I have a love hate relationship with Behringer. The picture is the left half of a MDX2600. I have a rack full of these and the 4 channel MDX4400.
1) If I am using this ahead of a digital recorder:
I set the Peak Limiter to just turn on at the point where the recorder distorts. It is fast on/off and is also good for peak limiting for broadcast. Also good ahead of the power amplifiers. I have been asked many times why my amplifier/speakers don't distort and how I get so much power out of them.
1a)On the compressor limiter:
If I am truly using it for limiting then the Ratio is set to max. If I am trying to reduce dynamic range to make the music louder then the Ratio is set to 4:1 more or less.
1b)The attack and release time is very adjustable on this unite. I use auto most of the time. In this mode it has two attack and release times. The slow response tries to "ride the volume" over a time period like if a human turned the volume by hand. The fast response tries to catch fractions of a word and is limited to a small range. By running the fast and slow response at the same time you get the benefit of both.
1c)I like to use Interactive Knee which switches into gain reduction mode softly. Over 3bd range. Not as good for peak limiting but sounds better.
1d)The Expander/Gate is good for removing background noise. The Gate can cause bad effects of not used carefully. It just simply turns
off the audio if there no volume. The Expander turns
down the volume if there is no audio. Sounds better.
2)If I am live and don't know the program well I some times have one of these on every input.
2a)If some one drops a mic or yellows the limiter cuts in and turns down the volume before I could get there.
2b)The Expander might be set to reduce the volume if the mic is not in use.
2c)What I am doing is having the gain adjusted or each channel, just to get it close. Then mix everything together and pass through one last limiter to keep the power amps out of distortion.
3)For "mastering" a recording:
3a)I usually set the levels for the instruments to be as loud as possible with out distortion. Some time each group of instruments are set to this level by them selves. Then I set the vocals to as loud as possible with no instruments. In the Song, the instruments start out full level. When the voices are added in the total is too much. One option is have the limiter turn down the total. (simple) What I usually do is daisy chain the limiters. So then the vocals come in the instruments are reduced. This way the voices stand out over the background. Between the words the background pops back up and gives you the notes to follow.
3b)In some music you want the drums to shake the house but you need the rest of the instruments to be heard. So I set the limiters to "duck" down the instruments and let the drums come through. It sounds like the drums have the power to drive over the rest of the instruments.
3c)This effect works if you have two singers that sing solo and together. The limiter can force the two back to the solo level.
3d)Yes....probably it adds some bad effects. But the voices stand out and your are so custom to hearing this effect in recorded music that it seems normal.
Sorry I talked too much.