Bose 901 Direct/Reflecting Speaker System

Introduction

Thank you for purchasing the BOSE 901 Series Ill Oirecl/Reflecl­ing speaker system. The listening enjoyment you will experience is the culmination of many years of research dedicated to the art of bringing superb musical reproduction into the home.
The BOSE 901 Series Ill. with its high proportion of reflected sound. nine full-range drivers. and electronic active equalization. is in­stalled. connected. and operated differently than conventional loudspeakers. The detailed installation and placement! instructions found in this manual are important. PLEASE TAKE THE TIME TO READ THESE INSTRUCTIONS CAREFULLY. Wilh proper installation. you will be rewarded wilh the unique listening pleasure pro­vided by your 901s.

Unpacking Instructions

The 90 Series Ill speaker system is packed in two cartons marked 1. “Part 1 and “Part 2 … The active equalizer is found in the carton filler material along with the “Part 1” speaker. Unpack bolh cartons carefully. Save the cartons and packing material for possible use later. If either of the speakers has visible damage when unpacked.
do nol place the damaged speaker(s) in operation . Repack the speaker{s) in the original carton with the complete packing mater­ial and notify your dealer immediately.

The 901 Series Ill Loudspeaker System

DESIGN FEATURES

1. Correct Balance of Reflected and Direct Sound
   The BOSE 901 Series Ill is designed to use your listening room walls to simulate the reflective properties of the much larger stage wall found behind the inslrumenls ol a live per­formance. The 901 Series Ill uses nine drivers. eight directed towards the back wall, and one driver directed into the lis­tening area, lhus recreating the proportion of reflected to direct sound experienced in the larger environment of a live performance.
2. Active Equalization
   The active equalizer electronically corrects for any deviation in frequency response caused by the mechanical design constraints of the speaker. This is accomplished by elec­tronically “contouring” the preamplifier signal; thus. the entire system radiates the correct balance ol total acoustic power at every frequency.
3. Multiple Full-Range Drivers
   To accurately reproduce Jhe Jimbre of every musical instru­ment, a loudspeaker system must reproduce every portion ol the frequency spectrum in correct balance; however, every loudspeaker has many inherent resonances that cause its response in certain portions ol the frequency range to be reduced or accentuated.
   The 901 system utilizes two unusual physical phenomena called “resonance splitting” (the acoustically coupled drivers force the resonances to “split” 10 different frequencies, thus smoothing the response) and “response averaging” (any driver response irregularity is “averaged” with the other drivers and becomes an insignificant ½ of the total power).

TECHNOLOGICAL INNOVATIONS

1. The New Full-Range High-Performance Driver
   In the 901 Series Ill driver, a combination of technological advances make possible ils outstanding performance:
   
   • A highly efficient magnelic structure with all parts as­sembled to precise tolerances to provide maximum mag­nelic field energy.
     
   • An aluminum helical voice coil, providing better utilization of magnelic energy.
     
   • A new cone and suspension for smoother, more controlled frequency response and lower distortion.
     
   • An injection molded frame, eliminating distortion of the magnelic field (caused by steel frames) and improving precision in assembly.
     The combination of the helical voice coil and precision as­sembly means lhat a 15 watt amplifier will produce lhe loud­ness that required a 50 watt amplifier with the Bose 901 Series II.
2. The New Active Equalizer
   The original 901 introduced the concept of active equaliza­tion lo home loudspeaker systems. It demonstrated lhe fundamental performance advantages of incorporating equalization as a part of the loudspeaker system design. The 901 Series Ill realizes additional advantages of active equalization with three new equalizer features:
   • More precise equalization of the audible sound spectrum is made possible by significantly more complex equalization circuits.
   • Additional control flexibility. permitting maximum speaker performance in a wide range of room positions (see SEC· TIONVI)
   • Control of response of the speaker beyond the audible range. This precise contouring of response at frequencies inaudible to the human ear allows the drivers and enclos­ure lo be designed for optimum performance character­istics.
3. The Acoustic Matrix’s” Enclosure
   The enclosure of lhe 901 Series Ill is designed specifically to work with nine full-range matched drivers in combination with the active equalizer.
   The enclosure incorporates three Reactive Air Columns (one for the front driver and one for each group of four drivers on the rear panels). The purpose of the air columns is lo provide reactive air loading to reduce the motion required of the driver cones al extremely low frequencies. thus allowing maximum efficiency with low distortion.
   Additionally, the enclosure partially isolates lhe acoustic pressure at each driver from other drivers to permit it to operate properly through the frequency range where reac­tive loading occurs.

