Operator Manual

PRO2 compressor modes (dynamic) 291
PRO2 Live Audio System
Owner’s Manual
Knee
The soft knee curves behave in a traditional way to blend the compression ratio around
the threshold setting (as described above), but more importantly they also have a
significant effect on the attack envelope shapes. The soft knee typically slows down
attack speed on signals in the knee area, which is desirable for natural sounding
compression because it compliments the reduced ratio effect of the soft knee. This
produces very gentle compression in the knee region.
The KNEE switch has three settings: hard (4dB); medium (12dB): and soft (40dB). In
hard setting the compressor still retains some soft knee characteristics. This is because
the implementation of an extremely hard knee produces undesirable sounding
distortion on low frequency programme material.
Corrective mode (exponential peak - fast)
This is a peak sensing compressor (like many older designs) with exponential attack
and release. It produces aggressive compression that gives good fast control and/or
limiting of dynamic material. It can be used to add colour to low frequency signals
making it ideal for controlling extremely dynamic instruments like the bass guitar. The
compressor tends to sound best with fast attack time settings that capture transients
and with release adjusted to taste to either emphasise or minimise distortion and
pumping effects.
Adaptive mode (exponential RMS - accurate)
This is a root-mean-square (RMS) sensing compressor with exponential attack and
release. The RMS averaging process interacts with the attack and release to produce a
very adaptive envelope character. This allows faster attacks on large (over-threshold)
signal changes and produces slower attacks on small signal changes, regardless of
attack time setting. The attack control is still active, allowing some user intervention
although the adaptive nature makes envelope control setting fairly non-critical. The
compressor is therefore very fast and simple to set up on most programme material. It
is also sonically accurate and works well for both compression and limiting of vocals and
many other sources. The most natural sounding compression is normally achieved with
soft knee settings.
Creative mode (linear peak - slow)
This is a peak sensing compressor with linear (dB rate) attack and second order
release. The compressor is very transparent, providing some dynamic control but
without unduly affecting the intentional dynamic content of the source material. The
linear attack provides a constant rate of attack, such that large changes in programme
signal level take longer to become compressed than smaller changes. Adding soft knee
noticeably delays these attacks, which can be particularly useful on drums where
compression can be applied to emphasise transients giving more punch while retaining
a good deal of artistic dynamic from the drummer.
The compressor normally sounds best with slower attack time settings, when it can be
used on difficult instruments, such as the acoustic guitar, with relatively fast release to
keep equal perceived loudness within a mix without producing excessive flutter or
distortion.
Vintage mode (adaptive peak - bright)
This is a peak sensing compressor with a partially adaptive nature. It produces
extremely subtle attack and release curves during the onset of compression that are
largely independent of the envelope control settings. However, as it is driven harder,
that is, signals are further over-threshold, the attack and release times become more
aggressive and gradually return to manual control so the operator can optimise the
capture (or otherwise) of larger transients etc. The peak sensing algorithm
intentionally increases harmonic overtones during compression, which adds a valve-like