Bose 901 Series IV Speakers Manual

The Bose 901 Series IV is a legendary direct/reflecting speaker system designed to reproduce sound with lifelike spaciousness and realism. It features nine full-range drivers per speaker (one facing forward, eight facing rearward), an active electronic equalizer, and a unique acoustic design that utilizes reflected sound to create a wide, enveloping soundstage. Below are key sections for safety, features, installation, setup, operation, and maintenance.

1. Features at a Glance 2. Installation & Placement 3. First-Time Setup 4. Specifications 5. Controls and Connections 6. Connecting to Your System 7. Using the Active Equalizer 8. Care & Maintenance 9. Regulatory Information 10. Troubleshooting

Features at a Glance

Key components: Two 901 Series IV speaker cabinets, Active Equalizer unit, Grille cloths, Owner's manual.

Feature	Description
Driver Array	Nine 4.5-inch full-range drivers per speaker (1 frontal, 8 rearward)
Active Equalizer	Required for proper frequency response and system protection
Direct/Reflecting Design	Utilizes both direct and reflected sound for spacious imaging
Impedance	8 ohms nominal
Power Handling	Up to 450 watts peak per system (with equalizer)
Equalizer Connections	Tape Monitor loop or preamp-out/power-amp-in connections
Grille	Removable acoustically transparent cloth grille
Cabinet Finish	Walnut veneer or optional finishes
Equalizer Controls	Bass, Midrange, Treble adjustment; Contour switch
System Protection	Electronic equalizer includes overload protection circuitry

Installation & Placement

Unpack and inspect contents. Choose optimal room placement for best sound.

Speaker Placement: Place speakers on stands or shelves. For optimal direct/reflecting sound, position them 1-3 feet from the rear wall and 2-4 feet from side walls. Angling them slightly inward towards the listening position is recommended.
Equalizer Placement: Place the active equalizer near your amplifier/receiver, within easy reach for adjustments.
Grille Installation: Carefully attach the cloth grilles to the front of each speaker cabinet using the provided pins or Velcro tabs.

WARNING! Speakers are heavy; lift with care using two people. Ensure placement is stable to prevent tipping.

First-Time Setup

Proper connection of the active equalizer is critical for system operation and sound quality.

Connect Equalizer to Amplifier: Using the provided cables, connect the equalizer via your amplifier's TAPE MONITOR loop (most common) or between the preamp output and power amp input.
Connect Speakers: Connect the left and right speaker wires from your amplifier's speaker outputs to the corresponding inputs on the active equalizer.
Connect Equalizer to Speakers: Connect the output cables from the equalizer to the 901 speakers. Ensure polarity is correct (red to red, black to black).
Power On: Plug the equalizer's power cord into an AC outlet. Turn on your audio system.
Initial Sound Check: Play music at low volume. Engage the TAPE MONITOR switch (or equivalent) on your amplifier to activate the equalizer circuit.

CAUTION! Never operate the Bose 901 speakers without the active equalizer connected and powered on, as this can damage the speakers and will result in incorrect sound.

Specifications

System Type: Direct/Reflecting® loudspeaker system with active equalizer.
Drivers per Speaker: Nine 4.5-inch (114 mm) full-range drivers.
Frequency Response: 35 Hz – 16,000 Hz (±3 dB with equalizer).
Nominal Impedance: 8 ohms.
Recommended Amplifier Power: 10 – 450 watts per channel (with equalizer).
Dimensions (H x W x D): Approx. 25.5" x 13.5" x 12.5" (648 x 343 x 318 mm).
Weight per Speaker: Approx. 48 lbs (21.8 kg).
Equalizer Power Requirements: 120V AC, 60Hz, 5 Watts.
Equalizer Controls: Bass, Midrange, Treble sliders; Contour Switch (Normal, Decrease, Increase).

Controls and Connections

The Active Equalizer is the control center for the 901 system.

