I <■::
Table of Contents
Introduction • .•
Unpacking Instructions
Installation
ill.
A. Placing the Speakers ,
B. Connecting; the Speakers •
■;'^/;i;\/::Wire^;S'e^^^ i.--.- z
2! ^;Phâsihÿ/WÍпhg''.
'3/ ■'.'Fusing,'-- ■ ' •
C. Connécting the Equalizer; . i -•■ vï v. >:V
1, Using ihe Tap.e MohitprCircuil, . . ,. ''•■ ■■.••'; " ' . , •
2. -Osing Separa'té^Gbmpbhérits;-Connecting'Betwèeh^Jihè.T ,
; ' ;3.' ,‘Using:the;P.re^ ^
. 4. iUsingTour-Ci;^ . :
Connecting Other Equipment ; "
IV.
A. Tape Reççrâers ; --H
B. ■ Heabphopys;^ Conventional:.Speàké
V.
• A. So,urce:'and::Rb6m.Gorhp'pns^^^^^^
•:r
VII. Warranty
B] Adjusting the-Source and Rdprn Cornpdnsation Controls
: y C. .Speaker■placement : ....
. D. Room Acoustics
VI. Technical Information
A. Specifications ■'
B. Voltage Conversion
C. In Case of Difficulty
D. Care-and Maintenance . :• ,
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12
14
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I. Introduction
Thank you for purchasing the BOSE 901 Series IV Olrect/Reflecting® speaker system. The listening enjoyment you will ex
perience Is the culmination of many years of research dedicated
to the art of bringing superb musical reproduction into the home,
The BOSE 901 Series IV. with its high proportion of reflected
sound, nine full-range drivers, and a newly-designed electronic ac
tive equalizer, 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. VVith proper installation, you will be rewarded with
the unique listening pleasure provided by your 901 speakers.
II. Unpacking Instructions
The 901 Series IV speaker system Is packed in two cartons mark
ed “Part 1” and Part 2.“ The active equalizer is found in the car
ton filler material along with the “Part 1“ speaker. Unpack both
cartons carefully. Save the cartons and packing material for
possible use later. If either of the speakers has visible damage
when unpacked, do not place the damaged speaker(s) in opera
tion. Repack the speaker(s) in the original carton with the com
plete packing material and notify your dealer immediately.
III. Installation
Your 901 Series IV speaker system consists of three parts: two
speakers {marked “Pan 1 ” and “Part 2“) and an electronic Active
Equalizer packed in the “Part V* container. Installation consists
of three steps: 1)placing your speakers for best sound, 2) connec
ting the speaker to your amplifying equipment, and 3) connecting
the equalizer to your amplifying equipment.
If you place the speakers within the ranges suggested here, the
unique adjustments found on the 901 Series IV equalizer will allow
you to achieve optimum performance. (See SECTION V).
A. PLACING THE SPEAKERS
Unlike conventional speakers, the 901 Series IV functions with
the acoustics of your listening room, simulating the spatial
characteristics of the larger environments associated with a live
performance. This important advantage allows considerable
■freedom of placement and produces an unusually large “best
listening area." Outstanding performance can be obtained
under a wide variety of placement positions. (See Figure 2.)
The following guidelines in placing the speaker cabinets will
help you obtain the best performance. The basic idea is to pro
vide space to allow the sound to develop around the speaker
system.
1. The angled grille panels found on the enclosure are the
rear face of the 90i speaker (see Figure 1). Point this por
tion of the speaker toward the reflecting wall (the wall
behind the speaker). The point of the “V“ should be bet
ween 12’ and 24*’ from the reflecting wall. Best results will
be obtained with the speakers placed between 12" to 18"
from the reflecting wall.
2. Speakers should be placed at least 18" above the floor or
below the ceiling (see Figure 1). Distances closer to the
ceiling or floor restrict the reflected sound energy.
3. The speakers should be at least 18" from a side wall or
opening into an adjacent room. (Suggested distances are
3' to 5'.) Large objects (such as furniture) should be at least
24“ away from the side of the speaker.
