FabFilter

I use Pro L only on the master bus with 4x over sampling and isp enabled. I use this for my mastering limiter because it is the most versitile limiter I've have, though typically I go for absolute transparency which Pro L does very easily. It also can give you pumping brutal limiting if you're into that. Mainly, the fact that it is the best true peak limiter on the market is why it's my one and only master limiter. I'm guessing you could use it on individual tracks, but I prefer the flux pure limiter for that.

Pro MB is a multiband compressor/expander, so I would use that anywhere you would need dynamic equalization. There is a technical difference between a dynamic equalizer and a multiband compressor, but if you are just starting out then that is the best way to describe it. Basically, you can compress sections of the frequency range based on its own dynamics, external signals, or the dynamics of another frequency range in the same sound. I use it on full drum kits if I can't get separate tracks to control hi hats or the kick or snare, or bass lines that I like the tone but want to control the lows only when they get over a particular volume.

Pro C2 is a compressor, so it does to the entire sound what the MB can do to sections of a sound, though the MB can also be used on the entire frequency range of. Compressors help control the difference between low and high volumes in your sound, often described as "dynamic range". Compressors reduce the dynamic range, pushing the high level information down so that you can turn up the volume overall: reducing the dynamic range. Expanders do the exact opposite, increasing the dynamic range by making the low level information quieter, increasing dynamic range. Compressors are used on most everything, at least lightly, these days.

Huugh!!!

many thanks. if MB can do all what Compressor does, what is the reason to use single Compressor?

Great answer by Mdjagg. I use these tools similarly. To answer your most recent question, Pro-C2 does have some cool options and metering views that Pro-MB lacks.

The many ways compression can be used is a vast topic, but for cases where you want to compress a track Pro-C2 has the most options and flexibility out of the 3 plugins being discussed. It includes some cool metering options and "style" options that change the way the compressor behaves and how much extra "character" is added to the original sound, so Pro-C2 is a great tool for the many different ways you might use compression. I sometimes use Pro-C2 to tame the dynamics of a track so the loudest parts don't peak out in an annoying way. I sometimes use Pro-C2 to add "character" like pumping or grittiness as a harmonic tool, for example making a copy of a drum track pump and distort and then mixing that in with my clean drum track to make the drums sound beefier.

I reach for Pro-MB when I want different frequencies to get different compression treatments. Pro-MB specializes in this, but it has fewer compression options and different metering than Pro-C2. Sometimes I use Pro-MB to tame the low frequencies of a bassy track while leaving the high frequencies untouched so controlling the lows doesn't take the bite out of the highs, such as making a bass sound more controlled or sidechaining to punch holes in the bass track whenever the kick drum is loud. Sometimes I use Pro-MB to compress/control a tight band at the muddy mid frequencies around 500 Hz (frequency differs per mix). This clears the mud a bit, but only when the mud rises above a specific volume, and it leaves the lows and highs untouched.

I reach for Pro-L to limit a mix for mastering purposes. Full mix limiting or bus limiting are unique problems that require special processing which Pro-L specializes at in a way that Pro-C2 and Pro-MB don't. You can boost the volume of the full mix to loud levels and peaks that would otherwise be too loud and distort are limited to a "brick wall" level.

So these 3 plugins specialize in different uses. In my opinion Pro-C2 is a great compressor, but there are many great plugin compressors so I don't use it on every mix. In my opinion Pro-MB is one of the best plugin multi-band compressors on the market and I find myself using it on almost every mix now that I understand how to use it (which took a while). In my opinion Pro-L is one of the best plugin limiters on the market and these days I use it as my go-to final plugin on my master bus to master every mix.

@Ladislav That is a completely fair question. First you have to realise that Pro MB IS a compressor. Knowing that, it has the ability to compress Multiple Bands AND the single Full band like the Pro C2. If you can just afford one,... That's a tough one. Pro C2 is much more 'classic' in its design, which makes it a bit easier to use. But honestly, I guess the MB is technically more versatile. I'd take the MB if I had to only have one, I'm glad I don't. You don't really get to see the knee settings in MB, but you can see the compression happening which is the most important part. The great part about Pro C2 is the fact that there are several different algorithm modes to choose from which change the way the attack and release souund. This is VERY usefully if youre mixing music. If you're just controlling vocals for a podcast, for example, then MB would probably be just fine.