Operator Manual

290 Appendix A: Application Notes
PRO2 Live Audio System
Owner’s Manual
Attack
The attack control adjusts the time taken for the compressor to respond to an
over-threshold signal. The shape of the attack can be selected from one of the five
mode combinations mentioned above, making the compressor easily adaptable for a
wide number of creative and corrective applications.
Release
The release control adjusts the time the compressor takes to recover after the
programme material falls back below threshold. Both attack and release also respond
to changes in programme level that remain over-threshold. For example, a signal that
reduces in level but remains above threshold will still trigger a release, but in this case
it will only be a partial release - because the compressor will still be required to
generate gain reduction, but now, as appropriate for the new lower signal level.
Knee
Most compression sounds more natural in soft knee mode. Soft knee compression blurs
the distinction between over-threshold and under-threshold signals, such that signals
that are a long way below threshold remain unaffected by compression, and signals that
near the threshold get compressed, but at greatly reduced ratios. When signals are
just over-threshold the compressor ratios are still somewhat reduced; it is only when
signals go well over threshold that the full ratio compression is applied. When using a
harder knee setting the compressors operate in a more clinical way with a more defined
transition between under-threshold and over-threshold; this is better suited to limiting
style compression.
Gain
The gain control provides adjustment of the make up gain so that the level of the
outgoing compressed signal can be matched to the incoming uncompressed signal.
Side chain filter
A band pass filter is provided that acts on the side chain signals. This can be used to
make the compression frequency selective. The controls for this are frequency,
adjustable from 50Hz to 15KHz, and bandwidth selectable as wide, medium or narrow.
Additionally, there is a listen function that places the filtered side chain onto the solo
bus and a side chain filter in to activate or eliminate the filter action.
Compressor envelope modes
The five envelope modes, or signatures, are the key to the sonic character of the PRO2
compressors, and they allow adjustment far beyond the normal capabilities of simple
attack and release settings. They largely fall into two application types:
1 Compressors that are good at capturing and controlling dynamic transients:
corrective mode and vintage mode.
2 Compressors that emphasise dynamic transients and provide creative control of
levels within a mix: adaptive, creative and shimmer modes.
The Vintage and Adaptive compressors tend to morph a little between these two
categories depending on threshold control settings. This makes them easy to use
intuitively with minimal fine-tuning of the envelope control settings.
Further refinement and enhancement of the envelope modes is provided by
combination settings of the three-position KNEE switch. It is best to understand the
operation of these two functions in more depth before looking at the detail of the
compressor signature switching.