Say we had an upward expander with a ratio of and a threshold set at 0 dB. If the incoming signal were at 1 dB 1 dB above the threshold , the signal would be amplified to 3 dB at the output. If the signal were at 2 dB 2 dB above the threshold , the signal would be amplified to 6 dB at the output.
The louder parts of the signal are now louder. In a downward expander, a ratio of x:1 attenuates signal to a level of x dB below the threshold for every 1 dB it drops below the threshold. Say we had a downward expander with a ratio of and a threshold set at 0 dB.
If the incoming signal were at -1 dB 1 dB below the threshold , the signal would be attenuated to -3 dB at the output. If the signal were at -2 dB 2 dB below the threshold , the signal would be attenuated to -6 dB at the output. The quieter parts of the signal are now quieter. With the threshold, ratio, and input level, we can determine the output level using this equation this works for downward and upward expansion :.
Knee, attack time, and release time for expanders would all work the same as in compressors. Makeup gain is only really necessary for upward expansion. As louder parts become louder, the signal will be louder after the expander than before, which can eventually lead to distortion of your gain-staging is off. The makeup gain can be used to attenuate the signal, returning the louder parts to their previous level.
An expander can be used to achieve the opposite result of a compressor, expanding the dynamic range rather than compressing it. Therefore, expanders are best used when you want to have a wider dynamic range. Expanders can be used to make instrumental or vocal performances a bit more varied in volume. This can be very useful if you want a more organic sound. This can, however, reduce presence in the mix.
It can also potentially cause unnatural pumping, as these expansions in dynamic range are caused by mathematical processes ignorant to musical phrasing. One of the main uses of expanders is in mixing a recorded drum kit. Each drum is individually mic'd, allowing each to have a separate channel on the mixer.
However, total isolation is difficult, and bits of the other drums are bound to bleed through into other microphones. An expander can be used, for example, to decrease the volume of the hat in the snare mic. As the hat will be further away from the mic than the snare, it will be quieter than the snare when picked up by the snare mic.
Therefore, downward expansion can be used to attenuate it. With the same logic, you can use expanders to remove reverb from drums. The reverb signal will be lower than the threshold, causing it to be attenuated in between the drum hits.
Listen to the example below:. The reason this works with drums is that, after each drum hit, there is space for the signal to drop below the threshold level. Lastly, expanders can be used like compressors for sidechaining purposes. This is interesting, as it can cause an element to play more loudly while another element is playing.
Check out this example of sidechain compression in action. The first audio file is a drum loop. The second is a sample of vinyl static. And hear the added layer of texture it gives to the drums when both are played together.
Our last dynamics processor is a gate, which is essentially the extreme version of a downward expander. Gates provide a floor level which signal must cross to get through the gate. If the signal is too quiet to reach this floor, it will be attenuated to silence. We send three signals through it, at levels of 2 dB, 4 dB, and 8 dB below the threshold.
With this ratio, the expander would output signals at levels of 4 dB, 8 dB, and 16 dB below the threshold. However, if we turned the ratio up to very high , the expander would output signals at levels of 8 dB, 16 dB, and 32 dB below the threshold.
These signals are now much further apart and much closer to being inaudible. Eventually, as the ratio increases, any signal will be greatly attenuated, and all signal that passes through the gate will have to cross this floor level. Every gate will have at least three parameters: threshold, attack time, and release time. These all function the same as in compressors and expanders. Some gates will also have a hold parameter, causing the gate to remain open for a period of time in ms after the signal has dropped below the threshold and before the release phase begins.
Some gates will also offer the ability to have the gate close at a different level than the threshold, which is only used for opening the gate. This parameter is often called the close or return level. And just like the fact that some limiters have an adjustable ceiling, some gates will have an adjustable floor level. Now that we know a gate is essentially an expander with a high ratio, take a look at our expansion output level equation again:. As the ratio increases, that total fraction will become larger and larger.
As expected, as the ratio increases, the output level for a signal that falls below the threshold will become quieter and quieter. Eventually, the signal will not be able to pass if it is below the threshold—a gate.
This can be on a vocal to eliminate breaths, or can be used as an expander to isolate louder signals in a recording e. Gates are equally useful in a studio recording or live sound context. They can also be used in a similarly creative way as the expander example above. However, a gate would cause that static sample to pump harder and therefore have a more difficult time blending with the drums.
Therefore, you may just want to use an expander for that. In fact, if one segment causes your compressor to work dramatically harder, you should consider using automation or clip gain to control the level that feeds into it. Skip to primary navigation Skip to main content. Audio compression is one of the most important tools in your producer tool kit. What is compression in music?
Why is audio compression used in mixing? But even within the same sound, quiet details can be easily overshadowed by the loudest moments. How does audio compression work? A compressor includes several controls to help you control exactly how it behaves: Threshold The level where the compressor begins working is called the threshold —you set it with a dB control to determine the parts of the signal the compressor acts on.
Set the threshold high and the compressor will only reduce the gain of the most aggressive transients Set the threshold lower and it compresses more of the signal.
Ratio The ratio control determines how much the compressor reduces the gain once the signal passes the threshold. How to use a compressor properly Using a compressor can be difficult when you first start mixing. Here are some questions you can ask yourself to help make good decisions with compression: 1. Do I need it? What parts of the sound get louder or quieter? Check out the video to see some DAW demonstrations about how compressors shape the sound of vocals, snare and kick drums in a mix.
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Skip to content What is Compression? Compression in Music Overview. Table of Contents. By using the key input and sidechain, you can have your kick drum trigger a compressor on the bass. That means that every time the kick drum hits, it will literally turn down the bass slightly. The key input is where you plug in the track you want to trigger the compressor. Put the compressor on the bass, and then set the key input to be the kick drum.
Then, you can set the compressor as you would any normal compressor, except that it is only triggered when the kick drum goes over a set threshold. The key is to use it subtly. The only time this is used is in electronic music for effect. The other benefit of this feature is that it can save you time on the editing side.
Gentle sidechaining will take some getting used to. Thankfully, the results are fairly obvious, and you can bypass the function and fiddle around until you're happy with the results. Over time, your instincts will tell you what sounds right. Everybody talks about book smarts, but making a great mix is as much a process of intuition as it is a process of science. You'll see what I mean as you experiment with your mixes. Remember though, none of what you've learned will matter if you don't know how to get your music out there and earn from it.
Want to learn how to do that? So what does DAW stand for? Back in the…. When I think of the best rock bands that have ever existed, my thoughts immediately turn to England. The Beatles. Led Zeppelin. Pink Floyd. The Rolling Stones. Judas Priest. The Who. Deep Purple.
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