Bose 901 Series II - Manual (Page 10)

E. 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.
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 sourtd 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.
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