Bose 901 Series II - Manual (Page 13)

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.
C. IMPROVING ROOM ACOUSTICS
The acoustical properties of a listening room have a very large effect on the quality of sourvj produced in
that room by a sound system. An overly "live" room has hard walls and little in the way of soft soursd
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.
D. 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 likir>g. 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.
E. 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.
13