Tip 08 – All About Compression!

Tips8

Hey guys,

Here’s my new production tip for this time. I’ve always had tons of questions on compression. Compression can seem really hard to understand, but once you understand the basics of compressors and how (and why) they work, it will make your music production / audio engineering life so much easier. So let’s just dive in! 🙂

Traditional compression

“Making loud sounds quieter”. For example, if you have peaks in your signal or recording, you can use a traditional compressor to turn down the peaks. This way, the loudest part of the signal and the quietest part of the signal are brought closer together, meaning you are reducing the dynamic range. Once you have the compressor set to your liking, you can use the make-up gain most compressor have to turn up the signal a bit, in order to restore some of the volume you lost while compressing.

In this image you can see the red lines, these are the highest and lowest values of amplitude of the sound in this example. This is also called the dynamic range. The dark blue line is the compressors threshold. When the sounds level gets above the threshold, the compressor kicks in and reduces the signal above the treshold. The light blue area is the part of the sound that gets affected by the compression. The compressor reacts the way you set it up, by using the threshold, ratio, attack, release, knee shape. We will be getting into that later on.

Normal-Compression

Upward Compression

Making quiet sounds louder”. So instead of taming the peaks of the audio sample you’re working with, and turning up the gain like you would with normal compression, this technique actually focuses on the quiet parts of your audio signal, and turns them up. The result is similar to traditional compression, in the way that it also decreases the dynamic range of your track. But instead of bringing the peak down, it brings the dips up.

In this image you can see the red lines, these are the highest and lowest values of amplitude of the sound in this example. This is also called the dynamic range. The dark blue line is the compressors threshold. When the sounds level gets below the threshold, the compressor kicks in and boosts the signal below the threshold. The light blue area is the part of the sound that gets affected by the compression.

Upward-Compression

Expanding

“Making quiet sounds quieter.” This is actually a way to increase the dynamic range. For example, this can be used if you have to work with an overcompressed audio file and you want to bring back some life into it.

In this image you can see the red lines, these are the highest and lowest values of amplitude of the sound in this example. This is also called the dynamic range. The dark blue line is the compressors threshold. When the sounds level gets below the threshold, the compressor kicks in and reduces the signal even more. The light blue area is the part of the sound that gets affected by the compression.

Expansion

Upward Expansion

“Making loud sounds louder.” This is actually a way to increase the dynamic range. For example, this can be used if you have to work with an overcompressed audio file and you want to bring back some life into it. This is a great way to enhance the transients that are already present in the source sound.

In this image you can see the red lines, these are the highest and lowest values of amplitude of the sound in this example. This is also called the dynamic range. The dark blue line is the compressors threshold. When the sounds level gets above the threshold, the compressor kicks in and boosts the signal even more. The light blue area is the part of the sound that gets affected by the compression.

Upward-Expansion

 

Limiters

“Preventing sounds to go over a certain threshold level” A brickwall limiter is basically a traditional compressor with a ratio set to infinite. It will prevent the audio signal to go above a certain threshold. This means more you push the input signal of your limiter, the more it reduces the dynamic range. In today’s loudness wars, a good limiter is an invaluable asset to your mastering chain.

Compressor’s Settings:

Threshold:
This is the level at which the compressor or expansion starts.

Attack:
This is the response time of the compressor. The attack determines how quickly the compression or expansion will kick in. If you want to tame the peaks of transients, a fast attack is needed. But if you like the transients and only want to ‘control’ the sound following the peaks, a slower attack is needed.

Release:
The release determines how long it will take before the compression or expansion will turn off. The timing on this is important. If you have tweaked your attack settings (a bit slower) so the transients will push through, yet your release is so slow, the compression is still working when the next transient hits, you are missing the punch.

Ratio:
Determines the amount of compression applied to the signal over the threshold. For example; if you set your ratio to 2:1, and your input signal goes over the threshold by 6dB, after compression the output signal will be 3 dB above the threshold. If you now set the ratio to 3:1, the output signal will be at 2 dB above threshold. Set it to a ratio of 6:1, and the output signal will be 1 dB over the threshold. Set it to infinite and you have a limiter. J

Knee Shape:
Using a soft knee shape is a way to make the transition from ‘no compression’ (above the threshold) to ‘compression’ (below the threshold) a bit smoother. It uses a curve from where the gain reduction starts. However, a hard knee setting does the exact opposite. The transition from the untreated to the treated signal is instant here.

Creative Compression techniques:

Parallel Compression:
Parallel compression is where you combine a treated (compressed) version of the signal with an untreated (uncompressed) version of the signal. This basically leaves the transients intact, but increases the low levels of the signal, similar to upward compression. Some compressors these days include a ‘mix dry/wet’ knob, which you can use to control the parallel compression.

Sidechain / Ducking:
A form of compression where you control the compression of a sound using a separate input signal. When the separate input signal reaches above a certain threshold, compression kicks in on the signal you want to compress. This is a great tool when you use the kick of your track to sidechain compress your bassline. It means every time you kick plays, the bassline gets compressed (reduces the gain) and it makes room for the kick to push through. Can also be heard on any decent radio station, when the DJ speaks, the music gets turned down.

Gating:
A noise gate is a tool that attenuates the signal below the threshold. Similar to expansion. However, a gater attenuates the signal by a fixed amount. When the input signal falls below the threshold no output signal is given. This is a great tool to use on vocal recordings. If you want to remove any low volume noises and background sounds during the take, you can set the gate threshold to be just above those signals. Setting the threshold there means the gate will not output any levels below that threshold. Way easier than manually removing all unwanted noise!

De-Esser:
A De-Esser is a compressor that primarily focusses on a specific frequency range, particularly focused on controlling the sibilant consonants (on the S and Z’s) on vocal recordings.


 

That’s it for this time. Hope this production tip helps you with your tracks. Happy producing!

And if you need any help, you know where to find me! 🙂

Michael de Kooker