Tourbuss – Drawmer Tourbuss for Digidesign Venue User Manual

Page 11

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operator’s manual


Using the SDX100


0dB to +20.5dB

During compression the signal is attenuated,
gain may be required to produce the desired
output level. Only apply gain until the limiter
operates on signal peaks.

G.R. Meter

0.0 to -30dB


When enabled the signal is passed through to
the limiter without compression, effectively
turning the Compressor plugin into a stand alone
limiter that can be used at the end of the chain
of plugins open within the Venue system.

Setting up the Compressor is simpler if the Peak Limiter threshold is at maximum. The Ratio setting depends
on how firmly the signal dynamics need controlling; as a rule, higher ratios provide a higher degree of control
but also tend to be more audible when high levels of gain reduction are required, We suggest less than 2.5:1
for vocals, even less for full mixes, and more for dynamic single tracks. With soft-knee active transition is far
less pronounced without compromising the sound quality, whilst hard knee can be used more creatively.

If the Attack & Release switch is set to Auto, setting up is now simply a matter of adjusting the Threshold
control until the desired amount of gain reduction occurs. This is judged partly by ear and partly by observing
the gain reduction meter. Usually, a maximum gain reduction of between 8dB and 12dB will be adequate. The
ideal is to set it comfortably above the “comfort” level whilst below the “danger” level, to capture the performer’s
dynamics but catch any peaks that occur.

Rotate the Gain control until as near to 0dBfs signal output is seen at the output VU meter. Set it so that the
limiting only occurs on signal peaks.

At this point, the Auto Attack & Release switch may be disabled if manual control is wanted. A slow attack
time is often used to accentuate the beginning of percussive or plucked sounds such as drums, basses and
guitars. A long attack time can also permit peaks to pass unattenuated; the limiter will pick these up, so it is
quite common with slow attack times to see increased limiter activity. A fast attack time will bring the input
signal under control very quickly to catch any peaks.

Consider that Compression during a mix increases the subjective level of background noises during pauses
and quiet passages. Unless the noise contamination is serious, the TourBuss expander should be active in
the plugin chain to attenuate this noise to a very high degree, without compromising the wanted signal.

Pumping is a phrase used to describe heavy compression that has incorrectly set envelope parameters
where the compressor gain change as it attacks and releases can be heard. This is more often an indication
that Release is set wrongly. Manual Release time should be set short enough so that the system gain control
has returned to normal before the next signal peak occurs, and, in general, it should be set as short as
possible before audible gain pumping occurs.

Apparent Dullness of Compressed Material
Compressors are often accused of dulling the sound being processed. Most of the energy in typical music is
contained within the bass sounds. This high energy causes the Compressor to operate, and so any quieter,
high frequency sounds occurring at the same time as the bass sound will also be turned down in level. This
is why the cymbals and hi-hats in a heavily compressed drum track seem to dip in level whenever a loud bass
drum or snare drum beat occurs.

The solution is either to use less compression or increase the attack time to allow the leading edge of the
brighter sounds to pass through the Compressor before the gain reduction occurs. In extreme cases, it may
be necessary to add a little artificial brightness to the processed sound using equalisation, though the soft-knee
compression used in the Drawmer TourBuss tend to minimise this side effect.

Compressor Setup and Operation