Installation

Your 901 Series 111 speaker system consists of three parts: two speakers (marked “Part 1” and ··part 2 ‘) and an electronic Active Equalizer packed In the “Part 1” container. The installation consists of thrt?e steps: 1) placing your speakers for best sound. 2) connecting the speaker to your amplifying equipment. and 3) connecting the equalizer to your amplifying equipment.

PLACING THE SPEAKERS
Unlike conventional speakers. the 901 Series Ill functions with lhe acoustics of your listening room. simulating the spatial char­acteristics of the larger environments associated with live per­formances. This important advantage allows considerable free­dom of placement and produces an unusually large .. best I isten­ing area.” Outstanding performance can be obtained under a wide variety of placement positions. (See Figure 2. J
The following guidelines in placing the speaker cabinets will help you obtain lhe best performance. The basic idea is lo pro­vide space to allow the sound to develop around the speaker system.

1. The angled grille panels found on the enclosure are lhe rear face of the 901 speakers (see Figure 1 ). Point this portion of lhe speaker toward the reflecting wall (the wall behind lhe speaker). The paint of the “V” should be between 12″ and 24″ from the reflecting wall. Best results will be obtained with lhe speakers placed between 12″ to 18″ from lhe reflecting wall.
2. Speak<?rs should be placed at least 18″ above lhe floor or below the ceiling (see Figure 1). Distances closer to lhe ceiling or floor restrict the reflected sound energy.
3. The speakers should be al least 18″ from a side wall or open­ing into an adjacent room. (Suggested distances are 3′ to 5′.J Large objecls (such as furniture) should be at least 24″ away from tt1e side of the speaker.
4. Best results will be obtained with the speakers spaced apart 6′ to 1 0′; however. separation as small as 3′ or as great as 15′ will give excellent results in most rooms.
   you have not decided where to place your speakers and would like more information. SECTION VI (LIVING WITH YOUR BOSE 901 SPEAKERS) provides several additional sug­gestions for speaker placement.

CONNECTING THE SPEAKERS

1. Wire Selection
   If the wire used to connect the speakers to your power am• amplifier has too much resistance, the audible coloration of the sound, and loss of power can result. The table below summar­izes maximum wire lengths for 18-, 16-, and 14-gauge, two­conductor, stranded copper wire for use with one or two pairs of BOSE 901 loudspeakers.
   In most instances, copper zip-cord, readily available at most electrical and hardware stores, can be used for speaker con­nection. This wire usually has a ribbed tine(s) along one side of the insulation so that each wire can be identified for proper phasing of your speaker system.
2. Phasing/Wiring
   It is important that the amplifier connections for both 901 speaker systems be identical (see Figure 3) so that bothspeakers work together (in phase).
   • Start with the speaker marked ” Part 1.”
   • Place it on the left side of your room facing the speaker system.
   • Locate the”+” and”-” terminals on the bottom of the speaker.
   • Using the speaker wire (which is marked to distinguish one conductor from the other), connect the “Part 1” speaker terminal marked .. _ .. to the terminal marked “com,” “negative,” or “minus” on the left channel amplifier output. (When connecting the 901 Series Ill loud speakers to your amplifier, if there is a choice of impedances on the amplifier output, use the terminal marked “8” or “8 ohms.” If two pairs of 901 Series Ill loudspeakers are being connected, the terminal marked “4” or “4 ohms” on the receiver or amplifier should be used.).
   • Connect the”+” terminal on the left speaker to the termi• nal marked ··pos.” “positive,” or “plus” on the left channel output of the amplifier or receiver.
     NOTE: Use only the terminals marked “·I·” and “-.” The terminal marked”*” is intended for future electronic de­velopments and should not be used with conventional amplifying equipment.
   • Place the speaker marked “Part 2” on the right side of the room and repeat the connection procedure for the right amplifier channel.
   • If you are using an amplifier rated at over 100 watts rms per channel. fuse your speakers as outlined in SECTION 3.
3. Fusing
   Any loudspeaker is subject to damage if the amplifier powering it should fail. The use of a fast-acting fuse in series with each speaker will minimize the possibility of serious damage to your speaker.
   For amplifiers rated at under 100 watts RMS per channel. no fusing is required. Amplifiers rated over 100 watts per channel should be fused with a fast blow. 3-amp fuse.
   Purchase fuse holders and the appropriate fast-acting fuses. Connect the fuse holders in series with the positive wire going to each speaker, placing the fuse in an easily accessible location.
   BOSE Corporation recommends the use of the Buss AGC SeriesorthelittlefuseAGSeriesasspeakerfuses.

