8
DRAWMER
T
HREE
-
SUM
O
PERATOR’S
M
ANUAL
Most conventional compressors work by processing the
full-band of the music, where the whole of the signal is
compressed using the same controls, however, this is by
no means perfect. A problem occurs whereby when a peak
occurs, such as the beat of a kick drum, all of the signal
is effectively "turned down" by the compressor, including
the vocals, guitar, hi-hats etc. even though these may not
need compressing. In addition, when processing complex
mixes using a conventional compressor, you can easily
reach the point where gain pumping becomes audible, with
high-energy, low-frequency sounds affecting the gain of
the whole mix. Multi-band compressors were designed to
avoid these problems, by treating different sections of the
frequency spectrum independently.
The Drawmer Three-Sum has been designed to allow the
audio to split into three separate frequency bands by means
of a crossover circuit, each band then being treated with a
separate compressor and, at the output, the various bands
are again combined to provide a full-range signal. In addition,
unlike conventional three band compressors, the Drawmer
Three-Sum allows the three signals to be sent to three
independent compressors, each giving their own unique
flavour to the music - some warmer at bottom end
compression, others providing an enhanced top end. The
control is entirely with the operator.
The Drawmer Three-Sum, where each band's compressor
can be adjusted separately, is a very versatile and powerful
tool. For instance, the perceived amount of bass can be
increased by setting a higher ratio or lower threshold for
the bass band than in the mid and high bands. Similarly,
if you feel the mid frequencies of the mix are lacking, simply
turn up the output level of the mid-band compressor - using
more compression in the mid-band can often help lift out
the vocals. Likewise, compress the top end a little harder
to give it more brightness or enhancement. If the gain
reduction of each band is controlled by adjusting the make-
up gain knobs on each of the three
compressors then the overall levels of
signal peaks will not increase but the
sound will be much more impressive.
However, no matter how much care is
taken, it is quite possible to fully control
the signal in each band but still end up
with a signal that is too high in level
when the bands are combined.
Therefore an output gain control has
been provided on the Three-Sum to trim
the whole stereo signal, followed by a fast acting limiter
that will catch any overshoots. To ensure transparency
the limiter design is ‘two stage’, applying different
processing to the H.F. content of the material. In
applications where the dynamics of the material need to
be retained to create an open sound, set the output gain
so that the limiter only activates on fast signal peaks.
Setting up the Cross-Over Points
.
Which cross-over frequencies should be used? This
invariably depends on the material being processed, the
settings of a mix will be very different from that of a full
drum kit, however the general rule of thumb is that in most
circumstances the cross-over points need to
be set in such a way as to separate the main
bass and treble sounds from the mid-range.
Keeping in mind that instruments have
harmonics that can extend over several
octaves, the goal is to try to partition your
mix into bands. Play your mix, and mute the
bands not required. Now you can hear exactly
which frequencies are contained in each
band, and can tune in to the signal.
On a full mix the kick drums and bass instruments will be
mainly in the low band while the mid band should be set
wide enough to accommodate the full vocal range, except
for perhaps the highest harmonics and breath noises -
OPERATION
CHAPTER 3
