Midas XL8, Operator'S Manual, Page: 296 / 342

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Chapter 16: Application Notes
XL8 Control Centre
Operator Manual
XL8 compressor modes (dynamic)
This section aims to provide an understanding of the compressor modes contained
within the XL8 Control Centre.
Description
The XL8 compressors have five primary operating modes (only four on 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 defined
and explained:
Threshold
The threshold adjusts the operating point of the compressor. Signals that go over this
point, or
over-threshold , will be affected by compressor action. Signals that stay below
threshold will not trigger any compression although they may still be affected 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 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.