Posts Tagged ‘ Expansion ’

So what’s the point of expansion?

You’ve used gates, right?

If you’ve ever recorded something with a microphone, you’ve probably had a situation where the background noise was just a little too high (or the acoustic sound was just a little too quiet) and the background noise was bugging you in the mix.

So you reached for a gate, eh?

Set the threshold, maybe adjust the attack and release (I usually prefer an instant attack and fairly gentle release) and call it a day. Bingo! No noise in between playing!

That usually works fine for busy mixes where there’s always something going on, or there is a rich background texture. But in sparser mixes, you might notice that the difference between the silent and non-silent sections of a track is rather uncomfortable. When the instrument is playing, you get a rich subtle ambience (or refrigerator hum, if that’s how you roll). When the instrument stops, the life gets sucked out of the track.

Pure digital silence.

What an expander does is reduce┬áthe level of the background noise without killing it entirely. It makes the quiet stuff quieter. It helps you push the background noise out of the way when it’s not needed, but doesn’t totally suck the life out of your track.

Just be careful that you’re not using heavy compression after the expander. Expanders can be quite subtle in their effect, and compressing the resulting sound can destroy your careful balance of threshold and ratio. If you like following your tail in circles, lower the threshold of the expander to compensate for the heavy compression. In general, though, it’s not a good idea to have two processes fighting each other. If you want to use an expander, it’s probably because subtlety is important to you. Use a gentle compressor.

-Kim.

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Downwards or upwards?

Every now and then, people ask about upwards compression or upwards expansion. Often when this is raised there is some confusion about what “upwards” means, and how it might be different to regular compression or expansion. This confusion is sometimes exacerbated by a misunderstanding about how compressors work (as distinct from what they’re used for).

Essentially, “regular” compressors and expanders both work by reducing gain – that is, lowering the volume. Compressors do it by reducing gain when the volume level of the audio goes above a certain amount, and expanders do it be reducing gain when the volume level goes below a certain amount.

Limiters and gates are extreme versions of the above. A limiter is an extreme version of a compressor – reducing the gain so much that the output level never excedes a certain amount. A gate is an extreme version of an expander – reducing the gain so much that the output level is silent.

Because compressors and expanders work by reducing gain, they can be referred to as operating downwards. You might refer to a regular compressor as a downwards compressor and refer to a regular expander as a downwards expander.

(Sometimes this is a source of confusion because compressors are often used to make sounds louder – because the loudest parts of the sound art turned down, the whole track can be turned up without distorting.)

In contrast, some compressors and expanders can operate upwards. They work by increasing gain. Upwards compressors work by increasing gain when the volume level of the audio goes below a certain amount. Upwards expaders work by increasing gain when the volume level goes above a certain amount.

Upwards compressors and expanders aren’t too common – possibly because they can be unstable and produce really loud levels! Still, sometimes these terms arise and it’s good to understand their meaning. In essence:

Upwards compression – reduces dynamic range by making quiet sounds louder
Downwards compression – reduces dynamic range by making loud sounds quieter
Upwards expansion – increases dynamic range by making loud sounds louder
Downwards expansion – increases dynamic range by making quiet sounds quieter

-Kim.