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How to mix with compression?
I can bet all my money saying that you haven’t have heard any production that must have been done without using compression. Have you?
Compression is a very necessary effect that shapes your sounds to fit well in the rest of the mix. You need a compressor even to shape that whole mix. It’s important at many stages of music production.
So let’s understand, how to mix with compression.
To understand better, mixing with compression can be divided into a few steps-
- Understand how compressor works.
- Know when to actually use compressor.
- Use threshold correctly.
- Dial the attack correctly.
- Dial the release correctly.
- Setting the ratio.
- Setting the knee.
- Setting the makeup gain.
- Analyzing gain reduction.
- Choose the compression detector type accordingly.
- Serial compression
- Parallel compression
- Compressing individual track vs group channel.
These steps pretty much summarize how you can make use of the compressor while mixing. These are very important steps that you don’t want to ignore when you are starting to mix.
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1. Understand how compressor works
Starting with a compressor can look intimidating at first glance.
The most important thing however in the first place is to know that how does a compressor works..
Compression is simply a tool that reduces the dynamic range of the sound, based on the input that you give. Dynamic range is the ratio of the highest and the lowest amplitude points in an audio.
It indicates the range of how much high and how much low amplitude moments a performance contains. The high amplitude points are called the peaks as you must be aware of.
These peaks are due to the transient sounds like the drum hits, guitar plucks, keyboard hits etc. A compressor is used to take these peaks down depending on the threshold set into it.
- So in simple terms a compressor reduces the peaks of the sound to flatten the sound and make it more even in amplitude.
Also read – Should You Compress Your Master And How
A Compressor has six main settings which are the Threshold, Attack, Release, Ratio, Knee and Make Up Gain.
To shape the dynamics of the sound you need to dial these settings and depending on them the degree of compression applied to your sound will vary.
So that’s another thing to remember here that you can even control the amount and shape of compression applied to your sound with a compressor.
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2. When to actually use compressor
Compression being a very necessary tool cannot be used simply because it’s a necessary tool. You have to have a solid reason for the sounds to be compressed.
In mixing, the first step is to achieve a good level balance between all the instruments. This requires that the performances should be pretty much in a disciplined shape. T
o get a consistent level of each instrument, you don’t want the instrument to jump up and down in volume all over the place.
But this is inevitable.
Almost every instrument will have ups and downs in it’s level. This will make it jump out of the mix sometimes or get lost when its quieter.
You can reach out for a fader. But essentially in this situation, you cannot dial a fixed fader setting that stays stable for the whole performance regardless of its changing levels and make it flat and even throughout.
To tackle with this problem you need to use compression on such a sound.
Another use is to enhance the peaks of a flat sound. If the drum is not punchy enough, you need a compression because you cannot enhance its peak with a fader.
There are also situations where the compressor is needed only to give color to the sound.
Also read – Saturation Before Or After Compression – Explained
3. Setting the compressor threshold correctly
A compressor threshold is that level of amplitude of the sound from which the compressor starts acting.
Until the sound reaches this threshold, the compressor sits idle and no compression is performed on the sound. The lower the threshold the higher the amount of compression is applied on the sound.
Now, there’s a mystery with setting the threshold of a compressor.
When you set the threshold on a snare for example, as low as -15 dB, the snare doesn’t get compressed that much and you kind of hear the same sound with just a little reduction in its level.
Whereas when you set the threshold to -5 dB on a kick drum, the result is pretty drastic and you hear that the kick has got compressed a lot and has got quieter.
What just happened?
- It’s because the threshold is not an independent control. The threshold is dependent on something else and that control is called the Input Gain.
An input gain controls the level of the incoming signal in a compressor. If the signal coming in a compressor is of low amplitude due to the input gain set lower, the threshold will also have to be set low so that the signal crosses it and triggers the compressor. Whereas if the input gain is raised, the signal will be louder and is easy to cross the threshold set at a higher level.
In case of the snare and the kick in the example above, the difference was in their input gains.
The snare had a very low input gain and the kick had a high input gain hence their thresholds were so different and the results too.
- Whether you need to reduce or enhance the peaks of a sound, the threshold should be set to a level where the incoming signal can cross it to trigger the compressor.
4. Dial the compressor attack correctly
The attack of a compressor is the moment when the compressor grabs the signal. It deals with time and not the amplitude. An attack can be quick, medium or slow.
If the threshold tells the compressor to act from which point of amplitude, the attack tells the compressor at which point of time to start acting from.
Every sound has the initial transient whether it is gradual or sharp. Generally compression is applied on the sounds that have a sharp or quick transient. It does not need to be applied on the sounds which are already levelled like the buzzy square wave synths or the distorted guitars etc.
The rule for setting the attack time in a compressor is that, when you want more punch and knock in your sound, the attack of a compressor should be set to medium or slow.
