Setting limiters on Berry LMS

Hey,

I wanted to set up limits on our bins, and was wondering if anyone could give a bit of an explanation on how it works. I have a berry LMS.

Had a play around with it but not entirely sure how to go about it

Thanks

Hi mate,

Bins are loaded with pd186's so RMS is 700W

Amp powering them is a Proline 2700 currently running one a side at 8ohm so 900W

Dont know what the input sensitivity is though im afraid? And am at work so cant find out till later.

Yep its a DCX2496

Cheers

drivebycar wrote: Hi mate, Bins are loaded with pd186's so RMS is 700W Amp powering them is a Proline 2700 currently running one a side at 8ohm so 900W Dont know what the input sensitivity is though im afraid? And am at work so cant find out till later. Yep its a DCX2496 Cheers

Hmmm ok, i cant find the 2700 input sensitivity either... bit annoying.

All the other t.amps seem to be 0.775v so ill do a worked example with that and if the 2700 is different just do it again with 1 or 1.4 or whatever it is.

Have a read of this thread from a while ago......

http://www.speakerplans.com/Forum/output-levels-input-sensitivity-dbu-dbfs-ummmm_topic23486.html?KW=%2B22dBu

... it will explain in a bit more detail the following maths.


0.775v = 0 dBu

The ultradrive says +22dBu = 0dBfs so in order to output 0 dBu we set the limiter to -22dBfs.

With the limiter set at -22dB the output from the ultradrive will be constrained to 0.775v and the output from the amp to 900w. To further drop this to 700w we work out the dB power ratio of 900/700 and subtract this from the previous -22dB...

10 Log (900/700) = 1.091dB

-22 - 1.091 = -23.091dB

Setting the limiter to -23.091dBfs should keep the output power down to 700w IF the proline has 0.775v input sensitivity. For different sensitivities see below.


0.775v = 0 dBu (as before )
1v = 2.22dBu
1.4v = 5.14dBu

So if for example its 1v not 0.775v just add 2.22dB to the previous answer giving -20.871dBfs.

Hope that makes some sense. If not then check that thread i posted ^ chickenfizz shows another method for working this out that is i think equivilant? not totally sure though.

LASTLY (at last!) I reckon you can probably safely put 900w into your bins anyway, would be very unlikely to cause a problem so you could just set the limiters to stop the amp clipping (-22dB) and not bother shaving off that last decibel

EDIT: utterly forgot about release time. This parameter changes how long the limiter takes to open up again (under the control of an envelope, it dosent just ping open suddenly once the times up!) I reccomend for proper "limiter" behaviour setting it for the longest time possible or at least 5 seconds.



Edited by AlfieDring - 10 June 2009 at 3:20pm

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.

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

jonminns wrote: I genuinely think ultradrive limiters are brilliant Fairly unaudible, and they work I've overpowered v18s in tough boxes with the limiters taking 12dB off constantly all night to see what happens... nothing DBX DRPA limiters are sh*te however

+1  used correctly they can be very useful

Tony