Dynamics Processing Effects

Quick Note on Effects

Audio effects are more powerful than ever and can do ridiculously amazing things. However, the best tool to use them properly is your ear. Fortunately for traditional musicians, the best way to train your ear is to perform and attend acoustic performances. Knowing what sounds good is more than half the battle, and completely essential.

The best effects are the ones that come naturally. The quality of performance, space, and equipment can render many effects unnecessary. That being said, they are amazing tools to improve or color a performance.

Dynamics in the Context of Audio

We all know what dynamics are—the varying degrees of musical volume/intensity, usually described as piano, mezzo-piano, mezzo-forte, and forte. Dynamic range is the distance between the softest and loudest part of a piece of audio. Musicians understand the important of dynamics and how to implement them naturally. In audio, we must quantify dynamics in a holistic manner, with a well-trained ear and a profound knowledge of our available tools. The basic dynamic effects are compressors, limiters, gates, and expanders.

The Mighty Compressor

Compression lowers the dynamic range of the affected audio. It does this by squashing the loudest parts and/or raising the quiet parts of the audio.

Key Parameters:

Ratio: This determines the overall compression. The first number is how much the signal must go over the threshold for the output signal to raise 1 dB. For example, at 4:1, a signal that is 12 dB over the threshold will be output at only 3 dB over the threshold. 3:1 is fairly common for vocals, but depends largely on the singer’s technique. There is almost always a gain reduction meter that shows how much the compressor is altering the audio. A safe practice is to keep the reduction less than -6 dB, often less. Too much and the song sounds boring and unnatural.

Threshold: The point at which the compressor begins to function.

Attack: The time it takes the compressor to begin affecting the audio. If you want to keep the attack of an instrument at full volume, then have the compressor kick in (as is often the case with drums), you should set the attack for long enough to allow that audio through.

Release: How long the compressor continues to function after the audio drops below the threshold. Too short may sound unnatural, while too long could reduce quiet audio too much.

Knee: The shortest knee kicks in immediately at the threshold and is always reducing at the chosen ratio. A softer knee has a more gradual compression curve that could kick in much sooner than the threshold and gently increases the ratio as the signal gets louder.

Input/Output Gain: Most compressors have an output gain to compensate for the compression. Some also have an input gain, if the signal is too low coming into the compressor (this can be remedied elsewhere though).

Mix: Usually, a compressor affects 100% of the audio it receives. If there is a mix parameter, it’ll let a percentage of the unaltered audio through with a corresponding percentage of compressed audio (always adds up to 100%). Mix parameters are common on many audio effects.

Studio One's built-in compressor

Each DAW has their own built-in compressor. Note each basic parameter.

Supercharger GT compressor, by native instruments

Some compressors are used for their unique sonic signature.

Limiter

A limiter is simply a compressor with a high ratio (usually 20:1 or infinite). These are usually used to prevent audio clipping since the signal isn’t allowed to go too high. However, if the attack is long enough, clipping could still occur. Limiters are also a good way to tame the highest audio peaks without affecting anything else.

A simple peak limiter

A simple limiter set to keep everything over -1 dBFS under control.

Gate/Expander

A gate lowers the level of an incoming signal by a set amount the moment it goes below the threshold. For example, if the threshold is set at -30 dB and the attenuation is set at 10 dB, then if the audio dips to -30.5 dB, it’ll be attenuated to -20.5 dB. Gates are often too jarring, but if they’re set right, they can clean up audio nicely. They’re a good way to keep noise, breaths, hum, etc . . . under control without having to automate or clean up every spot.

PreSonus Gate plug-in that comes with studio one

A simple gate, set to deaden the signal the moment it drops below -40 dB.

An expander has a similar function, but the decrease is set to a ratio. It’s basically the opposite of a compressor—the decrease varies with how far under the threshold the audio dips. Expanders are rarely jarring since the expansion doesn’t all happen at once.

Resources for this Section

Chapter 9 in this book goes through dynamics processing in depth.

Waves is the No. 1 plug-in manufacturer. This link is to their videos on compressors.