Whereas when you want to flatten the level of the sound, you need a quick attack.
- What happens when you set the attack to a slower setting, the compressor starts acting slowly. This allows the initial transient of the sound to pass through the compressor untouched and after the transient is passed, the compressor grabs the remaining part of it and lowers it. Hence overall, the punch of the sound gets enhanced when the makeup gain is raised.
When the attack is quick, the opposite happens, the compressor grabs the initial transient of the signal and reduces its level. This brings the initial transient of the sound down, equal to level of the rest of the sound.
The result is a flatter and even envelop of that sound. This prevents the signal from clipping and also makes a sloppy performance neat and tight.
The sounds that benefit from the fast attack are-
- Vocals
- Bass guitar
- Any uneven performance that has random peaks at certain places.
The slow attack compression sounds good on-
- Drums essentially, so that their peaks can come through.
- Any instrument that needs a bit more energy.
5. Dial the compressor release correctly
Now I must highlight this that only setting the attack is not going to do the job. The gain reduction applies well when there is a strategic combination of the attack and the release.
Since the attack controls the time of the onset of gain reduction, the release setting tells the compressor until when this gain reduction phenomenon should carry on.
Always remember that the release is effective only after the attack. People get confused with this.
In other words, if you see the attack and release timing to be the same for example 10 milliseconds, then the release will only be applicable 10 milliseconds after the attack has commenced. Do not think that attack and release will work together.
Here are four common go to combinations of the release with attack that has been used for decades:
Fast attack and fast release-
When you set fast attack and fast release in a compressor on any sound, the fast attack will grab the initial transient of the sound almost instantly.
Depending on the ratio the gain reduction will be applied but only for a short amount of time, probably only till the sound’s transient lasts.
This setting is best for flattening the sound as only the transients are reduced and as soon as the transients are over, the compressor releases the sound due to quick release setting. Hence the lower level sustain of the sound doesn’t get affected and stays at the same level.
The result of this is less transients.
Slow attack and fast release-
As is with the working of a compressor, the slow attack will capture the sound only after some of the initial transient has passed through unaffected.
- This setting is best for drums as the initial transient is needed for them to punch through the mix. Setting even the release time quicker will let the compressor free the sound quicker hence not affecting the tail of the drums for too long. This creates a slight separation between the transient and the sustain of the envelop.
The result of this is punchier drum transients with sustain.
Fast attack and slow release-
Fast attack setting will start gain reduction of the initial peak of the sound very quickly and slow release keeps this effect sustained for a longer duration before the compressor gain reduction resets.
Now by looking at this setting you can easily understand what’s going on here. The quick gain reduction that stays for a while resets only between the drum hits and not during the drum hits.
This keeps the envelop of the drum sounds pretty much consistent without much re-balancing of it.
The result of this is a neat and consistent level.
Slow attack and slow release-
The slow attack will start gain reduction after allowing the transients to sneak past the compressor and the slow release will keep pressing down the body or sustain of the sound.
This setting will reduce the body of the drum but will make it’s punch as it is.
This setting turns the compressor from a dynamic range reduction tool into a dynamic range enhancing tool as this setting will increase the sound’s dynamic range.
The result is more punchy drums with less body or sustain.
6. Setting the ratio
The ratio of a compressor determines by how much amount the incoming signal will get reduced. The “syntax” of writing a ratio is x:1, where x represents the incoming audio signal and 1 represents the resulting amplitude of that signal after gain reduction.
In other words when x dB of incoming signal enters the compressor, it will get reduced to 1 dB.
There are four categories of compression depending on the ratio – Mild, Moderate, Medium and Strong.
Mild Compression
The ratio of 2:1 to 3:1 falls in the category of Mild Compression. Generally this ratio sounds transparent and this makes it perfect for drums and other percussive instruments.
Depending on the attack, release and threshold, this ratio just makes sure that the drums sound more cohesive and tight.
Moderate Compression
The ratio of 4:1 falls in the category of Moderate Compression. This is the setting I usually keep on my guitars and bass as it works perfectly well on them.
I also use it on my mix bus as I have seen the mix engineers use 4:1 ratio on their mix bus.
Moderate Compression is a setting which is not even transparent and it’s not intense either.
You get a fair amount of control over the sound, of course it depends on the rest of the settings as well.
Medium Compression
The ratio 6:1 falls under the category of Medium Compression. This much amount of gain reduction is very apparent as the signal becomes much quieter.
I like medium compression to be used on rap vocals and sometimes on bass as it will make the sound more tight and very consistent. Threshold and attack release play equally important role.
It cannot be said exactly on which sound to use this ratio but it is applicable to almost most of the sounds that need extra control. Some spots like a single note or a single word that may be jumping out at you can be tamed with this ratio.
Strong Compression
The ratio 10:1 falls under Strong Compression. It’s not common to use this much amount of ratio on just any sound. This much amount of gain reduction is used in special cases.
