V O R S I S H D P 3 G U I
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HD P3 / Aug 2006
frequency. Each of these compres-
sors has the normal controls to be
expected of a good compressor. In
order:
THRESH — Threshold, the level
(within the frequency band) above
which gain reduction is applied.
RATIO — The proportion by
which a signal exceeding the thresh-
old is reduced in level. “3:1” means
that a change in signal level above the threshold by 15dB will be reduced
to only a 5dB change in level.
ATTACK — How quickly the compressor responds to a signal
exceeding the threshold.
RELEASE — The speed with which the compressor recovers as the
exciting input signal reduces or disappears.
These all act just as would be expected on an ordinary compressor. The
nature of a multi-band compressor means that slightly more complex
approaches to inputs and outputs have to be employed, paradoxically to
make the unit simpler to operate. In particular, the relationships of “Drive”
and the three “Thresholds”, and again “Makeup” and the three “Trims”
will be explored.
On the GUI’s compressor screen it is no accident that the three bands’
“Threshold” controls are in the same vertical line as “Drive”, and that the
three bands’ “Trim” controls are in line under “Makeup”.
In the HD P3, the three traditional “Threshold” controls may be
regarded as simply offset trims per band of the overall “Drive” control. In
other words, it is the differences between the three threshold values that
are far more salient than their absolute values, which get subsumed by the
overall “Drive” control. For example, it is common (since there is
generally less energy at higher frequencies) to want to reduce the HF
band’s threshold (i.e. make it compress sooner) in relation to the lower
bands; in that way all the bands are more likely to start compressing at the
same time with applied program material. Again, it is the three thresholds’
relative differences that are important, not their absolute indicated values.
Similarly, the three bands’ “Trim” controls may be regarded as offsets
to the overall “Makeup” control; it is usual to need to adjust a band’s output
in relation to the other two for best tonal balance, or lunatic effect.
The power of these approaches is that overall amounts of compression
and output level may be adjusted without worrying about disrupting the
hard-won internal balances of the three compressor bands settings.