CONNECTING THE EQUALIZER
IT IS MOST IMPORTANT THAT YOU FOLLOW THESE IN­STRUCTIONS FOR OPTIMUM PERFORMANCE OF YOUR 901 SERIES Ill SPEAKER SYSTEM.

1. Using the Tape Monitor Circuit
   The connection methods described in this section can be usedw1th virtually all integrated amplifiers preamplifiers. an<J receivers. t Using the tape monilor circuil . has two advantages: When using conventional lou<Jspeakers or headphones, lhe I ape monitor circuit allows disconnection of the Active Equal­izer by turning off the tape monitor switch on your control am­plifier; this is important because conventional speakers and headphones should not be used with the Active Equalizer. (See SECTION V.l Also, optimum system noise performance is obtained when connecting the equalizer in the tape moni• tor circuitry,
   When using this procedure, you should realize that the 901 equalizer is being connected to your equipment as ii it were a tape recorder, using the tape monitor connections of your control amplifier.
   NOTE: Check your control equipment to determine if your unit has any additional switching flexibility. Some recently in­troduced units now feature switching facilities called Tape Monitor 3, External Equalizer/Processing, or Noise Reduc­tion Connections. The equalizer can be connected to these terminals allowing greater system flexibility if required.
   Referring to FIGURE 4. connect the Active Equalizer ac­cording to lhe following instructions:
   • Turn off all power to your high-fidelity system.
   • If you have a tape recorder, disconnect it from your con­trol amplifier.
     (Instructions in SECTION V will tell you how to reconnect your tape recorder to the system after the equalizer has been installed.)
   • Using one of the cables supplied with the equalizer, con­nect the LEFT channel OUTPUT of the equalizer to the LEFT or .. A .. channel of the tape monitor circuit of your control amplifier. (This terminal may also be labeled PLAYBACK or TAPE IN.)
   • Connect the RIGHT channel OUTPUT of the equalizer to the RIGHT or –9– channel tape monitor connection of your control amplifier
   • Connect the LEFT channel INPUT terminal of the equal­ izer to the LEFT or .. A .. channel TAPE RECORD connec­tion of your control amplifier. (This terminal may also be labeled TAPE OUT or REC OUT.)
   • Connect the RIGHT channel INPUT connection to the RIGHT or .. 8 .. channel TAPE RECORD connection of your control amplifier.
   • Plug the ac power cord ol the equalizer into a –switched ac outlet on your control amplifier so that the equalizer will automatically be turned on or off with the power switch ol your equipment.
     If the preceding steps are unclear, it may be due to the differ­ent nomenclature used by various manufacturers of amplify­ing equipmenl. Consult your control amplilier’s instruction manual and refer to Ille section describing the connection of a lape recorder. Remember, the equalizer is connected just like a lape recorder.
   • h. Place lhe TAPE switch ol the equalizer in lhe MONITOR position.
     As you slide lhe .. frequency contour”· controls from one
     extreme lo lhe other. you wi II delecl a delenl ( identified by a .. dol .. on the front panel). Place the TREBLE and MIDBASS controls at this position. Set the “BELOW 40” control in the .. dolled·· or out position.
   • Place the TAPE MONITOR or TAPE FUNCTION switch of your control amplifier in the NORMAL or OUT position.
   • Turn your system on. (Be certain that the equalizer is plugged into the switched ac oullel of your control ampli­fier and observe that the pilot light on the equalizer is on.)
   • Play the entire system as you normally would. using record player or AM/FM source to be sure ii is operating properly. (Do not use a tape recorder for this portion ol lhe test.)
   • Turn the BALANCE control of the control amplifier to the extreme left and right to check for proper connection of the left and right channels. (If the channels are reversed. check your amplilier or speaker connections carefully.)
     You have now tested the amplifier. wiring. and speaker sys­tems. but not the equalizer. as it is not yet switched into
     the system.
     If your system is not functioning at this point. please go back and check all connections as any errors in connection of your system must be corrected before proceeding further.
   • With lhe system now playing. turn lhe TAPE MONITOR or TAPE FUNCTION switch on your control amplifier to the MONITOR or ON position. The sound should stop. II the sound does not slop. recheck Steps –a·· through ··1:·
