Along with EQ, compression is the most useful tool you having in your mixing tool belt. This is a tool designed to control and rein in dynamic range in your audio so that you get a more consistent level and more energy out of your audio. A lot of people either don’t know how to adjust their compressor or they are using it with the wrong settings, so today I thought I’d cover 5 tips to employ when using a compressor in mixing.
Tips for Using a Compressor
Keep these five tips in mind when using a compressor in mixing and you’ll get much better results in a fraction of the time.
Know Its Parameters
Let’s begin with an easy one but a necessary as aside from knowing a higher ratio squashes audio, a lot of people don’t know what any of the other compressor parameters control or mean.
Here’s a snapshot taken from my audio compressor settings chart article followed by a quick recap of each:
Threshold
The threshold determines how much of the peaks will be affected and compressed. Setting this higher means the peak needs to be louder before compression will be applied. Conversely, setting your threshold lower means more of the dynamic range will be affected and ultimately brought down.
The compressor’s threshold should be set alongside the other parameters for the best results.
Ratio
The compressor ratio is the degree to which any decibels which exceed the threshold will be attenuated as I explain here:
The ratio is measured in an XdB:1dB formula where “X” is the number of dB over the threshold which will be reduced to 1dB. For instance, a 2:1 ratio means every 2dB which exceed your threshold will be output at 1dB. So if your threshold is set and a peak goes 10dB over it, your NEW peak right there will instead by 5dB.
While you don’t need to track the math behind it, you just need to remember that a higher ratio means peaks get turned down more drastically.
To preserve more of the dynamics for a more natural and transparent sound, a lower ratio works best. If your audio is excessively dynamic to the point that it’s making it difficult to set the level and thus needs a lot more control, you should aim for a higher ratio.
When you’re not sure, the best compressor ratio is 4:1 as this is a nice compromise between too aggressive while still controlling your dynamics which works well.
Still, different instruments will typically call for different ratios as they typically have different degrees of dynamics to them (which I’ll cover in a moment.)
Knee
The knee of the compressor is used to create a smoother compression by introducing compression BEFORE the level reaches the threshold, albeit at a lower ratio:
A higher/softer knee begins applying a relative and increasingly aggressive ratio the closer your peaks get to the threshold.
This works better for audio with more complicated dynamics in getting more transparent results.
Conversely, if you have a much simpler piece of audio with clearly defined and consistent peaks like an isolated snare or kick, a lower/harder ratio (all the way down to 0dB) works better as you want that threshold to be strictly enforced.
Attack
The compressor’s attack determines how quickly compression is applied once that threshold is reached.
Measured in milliseconds, a few milliseconds of attack/delay of your compression is useful for preserving the initial “punch” of your audio.
For instance, if you set an instant/as fast as possible attack when you’re compressing your snare, it will pull down those initial transients, making that snare not hit as hard and even muffling and masking it in the mix.
Release and Hold
The release and hold are the off ramp back to a fully uncompressed sound and an added delay before said off ramp, respectively, which engage once your audio no longer meets the threshold.
Without any release or hold engaged, your audio will sound choppy as it instantly and oftentimes awkwardly snaps back to its uncompressed state.
I’ll talk more about ideal settings about all of these parameters shortly, but that’s what they each do.
Output Gain
I know I talk about it all the time, but output gain is essential for maintaining proper gain staging:
Compressors ultimately make your audio quieter without makeup or output gain factored in because they bring down the peaks of your audio by design so that they’re more consistent with the rest of the audio.
We offset that to achieve more or less the same volume we had on the input using output gain.
Just make sure that to maintain gain staging that you match the same volume via the output gain dial as you had without the compression. You can match these by simply toggling the compressor on and off while your audio plays, ensuring it sounds as close to the same as possible whether it’s engaged or not.
With that very important coverage on the main parameters of your compressor in mind, let’s move on to the next tip on using a compressor in mixing.
Use More Than One
A lot of musicians and producers make the mistake of throwing too much at a single compressor.
This requires using more aggressive settings to get the same results you could get from spreading your dynamic control duties across two (or more) compressors.
The difference is you’ll get a more artificial and processed sound to where you can hear the compressor doing all that heavy lifting when you throw it all at one.
For a more natural and transparent sound which is best for most genres, try serial compression, meaning lining two compressors back to back in your signal chain.
The first of the two does involve the more aggressive ratio and settings of the two and is used for getting the dynamics under control. I like a FET style compressor (this tutorial/overview link includes a great FREE FET compressor) in this case:
I like a ratio of 4:1 if not 8:1 (more on this later) and gain reduction of at least 5dB if not 10 or more dB (depending on how much your source needs).
Follow this up with an optical compressor (this includes a great FREE opto style compressor):
We’re just looking to smooth out the remaining peaks a little bit more, achieving 1-2dB, maybe 3dB at most on the loudest remaining peaks.
Try this combination to distribute your compression duties, particularly on audio with a greater dynamic range which needs more control.
Account For Transients
I touched on this when I was going over the attack parameter earlier, but a lot of people make the mistake of forgetting about their audio’s transients when using a compressor a track, so it bears repeating with its own point here.
As I covered in my comparison of low frequency vs high frequency, higher frequencies are shorter and are able to move faster.
As such, we typically hear the higher frequencies of a track just before we hear the full sound. This helps draw the ear to listen for the remainder of the sound.
On that note, if it ever sounds like a track is being lost in the rest of the mix despite sitting just right from a level perspective, try increasing the attack on its compressor(s).
This will help that track “punch” through the mix and assert itself to sit better as a whole.
If your track is still lacking punch, check out my tips for adding audio transients to your audio.
Use Parallel Compression
I mentioned serial compression, but don’t forget about the benefits of parallel compression in your mix.
This involves duplicating your audio somehow then applying extreme compression to that duplicate, finally blending it in beneath the original instance of that track:
You can’t really mess up the parallel compression settings, just set virtually everything as aggressively as possible. There are a number of ways to apply it to a track to get that duplicate benefit without even having to create a duplicate of the track.
Using parallel compression as an aux send is ideal for this; simply drop your compressor of choice on a fresh Aux/Return track with the above settings, then blend in the amount you want on a track via its corresponding send dial.
As you can see, I recommend blending it in until you can just hear that parallel compressed version of the track on top of the “dry” track, then back it off 1-2dB.
This thickens out and adds energy to that track with subtlety so that the listener can’t hear it, but they can feel the effect in the mix.
Use Settings Appropriate For Your Instrument
I’ve teased this one amongst all the other tips, but different instruments typically have different dynamic control needs.
Thus, different instruments require different settings for your compressor.
Thankfully I put together a complete compression cheat sheet which shows the best settings visually for every practical instrument you’ll encounter in your next mix.
For instance, I made one for just the drum compression:
Imagine that, but for every instrument (plus vocals) in your mix. AND it’s free, so grab my free compression cheat sheet and never wonder again where to set any parameter the next time you’re compressing anything in your mix.