Front Panel: POWER switch, BASS / MIDRANGE / TREBLE slider controls, CONTOUR switch (Normal, Decrease, Increase).

Rear Panel Connections:
• AMP INPUT (from amplifier speaker outputs)
• SPEAKER OUTPUT (to 901 Series IV speakers)
• TAPE MONITOR IN/OUT (to connect to receiver/amp tape loop)
• PREAMP OUT / POWER AMP IN jacks (alternative connection)
• AC Power Cord

Initial Settings: For first use, set all sliders (Bass, Mid, Treble) to the center (12 o'clock) position and the Contour switch to NORMAL. Fine-tune to your room and taste.

Connecting to Your System

Method A: Tape Monitor Loop (Most Common)
1. Connect TAPE OUT from your receiver to EQ INPUT on the equalizer.
2. Connect EQ OUTPUT from the equalizer to TAPE IN on your receiver.
3. Connect your amplifier's speaker outputs to the AMP INPUT on the equalizer.
4. Connect the SPEAKER OUTPUT from the equalizer to the 901 speakers.
5. To activate, press the TAPE MONITOR (or TAPE 1/TAPE 2) button on your receiver.

Method B: Preamp Out / Power Amp In
1. Disconnect cables between preamp output and power amp input on your system.
2. Connect preamp outputs to EQ INPUT on equalizer.
3. Connect EQ OUTPUT from equalizer to power amp inputs.
4. Connect speaker wires as in Method A.

Tip: Always power off all components when making connections.

Using the Active Equalizer

The equalizer corrects the speaker's natural response and allows tonal adjustment.

Contour Switch: Use for broad adjustments. NORMAL for most music. DECREASE for bright recordings or rooms. INCREASE for added fullness.
Slider Controls: Use for precise fine-tuning. Adjust Bass for low-frequency impact, Midrange for vocal presence, Treble for high-frequency clarity.
Room Adjustment: Optimal settings depend heavily on room acoustics and placement. Experiment with small adjustments while listening to familiar music.
System Protection: The equalizer includes circuitry to help protect the speakers from amplifier overload. Ensure it is always powered when the system is on.

WARNING! Avoid extreme slider settings. Do not attempt to bypass the equalizer.

Care & Maintenance

Unplug the equalizer before cleaning. Use a soft, dry cloth for speaker cabinets and grilles. Do not use liquids, solvents, or abrasive cleaners.

For grille cloth, gentle vacuuming with a brush attachment can remove dust.

CAUTION! Do not remove driver covers or attempt to service the internal components. Keep speakers away from direct heat sources and excessive moisture.

Regulatory Information

Compliant with applicable safety and electromagnetic compatibility standards. The Bose 901 Series IV and Direct/Reflecting are trademarks of Bose Corporation. This product is protected by patents granted and pending.
For technical support or service, contact Bose Customer Service or visit www.bose.com.

Troubleshooting

Symptom	Possible Cause	Corrective Action
No sound from speakers	Equalizer not powered/activated	Ensure equalizer is plugged in and powered on. Engage TAPE MONITOR switch on your amplifier.
Distorted sound	Equalizer bypassed or incorrect connection	Verify all connections are secure and the equalizer is in the signal path. Check for overdriven amplifier.
Weak bass or thin sound	Equalizer sliders set low	Adjust Bass and Midrange sliders upward. Try Contour switch INCREASE position.
Sound is dull or muffled	Grilles obstructed; Treble setting	Ensure grilles are clean and properly attached. Adjust Treble slider upward.
One speaker quieter than the other	Connection or balance issue	Check speaker wire connections at both amplifier/equalizer and speaker. Verify balance control on amplifier is centered.
Hum or noise	Ground loop or faulty cable	Check all audio cables for secure connection. Try a different outlet for the equalizer.

Reset: Set all equalizer sliders to center and Contour to NORMAL as a baseline.

Service: Do not open speakers or equalizer. Contact Bose authorized service for any repairs.