Using an Expander in Musical Mixing
Because the expander works much like a gate, you can use the same basic starting points. Choose the gate or expander based on the type of overall attenuation of the signal you want. For example, the expander is a good choice if you have an instrument that contains sounds that are too loud but that you don’t want to remove completely (you just want to reduce them a little).
A vocalist’s breath is the perfect situation for using an expander over a gate. In this case, you can set the expander’s threshold just below the singer’s softest note and start with a low ratio (1.5:1 or 2:1, for instance).
See whether the breath sounds improve, and if they don’t, slowly dial up the ratio until you get the effect that you want. Be careful not to overdo it though. If the breath sound drops too far away from the vocal, the vocal sounds unnatural.
If you use a high ratio in your expander (6:1 or above), the effect you get is similar in sound to that of the gate, only you end up having less control of the sound because you don’t have the hold or release parameters to adjust. So, if you have to use a high ratio on a signal, a gate may be a better choice for that situation.