by Daniel Strongin 19 Sept. 17
In this tutorial, I’ll be going over what a compressor actually is, its basic controls, and how to use a compressor in your tracks. Before we get started, I want to let you know that I release tutorials every week on music production topics such as sound design, mixing, mastering, and arrangement. So go ahead and subscribe so you don't miss my next release.
What Does a Compressor do? How does a Compressor Work?
Many beginner and intermediate producers struggle to understand what a compressor is and how the basic parameters function. Also many producers who know what a compressor is and what its basic parameters do, don't know where to put the compression in their music. Should you put it on this drum hit on this group of synths? Do you put it on your bass? That is what we are going to go over in this tutorial
So, what is compression? To understand compression you first need to understand what “dynamics” means. Dynamics refers to an audio signal that has quiet parts and loud parts. The difference between the quieter and louder parts is your dynamic range. For example, if your audio signal is clipping, there will be no quiet parts and everything is going to be boosted so there will be no dynamic range. So, in technical terms, a compressor is an audio processing device that reduces the volume of loud sounds and amplifies the quieter ones thus reducing or compressing your audio signal’s dynamic range. In simpler terms you can think of a compressor as an automatic volume control. Imagine that you have your hand on a volume fader and you are moving the fader up in volume when the audio signal gets quiet and you're moving the fader down in volume when the audio signal gets loud. This is essentially what a compressor does. It will help to keep this image in your mind when I go over the controls of a compressor and its practical applications.
Now that you have a basic understanding of what compression is, let's go over a compressor’s parameters so you understand how to control your compressor. Although there are many controls on a compressor, this tutorial will discuss only the four main controls. Limiting the controls we cover will keep you from becoming confused with a bunch of parameters and make it possible for you to apply the principles and techniques to your own music immediately.
The first control that I want to go over is the Compressor threshold. The threshold control sets the level at which the compression effect is engaged. A lower compressor threshold means a bigger part of the audio will be compressed and a higher compressor threshold means that only the peaks of the audio will be compressed.
The second basic control is the compression ratio. The compression ratio sets how much compression is applied or how strong the compressor is. The lowest compression ratio that you can have is one-to-one which applies no compression. If you then set your compressor to a compression ratio of two-to-one ratio, this means that a signal exceeding the threshold by two decibels will be attenuated down to one decibel above the threshold, or a signal exceeding the threshold or by eight decibels will be attenuated down to four decibels.
The third control is the compressor attack. The compressor attack sets how quickly the compressor starts to work. A shorter attack will make the signal reduction happen quicker and a longer attack will gradually reduce the signal.
The next control, I’m going to discuss is the compression release. The compressor release sets when the sound drops back below the threshold. The compressor does not instantly stop compressing the sound instead it gradually reduces the compression. With the shorter release, the compressor is going to release its clamp on the sound very quickly, and with the longer release it's going to be compressed longer and keep the gain reduction more constant.
As a general rule of thumb, I like to keep all my sounds at every single stage in the signal flow at minus 6 decibels on a peak meter. That means that the highest point that I will have my sounds coming out of the signal flow is minus 6 decibels. Any place where there could be a change in volume is a stage in the signal flow. For example, if my source is a synth, I will not exceed negative 6 decibels coming out of the synth. Also, if I do processing on that synth, for each processor I put on I will make sure that nothing more than negative 6 decibels is output out of that specific plugin. If that synth is in a group of channels that come together to make one channel, then I'll make sure the output of all those synths is no greater than negative 6 decibels. Taking this a step further, my master output will also have no more than negative 6 decibels outputting. This means every stage does not pass the negative 6 decibel mark on a peak meter. All of your channel strips in your DAW will have a peak meter which is the most common meter used. If your plugins don't come with any peak meters, you can always check the channel strip to see where it is peaking. Some audio engineers might tell you that negative 8 negative 10 or negative 12 might be the most optimal range for having your sounds peaking at. However, negative 6 decibels is what has worked best for me for EDM specifically.
