Impmooc – Week 4 – Dynamic Processors

Hi there! My name is Karyn Ellis. I am a professional songwriter / performer from Toronto, Canada. As I mentioned last week, I am quite new to hands-on music production. I have been checking out the various dynamic processors on my DAW, but given my technical limitations I think it will be more helpful for both of us if I steer away from an attempt to demonstrate and instead concentrate on the theory behind this topic.

In the following lesson, I will describe the concept behind dynamic processors and look at the four basic parameter settings related to them.

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DYNAMIC PROCESSORS are post-production effects designed to manipulate the dynamic range of a piece of audio. That is, they affect how many decibels there are between the quietest and loudest levels.

Dynamic Processors can either:

(A) reduce dynamic range through COMPRESSION, or
(B) increase dynamic range through EXPANSION

To compress (reduce) the dynamic range of a piece of audio, you can either increase the levels of the quiet parts to make them louder or decrease the levels of the loud parts to make them quieter. Compressors and limiters fall under this category.

  • While either method can effectively decrease the dynamic range, a compressor or limiter usually brings down the levels above a certain threshold rather than brings up the levels of the quiet parts. This is called DOWNWARD COMPRESSION and is  usually what people are referring to when they talk about “compressors.”

To expand the dynamic range of a piece of audio, you can either decrease the levels of the quiet parts to make them quieter or increase the levels of the loud parts to make them louder.  Expanders and noise gates fall under this category.

  • Expanders and noise gates usually use the first method: decreasing quiet levels. In the case of gates, quiet levels (those that fall below the threshold) are in effect reduced to signal off.

FOUR MAIN PARAMETERS OF A DYNAMIC PROCESSOR

THRESHOLD
RATIO
ATTACK
RELEASE

1) THRESHOLD: The level where the dynamic processor starts to function.

If audio crosses over this dB value, the other parameters kick into effect.

  • Above this dB value in a compressor/limiter, the sound is processed (below it, the signal passes through unchanged.)
  • Below this dB value in an expander/noise gate the sound is processed (above it, the sound passes through unchanged.)

In other words, a compressor/limiter lowers the volume of a signal when it gets too loud, and an expander/gate lowers the volume of a signal when it gets too quiet.

2) RATIO: How much the level is affected once it has crossed the threshold.

Ratio is expressed as INPUT:OUTPUT

  • 1:1 — for a signal level 1dB past the threshold, 1dB will be outputted. In other words, nothing changes.
  • 2:1 — for a signal level 2 dB past the threshold, 1dB will be outputted. The output will be half of what goes in.
  • 4:1 — for a signal level 4 dB past the threshold, 1dB will be outputted. The output will be one quarter of what goes in. In the case of a compressor, this ratio is considered to be heavy compression.

The higher the ratio, the more extreme the dynamic processing…

  • 10:1 — for a signal level 10 dB past the threshold, 1dB will be outputted. In the case of expansion, this ratio or higher is considered to be a noise gate. In the case of compression, this ratio or higher is considered to be a limiter.
  • 30:1 — for a signal level 30 dB past the threshold, 1dB will be outputted. This essentially stops the sound. In the case of compression, this ratio along with low attack and release times is considered to be a BRICK WALL LIMITER.

3) ATTACK: How quickly the volume fader kicks in once the signal has crossed the threshold.

  • This is expressed in milliseconds [ms]. The lower the rate, the faster the fader will move.
  • The attack rate controls how much of the transient will be allowed through unaffected by the processor. The TRANSIENT is the part of a sound where the amplitude changes a lot in a small amount of time, for example at the head of a drum hit.

4) RELEASE: How quickly the volume fader returns to normal once the signal has crossed back from the threshold.

  • This is expressed in milliseconds [ms]. The lower the rate, the faster the fader will move.

The ATTACK and RELEASE values are set according to the type of sound and the desired impact. If the source swells in, a longer attack and release could be a good choice. If it the sound itself is “punchy”, a low attack and release could work well. A shorter attack also gives the sound punchiness, whereas a longer attack softens the sound.

  • In compression a fast attack can stop the transient coming through, but it can also soften the character of the sound somewhat. A longer attack time allows more of the transient through but means there could be a larger volume peak. On the other hand, a noise gate is usually set with a low attack so that the transient comes through, otherwise the sound would swell in.
  • If the release time is too long, it can result in a “pumping” sound because the processor hasn’t released before the next input comes in.

There are additional setting available to fine tune how the processor will affect the sound, but for now these are the basic parameters to consider when setting up the dynamic processor to control the signal.

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REFLECTION on the PROCESS:

Thank for taking the time to check out my lesson. Any feedback you have would be great!

This was a fascinating topic to learn about – one that I could spend hours and hours (and hours) on for sure! This lesson is rather dry, I know. Sorry about that! That is the rather technical nature of it. But the creative possibilities this stuff opens up once it is understood is so cool! I loved discovering how big the effects of the different parameters are on the sound, and I am excited to apply this stuff to my own projects once I get a better handle on the DAW. I can also imagine applying this information to situations where I am working with other professionals who are mixing my music for me. How awesome to have the ability to describe the sound I want using technical language!

I hope what I have written is helpful for you too. Of course, I am still at the beginning stages of learning this stuff so please let me know if I’ve confused anything, or if something is not clear.

Thanks again for reading!

Best, Karyn

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