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WHAT IS THE BBE PROCESS?
The BBE process was developed to overcome the phase and
amplitude distortion inherent in most speaker systems.
When the complex audio waveforms pass through a speaker, their
proper phase order is lost. The higher frequencies are delayed which may
cause lower order frequencies to reach the listener's ears first or
simultaneously with the higher frequencies. This is known as "envelope
distortion" and gives the listener a "muddy" or "smeared" perception of the
music program.
The BBE process imparts a pre-determined phase correction to the high
frequencies where most of the harmonic information exists. This is done by
breaking the signal into three sub-bands: a low frequency band which is
crossed over at 150Hz, a mid-range band which is crossed over at 1200Hz
and the high frequency band that handles everything else up to 20kHz.
The low band is delayed about 2.5ms (milliseconds) through a passive
low pass filter. By delaying the mid-range band about 0.5ms through an
active band pass filter and using the high frequency band as a reference, a
voltage controlled amplifier (VGA) then makes continuous adjustments to
maintain a constant level of harmonic content per amount of mid-range
program at the output.
USING THE BBE 702
The BBE model 702 is a card format of the BBE process that is
designed to operate in the dbx 900 series of modular mainframes.
The BBE 702 is a single ended processor to be used "in line" in the
audio signal chain. This may be accomplished by using an insertion point
either on an individual channel or sub group, or on the main outputs of the
mixing console.
The BBE 702 should not be used in an effects loop since the phase shift
in the BBE process may cause phase cancellation in the program.
The BBE process may be used on the entire mix of the program or on
individual instruments such as violin, clarinet, guitar or vocals.
It is recommended that any equalization be reduced as much as
possible prior to introducing the BBE process so the original mix is
processed correctly. Equalization may be added later to suit the listener's
taste.
Whether used live or in the recording studio, the BBE process will
increase the overall intelligibility of program material in the most demanding
of circumstances.
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