Expanders Role in Home Recording
In music mixing, the expander is to the gate what a compressor is to a limiter — instead of reducing the volume of notes below the set threshold by a specified amount, the expander reduces them by a ratio.
In other words, with the gate, you set a certain amount, in dB, that a signal is reduced, and with the expander, you reduce the signal by setting a ratio. The ratio changes the signal gradually, making the affected signals sound more natural.
You use an expander when you want to subtly reduce noise from a track, rather than just filtering it out completely. A classic example is when dealing with the breath sounds from a singer. If you use a gate, the resulting track sounds unnatural, because the gate filters out the breaths completely.
However, you can set the expander to reduce the breath sounds just enough to be less noticeable, but still leave a little of the sound so that the singer sounds normal. (Everyone has to breathe, right?)
Use the following settings to get started:
Threshold: The threshold in an expander works the same way as with the gate — anything below the threshold is affected and signals above the threshold pass unaffected.
Ratio: The ratio dictates how much the signal is attenuated by the expander. When using a ratio of 2:1, for instance, the expander reduces signals below the threshold by a factor of 2. In this case, a signal that is 10dB below the threshold is reduced to 20dB below it; likewise, a signal that’s 2dB below the threshold would be reduced to 4dB below it.