4. Best results will be obtained with the speakers spaced
apart 6' to 10'; however, separation as small as 3' or as
great as 15' will give excellent results in most rooms.
If you have not decided where to place your speakers and
would like more information, SECTION V (LIVING WITH YOUR
BOSE 901 SPEAKERS) provides several additional suggestions
for speaker placement.
Installation
B. CONNECTING THE SPEAKERS
1. Wire Selection
If the wire used to connect the speakers to your power ampli
fier has too much resistance, audible coloration of the
sound and loss of power can result. The table below sum
marizes maximum wire lengths for 18-, 16-, and 14-gauge,
two-conductor, stranded copper wire for use with one or
two pairs of BOSE 901 loudspeakers.
TABLE 1
RECOMMENDED CONNECTION WIREt
.Wire Length
One Pair
of 901s
27 feet
Wire Length
Two Pairs
of 901s
13 feet
Type of Speaker
Hook-Up Wire
18-gauge zipcord
(or two-conductor wire)
i
42 feet
21 feet
1
67 feet
34 feet
16-gauge two-conductor
wire
14-gauge two-conductor
wire
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 line(s)
along one side of the insulation so that each wire can be
identified for proper phasing of your speaker system.
tThe wire lengths snown m Table i were calculated on the bass oJ a rnaJtimum auditHe
colorat on ot ^0 5dB Following ihegudelmes provided, the most discerning listener
will be unable to detect any coloration introduced by the speaker wire Most listeners
will not notice any eHect isven if wire lengths are increasec by as much as 5054
2. Phaslng/Wiring
ft is important that the amplifier connections for both
901 speaker systems be identical (see Figure 3) so that
both speakers work together (in phase).
a. Start with the speaker marked "Part 1."
b. Place it on the left side of your room facing the
speaker system.
c. Locate the “ + " and terminals on the bottom of
the speaker.
d. 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 IV
loudspeakers 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 IV
loudspeakers are being connected, the terminal marked
"4" or "4 ohms" on the receiver or amplifier should be
used.)tt
e. Connect the “-f" terminal on the left speaker to the
terminal marked "pos." "positive.” or “plus" on the left
channel output of the amplifier or receiver.
NOTE: Use only the terminals marked “ + " and
The terminal marked is intended for future electro
nic developments and should not be used with conven
tional amplifying equipment.
ttNote When operating your 90is m stereo, only one equalizer is required if addi*
tioriat pairs of 901$ are used, they can be purchased without the equalizer. These
speakers are sokJ as ' add-on'' pairs and can be connected as extensor speakers or
used in addition to the iirst pair of speakers
When connecting two pairs of 901 speakers to your equipmeni, v/ire the speakers m
parallel: most recently manufactured receivers or amplitiers wjI operate two pairs of
901$ wired n this manner. However, if your receiver or amplifier is not caceWe of
4-ohm ocerato.^ with two pairs of 90is. w^re the speakers in se.nes. Contact your
dealer if any further assistance is required
f. Place the speaker marked “Part 2” on the right side of
the room and repeat the connection procedure for the
right amplifier channel.
g. 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.
CMANNELOUTPUT CHANNEL OUTPUT
Purchase fuseholders and the appropriate fast-acting fuses.
Connect the fuseholders in series with the positive wire
going to each speaker, placing the fuse In an easily acces
sible location.
Referring to the speaker connection diagram, the fuseholders should be inserted In (he positive wire connecting
each speaker. Be sure to place the fuse In an easily acces
sible location. BOSE Corporation recommends use of a 3ampere. fast-acting Buss AGC Series or Littelfuse AG
Series. A fuse kit containing fuses and holders can be
obtained from BOSE Customer Service Department for
$5.00. Ask for part number 108938-3.
M
Installation
C. CONNECTING THE EQUALIZER
IT IS MOST IMPORTANT THAT YOU FOLLOW THESE IN
STRUCTIONS FOR OPTIMUM PERFORMANCE OF YOUR 901
SERIES IV SPEAKER SYSTEM.