My Video Shows How to Use a Compressor
In my YouTube video on using a compressor, I go through an audio example which shows how adjusting the compression ratio. Compressor attack and compression release affects the sound. If you watch this video, you can hear how the ratio and times affect how the compressor reacts to the audio. You can compare the sound when the compressor threshold is very low at, negative 34.2 decibels and when it is much higher. This exaggerates what the compressor does so you can hear how the parameters react.
The final basic parameter that you need to know to understand compression is the gain reduction. Every compressor has some sort of gain reduction meter and this simply tells how many decibels the compressor is reducing. As you use the compressor, look at the gain reduction to see how the different changes in the parameters affect the compressor. You always start with the ratio of one-to-one when no compression is being applied. When you turn it up, you’ll be able to hear the affect made by the compressor. As you turn the ratio up, the compression gets stronger and there is more gain reduction. To understand gain reduction better experiment with your compressor. For example, turn the attack control up and down and you’ll be able to hear that as you turn the attack time up, the signal actually gets louder because the time it takes for the compressor to kick in is longer so it doesn't compress the audio. So, turning up the attack time it lets more of the signal go through uncompressed. Next, experiment with changing the release time and you will hear that at one millisecond the compressor is trying to release its clamp on the audio as quickly as possible which causes it to distort. Then, as you raise the release time, the compressor is clamping down on the audio even harder and not letting the compressor recover or release its clamp. This means the gain reduction is pretty constant and pretty steady when it is raised up.
When to Use Compression
Now you know what compression is and what the four basic parameters do. The next step is to find out how to you apply this to your own music and which sounds to apply it to. This is where a lot of producers get lost. I’ll begin by going over some common uses of compression. In my YouTube video on compression I use Ableton's compressor because it is simple and doesn't have a lot of other controls on it which makes it easier to understand what is going on. However, you can use any compressor as they all operate the same way.
How to Use a Compressor to Balance Inconsistent Volumes
The first situation where I recommend using compression is to balance out the inconsistent volumes in your individual elements. Now this could be anything from a drum hit, to a lead sound, or your bass or synths. It applied to anything which has an uneven dip in volume or which causes the signal to be too loud at certain parts. When this happens, you need to compress this individual sound. In the YouTube video I demonstrate this process by playing an audio clip that has imbalance in its volumes and then go over how to compress it. Listen to the video and you can hear that the original clip has a lot of quieter parts and also louder parts. It's really inconsistent so this sound is going to be lost in the mix and be hard to hear for the listener.
An Example Using Compression Ratio, Compressor Attack, and Compression Release
When you have inconsistent volumes in a mix, the first parameter to set is the compression ratio. If you want a moderate amount of compression, keep it at four-to-one or even a little bit higher so the compressor will be fairly strong. Then set the compressor attack. Try keeping it at its lowest setting, .01 milliseconds as you want the compressor to clamp down on the entire sound so you don't want any of the imbalances to be left untouched by the compressors. Then set the compression release. Try setting the release time fairly long, like around 194 milliseconds because you want it to compress everything and you don't want to have the compressor’s clamp released too soon. You want to make sure you have all the audio in there and it's really keeping everything consistent.
Setting the Compressor Threshold
Listen to your mix to adjust the compressor threshold where it really evens out and you can no longer hear the dips and rises in volume. After you finish compressing the sound, try listening to the difference by first listening with the compressor turned off and then listening with the compressor on so you can hear how the compressor makes the sound more consistent.
How to Use a Compressor to Glue Your Sounds Together
The second situation where I use compression is for gluing your sounds together. Often you will have a lot of different elements playing in your mix and you will want them to be more glued together and more consistent in volume so they are steadier in the mix. This allows the listener to hear all the different elements that are playing. One common example of where you're going to have a lot of different elements and smaller sounds playing is with your drums. Of course, you try to get each drum hit as balanced as possible volume-wise, but this can be pretty difficult sometimes. When this happens, you can use your compressor as an automatic volume control to balance some of these levels for you. It works great for gluing together a bunch of sounds. In the YouTube video I use compression to glue together the sounds in a drum loop. Watch the video to see and hear the results.
