Q: I understand what the threshold and attack controls do on my compressor, but the ratio thing is harder to understand. Got any tips?
A: The ratio simply sets the degree of compression once you have exceeded the threshold level. A ratio of 2:1 is considered mild compression and this means that when your incoming level rises by 10dB, the outgoing level rises by only 5dB. TThus 4:1 would mean your 10dB incoming level becomes an outgoing level of … yup, now your output rises by 2.5dB. See? It’s really pretty simple.
In general, you probably wouldn’t use a compression ratio of more than 5:1 for your average vocal track. Ratios above 10:1 (do the math) are usually considered to get into the realm of limiting.