1. Using The Tape Monitor Circuit
The connection methods described in this section can be us
ed with virtually all Integrated ampiifers. preamplifiers, and
receivers.t Using the tape monitor circuit has two advan
tages: When using conventional loudspeakers or head
phones. the tape monitor circuit allows disconnection of
the Active Equalizer by turning off the tape monitor switch
on your control amplifier: this is important because conven
tional speakers and headphones should not be used with
the Active Equalizer. (See SECTION IV.) Also, optimum
system noise performance is obtained when connecting the
equalizer in the tape monitor circuitry.
When using this procedure, you should realize that the 901
equalizer is being connected to your equipment as if 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 re
quired.
fTo make connection easier, we are going to refer to all of these various com •
ponenis as the ”00 01(01 amplifier."
Referring to FIGURE 4. connect the Active Equalizer accor
ding to the following instructions:
a. Turn off all power to your high-fidelity system.
b. If you have a tape recorder, disconnect it from your
control amplifier.
(Instructions in SECTION IV will tell you how to recon
nect your tape recorder to the system after the equalizer
has been installed.)
c. Using one of the cables supplied with the equalizer, con
nect 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.)
d. Connect the RIGHT channel OUTPUT of the equalizer to
the RIGHT or "B” channel tape monitor connection of
your control amplifier.
e. Connect the LEFT channel INPUT terminal of the equal
izer to the LEFT or "A" channel TAPE RECORD connec
tion of your control amplifier. (This terminal may also be
labeled TAPE OUT or REC OUT.)
f. Connect the RIGHT channel INPUT connection to the
RIGHT or '‘B” channel TAPE RECORD connection of your
control amplifier.
g. Plug the ac power cord of the equalizer into a "switched'’
ac outlet on your control amplifier so that the equalizer
will automatically be turned on or off with the pov/er
switch of your equipment.
If the preceding steps are unclear, it may be due to the dif
ferent nomenclature used by various manufacturers of
amplifying equipment. Consult your control amplifier’s in
struction manual and refer to the section describing the
connection of a tape recorder. Remember, the equalizer is
connected just like a tape recorder.
THE FOLLOWING STEPS ARE PROVIDED TO ENSURE
THAT THE EQUALIZER IS PROPERLY CONNECTED TO
YOUR HIGH-FIDELITY SYSTEM.
h. Place ihe TAPE switch of the equalizer in the MONITOR
position.
As you slide the LOW and HIGH FREQUENCY SOURCE
AND ROOM COMPENSATION controls from one ex
treme to the other, you will find a detent in the middle
of the control's travel. Place both the LOW and HIGH
FREQUENCY SOURCE AND ROOM COMPENSATION
controls at this position. Set the LOW FILTER control
in the "out" position.
i. Place the TAPE MONITOR or TAPE FUNCTION switch
of your cor^trol amplifier in the NORMAL or OUT position.
j. Turn your system on. (Be certain that the equalizer is
plugged into the switched ac outlet of your control am
plifier and observe that the pilot light on the equalizer
is on.)
EQUALIZER
AMPLIFIER
CONNECTIONS •
Ir L R (. R L R I
UPtRECORDER
- CONNECTIONS -
OOOO OOOO)
t— arrurl I mr I—' '— umii
mOnI
o
REC
6 o
CONTROL AMPLIFIER
.Ftguf*4
----------
mn
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k. Play the entire system as you normally would, using a
record player or AM/FM source to be sure it is operating
properly. (Do not use a tape recorder for this portion of
the test.)
l. 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 amplifier 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 alt connections, as any errors in connec
tion of your system must be corrected before proceeding
further.
m. With the system now playing, turn the TAPE MONITOR
or TAPE FUNCTION switch on your control amplifier to
the MONITOR or ON position. The sound should stop. If
the sound does not stop, recheck Steps “a" through "I."
n. Now, place the equalizer TAPE switch in the NORMAL
position. The sound should now return. If the sound
does not return and the equalizer pilot light is on, then
the equalizer is probably connected incorrectly.
Recheck Steps "a" through "I."
