Bose 901 Series II User manual

OWNERSIMANUAINEO)
SOnSERIESM
DinE
GWAR
Egle
CMING
SP
EMWERIS
SIEM
MTUI Sz.

VI
VIL
VIH.
901 SERIES TILT OWNER’S MANUAL
TABLE OF CONTENTS
A. Speaker Placement
B. Connecting The Speakers
1. Selecting The Speaker Wire
2. Phasing Your 901 Speakers
3. Fusing Your 901 Speakers
C. Connecting The Equalizer
1. Preferred Method
(Using The Tape Monitor Circuit)
2. Alternate Method |
(Using
PRE-AMP
OUT
and
MAIN
IN
Connections
with Receiver or Integrated Amplifier)
3. Alternate Method I!
(Using separate PREAMPLIFIER and POWER AMPLIFIER)
4. Alternate Method II!
(Using FOUR-CHANNEL DECODER)
D. Connecting A Tape Recorder
E.
Connecting
Headphones
or
Conventional
Speakers
Getting The Most Out of Your 901 Speakers
Adjusting Speaker Placement
Adjusting The Equalizer Controls
Improving Room Acoustics
Selecting The Right Amplifier
The Qnty non Better Than A Pair of 901s
mopper

l. INTRODUCTION
Thank you for purchasing the BOSE 901 Series II Direct/Reflecting® speaker system. The listening enjoyment ex-
perienced with your BOSE 901s culminates many years of research and dedication to the art of bringing the finest
musical reproduction into your home.
THE BOSE 901 with its unique shape, 9 drivers, and Active Equalizer incorporates a number of major advances in
speaker technology. It is designed, installed, and connected differently from conventional loudspeakers. These major
differences contribute directly to the new level of realism of music reproduction provided by the 901 speaker system.
The detailed installation and placement instructions are important. PLEASE TAKE THE TIME TO READ THIS
MANUAL, as this is the only way you will obtain the full benefits of the 901’s unique design. You will be amply
rewarded by the listening pleasure which your 901s provide, when properly installed.
Il. UNPACKING YOUR 901s
The 901 speaker system is packed in two cartons marked “Part 1” and “Part 2.” THE ACTIVE EQUALIZER IS
CONTAINED IN A CARDBOARD WEDGE FOUND IN PART 1. Unpack both cartons carefully. (Save the cartons
{v and packing materials for possible use later.) If either the speakers or the Equalizer are visibly damaged when you un-
pack them, do not place the system in operation. Repack the speakers and the Equalizer in the original cartons and
notify your dealer immediately. (See Section V.)
Ill. INSTALLATION OF YOUR 901s
A. SPEAKER PLACEMENT
One of the most important advantages of the BOSE 901 speaker system is that it is designed to operate properly
in most listening rooms, not in anechoic test chambers. The superior dispersion characteristics of the 901 allow
considerable freedom of placement and an unusually large “best listening area.” To obtain the full performance
of the 901, you must follow the placement guidelines in this section.
The angled (vee shaped) grille cloth panels are the back of the 901. Point the vee toward the wall. The distance
of the speakers from the wall is very important. The point of the vee should be 12 inches from the wall. 20 Cc
(Although the 901 was designed to be placed 12 inches from a reflecting wall, satisfactory performance can be ;
obtained anywhere within the range from 8 to 24 inches.) The point of the speaker should be aimed directly at
the reflecting wall, and NOT directly into a corner (See Fig. 1).
+18"-36'
46 - FA
~_ DO NOT PLACE HERE
(Half-way point between
ceiling and floor)
É
18”-36”
Ke -4
FIG. 1
The reflecting wall ideally should be made of a dense, solid substance such as wood, brick, cement block, plaster,
or sheetrock. Substances like glass, pegboard, cork, or acoustic tile make ineffective reflecting walls. (The
Equalizer is designed to accommodate surfaces which might otherwise present problems. [See Section IV B.] )

