Verify EQ is active (BYPASS OUT).
Distortion at high volume	Amplifier clipping, underpowered amp	Reduce volume on amplifier. Ensure amplifier meets recommended power (10W min).
Hum or buzz	Ground loop, poor cable connections	Ensure all components plug into same AC circuit. Try different RCA cables for EQ loop.
One channel louder than other	Unbalanced level controls	Adjust CHANNEL 1 & 2 LEVEL knobs on equalizer to center position, then balance using receiver balance control.
Sound seems "echoey" or diffuse	Room too reflective, speakers too far apart	Add room furnishings (rugs, curtains). Move speakers closer together slightly.

Reset: Power cycle all components. Re-check tape monitor loop connections.

Service: Do not open speaker cabinets or equalizer. Contact Bose authorized service for repairs.