Manual

205 PRO X User Manual
Appendices
Appendix A: Application Notes
This chapter provides more in-depth information on certain areas and functions of the PRO X.
Spatial imaging system (SIS™)
Although conventional consoles can be used for three-channel mixing, the methods for doing so are complicated and unorthodox. This forces the engineer to work
in unaccustomed ways, limiting creative exibility, and making use by visiting operators impractical. The spatial imaging system (SIS™) has been developed to
overcome this.
The following are just some of the advantages provided by SIS™:
• Backing vocalists can be panned slightly towards the centre cluster to improve intelligibility, while keeping the featured vocal ‘front and centre’.
• Musical instruments can be placed in a conventional mix and then easily switched to the centre for solos.
• In theatrical productions, SIS™ lets you pan an actor’s voice across three channels, following their on stage movements. In stereo-only productions the centre
output can be used to provide a mono-to-mix-base feed activating a single ‘left + right to centre’ switch.
• The ability of SIS™ to feed centre-panned signals equally to both left and right outputs, as well as the centre, is particularly useful for distributing the load of high
energy, centre-panned sounds across all FOH loudspeaker arrays.
PRO X compressor modes (dynamic)
This section aims to provide an understanding of the compressor modes contained within the PRO X Control Centre.
Description
The PRO X compressors have ve primary operating modes (only four on the inputs). These change the signature (or shape) of the attack and release envelope curves,
interactions and timings. Before dealing with this in detail, some of the generic terms are dened and explained:
Threshold
The threshold adjusts the operating point of the compressor. Signals that go over this point, or over-threshold, will be aected by compressor action. Signals that stay
below threshold will not trigger any compression, although they may still be aected by compression releases from previous over-threshold signals.
Ratio
The compression ratio control provides control of the amount of compression that is applied to over-threshold signals. This is expressed as a ratio of signal level
changes from input to output. For example, when the compressor is set to 2:1, every 2dB input level change will only generate a 1dB output level change (assuming
the signal levels are over-threshold).
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 ve 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. This is 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 unaected 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 dened 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. It
can also be used to drive the clipper hard (see “Soft clip level”) to produce more pronounced eects.
Side chain lter
A band pass lter 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 ltered side chain onto the
solo bus and a side chain lter in to activate or eliminate the lter action.