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 IV AND III EQUALIZERS ARE NOT
COMPATIBLE WITH THE 901 SERIES I AND II SPEAKER
SYSTEMS. HOWEVER, THE 901 SERIES IV EQUALIZER IS
COMPATIBLE WITH THE 901 SERIES 111 SPEAKER
SYSTEM
Installation
2. Using Separate Components, Connecting Between the
Preamp and the Amplifier
The equalizer can be connected between separate pream
plifier and power amplifier units (see Figure 5). This con
nection method provides complete flexibility of the pream
plifier tape monitor functions for use with one or two tape
recorders in the conventional manner. The disadvantage of
this connection method involves using conventional loud
speakers and headphones because the equalizer is per
manently wired into the circuit. (See SECTION IV.) If you do
connect the equalizer in this manner, it is suggested that
the gain controls of your power amplifier be reduced slight
ly from fully clockwise for optimum system noise (consult
your amplifier owner’s manual for further recommendations).
AMPLIFIER
CONNECTIONS
lanan
n
M'
R (2^
1
EQUALIZER
flRIT
3. Using the Preamp-Out/Main-ln Circuit
An alternate method of connecting the BOSE Active Equal
izer makes use of the PREAMP-OUT and MAIN-IN jacks
provided by many manufacturers on their receivers or in
tegrated 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 IV.) 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.
TAPE RECORDER
CONNECTIONS
R L R L
I O O O O I
'— ajTRjT
------
«vr —'
■O *■
L (3^
INPUT OUTPUT
RgureS
PREAMPLIFIER
To use this method of connection, refer to your receiver
and integrated amplifier owner’s instruction 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 PREAMPOUT terminals to the equalizer INPUT terminals, and con
nect 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 (he NORMAL position.
Tape recorders are now connected to the receiver or
amplifier in the conventional manner.
A. Using Four-Channel Equipment
Most quadraphonic receivers have four-channel tape moni
tor or preamp out/main in connection jacks. These connec
tion jacks can be used for the BOSE equalizer.
If two pairs of 901s are used, two active equalizers are re
quired. Connect one equalizer for the front channels and
one for the rear channels.
If conventional speakers are used with the 901 s, 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 equalizer is con
nected 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
tions of this manual before proceeding. Also, be certain to
recheck your speaker phasing.
Note: Due to the spatial and spectral properties of the
901 Series (V 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 characteristics, such as the Bose
Direct/Reflecting® 601 or Model 501 speaker systems
These speaker systems have been designed by Bose to
match the 901 system when used in quadraphonic
operation.
11
IV. Connecting Other Equipment
A. 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 five steps carefully.
1. Turn all power off.
2. Connect the RIGHT channel TAPE IN jack on the equalizer
to the RIGHT or “B" channel OUTPUT jack on the tape
recorder.
3. Similarly, connect the LEFT channel TAPE IN jack on the
equalizer to the LEFT or “A” channel OUTPUT jack of the
tape recorder.
4. Connect the RIGHT channel TAPE OUT jack on the equal
izer to the RIGHT or “B" channel INPUT (or LINE IN) jack
of the recorder.
5. Similarly, connect the LEFT 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 headphones) and your
control amplifier has two tape monitor circuits, an additional
connection procedure is required:
1. Connect ‘’Y” connectors to both channels at the tape out
put connections of your tape recorder.
2. Connect one side of each “Y” connector as described in
Steps 2 and 3 of "Connecting Your Tape Recorder."
3. With the remaining output from each channel "Y" connec
tor. connect cables to the unused tape monitor input con
nections of Tape Monitor 2 found on your control amplifier.
4. To play your tape recorder with your 901 s, place the tape
monitor of your 901 equaiizer in the monitor position (in) us
ing the TAPE MONITOR 1 circuit.
5. To play your tape recorder with conventional speakers and
headphones, place the TAPE MONITOR 2 switch of your
control amplifier on. Your tape recorder will then be con
nected directly to your high-fidelity system and will play
without the equalizer.
NOTE: Contact your BOSE dealer concerning the availabili
ty of "Y" connectors and any further connection advice.
