Drawmer THREE-SUM Manual del usuario - Página 8

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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

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.

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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.

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 -

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CHAPTER 3