Audio compression is probably the most complicated effect to master, don’t you think?
It’s hard to hear, hard to control — and even knowing what the different compressor settings are for, you can still make many mistakes and destabilize a mix if you don’t use it correctly.
Whether you’re a beginner or not, bad habits can be picked up quickly.
That’s why I’ve compiled in this article 8 of the most common compression usage mistakes, drawing inspiration from the questions I receive via email, what I hear around me, and my own experience… or rather, my own mistakes. 😉
1. Too Much Compression
This is the trap of compression: in the effort to level the volume of each track, of each instrument, you end up over-compressing them.
Typically, if you have -10 dB of Gain Reduction (GR) across all your plugins, it might be a sign that you need to ease up.
Indeed, when a track is over-compressed, it will have a uniform volume but the result will be absolutely unnatural. You lose realism.
If the instrument is a synth, it may not be very serious. But if it’s a more “fragile” instrument like an acoustic guitar or a voice, excessive compression will be much more problematic.
And generally speaking, for a mix to sound good, it’s important that it retains a certain dynamic — to avoid falling into the loudness war, in particular.
Basic solution (at the risk of stating the obvious): Compress more lightly. A few decibels of GR can take you further than you think.
Advanced solution: If you really want to apply significant compression to a track, try to do it sequentially:
- with two plugins in a row;
- or by compressing at several points in your mix (on the track, on the bus/group, on the master).
2. Compressing “Because It’s Necessary”
Undoubtedly a mistake we all make / have made at one time or another.
You can often read on Facebook or forums phrases like this:
- “You always have to compress the guitar”
- “For vocal tracks, you need two compressors in a row”
The problem is that in many cases, tracks don’t need compression. In fact, it depends:
- on the base recording;
- on the mix and artistic choices;
- on the musical genre.
It’s impossible, therefore, to predict exactly whether a track will need compression, let alone what settings should be applied.
I’ll take a concrete example: guitar recordings in metal. Due to the high saturation generated by the amplifiers, the recorded signal often has a very reduced dynamic range:
What would compression be useful for in this case?
Probably not much.
In comparison, a funk guitar will likely need it more to stand out in a mix:
In other words, there are no rules. There is no “You absolutely have to compress this instrument”.
Solution: If you often make the mistake of adding a compressor simply because you read somewhere that you should compress this or that track, you risk destroying your mix.
Force yourself to ask the right questions each time: Do I really need compression here? Is the dynamic range of the instrument really too large that I can’t position it in the mix using the volume slider?
Note that this advice applies not only to classic compression but also to multiband compression, which is a super useful tool but is often used “by principle” rather than because there is a real need.
3. Compressing in solo
A mistake I made for a long time.
When starting out, and when not comfortable with compression, one tends to isolate the track in solo to adjust the compressor. This makes sense, as it allows for better hearing of what is being done.
However, this is a bad idea.
There are many different uses of compression, but the goal is often to reduce the dynamic range of a recording so that the track integrates better into a mix. For example, by homogenizing the volume of a voice so that all the lyrics remain intelligible.
So, if you set your compressor on the track in solo, it implies that you are taking it out of context: you will not have a scale to estimate whether the amount of compression you are applying is adequate.
Do you need -2 dB of gain reduction? -5 dB? -10 dB?
In “solo” mode, it is impossible to know.
Solution: always place your tracks back in the context of mixing when adjusting your compressors! (note that this does not prevent, from time to time, checking by putting the track in solo).
4. Compressing while only looking at the numbers
On most compressors, the settings can be controlled very precisely: attack and release in milliseconds, threshold in decibels… and of course, there is usually a meter indicating the amount of gain reduction applied to the signal.
Since compression is a complex thing, we tend to rely a bit too much on these numbers rather than paying attention to the sound.
Depending on the compressors, an attack of 1 millisecond will not have the same effect. Depending on the input signal, the behavior of the compressor will also be different.
The risk, if one looks too much at the indicated numbers, is to compress mathematically, adjusting the various parameters out of habit or because one read that an attack of X milliseconds was good — instead of focusing on the sound.
Solution: “If it sounds good, then it is good!”
Try to set your compressors by ear, without your choices being biased by the numerical values indicated by your plugins.
5. Setting an attack that is too fast
By default, when using a compressor, it is because one seeks to control the dynamics of a sound. One tends to choose a fast attack, thinking “I want to compress the entire signal.”
The problem is that by following this type of approach, the transients are crushed.
Transients are the peaks of high amplitude found at the beginning of certain sounds. For example, the snap of a consonant at the beginning of a word or the hit of a drum with a stick.
If we attenuate the transients too much by using a compressor with a fast attack:
- it will harm the dynamics of the track, making the piece flat and uninteresting;
- saturation effects may appear, especially if the attack is really very fast.
Solution: In many cases, it is interesting to let the transients pass partially by choosing a medium attack (> 10-15 ms): this will prevent them from being crushed.
Be careful! This does not mean that one should never use a fast attack! But at least, do it sparingly and with awareness. If you feel that the piece lacks dynamics, it may be because your attack settings are too fast… 😉
6. Using plugin presets
Compression plugins often come with a more or less significant number of presets, meant to help you in setting the effect.
However, very often, using them is a bad choice.
If you have been following Projet Home Studio for a while, you probably know that I don’t like presets.
This is not just a bias.
The result of using a compressor on a track is completely dependent on the input signal, its dynamic range, and especially its sound level.
If you use a preset, it has necessarily been set up for a different input signal. Necessarily different: it may be louder, it may be quieter, it may have been recorded closer or further from the instrument.
From this observation, could we simply rely on a preset to set our compressor?
Of course, the answer is no.
However, it is completely logical and normal to base yourself on presets by modifying them: very often, they can provide indications on how the various parameters of the plugin can be adjusted to achieve a particular sound.
Solution in summary: Do not use presets, or modify them: they are starting points.
7. Incorrectly adjusting the Make-Up Gain
The make-up gain, also called gain compensation, is one of the most important settings of compressors.
Compression involves reducing a signal. It always results in a loss of volume. Therefore, it is necessary to compensate for this loss by raising the overall level of the signal: this is what make-up gain is for. Simply put, if your plugin generates a gain reduction of -2 dB, you will set your output gain to +2 dB.
But be careful! When the volume of a sound is increased, it often seems to sound better. This is a well-known psychoacoustic effect.
Also, if your make-up gain is too high, you will believe that your mix sounds better when it does not.
Solution: take the time to adjust the make-up gain so that the perceived sound level at the input and output of the plugin is identical. Do not hesitate to activate/deactivate the plugin successively while adjusting this parameter.
To go further…
If you apply the few tips from this article, your mixes will be significantly improved.
However, if you are not perfectly comfortable with compression, do not hesitate to take some time to review the basics — for example from my compressor settings guide! 😉