When using Expand mode in combination with a negative range, the signal will be attenuated as soon as it drops below the threshold, increasing the perceived dynamics of the signal around the threshold. This is the most common type of expansion and with higher ratio and range values, it moves closer and closer to being a gate.
Many people don’t realize there are two types of expansion. Downward expansion is a popular choice for minimizing low-level noise like hiss and hum. It’s the opposite of a compressor: compression progressively reduces the output level above a certain threshold, while a downward expander progressively reduces the output level below a certain threshold. For example, with 2:1 compression, a 2 dB input level increase above the threshold yields a 1 dB increase at the output. With 1:2 expansion, a 1 dB input level decrease below the threshold yields 2 dB of attenuation at the output.
by Nick Messitte, iZotope Contributor September 18, 2019
In an earlier article called “Expanding on compression” I covered unusual forms of dynamic processing, including upwards compression. Neutron 3 offers the ability to implement upwards compression, so I thought it would be useful to cover it further.
Today I want to dig in to compression and expansion. I understand compression. I am starting to understand expansion. I really don’t understand the difference between “downward compression” (the typical) and “upward compression” (not so typical).
Waves has a plugin — MV2 — that combines an upward compressor and a downward compressor. Warren Huart (Produce Like A Pro Academy) thinks highly of it.
I am confident that the iZotope Neutron 2 processor can function similarly to the MV2. There are 2 compressors, both of which can do downward compression (positive ratios) and upward compression (negative ratios).
Set Compressor 1 to the negative ratio and “upward” threshold, set Compressor 2 to the positive ration and “downward” threshold. Use the output gain control to adjust.
Now we get to try it in practice.
“When many engineers say ‘compression’, what they mean is “downward compression.” In other words, bringing down the level of the signal above the threshold that you set on your compressor, to make louder things quieter. But all too often, we forget about upward compression, where quieter sounds are brought up to the threshold point; this technique can be quite handy in certain situations for a more transparent effect (it can also be approximated with parallel compression, if you don’t have an upward-compressor on hand).
Reference pointer for my Compression post coming up.