B. CONNECTING HEADPHONES AND CONVENTIONAL
SPEAKERS
It is important to realize that the BOSE Active Equalizer ir
troduces substantial boost in the range below 100 Hz an
above 5.000 Hz to match the power response of the 90
speakers. Consequently, conventional speakers or headphonet
if played with the equaiizer in the circuit, will sound unnaturi
with both treble and bass being emphasized.
MORE IMPORTANTLY. HEADPHONES AND CONVENTIONAL
SPEAKERS MAY ACTUALLY BE DAMAGED IF PLAYED WITI
THE ACTIVE EQUALIZER IN THE CIRCUIT.
For this reason, it is important to switch the Active Equalize
out of the circuit by placing the tape monitor switch of you
control amplifier in the OFF or NORMAL position when playin
conventional speakers or headphones with your high-fidelit
system.
tAny speaker system other than the BOSE III or IV system.
VC; ^
V. Living with your BOSE 901 Loudspeakers
The effect of listening room acoustics Is to radically modify
the tonal balance of any loudspeaker. This effect can be
greater than the difference between two loudspeakers of
substantially different cost.
As part of its ongoing research in sound reproduction, BOSE
Corporation has carried out an extensive program examining
the acoustic properties of a wide range of listening rooms.
The development of the 901 Series IV loudspeaker is an
important result of this research and development. The 901
Series IV loudspeaker system solves the problem of the effect
of the room on speaker performance with a new equalizer
design that provides controls specifically designed to compen
sate for the effects of room characteristics, musical sources,
and speaker placement.
A contribution in achieving this new performance is the new
driver used with the 901 Series IV. This new driver assembly
has an improved efficiency in the range of 10-15 kHz.
Improvements in components, adhesives, and manufacturing
techniques have also made possible further improvements in
the high-power handling capability of the driver. The power
handling capability of the speaker system has been improved
to the point that there are no restrictions on the size of the
amplifier used with the 901 Series IV in non-commercial ap
plications. providing the fusing recommendations in this
owner’s manual are followed.
The combination of new equalizer controls. Improvements in
high-frequency efficiency, and high-power handling capabili
ties make the 901 Series IV speaker system unusually flexible
with respect to location In the listening room, room acoustics,
and choice of power amplifier.
14
A. SOURCE AND ROOM COMPENSATION CONTROLS
The 901 Series IV Active Equalizer Controls have been design
ed from a radically different vantage point. Currently available
tone controls found on amplifiers and receivers feature bass
and treble controls that are primarily designed around estab
lished circuits. These circuits were designed without any
specific compensation requirement and therefore cannot
compensate for the specific effects of room acoustics.
For example, most current bass controls not only adjust the
mid-bass normally affected by room acoustics, but also the
deep bass and lower midrange. Also, adjusting the treble con
trol, will adjust the extreme highs out of proportion to the
upper treble and midrange. The new 901 Series IV equalizer
addresses this dilemma with two new controls called Source
and Room Compensation Controls.
Certain portions of the midbass of any speaker system will
tend to vary dramatically as a function of listening room
acoustics. BOSE has addressed this problem with the LOW
FREQUENCY CONTROL that provides up to 16 dB Of change
in the 100 to 400 Hz range. This frequency contouring circuit
is designed to provide the compensation required to match
the acoustics of your listening room.
The HIGH FREQUENCY CONTROL is a shelving function that
begins affecting the sound at 1 kHz and can significantly ad
just the speaker's presence and sonic detail over the
midrange and high-frequency range without sacrificing perfor
mance at the extreme high frequencies. Regardless of the
acoustics of your listening room, this control allows the
speaker system to achieve the correct spectral balance.
B. ADJUSTING THE LOW AND HIGH FREQUENCY SOURCE
AND ROOM COMPENSATION CONTROLS
1. Select a well-recorded familiar record with a full orchestral
passage or a record with a large number of diverse musical
instruments that span the entire frequency range. Select a
recorded passage that has sustained music over several
seconds so you can observe the effects of the controls.
2. Preset the HIGH FREQUENCY Control in the center.
3. Move the LOW FREQUENCY Control back and forth
several times over the extremes of the control's range and
carefully listen to its effect. You will notice a dramatic
change in the basic fullness or body of the sound without
changing the deep bass or midrange. Starting with the con
trol at the extreme left, slowly move the knob until the
balance of the sound is rich and full, but without excessive
heaviness.