The
following
guidelines
should
be
followed
in
placing
the
speakers
relative
to
other
surfaces
in
the
room.
The
basic
idea
is
to
provide
space
around
the
speakers
to
allow
sound
waves
coming
from
the
rear
of
the
speaker
to
properly
disperse.
.
1.
2.
The
speakers
should
be
placed
18
to
36
inches
from
the
floor,
LC-
34
If
you
are
hanging
the
speakers
from
the
ceiling,
they
should
be
Positioned
18
to
36
inches
from
the
ceiling.
DO
NOT
place
your
speakers
exactly
half-way
between
the
floor
and
the
ceiling.
(See
Fig.
1.)
EG- JA
The
speakers
should
be 18
to
36
inches
from
the
side
walls
or
from
openings
into
adjacent
rooms.
The
speakers
should
be
at
least
18
inches
from
nearby
massive
objects
such
as
bookcases,
cabinets,
or
other
large
pieces
of
furniture.
The
separation
between
the
speakers
should
be
between
4
and
15
feet.
(Best
results
will
be
obtained
with
a
separation
of
6
to
12
feet.)
A?
2-
In
general,
you
should
use
common
sense
and
be
sure
to
select
an
arrangement
which
does
not
appear
to
block
the
radiation
and
reflection
of
the
sound
into
the
room.
The
901s
can
be
placed
on
pedestals
or
tables,
on
top
of
cabinets,
or
on
shelves,
as
long
as
the
preceding
guidelines
are
followed.
If
the
speakers
are
in
a
room
with
a
color
television,
DO
NOT
place
the
speakers
closer
than
3
feet
to
the
television.
All
loudspeakers
are
equipped
with
powerful
magnets
which
may
disturb
the
delicate
adjust-
ments
of
your
color
TV.
CONNECTING THE SPEAKERS
1.
SELECTING THE SPEAKER WIRE
If
the
wire
chosen
for
connecting
the
speakers
to
your
amplifier
has
too
much
resistance,
audible
colora-
tion
of
the
sound
and
loss
of
power
can
result.
The
table
below
summarizes
the
permissible
wire
lengths
for
18,
16,
and
14
gauge
two-conductor
copper
wire
for
one
or
two
pairs
of
BOSE
901
speaker
system(s).
Copper
zipcord
wire
is
readily
available
at
most
electrical
and
hardware
stores.
This
wire
usually
has
a
ribbed
line
running
along
one
of
the
two
conductors
so
that
the
conductor
can
be
identified
at
each
end
for
obtaining
the
proper
phasing
of
your
BOSE
901
speakers.
TABLE
1
—
WIRE
LENGTHS
FOR
EACH
SPEAKER
Type
of
Speaker
One
Pair
Two
Pairs
Hook-up
Wire
of
901s
of
901s
18
gauge
zipcord
33
feet
14
feet
(or
two-conductor
wire)
16
gauge
two-conductor
54
feet
23
feet
wire
14
gauge
two-conductor
86
feet
36
feet
wire
PHASING YOUR 901 SPEAKER
It
is
important
that
the
connections
to
the
speakers
and
the
receiver
or
amplifier
be
the
same
for
both
channels
so
that
the
two
speakers
are
in
phase
with each
other.
The
two
terminals
on
the
bottom
of
the
901
are
marked
“8
OHMS”
and
“COM.”

RECEIVER
COM. 8OHMS COM. 8-OHMS
FIG. 2
Start with the Part 1 portion of your 901 system. Place it on the left side of your room. Connect
this left speaker to the left channel speaker output terminals of your amplifier or receiver. (If there is a
choice of impedances on the amplifier output, use the terminal marked ““8Q2” or “8 OHMS”) *
Connect the “COM” terminal on the left speaker to the “COM” terminal on the left channel output of your
receiver or amplifier output. Connect the “8 OHMS” terminal on the left speaker to the “8 OHMS” ter-
minal on the left channel amplifier output. Connect the right speaker (Part 2) in the same manner to the
right channel amplifier outputs (See Fig. 2).
Because of the differing terminology which various manufacturers use on their receivers and amplifiers, we
have provided the chart below to assist you in identifying the proper connection points.
STANDARD RECEIVER/AMPLIFIER TERMINAL MARKINGS
“COMMON” Terminal “COM” “8 OHMS” Terminal "BQ"
also known as so” also known as “Hot” or
“Ground” or “Positive” (+)
“Negative” (—)
If stranded wire is used, be sure that the loose strands do not touch or short-out the speaker or amplifier
terminals. Also make certain that all amplifier and speaker terminals are tightened securely.
*
If two pairs of 901s are being connected in parallel, the terminal marked “492” or “4 ohms” on the
receiver or amplifier should be used. (See Section IV E.)
3. FUSING YOUR 901 SPEAKERS
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 speakers. BOSE Corpo-
ration recommends the use of a 3-ampere fuse, such as a BUSS AGC 3 or a LITTELFUSE 3 AG
(3 amp). The fuse should be connected in series with either of the two wires in the cable to each
speaker. A fuse holder, like a BUSS 3833-1 or a LITTELFUSE 356001 , may be used for convenience. (For
two pairs of BOSE 901s, use two 6-ampere fuses.)
CONNECTING THE EQUALIZER
THIS PART OF THE INSTALLATION DIFFERS FROM THAT OF CONVENTIONAL SPEAKER SYSTEMS.
BE CERTAIN TO FOLLOW THE INSTRUCTIONS GIVEN BELOW, STEP BY STEP.
1. PREFERRED METHOD
(Using The Tape Monitor Circuit)
To
provide
the
proper
balance
at
all
frequencies,
the
901
Active
Equalizer
must
be
connected
in
your
sound

