Bose 901 Series III User Manual
Owner’s Manual
Table of Contents
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1. Introduction
II. Unpacking Instructions
III. The 901 Series III Loudspeaker System
A. Design Features
B. Technotogical innovations
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IV. Installation
A. Placing the Speakers
B. Connecting the Speakers
1 Wire Selection
2 Phasing/Wiring
3 Fusing
C. Connecting the Equalizer
1 Using li)e Tape Monitor Circuit
2. Using Separate Components: Connecting Between the Preamp and the Amplilier
3 Using the Preamp Oul/Main in Circuit
4 Using Four Channel Equipment
Connecting Other Equipment
A, Tape Recorders
B. Headphones and Conventional Speakers
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VI. Living with your BOSE 901 Speakers 16
A Adjusting Your Equalizer Controls
B Speaker Placement
C. Room Acoustics
VII. Technical Information
A. Specificalions
B Voltage Conversion
C in Case of Difficulty
0 Care and Maintenance
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VIII. Warranty 20
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I. Introduction
Thank you for purchasing the BOSE 901 Series III Direct/Reflecting* 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 III. with Its high proportion of reflected sound,
nine full-range drivers, and electronic active equalization, is in
stalled. 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 With proper installa
tion. you will be rewarded with the unique listening pleasure pro
vided by your 901's.
II. Unpacking Instructions
The 901 Series III speaker system is packed in two cartons marked
"Part 1 and "Part 2. The active equalizer is found in the carton
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 operation Repack the
speaker(s) in the original carton with the complete packing mater
ial and notify your dealer immediately
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III. The 901 Series III Loudspeaker System
A. DESIGN FEATURES
1. Correct Balance ot Reflected and Direct Sound
The BOSE 901 Series III is designed to use your listening
room walls to simulate the reflective properties of the much
larger stage wall found behind the instruments of a live per
formance. The 901 Series ill uses nine drivers, eight directed
towards the back wall, and one driver directed into the lis
tening area, thus 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 elec
tronically ‘contouring' the preamplifier signal; thus, the
entire system radiates the correct balance of total acoustic
power at every frequency.
3. Multiple Full-Range Drivers
To accurately reproduce the timbre of every musical instru
ment, 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 of the frequency range to be
reduced or accentuated
The 901 system utilizes two unusual physical phenomena
called “resonance splitting ' (ihe acoustically coupled drivers
force the resonances to "splir to different frequencies, thus
smoothing the response) and “response averaging” (any
driver response irregularity is “averaged" with the other
drivers and becomes an insignificant ‘4 of the total power).
B. TECHNOLOGICALINNOVATIONS
1. The New Full-Range High-Performance Driver
In the 901 Series III driver, a combination of technological
advances make possible its outstanding performance;
• A highly efficient magnetic structure with all parts as
sembled to precise tolerances to provide maximum mag
netic field energy.
• An aluminum helical voice coil, providing better utilization
of magnetic energy,
• A now cone and suspension for smoother, more controlled
frequency response and lower distortion.
• An injection molded frame, eliminating distortion of the
magnetic field (caused by steel frames) and improving
precision in assembly.
The combination of the helical voice coil and precision as
sembly means that a 15 watt amplifier will produce the loud
ness 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 equaliza
tion to home loudspeaker systems It demonstrated the
fundamental performance advantages of incorporating
equalization as a part of the loudspeaker system design
The 901 Series III realizes additional advaniagcs of active
equalization with three new equalizer features:
• More precise equalization of the audible sound spectrum
made possible by significantly more complex equalization
circuits
• Additional control flexibilily. permitting optimum speaker
performance in a wide range of room positions (see SEC
TION VI).
• 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 enclos
ure to be designed for optimum performance character
istics.
3. The Acouslic Matrix"^ Enclosure
The enclosure of the 901 Series III is designed specifically
to work with nine full-range matched drivers in combination
with the active equalizer.
Tiie 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 to provide
reactiveair loading toreduce the motion required of the driver
cones at extremely low frequencies, thus allowing maximum
efficiency with lowdistorlion.
Additionally, the enclosure partially isolates the acoustic
pressure at each driver from other drivers to permit it to
operate properly through the frequency range where reac
tive loading occurs.
IV. 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. Installation consists of
three steps; 1) placing your speakers for best sound. 2) connecting
Ihe speaker to your amplifying equipment, and 3) connecting Uie
equalizer to your amplifying equipment.
A. PLACING THE SPEAKERS
Unlike conventional speakers. Ihe 901 Series III functions with
the acoustics of your listening room, simulating the spatial char
acteristics of the larger environments associated with live per
formances This important advantage allows considerable free
dom of placement and produces an unusually large "best listen
ing 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 901 speaker (see Figure 1) Point this portion of
Ihe speaker toward the reflecting wall (the wall behind the
speaker) The point of the "V" should be between 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
coiling or floor restrict the reflected sound energy.
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3 The speakers should be at least 18" from a side wall or open
ing 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 VI (LIVING WITH
YOUR BOSE 901 SPEAKERS) provides several additional sug
gestions for speaker placement
« A
I
if’W
J.
REFLECTING
WALL
Figure 1
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