Limiters and different mixers

[d&bhead]

Quick question,

 

Bit of a newbie question really.

 

We want to buy a decent sized rig.

 

But I have a question to do with the limiters we put in place and the output from the signal source.

 

Looking at the DJM800 mixer it has an output of +2Dbu so would that mean we should make sure the input gain on the limiter is set to at most -2Db?

 

or are we safe to run it at 0db.

 

Bear in mind that we might not be onsite with the kit, so is open to DJ abuse, what is the best way to limit the ability for the DJ to blow the rig?

 

Also do we have to work out which mixers (Band or DJ) we are using first and set the limiter accordingly?

 

Thanks guys

[Shez]

Where you set the limiter threshold depends entirely on what the gain of the amps is relative to the power handling of the speakers. It could be -2dBu, +2dBu, +20dBu or literally any other value.

You have to work backwards through the system from the speakers. What's the maximum signal level they can handle? Subtract the voltage gain of the amp from that and that's the maximum signal you should feed in to the amp. Minus a dB or 2 for headroom. There can be a few more variables but that's the basics of it.

[d&bhead]

Ok so no matter where the input trim is set on the limiter input, the limiter should kick in when the signal hits a specific level?

 

So what figures should I use from the speaker? Wattage etc

 

what figure should I use off the amp? Sensitivity etc

 

just trying to think how to dj proof the kit with optimal volume without them distorting from the mixer and frying a driver!!

 

Cheers

[Shez]

Do you have a specific limiter in mind? In your average LMS, the limiter is the last processor in the chain so no matter what you do with the proceeding elements in terms of EQ, compression, gain etc, the limiters will still do their job.

 

You can calculate max input level from the wattage and impedance of the speaker; it's the square root of the product of wattage and impedance. That's in volts; to convert to dBu, take the log and times by 20. You'll probably get a figure around 36dBu.

 

It's the gain of the amp you need - should be in the specs either as a multiplier (e.g. x60) or a dB gain (e.g. 35dB).

 

No matter what you do with the limiter, it's still possible for the djs to distort the mixer output if they turn everything up. It won't get any louder if the limiter is doing it's job but it'll still sound awful... See the current thread about djs for more!

[d&bhead]

and still pop the system at limited volumes???