4. Next, replay the same passage again and move the HIGH
FREQUENCY Control over the extremes of the range
several times, listening to its effect. Starting with the con
trol set at the extreme left, slowly move the knob until the
sound fills with instrumental detail clarity, and presence.
Note that since no room is typical, it will be rare that the
center setting of both controls is used. Accordingly, it is
important to realize that it is your adjustment of these
controls that will result in the speakers optimum perfor
mance.
LOW FILTER CONTROL
The 901 Active Equalizer features a newly-designed LOW
FILTER Control. The LOW FILTER Switch can be used to
reduce the lowest two octaves of bass energy without affec
ting the mid-bass response. This control is most useful in
removing record or turntable rumble.
•‘1(16*1 FSEOUISCV-
Ш
ICO УЛ f.gw 3U3M 10.0» »ло
FREOUEMCV IN СГС1БЗ PER SECOND
901 IV EQUALIZER CONTROL RESPONSE
C. SPEAKER PLACEMENT
Several options are possible regarding placement of your 901
in your listening room. Shelving that is deep enough to provid*
the necessary distances behind and to the side of the speake
system can be used. Make certain the shelving is substaniig
and not the same shelf used to hold your turntable, as possibi
acoustic feedback can occur.
Many people choose the attractive pedestals available wit
the 901 Series IV System. If you choose this method of suppor
instructions are provided with the pedestals for connectin
and mounting the speaker system, using the four predrille
holes (A) in the speaker bottom.
Another placement idea is to suspend the speaker syster
from the ceiling (see Figure 1). This placement method i
particularly attractive if wall surfaces are interrupted by wir
dows or doorways or if floor placement is difficult due t
furniture or the presence of children.
15
Living with your BOSE 901 Loudspeakers
If you decide to hang your speakers, place the Pan II speaker
on the left side of the room and the Part I speaker on the right
side of the room.’ Turn the speakers upside down and place
them on a covered surface or rug.
‘Please note that the reversed speaker placement is intentional and is
necessary when usir>g electronics products to be introduced by BOSE to
operate with the center terminal found on the 901 Series III and IV Loud>
soeaker.
THREE-CHAIN OR FOUR-CHAIN MOUNTING
Three-chain mounting utilizes the holes (B) near the front of
the cabinet, and a third pilot hole located near the ”V” of the
cabinet.
When suspending the speaker with four chains, use the four
predrilled holes (C) located near the corners of the speaker.
Insert four y^-inch eyehooks in place. The speaker system
weighs 35 pounds and care should be taken to ensure that
the speaker Is safely supported from the ceiling. A supporting
chain should be attached to a structural support, such as a
beam or joist.
If you have placed the speakers quite high in your listening
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 done by
increasing the length of the rear chain(s) holding the speaker
system in place.
INSTALLING THE RUBBER FEET
The speaker is supplied with four rubber feet and four screws.
These feet should be used to prevent possible damage to sur
faces such as shelves or tables. Insert the feet with the
screws in the four holes (C) located near the corner of the
cabinet.
D. ROOM ACOUSTICS
The acoustical properties of the 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 lack 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
furniture, hard walls) can be improved by the addition of rugs
and heavy drapery, which also serve to eliminate echoes and
standing waves. For acoustically “dead” rooms (e.g., rooms
with wall-to-wall carpeting, heavily upholstered furniture and
draperies.) furnishings should be rearranged or removed.
The unique controls on your 901 IV Equalizer are especially
helpful in compensating for the characteristics of different
rooms.
i»
B.c
B.C
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VI. Technical Information
A. SPECIFICATIONS
1. The system is packed In two cartons marked “Part 1”
and “Part 2.“
Shipping Weight: Part 1. 45.5 lbs. Part 2. 43.5 lbs.