Often with drum loops there are a lot of different small percussion hits in the mix including some which are a bit louder in volume and some which are a bit quieter area. You can use your compressor to rein in those sounds without have to go into each individual element and to fine-tune them. Again, you should start by adjusting the compression ratio. If you want a fair amount of compression, use around four-to-one to make sure You’re getting all the little drum heads to pop out in the mix.
Setting the Compressor Attack
You’ll want the compressor attack to be fairly quick but you also want to let some of the audio in before the compressor clamps down on it. This is because drums have sharp transients and you want these transients to come through in the mix. You want them to be punchy. You want them to be present. However, if you have your compressor clamped down on these drums it will take away from those transients. To avoid this, try setting your compressor attack to around 15 milliseconds to allow for the initial hit of the drums to come through. When you're setting the compressor attack, you'll have to listen to the source sound that you're working to find out how whether you want to reduce some of the transients. Do you want to have more of a punchy sound? This will determine where the attack goes.
Setting the Compression Release
Next, set the compression release. You're going to want the compression release to be a little bit longer here because you want to make sure you're getting all the audio compressed and you really want to bring out all the elements in the track and have its grip on the sound reduced gradually. You don't want to have the compression release too quick because you want to really get all the audio glued together. Having a longer release causes the compressor to release its grip on the audio more gradually. That means you will be getting all the elements compressed and not just have it grab a couple of drum hits and then release its grip on the sounds. Try putting the compression release up to around 150 milliseconds.
Setting the Compressor Threshold
To set the compressor threshold, you will need to listen to the audio so you can hear where to set it. What you are listening for when you set the threshold is the point where there is a more consistent volume in all the elements without giving too much gain reduction. On the video I set the compression threshold at around -19.1 because that is where I could hear the elements really glued together which resulted in the gain reduction being around five or six decibels. Remember that the more you compress, the less of a dynamic range you have. So, don’t go too crazy with the gain reduction. You want to do as little as possible while achieving your goal of gluing together your sounds.
Listen to Hear How Compression has Glued Your Sounds Together
After you finish, listen to the drum loop without the compression on and then with it on so you can hear how the compression makes the elements sound a lot more together, more consistent in volume and have that glued sound that you want so the listener can hear all the elements in your track.
How to Use a Compressor to Bring Out the Elements in Your Mix
The third most common use of compression is to bring out the elements in your mix to make them more present. I often want my main sound in the track to be a little more up front in the mix which makes it a little more powerful. I want to give my main sound a little more bite and I use compression to bring it out in the front of the mix. On the video I demonstrate this by playing a sample of a piano that will be the main part of the mix. The chords and pattern and timbre of the piano is great but I want to give it a little more presence and a little more impact. To do this I want to bring out the transients in the sound.
You can use this technique to bring out the sound of any main element that you're working on. Begin by going into your compressor. You probably want a fair amount of compression, because you want to bring any transients out. Try using a compression ratio around 4.3 or 4. For the compressor attack, since you want it to be more present in the mix and you want the initial hit of the sound to come through, you don't want to compress everything which would smush it down. That means, you don't want to reduce the dynamic range. You want to give more impact to the transients. To do this for a synth or a vocal that you're working on, try raising the compressor attack to around 16 milliseconds. This means that the 16 milliseconds of the initial transients will come through in the mix. When you set the compression release you want it a short release time around 30 milliseconds as you want the compressor to release its grip quickly. You want that compression to happen quickly so it gives more emphasis on the transients. If you use a longer compression release then the compressor would hold its grip on the audio and it wouldn't allow those transients to come through and bring it forward in the mix. Instead it would compress it down and reduce the audio.
After setting these parameters, listen to what it sounds like and adjust the compressor threshold. You will be able to hear a lot more presence on the transients. This should really bring them out and give the sound a little more bite, so it will be a little more up front in the mix. This will give your main element a little more impact. After you finish, listen to the sound without the compressor and then with the compressor to hear the difference.
Using compression is a great technique for bringing more presence to your elements.
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