Technical "complexity" of compression

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Technical "complexity" of compression

Postby KBD_TRACKER » Tue May 12, 2015 4:29 pm

I was reading "Understanding compression" in RA.
http://www.residentadvisor.net/feature.aspx?1595

Now the 4th paragraph said "By placing the Threshold point in the middle of this volume rise, the quieter section of the sound will remain uncompressed, while the upper section will have its dynamics compressed."

This raises an interesting point.
As I understand it, the article is speaking of the "quieter sections" of the music as they happen through time, through the music's continued temporal flow. And of course this would be correct.

But it could be also be understood as "at any given moment", and then imo it would be incorrect.
Because as I see compressors, when the sound input volume trespasses the threshold the compressor gain drops to less than 1 (in a manner determined by the ratio). When the input volume drops back to below threshold the gain returns to 1.
Therefore if in the total sound there are portions with a loudness > threshold, the compressor will trigger and then EVEN the quiet portions of the input sound (whose volume is < threshold) will see their gain diminished and thus be "compressed" .

For example a snare drum + acoustic guitar. Suppose the snare drum exceeds the threshold then the compressor kicks in, making BOTH the snare and the guitar less loud. Even though the guitar never crossed the threshold, its volume will drop also during compression.

(in all this I am leaving aside subsequent make up gain)

Overly fastidious or self -evident ??
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Re: Technical "complexity" of compression

Postby Stab Frenzy » Wed May 13, 2015 12:29 am

Self-evident, but probably not understood by a lot of people.
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Re: Technical "complexity" of compression

Postby ian » Sat May 30, 2015 10:12 am

Forgive me if I miss your point but isn't that where Attack and Release come in? Those parameters are where you fine tune your compression temporally. If you set your threshold to a point where your acoustic guitar will not trip it when solo-ed, your snare drum trips the compressor and that spike is clapped down on, so fine tune the attack and release so that the compressor starts acting when your snare pushes over the threshold and the compressors tail ends when the snare ends. Your ear probably won't hear any effect on the guitar. You could then slowly ramp down on the threshold if you still need further overall compressor.

By properly using the attack and release parameters you are in control of the "at any given moment" issue you speak of and compression is about finding the sweet spot and making the best trade off for your mix. The idea is similar to how you might want to put a low shelf on a deep bass sound to cut out muddiness in your overall mix; your low bass may sound less harmonically rich by itself if you ramp down on the frequencies bellow, say, 32 hz but you may end up with a cleaner overall mix. ( purely theoretical example)

Also, generally a snare will have it's own compression before reaching a master compressor.


Using notch filters to carve out little places in the harmonic spectrum for each important sound will also cut down on overall volume spikes and possible ducking from the master compressor.
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