system
before
the
final
stage
of
amplification.
The
connection
method
described
in
this
section
can
be
used
with
virtually
all
integrated
amplifiers,
preamplifiers,
and
receivers.
For
the
sake
of
simplicity,
we
will
call
these
various
components
the
“control
amplifier.”
The
901
Equalizer
is
normally
connected
to
your
control
amplifier
as
if
it
were
a
tape
recorder.
It
utilizes
the
TAPE
MONITOR
function
and
connections
of
your
control
amplifier.
CAUTION
TO PREVENT ELECTRICAL
‘SH
Series I
TO
QUALIFIED PERSONNEL.
TAPE RECORDER CONNECTIONS: | Corps COMMERTIONS
RECEIVER
FIG. 3
Referring
to
Figure
3,
connect
the
Equalizer
according
to
the
instructions
in
Steps
a
through
n:
a. Turn off all power to your equipment.
b.
If
you
have
a
tape
recorder,
disconnect
it
from
the
rear
panel
of
your
control
amplifier.
Instructions
in
the
next
section
will
show
you
how
to
reconnect
your
tape
recorder
to
the
system
after
the
Equalizer
has
been
installed.
THE
FOLLOWING
STEPS
WILL
CONNECT
THE
EQUALIZER
TO
YOUR
PREAMPLIFIER,
~
RECEIVER,
OR
INTEGRATED
AMPLIFIER.
READ
THEM
CAREFULLY.
pA
Using
one
of
the
cables
supplied
with
the
Equalizer,
connect
the
RIGHT
channel
OUTPUT
terminal
of
the
Equalizer
to
the
RIGHT
or
“B”
channel
TAPE
MONITOR
terminal
of
your
control
amplifier.
(This
terminal
may
also
be
labeled
TAPE
PLAYBACK
or
TAPE
IN.)
If
your
control
amplifier
has
two
tape
monitor
circuits,
see
Page
9.
d.
Connect
the
LEFT
channel
OUTPUT
terminal
of
the
Equalizer
to
the
LEFT
or
“A”
channel
tape
monitor
terminal
of
your
control
amplifier.
e.
Connect
the
RIGHT
channel
INPUT
terminal
of
the
Equalizer
to
the
RIGHT
or
“B”
channel
TAPE
RECORD
terminal
of
your
control
amplifier.
(This
terminal
may
also
be
labeled
TAPE
OUT
or
REC
OUT.)
f;
Connect
the
LEFT
channel
INPUT
terminal
to
the
LEFT
or
“A”
channel
TAPE
RECORD
terminal
of
your
control
amplifier.
g.
Connect
the
AC
power
cord
of
the
Equalizer
to
a
switched
outlet
of
your
control
equipment
so
that
the
Equalizer
will
automatically
be
switched
on
or
off
by
the
power
switch
of
your
integrated
ampli-
fier,
receiver,
or
preamplifier.
If
the
preceding
steps
are
unclear,
it
may
be
due
to
the
different
nomenclature
which
various
manu-
facturers
employ.
Consult
your
integrated
amplifier,
receiver,
or
preamplifier
instructions
and
refer
to
the
section
describing
steps
for
connecting
a
tape
recorder
to
the
tape
monitor
circuit.
Remember
that
the
Equalizer
connects
like
a
recorder.

THE NEXT SEVEN STEPS ARE TESTS WHICH MUST BE PERFORMED TO INSURE PROPER
OPERATION AND CORRECT INSTALLATION.
Place the TAPE switch on the Equalizer in the MONITOR position. Place the 3 frequency contour
controls so that they coincide with the indicated dots. These are the “NORMAL” positions of the
Equalizer controls.
Place the TAPE MONITOR or TAPE FUNCTION switch on your control amplifier in the NORMAL
or OUT position.
Turn the entire system on. Be sure that the Equalizer is plugged into an operating AC outlet by
observing that the pilot light on the Equalizer is on.
Play your system as you normally would, using a phonograph or AM-FM source (NOT a tape recorder)
to be sure it is operating properly.
This tests the rest of your system, since the Equalizer has not yet been switched into the system.
Any errors must be corrected before proceeding further.
Turn the BALANCE control of the control amplifier to the extreme right and left to check for
correct placement of the right and left channels.
With the system playing, move the TAPE MONITOR or TAPE FUNCTION switch on your integrated
amplifier, receiver, or preamplifier to the MONITOR or “ON” position. The sound should stop. This
TAPE MONITOR switch on your integrated amplifier, preamplifier or receiver should be left in this
position. If the sound does not stop, recheck Steps a through I.
Place the Equalizer TAPE switch in the NORMAL position. The sound should return. If the sound
does not return, and the Equalizer pilot light is on, then the Equalizer is probably connected in-
correctly. Recheck Steps a through |.
NOTE: If the TAPE MONITOR switch of your control amplifier is later switched out, the system
will continue to play but the Equalizer will no longer be functioning in the circuit. Since the system
will be playing and the Equalizer pilot light will be on, it will be possible, especially at low-volume
leyels or with certain musical selections, for you to be unaware that the Equalizer has been removed
from the circuit. Check the TAPE MONITOR switch on your control equipment periodically to
make certain it is still in the ON position.
If you do not have a tape recorder, the installation of the 901 system is now complete, and the system
is operating properly. If you do have a tape recorder, its connection to the system will be explained
in Section III D.

ALTERNATE METHOD |
(Using
PRE-AMP
OUT
and
MAIN
IN
Connections
with
Receivers
or
Integrated
Amplifiers
[Refer
to
Fig.
4.]
)
TAPE RECORDER CONNECTIONS
PRE-AMP MAIN-AMP
RECEIVER
FIG. 4
An
alternate
method
of
connecting
the
BOSE
Active
Equalizer
makes
use
of
the
PRE-AMP
OUT
and
MAIN
IN
jacks
provided
by
many
manufacturers
on
their
receivers
or
integrated
amplifiers.
To
do
this
refer
to
your
receiver
and
integrated
amplifier
owner’s
instruction
manual
for
separating
the
main
and
preamplifier
sections
of
their
units.
(This
is
usually
accomplished
by
removing
shorting
wires
or
plugs
and/or
moving
a
slide
switch).
Connect
the
PRE-AMP
OUT
terminals
to
the
Equalizer
INPUT
terminals,
and
connect
the
EQUALIZER
OUTPUT
terminals
to
the
MAIN
IN
terminals
of
the
receiver
or
integrated
amplifier.
With
this
method
of
connection,
leave
the
TAPE
switch
on
the
Equalizer
in
the
NORMAL
position.
Tape
re-
corders
are
connected
to
the
receiver
or
amplifier
in
the
conventional
manner.
The
disadvantage
of
this
method
of
connection
is
that
it is
difficult
to
use
conventional
speakers
or
headphones,
because
the
Equal-
izer
is
always
in
the
circuit.
ALTERNATE METHOD II
(Using
separate
PREAMPLIFIERS
and
POWER
AMPLIFIERS)
TAPE RECORDER CONNECTIONS] AMPLIFIER CONMECTIONS
OUTPUT
PRE
AMPLIFIER
MAIN-AMP
FIG. 5
The
Equalizer
can
be
connected
in
systems
that
include
separate
preamplifiers
and
power
amplifiers,
between
the
preamplifier
and
power
amplifier
(See
Fig.
5).
The
advantage
of
this
method
of
connection
is
that
the
tape
monitor
functions
of
the
preamplifier
are
still
available
for
connection
to
a
tape
recorder
in
the
conventional
manner.
One
disadvantage
of
this
method
of
connection
is
that
it
is
difficult
to
use
an
additional
pair
of
conventional
loudspeakers
or
headphones
because
the
Equalizer
is
permanently
in
the
circuit.
It
is
advisable
with
most
power
amplifiers
having
gain
controls
that
these
controls
be
turned
fully
clockwise
(consult
your
amplifier
manufacturer’s
owner's
manual
for
recommendations).

