Following the advice of one fellow here in the forum, I think that I should try to explain how a freaking compressor works with a simple language. Hope you find it interesting. I'm not a pro but I think this will give more light on this tricky subject. Let's start...
Let me explain it with my own words. Compressor is a signal processor. You can find it in most recording software as well as rack units. A compressor reduces dynamic range. What does it do?
The compressor tames the highest peaks of your sound wave and allows the signal to be louder. Given that the sound waves are more even, your wave sounds more punchy and tight. overuse of compressor kill dynamics and that's the reason you must be careful and not over compress you tracks.
In these example you can see the track after and before being compressed. What you might notice first is that the weird peaks you fin in the original wave are less pronounced in the compressed track. Also notice that the overall gain (volume) of the new track is almost the same. How does it happen? Well, let's analyze my compressor setting.
That's the point where you signal processor start to work. When the signal surpasses -18.0 dB it starts reducing the volume. How much?
That's the reduction you're applying to the portion for the signal that past your threshold. I'm using a 3 to 1 reduction. It means that if I have 3db going past the threshold I'm gonna end with 1db. Any compression stronger than 20:1 is considered limiting.
Attack & release
To put in easy words that's thow fast or slow your compressor active and deactivate. In this example I've used a fast attack and faster release. You can experiment with these knobs. Depending on the kind of source your compressing, these setting could vary (metal kicks benefit from high attack and some cymbals sound better with slow releases)
It's called hard knee compression when the processor kicks in quickly and soft knee compression when it comes gradually as the signal rises. I've used a soft-knee compression to make it sound more natural.
So you reduced the overall level of your track. Now what? Well, you can apply some Gain to increase the volume until the compressed track matches the uncompressed track.
You can hear both examples in here:
It would be nice of the experts to comment on this subject .