When used with a quick attack and quick release, this setting will make the sound pump. The effect will be easily audible but will feel too much and unnatural.
Use 10:1 ratio when you need a lot of energy in your drum room. A good tip would be to refrain from keeping the attack to the quickest setting. Keeping the attack fast with this ratio may introduce color in the drums.
Also strong compression is used when you have, for example, a single word that is too loud and you want to tame just that. Keep the threshold set for that one word only so that the rest of the signal can stay below the threshold and thus stays unaffected.
7. Setting the compressor knee
The knee of the compressor is a setting that will let you hear the compression taking place either abruptly or in a more natural and musical way. Both of the effects have their own place and both are used very commonly.
The knee of a compressor controls whether the compressor starts applying gain reduction exactly when the signal crosses the threshold level or should it start applying gain reduction when the signal is still below the threshold level.
- So, basically there are two types of knees in a compressor – hard knee and soft knee. The knee setting that tells the compressor to apply gain reduction right when the signal crosses the threshold is the hard knee. The result of the hard knee compression can be very clearly heard. You will be able to hear that the sound gets reduced right when the sound crosses past the threshold. This knee behavior feels aggressive as it works swiftly.
On the contrary, the knee setting that will tell the compressor to begin pushing down the sound a little earlier than it could cross the threshold is the soft knee setting.
This effect will result in a transparent compression and will compliment musically and will sound natural.
The hard knee will have a brighter sound and it also introduces distortion into the signal and it’s good for more energy and edginess in the sound whereas a soft knee sounds warmer and it being gentle, doesn’t distorts the signal which is good for soft RnB songs and nicely sung vocals.
8. Setting the makeup gain
You apply compression to make the instruments sound consistent by leveling the peaks with their sustain.
The result is that the instruments get reduced in volume and become quieter and could get lost in the mix.
To compensate with this side effect, the compressors come with a feature of makeup gain which is used to manually increase the overall level back to what was before compression or even more if you want.
Different compressors will have one out of the two makeup gain features which are automatic makeup gain and manual makeup gain.
The automatic makeup gain will apply the makeup gain automatically without your input and the manual makeup gain will need your input.
- Well, there’s a common problem that is seen with the automatic makeup gain enabled compressors which is – these compressors make the output of the signal feel louder than the original ones after the compressor has performed its work. The drawback of this is that most novice producers don’t understand this and they
- the signal.
This is the only downside of the automatic makeup gain feature and I will advise you to use the manual makeup gain whenever possible as it will allow you to listen to the effect of the compression first and let you later apply the makeup gain as per your need.
9. Analyzing gain reduction
When using compression, there’s one most important thing to pay attention to and that is the gain reduction.
Gain reduction is the amount of level of the signal that gets taken down by the compressor.
Why gain reduction is so important you ask?
The threshold and ratio are the two things that will control how much level is getting reduced. But only using these two will not give you a clear picture of how much signal is being taken down.
You need something to look at and clearly read what has actually happened to your sound in terms of level, which is what the gain reduction tells you.
- The gain reduction will show you the truth of how much level of your sound had dropped and as a compensation, how much makeup gain you need to boost. It shows you how much you peaks have come down after compression and as a result, most importantly, knowing the gain reduction will save you from overcompressing.
During mastering, its advised to have gain reduction as low as a dB or two.
10. Choose the compression detector type accordingly
The mechanism of a compressor is simple. There are two units that work in a compressor- one unit compresses the signal after getting triggered by the incoming signal and the other unit detects this incoming signal itself.
- This incoming signal can be detected in two ways – one is the peak level detection and another is the rms level detection. Choosing any one of these two will result in different behavior in the compressor.
The peak detector will read the peak signals in a very short amount of time comparing it with the threshold.
In other words the peak detecting compressor setting will track a very rapid moving signal and will keep triggering very rapidly. This tells that the compressor is actually tracking drums with a peak detector setting.
- A compressor with an rms level detector or the average level (not exact average) detector takes into account, a substantial amount of time which is commonly the window of about every one third of a second or almost every 300 milliseconds. It detects the signal’s average level for that much amount of time and compares it to the threshold. Essentially the sustained sounds like the melodic instruments are getting tracked with rms detector mode.
It’s up to you that what you want your compressor to track within your music and both will have different effects.
An inexperienced producer won’t be able to hear the effect of the compressor’s rms mode of detection so it’s better to have peak mode as it’s more commonly used by everyone.
11. Serial compression
There are times when you want to have more control of the sound which is not achievable in a single step. Suppose you want to take down the peaks of the sound and also want to give character to it.
For such purposes you’re going to need more than one compressor where each compressor fulfills a different responsibility.