ed before the final stage of amplifica-
ally, the Equalizer should be connected
prevent any possible overloading of the
ilable, we suggest carefully reading the
garding system connection. How you
of the Equalizer and/or your associated
Series I
REFER SERVICING TO E]
maa
FIG. 6
Since
the
Active
Equalizer
has
been
connected
to
what
are
normally
the
tape
recorder
terminals
of
your
integrated
amplifier,
preamplifier,
or
receiver,
extra
terminals
are
provided
on
the
Equalizer
for
the
connection
of
a
tape
recorder.
Follow
the
next
five
steps
carefully:
(Refer
to
Fig.
6.)
a. Turn all power off.
b.
Connect
the
RIGHT
channel
TAPE
IN
terminal
on
the
Equalizer
to
the
RIGHT
or
“B”
channel
w
OUTPUT
terminal
on
the
tape
recorder.
ë:
Similarly,
connect
the
LEFT
channel
TAPE
IN
terminal
on
the
Equalizer
to
the
LEFT
or
“A”
channel
OUTPUT
terminal
of
the
tape
recorder.
d.
Connect
the
RIGHT
channel
TAPE
OUT
terminal
on
the
Equalizer
to
the
RIGHT
or
“B”
channel
INPUT
(or
LINE
IN)
terminal
of
the
recorder.
e.
Similarly,
connect
the
LEFT
channel
TAPE
OUT
terminal
on
the
Equalizer
to
the
LEFT
or
“A”
channel
INPUT
(or
LINE
IN)
terminal
on
the
recorder.
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
(down).
A å M
CONTROL
AMPLIFIERS
HAVING
TWO
TAPE
MONITOR
CIRCUITS
Many
modern
preamplifiers,
integrated
amplifiers,
and
receivers
have
two
tape
monitor
functions
providing
the
same
monitoring
features
for
two
tape
recorders
instead
of
one.
However,
most
of
these
controls
are
constructed
to
prevent
both
monitoring
switches
from
being
turned
on
or
“activated”
at
the
same
time.
Since
the
BOSE
Active
Equalizer
must
be
in
the
circuit
while
the
901
speakers
are
being
used,
connecting
the
Equalizer
in
either
TAPE
1
or
TAPE
2
will
require
connecting
your
tape
recorder
to
the
BOSE
Equalizer
tape
monitor
circuit,
not
the
unused
TAPE
monitor
position
found
on
your
control
amplifier.
av

a M
D.
4. ALTERNATE METHOD IlI
(Using FOUR-CHANNEL DECODERS)
As
previously
stated,
the
BOSE
Active
Equalizer
should
be
connected
before
the
final
stage
of
amplifica-
tion
of
the
amplifier
channels
powering
the
901
speakers.
Additionally,
the
Equalizer
should
be
connected
at
a
point
in
the
signal
path
following
the
four-channel
decoder
to
prevent
any
possible
overloading
of
the
decoding
equipment.
Because
of
the
many
different
decoders
available,
we
suggest
carefully
reading
the
owner's
instruction
manuals
of
all
of
the
associated
equipment
regarding
system
connection.
How
you
connect
the
decoder
will
depend
upon
your
own
needs
for
control
of
the
Equalizer
and/or
your
associated
equipment.
CONNECTING A TAPE RECORDER
ROR RRR
CS PO
W x a ion
KX
REONORR SIR RRN
‘BOSE CORPORATION
"AMPLIFIER CONNECTIONS.
FIG. 6
Since
the
Active
Equalizer
has
been
connected
to
what
are
normally
the
tape
recorder
terminals
of
your
integrated
amplifier,
preamplifier,
or
receiver,
extra
terminals
are
provided
on
the
Equalizer
for
the
connection
of
a
tape
recorder.
Follow
the
next
five
steps
carefully:
(Refer
to
Fig.
6.)
a.
b.
Turn all power off.
Connect
the
RIGHT
channel
TAPE
IN
terminal
on
the
Equalizer
to
the
RIGHT
or
“B”
channel
OUTPUT
terminal
on
the
tape
recorder.
Similarly,
connect
the
LEFT
channel
TAPE
IN
terminal
on
the
Equalizer
to
the
LEFT
or
“A”
channel
OUTPUT
terminal
of
the
tape
recorder.
Connect
the
RIGHT
channel
TAPE
OUT
terminal
on
the
Equalizer
to
the
RIGHT
or
“B”
channel
INPUT
(or
LINE
IN)
terminal
of
the
recorder.
Similarly,
connect
the
LEFT
channel
TAPE
OUT
terminal
on
the
Equalizer
to
the
LEFT
or
“A”
channel
INPUT
(or
LINE
IN)
terminal
on
the
recorder.
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
(down).
CONTROL
AMPLIFIERS
HAVING
TWO
TAPE
MONITOR
CIRCUITS
Many
modern
preamplifiers,
integrated
amplifiers,
and
receivers
have
two
tape
monitor
functions
providing
the
same
monitoring
features
for
two
tape
recorders
instead
of
one.
However,
most
of
these
controls
are
constructed
to
prevent
both
monitoring
switches
from
being
turned
on
or
“activated”
at
the
same
time.
Since
the
BOSE
Active
Equalizer
must
be
in
the
circuit
while
the
901
speakers
are
being
used,
connecting
the
Equalizer
in
either
TAPE
1
or
TAPE
2
will
require
connecting
your
tape
recorder
to
the
BOSE
Equalizer
tape
monitor
circuit,
not
the
unused
TAPE
monitor
position
found
on
your
control
amplifier.
eF