   • Now. place the equalizer TAPE switch in the NORMAL position. The sound should now return. 11 lhe sound does not return and the equalizer pilot light is on. I hen the equalizer is probably connected incorrectly. Recheck Sleeps ··a– through –1:·
     NOTE 1 THE TAPE MONITOR OF YOUR CONTROL AM­PLIFIER MUST BE LEFT ··oN·· FOR THE ACTIVE EQUAL­IZER TO BE IN THE CIRCUIT. CHECK THE TAPE MONITOR SWITCH PERIODICALLY TO MAKE CERTAIN IT IS IN THE –oN·· POSITION.
     NOTE 2: THE 901 SERIES Ill EQUALIZER IS NOT COM­PATIBLE WITH THE 901 SERIES I ANO II SPEAKER SYS­TEMS
2. Using Separate Components, Connecting Between the Preamp and the Amplifier
   The equalizer can be connected between separate pream­plifier and power amplifier units (see Figure 5). This connec­tion method provides complete flexibility of the preamplifier tape monitor functions tor use with one or two tape recorders in the conventional manner. The disadvantage of this con­nection method involves using conventional loudspeakers and headphones because the equalizer is permanently wired into the circuit (See SECTION V) If you do connect the equalizer in Ibis manner. it is suggested that the gain controls of your power amplifier be reduced slightly from fully clockwise for optimum system noise (consult your amplifier owner’s manual for further recommendations).
3. Using the Preamp-Out/Main-In Circuit
   An alternate method of connecting the BOSE Active Equal­izer makes use of the PREAMP-OUT and MAIN-IN jacks provided by many manufacturers on their receivers or inte­grated amplifiers (see Figure 6). Using the PREAMP-OUT/MAIN-IN connection jacks retains the total flexibility of the tape monitor circuitry. However. this method of connection permanently connects the equalizer in the circuit; this may prove inconvenient if you are using conventional speakers or headphones. (See SECTION V.) Due to the circuitry char­acteristics of some receivers. the equalizer may not function if connected to these jacks. Also. system noise may increase slightly due to the connection of the equalizer immediately before the power amplifier input.
   To use this method of connection. refer to your receiver and integrated amplifier owner’s instn1ction manual for sep­arating the main and preamplifier sections of the unit. {This is usually accomplished by removing shorting wires or plugs and/or moving a slide switch.) Connect the PREAMP-OUT terminals to the equalizer INPUT terminals. and connect the EQUALIZER OUTPUT terminals to the MAIN-IN termi­nals of the receiver or integrated amplifier {see Figure 6). With this method of connection. do not use the tape recorder connection jacks on the equalizer and leave the TAPE switch (on the equalizer) in the NORMAL position. Tape recorders are now connected to the receiver or amplifier in a con­ventional manner.
4. Using Four-Channel Equipment
   Most quadraphonic receivers have four-channel tape moni­tor or preamp out/main in connection jacks. These connec­tion jacks can be used for the BOSE equalizer.
   If two pairs of 901s are used. two active equalizers are re­quired. Connect one equalizer for the front channels and one for the rear channels.
   II conventional speakers are used with the 901s. connect the equalizer in the channel powering the 901 speakers. For the channels operating the conventional speakers. use stan­dard connection cables and connect the input to the output jacks directly.
   Phase reversal occurs when the 901 equalizers is connected in the circuit. For this reason. your control amplifier’s speak­er phasing procedure should be repeated when using con­ventional speakers with the BOSE 901’s. This important pro­cedure involves listening to musical passages with deep bass. to determine the proper phase of your speakers. In most cases. this will require the reversal of one pair of speaker connections.
   For separate components. connect the equalizer after the output of the decoder. We suggest reading the related sec• lions of this manual before proceeding. /\tso. be certain to recheck your speaker phasing.
   Note: Due to the spatial and spectral properties of the 901 Series Ill system. optimum performance is obtained when all four speaker systems are identical. However. if four 901’s are not used. we suggest using speakers having similar spatial characterislics. such as the Bose Direct/ Reflecting·• 501 or Model 301 speaker syslems. These speaker systems have been designed by Bose to match the 901 system when used in quadraphonic opera lion.

