I can still remember when I actually heard the sound of compression for the first time. Instructors had given me countless demonstrations, but I could never really hear the difference between the various settings—especially when it came to the attack and release times.
For months, I would add a compressor to my tracks because I knew I was “supposed to.” I knew that compressors were used to reduce the dynamic range of a signal, which can make tracks sound big and fat, or punchy and exciting. But I had no idea how to make any of that happen.
I would open up whatever plug-in I saw on YouTube and scroll through the presets until I found something that made my tracks sound better. But my mixes always sounded disconnected, like each of the instruments were mixed separately, in isolation from the other tracks.
It wasn’t until I mastered the attack and release settings on my favorite compressors that I was able to make tight, cohesive mixes with punchy drums, controlled bass, consistent vocals and a little bit of glue to hold it all together. In this blog, we’ll break down everything you need to know about attack and release settings to help you learn how to use compressors like a pro.
HOW TO USE A COMPRESSOR
In order to understand how to set the attack and release times on a compressor, you need to know how to use the other controls too. Most compressors feature controls for threshold, ratio and make-up gain in addition to the attack and release settings.
The threshold setting controls when the compressor kicks in. The term threshold literally means a line that cannot be crossed without consequence, and in this case, that consequence is gain reduction. Some compressors, like the UA 1176 and LA-2A feature a fixed threshold, meaning there is no threshold control. Instead, you have to use the input gain setting to push the signal up against the threshold.
When the signal becomes louder than the threshold, the compressor reduces the gain based on the ratio setting. Without getting too mathematical, the ratio of a compressor determines how much gain reduction is applied to a signal after it crosses the threshold.
With a ratio of 2:1, for every 2 dB above the threshold, the compressor only allows 1 dB above the threshold through. With a ratio of 4:1, for every 4 dB above the threshold, the compressor only allows 1dB above the threshold through. With a ratio of 10:1, for every 10 dB above the threshold, the compressor only allows 1 dB above the threshold through. You get the idea.
However, there’s no need to get too technical when setting the ratio on a compressor. Just remember that high ratios make compression more audible and aggressive, while low ratios are better for subtle compression. Use your ears and choose whichever ratio sounds best.
The make-up gain setting should be used to add back however much gain you “knocked off” of the original signal using gain reduction. So, if you compress a signal by roughly 3 dB, use the make-up gain to increase the output level by 3 dB so you can accurately judge the difference between the original and the compressed sound.
Now that you know how the basics of how to use a compressor, it’s time to talk about how to set compressor attack and release times.
COMPRESSOR ATTACK AND RELEASE SETTINGS
The attack and release settings essentially control the reaction speed of a compressor. And with a little know-how, they can be used to make tracks sound any way you want.
Think of the attack setting as the reaction time of the compressor. It controls how long it takes for the compressor to kick in after a signal exceeds the threshold.
Fast Attack Speed (10 microseconds - 1 millisecond)
With a fast attack speed, the compressor kicks in almost immediately, which is great if you’re trying to prevent signals from clipping or tame unruly peaks. As for tone, fast attack times can be used to tighten up sloppy performances and make things feel a little more polished.
Setting the attack time too fast may suck the life out of a performance or push an instrument back in the mix making it sound farther away from the listener.
Fast attack speeds can also cause audible distortion or artifacts, especially when dealing with bass frequencies. To prevent this, try using a compressor with a built-in high-pass filter to bypass the bass frequencies.
The release setting controls how long it takes for the compressor to “let go” of a signal, or return it to an uncompressed state.
Slow Attack Speed (10 to 100 milliseconds)
With a slow attack speed, the compressor lets a bit of the initial signal through before it kicks in, which can be used to emphasize the impact of a signal, making it sound bigger and more aggressive.
However, slow attack speeds are not ideal for controlling dynamics. In fact, slow attack speeds can actually make performance with uneven dynamics even worse.
Fast Release Speed (50 to 100 milliseconds)
The release setting controls how long it takes for the compressor to let go of a signal. Fast release times are also great for increasing the perceived loudness of a track.
At low levels of gain reduction, fast release speeds sound the most natural However, when used at high ratios, fast release times can make tracks sound more gritty and aggressive. Just be careful, extreme compression with a fast release time can cause an unwanted pumping sound.
Slow Release Speed (2 to 5 seconds)
Slow-release speeds are great for smoothing out dynamic performances. It can also be used to push an instrument back in the mix, making it sound farther away from the listener. If the release time is too slow, a compressor may suck the life out of your performance, making it sound dull and flat.
HOW TO SET ATTACK AND RELEASE TIME
When it comes to setting compressors, discussing specific settings isn’t really helpful. Settings that sounded good for one instrument may not sound good for another. That’s why in most cases, engineers simply refer to attack release times as fast, slow or medium.
Generally speaking, faster attack and release times will give you more aggression, grit, and loudness, while slower times sound smoother. Many engineers choose to begin applying compression with a slow attack speed and a fast release speed for the most natural, transparent sound. These settings will help ensure that the dynamics of the performance are preserved while still taming the loudest transients.
Next, adjust the attack time as needed. Use a slower attack speed to preserve the transient, and a faster attack speed for more control. Then, adjust the release setting so that it breathes in time with the performance. To do this, simply watch the gain reduction meter and adjust the release time so that the signal just barely returns to 0 before the next transient. This helps give each of the tracks a more cohesive sound—like they’re all working in time together.
For even more control over your sound, try using two compressors in serial. Start with a compressor with a fast attack and fast release to smooth out peaks and tame transients, followed by a slower, more gentle compressor to make tracks sound bigger and fatter.
The most important thing to remember when setting the attack and release times on a compressor is to know what you’re trying to accomplish. Simply scrolling through presets or spinning knobs isn’t going to get you where you want to go.
Instead, decide what it is that you want to achieve before you reach for the compressor. Do you want to tame peaks and reduce the dynamic range of a performance? Do you want to glue tracks together with soft, slow compression? Do you want to add excitement and perceived loudness?
As long as you know what it is you want to accomplish, you can follow these simple steps to setting compressor attack and release times to get the job done.
How To Measure Dynamic Range
To get a visual of what your compressor is doing to your music, you can use the Dynamic Range section of LEVELS by Mastering The Mix. The oscilloscope will grow green and bounce around if your audio is nice and punchy. It will turn orange, then red if your audio is over-compressed.