Manual

21
2.3.8.1 Exponential/dB timing (Normal and Classic types)
The Exponential/dB curve is by far the most popular law used in a great many well-respected
compressors, and is the natural result of more recent analogue units employing logarithmic
sidechains and resistor/capacitor time constants. The Exponential/dB law has some
interesting characteristics. First, the time taken to complete a compression event tends to stay
the same however large the dynamic signal excursion is. Also since the peak rate of change
of gain increases with dynamic excursion, the resulting harmonic content due to compression
tends to follow the loudness of the programme in a way the ear expects. This helps to mask
the effects of the compression, and thus provides the most forgiving solution, being tolerant
to differing timing settings and programme material. This makes it the best choice for general
compression use and overall dynamic control of complex musical programme material.
The diagrams above illustrate the action of the exponential law. The first shows 10dB gain
reduction (scaled for comparison) and the second one shows 30dB. As can be seen, the initial
rate of change is much increased in the attack period and the total time for attack is similar
despite the increased level transition.
The CLASSIC type selection is a subset of the NORMAL type, with timing controls fixed to
nominal values to match a range of popular legacy units. All other controls behave as the
NORMAL type. This type selection is quick to set up and is most useful as a general-purpose
channel compressor.