Connecting Other Equipment

TAPE RECORDERS
Since the Active Equalizer is connected to your integrated amplifier. preamplifier. or receiver. where the tape recorder is normally connected, extra jacks are provided on the equalizer for the connection of a tape recorder. Refer to FIGURE 7 and follow the next live steps carefully.

1. Turn all power off.
2. Connect the RIGHT channel TAPE IN jack on the equalizer to lhe RIGHT or “B” channel OUTPUT jack on the tape recorder.
3. Similarly. connect lhe Leff channel TAPE IN jack on the equalizer 10 to the LEFT or “A” channel OUTPUT jack of the tape recorder.
4. Connect the RIGHT channel TAPE OUT jack on the equal­izer to the RIGHT or “B” channel INPUT (or LINE IN) jack of the recorder.
5. Similarly, connect the Leff channel TAPE OUT jack on the equalizer to the LEFT or “A’ channel INPUT (or LINE IN) jack on the recorder.
   NOTE: IF YOUR CONTROL AMPLIFIER HAS TWO TAPE MONITOR CIRCUITS, BE CERTAIN TO CONNECT YOUR TAPE RECORDER TO THE BOSE ACTIVE EQUALIZER, NOT TO THE UNUSED TAPE MONITOR ON YOUR RECEIVER.
   installation of the tape recorder is now complete. To play the tape recorder. simply place the TAPE switch on the 901 Active Equalizer in the MONITOR position (in).
   If you wish to play your tape recorder without using the equal­izer (for conventional speakers or hedphonesJ and your con­trol amplifier has two tape monitor circuits, an additional con­nection procedure is required:
   • Connect ·y· connectors to both channels at the tape output connections of your tape recorder.
   • Connect one side of each ·y· connector as described in Steps 2 and 3 of ··connecting Your Tape Recorder.··
   • With the remaining output from each channel ·y· connector. connect cables to the unused tape monitor input connec­tions of Tape Monitor 2 found on your control amplifier.
   • To play your tape recorder with your 901s. place the tape monitor of your 901 equalizer in the monitor position (in) using the TAPE MONITOR 1 circuit.
     To play your tape recorder with conventional speakers and headphones. place lhe TAPE MONITOR 2 switch of your control amplifier on. Your tape recorder will then be con­nected directly to your high-fidelity system and will play without the equalizer.
     NOTE: Contact your BOSE dealer concerning the availability of ·y· connectors and any further connection advice.

CONNECTING HEADPHONES ANO CONVENTIONAL SPEAKERS
It is important to realize that the BOSE Active Equalizer intro­duces substantial boost in the range below 100 Hz and above 4.000 Hz lo match lhe power response of the 901 speakers. Consequently, conventional speakers or headphones. if played with the equalizer in the circuit. will sound unnatural with both treble and bass being emphasized.
MORE IMPORTANTLY, HEADPHONES AND CONVENTION­ALI SPEAKERS MAY ACTUALLY BE DAMAGED IF PLAYED WITH THE ACTIVE EQUALIZER IN THE CIRCUIT
For this reason. ii is important to switch the Active Equalizer out of the circuit by placing the tape monitor switch of your con­trol amplifier in the OFF or NORMAL position when playing conventional speakers or headphones with your high-fidelity system.