10
CONNECTING HEADPHONES OR CONVENTIONAL SPEAKERS
It
is
important
to
remember
that
the
BOSE
901
Active
Equalizer
introduces
substantial
boost
in
the
range
below
100
Hz
and
above
3000
Hz
to
match
the
power
response
of
the
901
speakers.
This
means
that
if
other
speakers
or
headphones
are
played
while
the
Equalizer
is
in
the
circuit,
they
will
radiate
far
too
much
energy
in
the
low
bass
and
high
treble
ranges.
MORE
IMPORTANTLY,
HEADPHONES
OR
CONVENTIONAL
SPEAKERS
MAY
BE
DAMAGED
BY
PLAYING
WITH
THE
BOSE
901
EQUALIZER
CONNECTED
IN
THE
CIRCUIT.
For
these
reasons,
you
should
switch
the
Equalizer
out
of
the
circuit
by
placing
the
TAPE
MONITOR
switch
of
your
preamplifier,
integrated
amplifier,
or
receiver
to
the
OFF
(or
NORMAL)
position
when
play-
ing
your
system
through
headphones
or
a
pair
of
speakers
other
than
BOSE
901s.
IV. GETTING THE MOST OUT OF YOUR 901 SPEAKERS
A.
ADJUSTING SPEAKER PLACEMENT
There
are
3
reasons
you
might
wish
to
adjust
the
placement
of
your
901s:
to
change
the
frequency
response
of
the
system;
to
change
the
dispersion
of
sound
into
the
room;
or
to
change
the
appearance
or
usefulness
of
the
room.
The primary influence of speaker placement on frequency response occurs in the mid-bass region
(80-300 Hz). This frequency range includes the fundamental tones of male voice, the low guitar range,
string bass, cello, trombone, and tympani. Moving the vee (the back of the 901) of the speakers closer to
the wall than 12 inches will boost the response in this mid-bass range. Do not move the back of the speaker
any closer to the wall than 8 inches. Moving the vee of the speakers farther from the wall than 12 inches
will decrease the response in the mid-bass range. Do not move the vee more than 18 inches from the wall.
The frequency response in the mid-bass range can also be modified in the same way by moving the speakers
closer to or farther from the floor, the ceiling, or the side walls. In all cases, DO NOT place the speakers
closer than 18 inches from the floor, ceiling, or side walls.
ee a ee E Ye SEEDS
The
dispersion
of
sound
into
the
room
can
also
be
affected
by
moving
the
two
901
speaker
cabinets.
If
the
stereo
image
of
the
music
is
too
narrow,
simply
move
the
two
speakers
farther
apart.
It
is
recommended
that
the
speakers
be
placed
no
farther
apart
than
15
feet.
If
the
image
of
the
sound
is
too
broad,
or
if
there
appears
to
be
‘‘too
much
space
in
the
middle,”
the
speakers
can
be
moved
closer
together.
It is
recommended
that
the
speakers
be
moved
no
closer
together
than
4
feet.
FIG. 7