- To help you understand better I’ll give you an example. So here’s how Tom Lord-Alge deals with a vocal, applying serial compression: “To make a vocal command attention I’ll put it through a Teletronix LA3A and maybe pummel it with 20dB of compression, so the meter is pinned down. If the beginnings of the words then have too much attack, I’ll put the vocals through an SSL compressor with a really fast attack, to take off or smooth out the extra attack that the LA3A adds.”
Using compression in series can also benefit you in another way. You are not bound to dial the settings too hard when you are using compressors one after the other.
With this mode of compression you’re better off with a pretty moderate settings, the result of which is transparent and more controlled.
12. Parallel Compression
A consistent and ironed out instrument is very prominent in a mix but with that, it looses some of its life. The life is in the dynamics of the sound that makes it breathe in the mix.
A flat sound will have no punch and will not move you.
If you want your instruments to be standing confident in the mix and also depict life, they need to have both – a consistent level and also the dynamics.
To have this, you can make two copies of your sound and leave one as it is and compress the other heavily and blend these two signals into one.
This is called Parallel Compression or New York Compression.
You can send your track into a compressor with a strong setting that.. yes.. squashes the sound and flattens it. Now blend the output of this send with the original as per your taste.
This will make the original sound to retain the peaks as it is and also have a levelled body to stay audible in the mix.
This mode of compression gives you the best of both the worlds.
- This type of application is beneficial for the drums, acoustic guitars, tuned percussions, keyboards so that their sustain is raised by flattening their peaks with a brutally fast attack setting and also their peaks are not sacrificed due to their unprocessed version.
It’s also used for introducing the vintage character to the sound by processing the compressed version till it starts distorting and mixing this with the dry signal.
Here’s a warning though – when you parallel process sounds, they get louder, which leads you to assume that the sound has improved the way you had intended.
This is called Loudness Bias.
To avoid falling into this pitfall, make a separate channel and route the uncompressed and compressed sounds into it and control the level of this channel to set the balance in the mix.
You can adjust the levels of both the signals to how you want them to sound but not to set the balance in the mix.
13. Compressing individual tracks vs group channel
With mixing there’s always this dilemma of whether to compress the individual tracks or the group of tracks. The thought behind this is actually the effectiveness of both the options.
It creates so much confusion, whether the sound of the former is better or the latter.
As far as I have known and learned from the engineers is – they and also I like to prefer compressing the individual tracks separately.
The reason behind this is the control that it offers. Also the sounds in the tracks cannot be exactly the same hence there can’t be a one size fits all solution for all of them.
- Using individual compressor on every track may take extra effort but it is going to reward you with better results in the context of whole mix which is afterall the goal of mixing.
A tip that I can give you is to compress individual tracks but not to compress in solo. Always compress in the context of the whole mix.
This way you’ll be able to hear the relationship of that instrument with the rest of the mix better, which will guide your decision of compressing accordingly.
Mistakes while using compression
Compression is confusing for the new producers and a Swiss knife for the experts. Its is very mysterious to understand and more mysterious to work with. Here are a few compression mistakes that can occur while mixing-
- Giving full control to the presets.
- Setting the shortest attack time.
- Neglecting the gain reduction meter.
- Squashing too much sound.
- Compressing in solo.
- Compressing just for the sake of compressing.
1.Giving full control to the presets
As soon as you pull out a compressor and use a preset of it, do not leave it as it is. The preset is there as a starting point. Listen to the sound and then tweak the preset accordingly.
2. Setting the shortest attack time
Compression can get messy. Many beginners that I have taught go extreme with the compressor settings.
The attack time us one of them and needs to be handled carefully as it can distort the sound if it’s set to the most fastest time.
3. Neglecting the gain reduction meter
Its more important to keep the focus on gain reduction that any other reading.
The gain reduction will let you read the actual difference that the compressor has made in your sound. Also it will help you limit overcompressing.
4. Squashing too much sound
Squashing the sound too much is another way of mentioning over compression. In mixing, a little goes a long way.
Squashing the sound and sucking the life out of it will make your music sound unnatural and will be an uneasy experience for the listeners.
3 dB to a maximum 6 dB of gain reduction is all that is fine.
5. Compressing in solo
Mixing is a process of making all the instruments fit together to make the whole music a unified experience.
It makes sense then that if you want to make everything fit with everything else, better compress everything in context of everything else.
Don’t compress in solo.
6. Compressing just for the sake of compressing
Everyone watches tutorials these days and there’s always a compressor used in every mix session by every producer. Is that the only indication you need to use a compressor?
It shouldn’t be!
The only way to know you should compress is when you cannot level the instrument with a stable fader setting once and for all. Have a solid reason for applying compression.
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Conclusion
By this time you have been told all the necessary things about the compressor.
Being a versatile tool for mixing it’s useful in shaping the sound however you want.
This tool is also capable of giving character or color to the sound.
With so much to offer, learn all the basics of it and see what you can do with it!
