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Topic: What is compression?

  1. #1

    What is compression?

    Hi All

    I was hoping anyone would like to explain to me, in very simple English (since my English is somewhat limited), what exactly is compression in mixing. What does it do? Is it good or bad? I would be most grateful.

    THank you


  2. #2

    Re: What is compression?

    By using compression, the overall dynamics of a sound are "compressed" so that the range from the softest passage to the loudest is now smaller. For example, it can make the louder parts of recorded sound softer while making softer parts louder. The visual equivalent is to turn the contrast down on your monitor.

    Why do this?

    There are many artistic reasons to compress, including smoothing out a sound source that varies too much in its level, or just getting something to sound more "punchy." Getting into detail on this would require a huge discussion that you would probably find more easily with a search on the web. See my links at the bottom.

    One big use (and misuse) in recordings is to make everything "louder." This is done by compressing the overall signal, then turning up the level until the highest peak is just under 0db. Your music is now louder, but the dynamic range has been reduced. Do it tastefully, and it can add excitement and presence to your mix. Do it too much, and it can destroy your music (many examples in pop music today)

    The most useful easy thing you can do with compression is this. Imagine you have a recording that seems at too low a level, and you'd like to increase it. The problem is that there is a transient on the percussion track that already goes just about up to 0db. You don't want to go above 0db, as digital distortion is very ugly. If you add a little compression, you can tame that transient, and make it softer without greatly affecting the rest of the mix. Now the entire thing can be brought up in level until the percussion track again reaches just under 0db. End result is that the entire mix is louder.

    Another example I discussed recently on these forums. I wanted a real WHOMP on the bass drum in GPO. It can already be fairly powerful, but I needed something gut-wrenching. You can't just turn up the level, because it will eventually clip (go above 0db). There were only a few transients that reached near the peak level, but they were the barrier for the entire signal. My solution was to add some heavy compression. Now, those few high peaks were lower in level, and the entire signal could be boosted without clipping. It also added more sustain to the sound, since higher levels were lower than usual, and vice-versa. End result: WHOMP!

    This is just a very beginning look at compression. The topic can easily fill several books. Try prosoundweb.com or soundonsound.com for some good articles on compression and mixing in general.
    - Jamie Kowalski

    All Hands Music - Kowalski on the web
    The Ear Is Always Correct - Writings on composition

  3. #3

    Re: What is compression?


    Wow! Thank you so much for that explanation. Using the examples as you did, made me understand the whole concept much better. I've read a bit, but everytime the discussion becomes too complicated and technical too fast, that I simply don't understand what compression actually DOES in the first place.

    Thank you so much for taking the time to help me out.

    Kind Regards


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