BBE Sonic Maximizer 262 User Manual page 4

BBE 262 SONIC MAXIMIZER
The BBE Process - 'What It Is'
Loudspeakers have difficulty dealing with the electronic signals
supplied by an amplifier. These difficulties cause such major phase and
amplitude distortion that the sound reproduced by a speaker differs
significantly from the sound produced by the original source.
In the past, these problems proved unsolvable and were thus
delegated to a position of secondary importance in audio system design.
However, phase and amplitude integrity is essential to accurate sound
reproduction. Research shows that the information which the listener
translates into the recognizable characteristics of a live performance are
intimately tied into complex time and amplitude relationships between
the fundamental and harmonic components of a given musical note or
sound. These relationships define a sound's "sound".
When these complex relationships pass through a speaker, the proper
order is lost. The higher frequencies are delayed. A lower frequency
may reach the listener's ear first or perhaps simultaneously with that of
a higher frequency. In some cases, the components may be so
time-shifted that they reach the listener's ear ahead of some or all of
the harmonic components.
This change in the phase and amplitude relationship on the harmonic
and fundamental frequencies is technically called 'envelope distortion.'
The listener perceives this loss of sound integrity in the reproduced
sound as 'muddy' and 'smeared.' In the extreme, it can become diffi-
cult to tell the difference between musical instruments, for example, an
oboe and a clarinet.
BBE Sound, Inc. conducted extensive studies of numerous speaker
systems over a ten year period. With this knowledge, it became
2 - BBE 262 INSTALLATION INSTRUCTIONS
possible to identify the characteristics of an ideal speaker and to distill
the corrections necessary to return the fundamental and harmonic
frequency structures to their correct order. While there are differences
among various speaker designs in the
magnitude of their correction, the overall pattern of correction needed is
remarkably consistent.
The BBE process is so unique that 42 patents have been awarded by
the U.S. Patent Office.
The BBE Process - 'How It Works'
The BBE Process imparts a pre-determined phase correction to the
high frequencies where most harmonic information exists. This is done
by breaking the signal into three sub-bands or groups: a.) LOs (20Hz -
150Hz), b.) MIDs (150Hz - 1200Hz), and c.) HIGHs (1200Hz - 20kHz).
The low group is delayed about 2.5 ms (milliseconds) via a delay
within the passive low pass filter. The front panel LO
CONTOUR control allows for either a flat response or a boost at 50Hz.
The mid-range group is delayed only about 0.5ms and passes
through an active band-pass filter while the high frequency group
is passed through a VCA (Voltage Controlled Amplifier). The high
group is used as a point of reference to make dynamic amplitude
corrections to the high frequencies.
The RMS average loudness detectors continuously monitor both the
mid-range and high frequencies to compare the relative
harmonic content levels of the two bands and apply the appropriate
amount of control voltage to the VCA, thereby determining the amount
of high frequency harmonic content present at the final output of the
BBE processor.