Dynamics Processing Explained
via PT DYN3 plug-ins
by eddie ciletti
3rd March 2014
The difference between a compressor and
a limiter - you might even say the 'magic' - is really a matter of side
chain settings - Attack, Release, Ratio, Knee and Threshold. This
article, combined with the images below, will explain examples of Peak
Limiting (left) and Compression (right). The difference between ProTools
DYN3 dynamics plug and other dynamics plugs SHOULD be the emulation of
the various hardware non-linearities (distortions) that come from audio
transformers, signal and side-chain amplifiers and even 'mis-aligned' or
nearly broken signal processors. In Art, all of the possibilites
are acceptable if the means justifies the end result.
For Peak Limiting, note that the Attack
and Release are at their fastest - 10-micro-seconds (uS) and 5-milli-Seconds
(mS). The 'Knee' is set to "0," the hardest setting and the ratio
is set to 100:1, the highest setting. In this case, all that is necessary
is to adjust Threshold (lower the ceiling) until theamount of gain reduction
(GR) is between 3dB and 6dB. On transient-rich material like
drums, 3dB should be almost undetectable to the ear, 4.5dB GR is still
very acceptable and anything more than 6dB will be obvious. Sometimes,
you don't want obvious.
In this example, the snare consists of
the 'stick' (attack) and its resonance, the 'tone.' For the moment,
all we want to do is reduce the peaks created by the stick and not disturb
the tone, because peaks are what get in the way of making the signal louder.
A fast release ensures that the tone will not be affected. To assist
in visualizing, the raw signal is at top and the processed signal (via
AudioSuite) is at the bottom. Using Audio Suite is a good way to
see if the processing is serving its intended purpose. Now, some
people will say 'just listen,' but again, sometimes you want 'surgical.'
All dynamics processors implement Threshold
in either of two ways. The DYN3 Threshold merely lowers the ceiling
until the signal 'crashes' into it. On other limiters, Threshold
increases gain until the signal hits the ceiling. I prefer no gain
change so I can have control. I prefer to keep levels conservativwe
withint protools because I feel the metering is not particularlay accurate
- PT is so busy with graphics that it doesn't have time to report all of
the 'overs.' Note that an 'over' is not one instance of clipping,
but several instances in close succession. Some people use
external and internal clipping on purpose as their 'peak limiting.'
Since audio recording and mixing is both art and science, 'it's all good,'
except you should know that clipped transients on stereo tracks,
stereo sub mix or stereo master can degrade the depth of the stereo image.
I prefer NO overs. I avoid hot levels going into some plugs - in
digital, headroom is still important - and I avoid make-up gain unless
necessary. If i see a 'stuck' RED OVER, I figure out why and fix
Just as some peak limiters add gain when
Threshold is adjusted, I prefer those that don't and I rarely use make-up
gain unless the processed signal is too quiet. Compression essenttially
raises low level signals and reduces louder signals. The signal below
right is a bass. You can see the 'spikes' of the string being plucked
and you can see the notes. After processing, the spikes are controlled
and the notes are more consistent.
For Compression, the Attack is much slower
than peak limiting - 8-milliSeconds (mS) to 12-mS Attack is fast enough
to preserve some of the punch. Release speeds can range from Fast
(125mS to 250mS), Medium (250 to 750mS) and Slow 750mS to as many seconds
as the device will allow. In this case, the Knee is at max soft (30),
the ratio is low (3.2:1) the Attack is 16.7-mS and the release is 575.7-mS.
Threshold can be adjusted for more aggressive amounts of Gain reduction
(GR), although like Peak Limiting, I like to 'limit' processing to 6dB
primarialy because I often have multyiple sigjnal processors in a mix.
For example, I may use just a touch of compresson on the bass track, then
submix bass and kick together with another touch of compression to glue
them together, then submix the kit and use a dyn3 in series with a McDSD
ML-4000 multiband compressor (along with its stereo peak limiter).
All together that coudl be 12 dB of gain reduction!
Keep in mind that raising the signal level
6dB doubles the signal voltage. Reducing the signal level by 6dB
- through gain reduction or otherwise - reduces the signal voltage by half.
IMy multi-band processor of choice is the
ML-4000, I prefer it over other, more popular multi-band plugs.
is a sample ML-4000 tweak for killing snare ring. I will
be posting an updated article about my unconventional tips and settings
in the near future. If you are impatient, email