Additionally,
the
dispersion
can
be
adjusted
by
rotating
the
speakers.
For
instance,
if
you
wish
more
sound
to
come
from
the
left
side
of
one
of
the
speakers,
rotate
the
rear
of
the
speaker
(the
vee)
to
the
left.
This
technique
can
also
be
used
to
direct
sound
away
from
an
obstacle
(for
example,
a
piece
of
furniture)
or
an
opening
into
an
adjacent
room.
(See
Fig.
7.)
The
901s
also
can
be
hung
from
the
ceiling.
As
well
as
being
an
effective
and
interesting
decorating
approach,
this
is
a
useful
method
of
installation
where
speaker
placement
might
be
difficult
due
to
furniture,
location
of
doorways,
and/or
small
children.
The
hardware
is
readily
available
at
most
stores
carrying
decorative
lighting
accessories.
We
recommend
using
a
three
or
four
point
suspension,
with
three
or
four
pieces
of
decorative
chain
or
other
strong
material.
These
are
attached
to
the
bottom
of
the
901
cabinet
via
decorative
hooks
or
eyelets
screwed
into
the
cabinet.
Keep
in
mind
that
each
901
weighs
33
pounds;
therefore,
use
hardware
strong
enough
to
support
this
weight.
The
901
speaker
should
be
placed
no
closer
than
18
inches
from
the
ceiling.
If
you
prefer
to
suspend
the
speakers
far
above
the
listening
area
in
a
high
ceiling
room,
the
sound
can
be
directed
downward
by
angling
the
rear
of
the
speaker
down.
The
sound
will
then
be
directed
downward
after
it
is
reflected
off
the
rear
wall.
The
speaker
can
be
tilted
in
this
manner
by
adjusting
the
length
of
the
rear
chain(s).
B.
ADJUSTING
THE
EQUALIZER
CONTROLS
BELOW
40
HIGH
FREQ
TREBLE
LEVEL
e
e
BOSE
901
ACTIVE
EQUALIZER
(
]
MONITOR CONTOUR DECREASE
FIG. 8
BELOW 40
Another
way
of
altering
the
performance
of
the
901
system
is
to
adjust
the
Equalizer
controls.
The
first
Equalizer
control
is
labeled
BELOW
40.
This
control
causes
a
uniform
reduction
in
bass
response
of
approximately
8
dB
below
40
Hz.
If
distortion
occurs
when
you
are
playing
loud
musical
material
with
a
great
deal
of
deep
bass
content,
move
this
switch
from
the
dotted
position
to
the
CONTOUR
position.
This
will
allow
you
to
play
the
system
louder,
especially
with
low-powered
amplifiers
or
receivers.
This
control
is
effective
also
in
reducing
“rumble”
from
older
turntables
or
recordings.

12
The
effect
of
the
various
control
settings
upon
the
frequency
response
(taking
the
normal
or
“dotted”
posi-
tion
as
“flat”)
is
illustrated
in
Figures
9
and
10.
EQUALIZER RESPONSE IN DECIBELS
RELATIVE TO THE RESPONSE
OF THE EQUALIZER WITH
ALL SWITCHES IN THEIR
NORMAL POSITIONS
5
TREBLE LEVEL
SWITCH POSITION
BELOW 40
OW 40 CONTOUR
50
EQUALIZER REPSONSE IN DECIBELS
RELATIVE TO THE RESPONSE
OF THE EQUALIZER WITH
ALL SWITCHES IN THEIR
NORMAL POSITIONS
5
FREQUENCY RESPONSE CONTOURS OF THE BOSE 901 SERIES-II
ACTIVE EQUALIZER WITH THE HIGH FREQUENCY SWITCH IN
THE NORMAL POSITION.
500 1,000
FIG. 9
5,000 10,000
——t
TREBLE LEVEL
SWITCH POSITION
HIGH FREQUENCY
FREQUENCY RESPONSE CONTOURS OF THE BOSE 901 SERIES-1!
ACTIVE EQUALIZER WITH THE HIGH FREQUENCY SWITCH IN
THE DECREASE POSITION.
500 1,000
FIG. 10
1
5,000 10,000 N_ 20K
The
next
frequency
control
of
the
901
Equalizer
is
labeled
HIGH
FREQ.
If
the
control
is
moved
to
the
DECREASE
position,
the
frequency
response
of
the
system
is
decreased
in
the
high
treble
range
above
10
kHz.
This
control
may
be
used
as
a
scratch
filter,
or
to
modify
the
response
of
some
recordings
which
are
excessively
bright
in
the
high
treble
range.
TREBLE LEVEL
The
next
frequency
control
is
a
rotary
switch
labeled
TREBLE
LEVEL.
This
control
has
5
positions.
The
third
position
is
the
normal,
or
“dotted”
position.
The
“dotted”
position
is
the
preferred
position
for
use
in
rooms
of
average
acoustical
properties.
In
a
room
that
is
extremely
“bright’’
due
either
to
room
conditions
or
to
the
recording
you
are
playing,
you

