Bose 901 Series III - Manual (Page 5)

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.