Setting limiters on Berry LMS

AlfieDring wrote: Timebomb wrote: Yeah Proline 2700 is 0.775V unloaded which is -23.5dB on the dcx, the clip point drops a bit when you put some speakers on it and drive them them with a signal though, due to the voltage drop, we have had to put the limiter down to -24dB on the dcx (as far as it will go) and take the input attenuator on the amp down a little to stop it clipping.  Calcluated settings are never spot on, it depends on how much vairation in voltage gain your getting through the amp, wich vairies under different conditions. @ Drivebycar, listen to this ^^^! Real world conditions always take priority over the calculations of an unknown stranger @ Timebomb, what your saying is good advice overall but where's this -23.5dBfs on DCX figure come from? Have you measured it to be different from whats indicated in the manual? The specs indicate -22dBfs for 0.775vrms not -23.5

Edit, The -23.5dB limiter setting for the Proline came from sheet of limiter settngs i made up for different amps a while ago.  I was just taking it down another 1.5 dB to compensate for loading.

EG the behringer amps state +4dBU, so thats -18dB on the limiters, but thats loaded at 8 ohms (i think its 8 ohms, not sure).  Unloaded the behringers clip with the limiter at about -16.5dB.

The proline input states 0.775V, which is 0dBU, so the limiters can be set to -22dB, but thats unloaded, so i took another 1.5dB off for the seting sheet i made.    

Yeah for 0.775V input you could start with the limiter at -22dB, but keep an eye on the amp and be prepaird to take it down a bit.

Also worth noteing that the behringers input sensitivity is 3dB lower when in bridge mode, im not sure on the QSC equivilent though, i know the qsc 4050HD is the same in bridge/stereo mode.


Edited by Timebomb - 11 June 2009 at 5:01pm

If the RMX is the same as the behringer EP2500 wich mostly it is, then yeah -18dB is about right.

drivebycar wrote: So have the amps right open, and limiter set up as above, then bring the amp down if necessary?

Yeah, or bring the limiter down a bit more if needed and leave the amps fully up.  Though the DCX limiter only gos to -24dB so you might have to take the amps down a little.

Timebomb wrote: Also worth noteing that the behringers input sensitivity is 3dB lower when in bridge mode, im not sure on the QSC equivilent though, i know the qsc 4050HD is the same in bridge/stereo mode.

Can you clarify this? are you saying it's 3dB less sensitive, ie requires +7dBU for full output, or the other way, +1dBU?

I might have to do a bit of Berri bridging soon.

Thanks

Kieran

Thanks, very useful info, I'll give that a go.

I've sometimes used a less scientific approach and set the limiters as low as they go, -24dB, put a loud signal into the dcx, turned the amps up full, then raise the limiter until the amp just clips, then lower it a notch. A bit risky if you want to limit power to the driver, but works ok if you just want to avoid clipping. Not very easy when the amps are at the end of a 50m multicore though.

Exactly that, sometimes you have a weak signal, sometimes a strong one.  Changing input sensitivity just changes the working level or gain range of the input stage. 
Nothing will make your amp "louder", for a given set of connected speakers there will be a max spl based on the speakers sensitivity, power handling and power supplied.  The max amp power doesn't change, the sensitivity figure just tells you how large an input signal will produce full output.

If you use a higher sensitivity (ie 0.775V) Then yes, you will need the limiter to start working at a lower level, as the amp will reach its limits with a smaller input signal.