Carton Dimensions: 25%" x 16" x
2. The Speaker
Dimensions: 21 " Wide x 12%" High x 13" Deep
Weight: 35 lbs. Impedance: 8 ohms
3. Percentages of Reflected and Direct Sound Radiation
Power radiated by reflection: 89%
Power radiated directly: il%
4. Power Handling
Minimum Recommended Power: 10 watts rms per channel
at 8 ohms.
Maximum Recommended Power: No power restrictions on
amplifier size when used in non-commercial applications,
providing the fusing recommendations are followed.
5. Speaker Configuration
SPATIAL CHARACTERISTICS: Eight speakers reflecting
sound at 30® angles from the wall behind the speaker; one
speaker directed into the listening area to provide the op
timum ratio of reflected to direct sound and the proper
angles of the reflected sound incident upon the listener.
SPEAKER COMPLEMENT: Nine matched full-range speak
ers, 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 below system resonance and partially
isolated individual cells for each driver; air columns
emerge through rear of speaker cabinet for maximum effi
ciency.
6. The Active Equalizer
TAPE MONITOR SWITCH: Replaces tape monitor switch
on receiver or amplifier when equalizer is connected in
tape monitor circuit.
LOW FILTER CONTROL: Two-position. 5 dB decrease at
40 Hz.
SOURCE AND ROOM COMPENSATION
LOW FREQUENCY CONTROL: Continuously adjustable
slider, ± 8 dB adjustment over band from 100 Hz to 400 Hz.
HIGH FREOUENCY CONTROL: Continuously adjustable
slider, shelving control with range of ±8 dB at 10 kHz.
Dimensions:
Input impedance:
Harmonic distortion:
Noise (“A" weighted):
Minimum load impedance:
Maximum output voltage:
Maximum gain:
2^6* High X SXs' Deep x
Wide
80 kilohms
<0.1% (1.0-volt output)
90 dB below 1 volt
5 kilohms
2.5 volts
21 dB at 16 kHz (center
setting)
17
« - '
Technical Information
B. 110-220 VAC VOLTAGE CONVERSION
The BOSE Series IV Equalizer is designed to operate on one
power line voltage only.
Equalizers manufactured for 120 VAC operation are not convertable to 240 volt operation except by factory modification.
Equalizers manufactured for 240 VAC operation may be con
verted to 120 VAC operation by BOSE Authorized Factory Ser
vice Agencies. (The speakers require no voltage conversion.)
C. 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
901s are defective, and if so, what part of the system is defec
tive.
If one speaker sounds defective, DO NOT switch the
speaker cables, as this may damage the speaker operating
correctly. Instead, disconnect the wire of the speaker sus
pected of being defective 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.
If you hear distortion when both speakers are operating at
high sound levels that disappears when you turn the volume
down or push the Low Filter switch "In." you are probably
overloading the amplifier.
If the trouble seems to be in the equalizer, be sure that the
system operates properly with 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.
18
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 Vli of this manual.
D. 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
of your 901s, we suggest occasionally rubbing the cabinet
with linseed oil. After rubbing, use a dry cloth and polish off
any excess oil.
Grille cloths generally require no care, although they may be
carefully vacuumed if necessary.
VII. Warranty
FULL 5-YEAR WARRANTY
BOSE warrants this unit to be free from defects in materials and
workmanship for a period of five years from the original date of
purchase. During that period, BOSE will remedy all such defects,
without charge for parts or labor, upon return of the unit together
with the original sales receipt or other proof of purchase to BOSE
or to an authorized BOSE service agency. This warranty does not
extend to 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 to 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
this procedure:
1. Obtain a “Return Authorization“ number from the BOSE
Customer Service Department. 100 The Mountain Road, Fra
mingham. Massachusetts 01701.
2. Return the unit together with proof of purchase to BOSE Cor
poration, 100 The Mountain Road, Framingham. Massachu
setts 01701. freight prepaid, in its original shipping carton.
If 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 the trans
portation companies.
Your unit will be repaired and returned to you at BOSE’s expense.
If the defects cannot be repaired after a reasonable number of at
tempts by BOSE to do so. you may elect to 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.
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m
Printed In U.S.A. 111432
<S)
THE MOUNTAIN • FRAMINGHAM. MASS. 01701
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