135 lines
6.0 KiB
Markdown
135 lines
6.0 KiB
Markdown
+++
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title = "Dynamics"
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description = "Applying limiters, compressors, and a gate in Ardour"
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chapter = false
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weight = 6
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+++
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One of the problems you may encounter in a mix is that, depending on the
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material, the loud parts are too loud, and/or the quiet parts are too quiet.
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This kind of problem cannot be easily solved using faders to adjust the levels
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alone. You may set the levels so high that they clip, or you may add unwanted
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background noise by simply turning levels up. These are all problems with what
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is called the _dynamic range_, i.e., the difference between the loudest and
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quietest parts of your session. There are several types of tools for adjusting
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the dynamic range available mostly as third-party plugins within Ardour,
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including _limiting_, _compression_, and _gating_.
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## Limiting
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A _limiter_ is a tool that prevents the volume of a track from going over a
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certain level, usually the peak level (0dB) or something close to it. Many
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limiters have the option to boost the levels of the incoming signal before they
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are limited, and in this way you can "close the gap" between the loudest and
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quietest parts of your mix. A limiter can be used on the _Master_ bus to prevent
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the overall mix from clipping. Limiters are almost always used post-fader.
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In the example below, a plugin named _Fast Lookahead Limiter_ is used (if you
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don't find that specific one among your installed plugins, look for any other
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called "Limiter"). To set how much it limits, simply adjust the _Limit (dB)_
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slider. The _Fast Lookahead Limiter_ literally looks ahead in the signal by a
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few milliseconds, and when it sees that the signal is about to go over the limit
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you have set, it automatically turns the levels down.
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The _Input Gain (dB)_ slider determines how much the levels are increased before
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they reach the limiter, and the _Attenuation (dB)_ meter on the right-hand side
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shows how much the levels are being reduced at any given moment. While the
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reduction in volume is nearly-instantaneous, the _Release time (s)_ slider
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determines how long it takes the limiter to return to 0dB of _Attenuation_.
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Note that the "harder" one drives the limiter (by increasing the input gain
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and/or decreasing the maximum peak limit allowed), the more reduction the
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limiter is forced to make, and the more likely it is that artifacts of the
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processing will occur (such as distortions or erratic changes in volume). On
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the _Master_ bus, it is generally best to avoid excessive limiting.
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## Compression
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A _compressor_ boosts the overall volume of a sound, but then "squeezes" it
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depending on how loud it is. This can make vocals sound more even or drums
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sound fuller and louder. The end effect is similar to how a limiter can reduce
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the range between the quietest and the loudest sound, however the effect is
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more selective when using a compressor.
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A typical compressor will have these obligatory controls:
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**Threshold**
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: Sets the level at which the compressor will start to act.
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**Ratio**
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: Controls how much the compressor will "squeeze" the sound.
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**Attack** and **Release**
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: Control how quickly the compressor affects the sound.
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The _ACE Compressor_ plugin on the screenshot above has two additional controls:
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**Threshold level** (in dB)
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: Sets the level at which the compressor will compress or squeeze the sound.
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**Makeup gain** (in dB)
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: Boosts the whole signal after the compression occurs.
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To soften out a vocal, for example, you could set _Threshold level_ of −10dB or
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so and a _Ratio_ of 2.5, and then bring the volume back up with the _Makeup
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gain_. The other three controls — _Attack time_, _Release time_, and _Knee_ —
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allow you to control the shape of the compression.
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For soft vocal compression, you would want a semi-fast attack time so that the
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compressor catches the beginning of each word, a slower release time to let the
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voice ring out, and a soft knee radius to create a gentle form of compression
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that isn't too noticeable.
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If you want to make drums sound big, you might try a slow attack time so that
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you don't compress the pop of the drum, a fast release time so that the
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compressor can catch the next hit of the drum, and a large ratio to make the
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dynamics between the beginning and end of the drum hit similar.
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Below is a screenshot of a similar compressor from the [LSP plugins
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suite](https://lsp-plug.in/):
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{{< figure alt="LSP Compressor Mono" src="en/ardour7-lsp-compressor-mono.png" >}}
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If you want to speed up learning how to use a compressor, a generally good idea
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is to insert one scope visualization plugin before the compressor and one right
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after, then open both
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## Gating
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The simplest kind of a _gate_ allows a signal to pass through when it is over a
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certain level, and blocks the signal when it is lower than that.
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Gates are often used as a kind of noise reduction. For example, the gate on a
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microphone channel might only open while the singer is singing, preventing other
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background noises from coming through as well when she is not singing. Gated
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drums are also a very well-known studio production trick to make them sound
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"sharper".
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Here, the _Hard Gate_ plugin (from a suite of LADSPA plugins called
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[CMT](https://www.ladspa.org/cmt/overview.html)) displays a single control
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parameter, the _Threshold_ at which the gate will open and let the signal
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through.
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Other kinds of gates, such as the _LSP Gate_ plugin on the screenshot below, are
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more complex. They have independent control over how quickly the gate opens
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(_Attack_) and closes (_Release_), as well as other parameters quite similar to
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those described for the SC Compressor above.
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{{< figure alt="LSP Gate" src="en/ardour7-lsp-gate-mono.png" >}}
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## Continuing
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Now that we've explored some tools for getting the dynamic range exactly where
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you want it, it's time to look at adjusting the balance of frequencies present
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in each individual track and in your overall mix. In the next chapter, we'll
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learn how to use the equalizer to do just that.
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Next: [EQUALIZING](../equalizing)
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