I’ve only been learning mixing a couple years, and compression was one of the harder concepts to grasp. I think part of the challenge is that the concepts are often explained incorrectly, or have a couple of important aspects left out. I think people do this to simplify the concept, but for me it just made it a lot more confusing when I went to experiment with compression on my own. (I use Ableton but this should apply to any DAW)
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Compression DOESN'T always limit dynamic range --- It can also heighten dynamic range! I’ve seen a ton of tutorials that explain it as a tool that only limits the dynamics. However, if you open up your attack on a drum loop for example, you can leave the initial transients nice and loud. This means the compressor isn’t allowed to clamp down until the tails (the part after the transients; the more quiet part of the audio). In this example you are leaving your loud sounds loud and making your quieter sounds even quieter, effectively increasing your dynamic range.
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Attack and Release AREN'T always triggered by simply crossing the Threshold --- Here is the part that really confused me and is a little tricky to explain. I think every single video (even the Groove 3 full series on compression) I watched explained Attack and Release as functions that are triggered when the signal crosses either side of the threshold (i.e. The compressor begins to clamp down on the signal once the Attack is triggered via the signal passing above the threshold, but once the audio signal drops below the threshold the Release is triggered and that clamp eases off). It made sense to me. But then I experimented on my own and quickly found that this isn’t true:
Say I have a 3 minute long drum loop waveform and I set my threshold extremely low to the point that the entire duration of the loop audio exceeds the low threshold. Why can I hear the Attack and Release easing in and out, clamping and releasing? Why are my adjustments to the Attack and Release having any affect on the drum transients? Think about it. The signal passed the threshold as soon as I hit play and it remains above the threshold until the 3 minute loop is finished. In other words that first second should be the only time the Attack is triggered and have any affect on the sound of the drum loop; the clamp (according to the logic) should stay clamped on for the entire duration that the signal is above the threshold. Similarly, the Release shouldn’t be triggered until the 3 minute mark where the loop is over, the signal drops below the threshold and the compressor is finally allowed to start releasing its clamp on the audio.
But thats not the case; when you have an extremely low threshold you can hear the changes you make to the Attack and Release, even though that threshold line is set way too low to trigger them. The threshold determines when the compressor is allowed to turn on (and initially trigger the Attack, etc) but it is not the only thing responsible for triggering your Attack and Release.
Apparently, the Attack and Release are triggered by a change in the signal level. I would like to explain how this works in more detail, but honestly I have never found a tutorial that explains it. In online tutorials and courses, I only see the “threshold level” explanation for the Attack and Release triggers, which as I demonstrated, doesn’t make sense in a lot of situations. The only reason I know the "signal change" concept is because of a long winded, multiple-day-long reddit conversation I started awhile ago, but I still never fully got my head around how it functions.
Hopefully this helps somebody out there that is confused by the explanations they’ve seen. Also let me know if any of my info is incorrect, and of course, post if you know of any tutorials that go into a more complete and accurate explanation of how compressors function (and especially an in depth description of what triggers Attack and Release).
Submitted December 08, 2016 at 02:42PM by elgraysoReddit https://www.reddit.com/r/edmproduction/comments/5h8agr/2_things_nearly_every_compressor_tutorial_forgets/?utm_source=ifttt