How To Set The Level In a Club System

Hello,

we have a pretty decent soun system in my school and we organize party.
The chain goes like that:
CDJ/Vinyls -> XONE/XDJ -> preprocessor (with a limiter) -> amplifier -> speakers

I wonder how to set up the level correctly and when should the limiter be triggered according to the mixer?

We're facing the problem that each time the DJs (a bit novice sometimes) goes full gain on every part of the mixer, the sound distorts, but then it's difficult for other DJs to lower the sound because at the end the public also feel a lowering of the energy (RMS level lower...).
So how to set up the system so that they won't do it?
Does DJs always end up pushing up gain?

So there are three questions in this post,
thank you for your interest.

For something like this it helps to know both the system and how the DJs play. When I play on my own PA I set my speakers and live mixer channels to have 0db gain while letting the master channel sit at -3db. I try to never let my mix peak over +6db on my NXS2 setup. If that level is too loud I will either gain my songs lower or set an attenuation in the NXS2 master out settings.

Now that being said, if you know the system and a DJ likes to play more into the red then I would maybe put a negative gain on the amplifiers or if the live mixer has a pad button(usually by the gain knob) I would use that to apply a negative gain(most times -20db or -26db) and then use the gain knob to add makeup gain until the live mixer shows peaks around -6db or -3db. I always assume DJs will play louder and louder throughout the night so most times I set them to hit -8db or -6db. If they don't go louder progressively through the night I will adjust the channel fader on the live mixer during their set.

Now most hard limiters I have seen tend to kick in at -1db or 0db from the live mixer. Sometimes I will put a light compressor on the live mixer just to prevent clipping on the speakers.

What I would do is try to set the channel sensitivity of the preprocessor to be somewhere from -9db to -3db for each channel if the limiter is set to 0db. This will allow DJs to play their main mix into the yellow without clipping. If the processor has a limiter in the negative simply add the negative value to the sensitivity you are aiming for. So for instance if you want to do -3db reduction for headroom yet the limiter is set to -4db you should instead set sensitivity to -7db. That way you still have headroom but are less likely to hit the limiter which can often be very pronounced.