Living with your BOSE 901 Speakers

ADJUSTING YOUR EQUALIZER CONTROLS
The 901 Series Ill equalizer has been completely redesigned with new control features. allowing greater flexibility in opera­tion and speaker placement. These controls are particularly useful in establishing the overall balance of the speaker system with your listening room acoustics. Generally speaking. adjust­ing the frequency contour controls near the mid position will provide the best performance characteristics of the 901 system for most listening rooms. However, you are encouraged to ex­periment with different settings of the equalizer controls and your tone controls as these controls must ultimately be sel according to lo your own listening tastes.
MID-BASS FREQUENCY CONTOUR CONTROL

The perform­ance of any speaker system is affected by the acoustics of the listening room in particularly. the mid-bass region. which can be dramatically affected by the speaker’s placement. The BOSE 901 Series Ill Active Equalizer addresses mis problem with a unique new control called the ··Mid-bass Frequency Contour”· control. This continuously variable slider control adjusts the spectral response of tile 80-to 260-Hz range. If t11e speakers are placed close to the reflecting wall. the midbass response will increase. Reducing the mid-bass control will then restore proper performance. Similarly. placing the speakers further away from the reflecting wall will cause a decrease in the mid­bass response of the speaker system Increasing tile mid-bass control will then restore proper balance.

TREBLE FREQUENCY CONTOUR CONTROL
The ‘”Treble Frequency Contour” control is also a continuously variable slider control that contours the response of the speaker system upwards from 4,000 Hz to beyond audibility. This compensates for the general reverberant characteristics of your listening room. personal listening tastes. and high-frequency variations in program material (see SECTION CJ.
You may find that placing your speakers in front of curtained walls may require a higher selling of treble control. Similar­ly. if your room is excessively bright sounding. you may find a lower setting of the treble control provides a more pleasing sound.
BELOW 40 CONTROL

The Active Equalizer features a newly designed ··Below 40 Contour” control. The “Below 40” switch can be used to reduce the lowest octave of bass (30-60 Hz) energy without affecting the mid-bass response. The “Below 40” switch is also useful in reducing turntable or record rumble.

SPEAKER PLACEMENT

Several options are possible regarding the placement of your go1s in your listening room. Shelving that is deep enough to provide the necessary distances behind and to the side of the speaker system can be used if available. Make certain the shelving is substantial and is not the same shell used to hold your turn­table (as possible acoustic feedback can occur).
Many people choose the attractive pedestals available with the 901 system. These metal stands can be purchased from your BOSE dealer and are convenient in placing the speaker system in your room. II you choose this method of support. instructions are provided with the pedestals for connecting and mounting the speaker system. A new pedestal (Model PS-3) is available for the 901 Series Ill and utilizes a four-hole mounting pattern.
Another placement idea is to suspend the speaker system from the ceiling (see Figure 1 ). This is generally accomplished by using decorative chains and hardware available from most lighting accessory stores. This placement method is particularly attractive if watt surfaces are interrupted by windows or door­ways or floor speaker placement is difficult due to furniture or the presence of small children.
If you decide lo hang your speakers, place the Part 1 speaker on the left side of the room and the Part 2 speaker on the right side of the room. Turn the speakers upside-down and place them on a covered surface or rug,
You will notice that each speaker has four predrilled holes on the bottom. The holes have been provided to accommodate the rubber feet supplied or for locating eyehooks for ceiling hanging.
Screw heavy-duty eyehooks into the bottom of the speaker cabinet. Use either a decorator chain or wire to suspend the speakers from a ceiling stud. DO NOT fasten these chains into the plasterboard as this will not provide adequate support. Keep in mind that you are suspending a 35-pound speaker. Each chain should be able to support the weight of the entire speaker system alone. Be certain to fasten these chains to a wood joist or adequate ceiling support to prevent passible ceiling or speaker damage.
It you have placed your speakers Quite high in your room, the sound can be directed downward by angling the rear of the speaker down. The sound will be directed downward after it is reflected off the rear wall. This is accomplished by increasing the length of lhe rear chain(s) holding the speaker system