may
wish
to
move
this
control
to
Position
2
or
Position
1.
These
Positions
successively
decrease
the
fre-
quency
response
over
the
entire treble
range
(above
2000
Hz).
In
a
room
which
is
extremely
“dull,”
you
may
wish
to
move
the
TREBLE
LEVEL
control
to
Position
4
or
Position
5.
This
increases
the
frequency
response
throughout
the
entire treble
range.
Another
benefit
of
this
TREBLE
LEVEL
control
is
that
it
allows
the
use
of
the
901
system
in
front
of
reflecting
walls
which
are
covered
with
curtains
or
drapes.
If
your
reflecting
wall
is
covered
with
a
sound
absorbent
material
setting
the
TREBLE
LEVEL
control
to
Position
4
or
5
will
result
in
the
same
frequency
response
as
if
the
wall
had
no
draperies
covering
it.
In
the
final
analysis,
you
should
set
the
TREBLE
LEVEL
control
to
that
position
which
best
fits
your
listening
taste,
rather
than
following
any
rigid
guidelines.
IMPROVING ROOM ACOUSTICS
The
acoustical
properties
of
a
listening
room
have
a
very
large
effect
on
the
quality
of
sound
produced
in
that
room
by
a
sound
system.
An
overly
“live”
room
has
hard
walls
and
little
in
the
way
of
soft
sound
absorbing
material
like
rugs,
sofas,
and
drapes.
Not
only
is
music
listening
likely
to
be
unpleasant
in
such
a
room,
but
it
may
even
be
uncomfortable
to
carry
on
a
normal
conversation.
The
properties
of
such
a
room
can
be
greatly
improved
by
adding
some
sound
absorbing
material.
This
can
be
done
by
adding
a
rug,
cushioned
furniture,
curtains
or
drapes,
or
wall
hangings.
Rooms
which
have
too
much
absorbing
material
tend
to
be
acoustically
“dead.”
In
such
rooms,
music
will
seem
lifeless,
and
conversation
may
sound
as
if
you
were
outdoors.
A
“dead”
room
can
be
improved
by
re-
moving
some
sound
absorbing
material
such
as
curtains,
drapes,
or
cushioned
furniture.
SELECTING THE RIGHT AMPLIFIER
Most
modern
amplifiers
or
receivers
will
provide
satisfactory
performance
for
most
owners
of
the
BOSE
901
system.
We
recommend
that
you
select
an
amplifier
or
receiver
which
is
capable
of
delivering
25
watts
rms
per
channel
or
more
into
8
ohms.
If
your
listening
room
is
rather
large-or
“dead”
or
if
your
listening
tastes
call
for
fairly
high
volume
levels,
you
may
want
to
consider
purchasing
an
amplifier
or
receiver
which
can
deliver
50-70
watts
rms
per
channel
into
8
ohms.
An
amplifier
of
this
size
is
sufficient
to
satisfy
the
vast
majority
of
listeners.
Some
listeners
prefer
very
high
volume
levels.
If
such
levels
are
to
your
liking,
you
will
be
most
pleased
with
the
901
system.
The
BOSE
901
can
handle
much
more
power
than
conventional
loudspeaker
systems.
Listeners
who
demand
extremely
high
volume
levels
should
consider
amplifiers
in
the
power
range
of
100
to
270
watts
rms
per
channel
into
8
ohms.
To
reproduce
the
highest
sound
levels
in
the
home,
you
may
select
an
amplifier
capable
of
delivering
up
to
270
watts
rms
per
channel
into
8
ohms
without
exceeding
the
safe
operating
limits
of
the
901.
THE
ONLY
SYSTEM
BETTER
THAN
A
PAIR
OF
901s
The
901
was
designed
to
outperform
all
other
high
fidelity
speakers,
regardless
of
their
size
or
price.
If
we
were
to
make
a
speaker
twice
as
big
or
twice
as
expensive
as
the
901,
we
could
not
significantly
improve
its
performance.
However,
using
two
pairs
of
901s
substantially
adds
to
the
quality
of
the
performance.
The
advantages
of
a
second
pair
include:
expanding
the
spatial
properties
of
the
performance;
increasing
the
efficiency
of
bass
reproduction;
and
increasing
the
power
available
from
most
amplifiers.
The
ideal
placement
is
“around
the
corners”
from
the
first
pair
(See
Fig.
11).
The
same
distances
apply,
from
the
reflecting
wall,
floor,
ceiling,
and
side
wall,
as
for
the
first
pair
of
speakers.
The
effect
of
this
arrangement
is
to
bring
the
“stage”
out
around
the
listener
in
an
acoustic
Panorama.

14
Vi.
LISTENING AREA
FIG. 11
Since
the
second
pair
of
speakers
is
connected
in
parallel
with
the
first
pair,
a
second
Equalizer
is
not
required.
For
this
reason,
the
BOSE
901
is
available
at
lower
cost
as
an
“Add-On
Pair,”
without
the
Equal-
izer.
To
connect
the
second
pair
of
speakers,
simply
connect
the
8
OHMS
terminal
of
the
second
left
speaker
to
the
8
OHMS
terminal
of
the
first
left
speaker.
Connect
the
COM
terminal
of
the
second
left
speaker
to
the
COM
terminal
of
the
first
left
speaker.
Follow
a
similar
procedure
for
the
right
speaker.
Note:
If
your
amplifier
has
separate
output
connections
for
different
speaker
impedances,
you
should
connect
each pair
of
speakers
to
the
4
OHM
terminals
of
your
power
amplifier.
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,
that
you
return
only
that
part
of
the
system
which
is
defective.
If one speaker sounds defective, switch the left and right channel speaker cables at the point where they are connected
to the amplifier or receiver. If the trouble moves to the other speaker, it is not in the speakers or in the speaker wiring.
As noted earlier in this manual, if you hear distortion with both speakers at high sound levels which disappears when
you turn the volume down or switch the BELOW 40 switch to CONTOUR, you are probably overloading the ampli-
fier. If this is the case, leave the BELOW 40 switch in the CONTOUR position for the recording you are playing.
(See Section IV, D.)
If
the
trouble
seems
to
be
in
the
Equalizer,
be
sure
that
the
system
operates
properly
with
the
Equalizer
out
of
the
circuit.
Check
this
by
switching
the
preamplifier
or
receiver
TAPE
MONITOR
switch
to
the
OUT
or
NORMAL
position.
Be
certain
that
all
cables
are
connected
properly
and
that
the
cables
are
not
defective.
If
the
trouble
persists,
contact
your
dealer.
He
will
arrange
for
service
either
by
having
the
unit
serviced
at
a
Factory-
Authorized
Service
Agency
or
at
the
BOSE
Factory.
If
it
becomes
necessary
to
return
your
unit
to
the
Factory,
he
can
obtain
a
Return
Authorization
Number
which
must
appear
on
the
outside
of
the
carton
when
the
unit
is
returned
to
the
Factory.
Shipments
arriving
at
the
BOSE
Factory
without
a
RETURN
AUTHORIZATION
NUMBER
on
the
outside
of
the
carton
are
not
accepted,
but
are
returned
freight
collect
to
the
sender.
Units
must
be
returned
prepaid.
DO
NOT
SHIP
VIA
PARCEL
POST.
TECHNICAL INFORMATION
A.
The
System
is
packed
in
Two
Cartons
Marked
“Part
1”
and
“Part
2”
Weight: Part 1 — 44 pounds
Part 2 — 42 pounds
Carton Dimensions: 22-3/4"" W x 15” H x 16-1/2” D

