Bose 901 Series III - Manual (Page 4)

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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.