ROOM ACOUSTICS

The acoustical properties ol lhe room (such as the size. shape, construction, and furnishings) play an important part in the Quality of sound produced by your high-fidelity system.
A tack of bass response frequently may be attributed to walls of thin panel construction. large openings (e.g .. doorway), or ex­cessive window glass, which allow low frequencies to pass through rather than reflecting them into the listening room.
The overly bright sound of acoustically “live” rooms (e.g .. those with uncovered floors or scatter rugs. small. amounts of furni­lure, hard walls) can be improved by the addition of rugs and heavy drapery, which also serves to eliminate echoes and slancJ­ing waves. For acoustically “dead” rooms e.g… rooms with wall­to-wall carpeting, heavily upholstered furniture and draperies. furnishings should be rearranged or removed.
Finally. since no room is acoustically perfect. you are encour­aged to use your amplifier tone controls and equalizer controls to adjust the sound for your maximum liste,iing enjoyment.

Technical Information

SPECIFICATIONS

1. The system is packed in two cartons marked “Part 1″ and 11 Part 2.”
   Shipping Weigh!: Parl t, 45.5 lbs. Parl 2, 43.5 lbs.
   canon Dimensions: 2t>%” x t 6″ x 14 ½”
2. The Speaker
   Dimensions: 2 t” Wide x t 2%” High x t 3″ Deep
   Weigh!: 35 ll>s. Impedance: 8 ohms
3. Percentages of Direct and Reflected Sound Radiation
   Power radiated by reflection: U9%
   Power radiated directly: I I%
4. Power Handling
   Minimum recommended amplifier power: 10 watts RMS per channel at 8 ohms.
   Maximum Recommended Power for full dynamic range home listening: 70 watts RMS per channel al 8 ohms.
   Using high-quality equipment. the quality of the sound will remain the same over the 10 to 70 wall range. with the only difference being the maximum attainable volume. Twenty watts (in most listening rooms) should provide more than adequate volume levels.
   Maximum Recommended Power: 70 watts continuous with musical peaks up to 250 watts RMS per channel at 8 ohms.
5. Speaker Configuration
   SPATIAL CHARACTERISTICS: Eight speakers reflect sound at 30° angles from the wall behind the speaker: one speaker directed into lhe listening area lo provide lhe opti­mum rational reflected 10 direct sound and lhe proper angles of lhe reflected sound incident upon lhe listener.
   SPEAKER COMPLEMENT: Nine matched full-range speak­ers. utilizing aluminum helically wound voice coils; linear, high-excursion suspension; low impedance {0.9 ohms) voice coils connected in series.
   ENCLOSURE: Acoustic Matrix’. utilizing three Reactive Air Columns tuned well below system resonance and partially isolated individual cells for each driver; air columns emerge through the rear of the speaker cabinet for maximum efficiency.
6. The Active Equalizer
   B.ELOW 40 CONTOUR CONTROL: Two-position, eight-dB decrease at 40 Hz.
   HIGH-FREQUENCY CONTOUR: Continuously adjustable slider with center detent: shelving control with range of±2.5 dB above 4kHz.
   MIO-BASS CONTOUR: Continuously adjustable slider with center detent; +3 dB. -5 dB adjustment over the band from 80 Hz lo 260 Hz.
   TAPE MONITOR SWITCH: Replaces tape monitor switch on receiver or amplifier when the equalizer is connected in lape monitor circuit.
   • Dimensions:2Y,•” H1gl1 x 51/,o” Deep x 1 11/, •” Wide
   • input impedance:60 kilohms
   • Harmonic distortion:<. 1%( 1.0·VOIIOulpul)
   • Noise (“A” weighed:05 cJB below 1 voll
   • Minimum load impedance: 5 k1lol1ms
   • Maximum output voltage: 4 0 vols
   • Max1murn gain: 20 cJ8 al I 6 kHt