B. The Speaker
Dimensions:
20-9/16”
W
x
12-3/4"
H
x
12-7/8”
D
Weight:
33
pounds
Nominal
Impedance:
8
ohms
C.
Percentages
of
Direct
and
Reflected
Sound
Radiation
Power radiated by reflection: 89%
Power radiated directly: 11%
(Design
percentages
based
on
concert
hall
acoustics)
D.
Power
Handling
Continuous
sine
wave
power
at
any
frequency:
50
watts
Minimum
recommended
amplifier
power:
25
watts
rms
per
channel
into
8
ohms
Peak
power
handling
ability
(less
than
five
seconds):
400
watts
w
Maximum
recommended
amplifier
power
for
speech
and
music:
270
watts
rms
into
8
ohms
A
Damping
Factor
Any
amplifier
with
a
damping
factor
of
40
or
higher
meets
the
requirements
of
the
901.
(The
wire
size
recommenda-
tions
of
Table
1
on
Page
4
must
be
followed.)
F: Driver Complement
Each
unit
contains
9
high-compliance
full-range
drivers
with
high
energy
magnets
to
allow
large
excursions
without
audible
distortion
on
any
program
material.
The
drivers
are
acoustically
coupled
to
eliminate
audible
resonances.
Nominal driver diameter: 4-1/2”
Maximum driver excursion: +1/4”
Nominal
driver
impedance:
8
ohms
Weight
of
each
ceramic
magnet:
9.6
ounces
G. The Active Equalizer
Dimensions:
2-13/16"
H
x
9-1/4"
W
x
6-3/4"
D
w
Input
Impedance:
150k
ohms
Output Impedance: less than 100 ohms
Minimum
Load
Impedance:
5k
ohms
Maximum Output Voltage: 4.0 volts
Maximum Gain: 18 dB at 35 Hz.
l
VII.
ACCESSORIES
AND
OPTIONS
WALNUT FACINGS
The
BOSE
901
is
available
with
walnut
facings,
to
provide
the
rich
look
of
walnut
grain
around
the
entire
cabinet.
The
small
grille
panel
on
each
speaker
front
allows
a
choice
of
fabrics.
Walnut
facings
are
available
as
a
separate
add-on
kit.
PEDESTALS.
Specially
designed
pedestals
are
available
for
the
901.
They
are
18
inches
high,
and
available
in
either
white
or
black.
EQUALIZER
CUSTOM
MOUNTING
KIT
A
special
Equalizer
Custom
Mounting
Kit
is
available
for
custom
installation
of
the
Equalizer
in
a
cabinet
or
wall.
(Order
Part
Number
103491
for
your
901
Series
Il
Equalizer.)
For
additional
information
on
these
accessories,
contact
your
authorized
BOSE
dealer.
15

VIII. FIVE YEAR WARRANTY
We warrant the BOSE 901 speaker system to be free from defects in material and workmanship. BOSE will replace any
defective part and correct any defect in workmanship or performance, without charge for either parts or labor. The
obligation of BOSE under the terms of this warranty is effective only if the defect develops in a normal installation,
under normal use and service, within a period of FIVE years from the date of purchase, subject to the following terms
and conditions:
J You purchased your BOSE system new from an authorized BOSE dealer. Proof of purchase by original sales slip
or otherwise is required to expedite repairs under warranty.
2 The speaker is used in accordance with instructions in Owner’s Manual.
<A Such defect was not caused by abuse, neglect or accident, and no unauthorized repairs have been made.
4. Our responsibility is limited to the repair and replacement of units properly packed and returned PREPAID to
the BOSE Factory or BOSE Factory-Authorized Service Agencies. Return freight charges will be paid by BOSE.
Shipping cartons can be obtained from BOSE Dealers or the BOSE Factory. ANY DAMAGE IN TRANSIT due to ~~
improper packing is not covered by the warranty and will not be recognized as an insurance claim by our trans-
portation companies. DO NOT SHIP BOSE SPEAKERS PARCEL POST.
5, We assume no liability for installation labor or consequential damages.
6. All service must be provided by BOSE Factory or Factory-Authorized Service Agency. Failure to comply invali-
dates your warranty.
F The serial number must not be defaced, removed, or otherwise obliterated, and must correspond to the number
on the completed Warranty Card on file with BOSE.
There are no warranties, expressed or implied, other than as stated above.
SHOULD YOUR UNIT APPEAR TO BE DEFECTIVE, DO NOT RETURN THE UNIT TO THE FACTORY. TAKE
THE UNIT TO YOUR DEALER. HE WILL ARRANGE FOR REPAIRS.
IF IT BECOMES NECESSARY TO RETURN YOUR UNIT TO THE FACTORY, DO NOT RETURN YOUR SPEAK-
ERS WITHOUT FIRST RECEIVING A RETURN AUTHORIZATION NUMBER.
MOGE
BOSE CORPORATION ©® THE MOUNTAIN @ FRAMINGHAM, MASS. 01701
103476-773