110-220 VAC VOLTAGE CONVERSION
The BOSE Series 111 Equalizer is designed lo operate on one power line voltage only. If it becomes necessary to convert your equalizer to another line voltage, contact the closest BOSE Authorized Factory Service Agency or the BOSE factory. (The speakers require no voltage conversion.)
IN CASE OF DIFFICULTY
If you suspect that there is a problem with your 901 system. it is worth a few minutes of your time to determine whether your 901 s are defective, and if so. what part of the system is defective. If one speaker sounds defective, DO NOT switch the speaker cables. as this may damage the speaker operating correctly. Instead. disconnect the defective speaker’s wire at the ampli­fier output and reconnect to the amplifier channel operating correctly. (This can generally be done without disconnecting the correctly functioning speaker.) If the speaker system that sounded defective now plays correctly. the difficulty is not in the speakers or in the speaker wiring.
If bass and high frequencies seem weak, check to assure that the equalizer is in the circuit.
II you hear distortion when both speakers are operating at high sound levels that disappears when you turn the volume down or switch the “Below 40” switch to “Contour.” you are probably overloading the amplifier.
If the trouble seems to be In the equalizer, be sure that the sys­tem operates properly when the equalizer out of the circuit. This can be determined by disconnecting the equalizer from the circuit. Be certain that all cables are connected properly and that the cables are not defective. If the trouble still persists. contact your dealer. He will arrange
for service or have the unit checked for proper operation. The complete procedure for obtaining service is outlined in the warranty found in SECTION VIII of this manual.

CARE AND MAINTENANCE

Your 901 speaker cabinets and equalizer are made with an oil­rubbed walnut veneer finish. Any good-grade of furniture polish used for wood finishes can be used in normal dusting and cleaning; however. to maintain the beautiful appearance ol your 901s, we suggest occasionally rubbing the cabinet with linseed oil, After rubbing, use a dry cloth and polish off any excess oil.
Grille clothes generally require no care. although they may be carefully vacuumed if necessary.

Warranty

FULL 5-YEAR WARRANTY
BOSE warrants this unit to be free from defects in materials and workmanship for a period of live years from the original dale ol purchase. During that period. BOSE will remedy all such defects, without charge l<?r parts or labor. upon return of the unit together with the original sales receipt or other proof ol purcMse to BOSE or to an authorized BOSE service agency. This warranty does not extend lo damage resulting from improper installation. misuse. neglect or abuse, or to exterior appearance.
IN NO EVENT SHALL BOSE BE LIABLE FOR INCIDENTAL OR CONSEQUENTIAL DAMAGES.
Should this unit fail within the warranty period. you should contact your nearest BOSE dealer for service instructions. The dealer may ask you to return the unit together with proof of purchase 10 him. or direct you to return the unit together with proof of purchase to the nearest authorized BOSE service agency. Alternatively, you may elect to send the unit directly to BOSE by carefully following thrs procedure:

1. Obtain a “Return Authorization” number from the BOSE Cus­tomer Service Department. 100 The Mountain Road. Framing­ham, Massachusetts 01701.
2. Return the unit together with proof of purchase to BOSE Corpo­ral ion. 100 The Mountain Road. Framingham. Massachusetts 01701. freight prepaid, in its original shipping carton. Display the Return Authorization number prominently on the outside of me carton. II you need a new carton. your dealer or BOSE Corporation will provide a free replacement carton. Any dam­age in transit due to improper packing is not covered by the warranty and will not be recognized as an insurance claim by lhe transµortation companies.

Your unit wilt is repaired and rel turned to you at BOSE’s expense. II the detects cannot be repaired after a reasonable number of at­tempts by BOSE to do so, you may elect lo receive a refund or replacement. but only if the unit is returned to BOSE-free and clear of all liens and other encumbrances.
This warranty gives you specific legal rights. and you may also have other rights which vary from state to state. Some states do not allow the exclusion or limitation of incidental or consequential damages. so that the above limitation may not apply to you.
A postage-paid registration card is provided requesting informa­tion about you and your high-fidelity system. The return of this card is encouraged. but is not a condition to coverage under this warranty.

FAQS

References

• User Manual