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Ultradrive DCX2496 Gain, Clip & Limiter Setup

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URL: https://forum.speakerplans.com/forum_posts.asp?TID=43567
Printed Date: 29 March 2024 at 3:51pm
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Topic: Ultradrive DCX2496 Gain, Clip & Limiter Setup
Posted By: Biggus
Subject: Ultradrive DCX2496 Gain, Clip & Limiter Setup
Date Posted: 29 September 2010 at 10:10am

I’m still quite new to professional PA setup so please forgive me if some of the things I ask are obtuse, but I’m still learning. I’ve done a search on the forum but can’t find direct answers to what I want to know.

At present I’m setting up my berry DCX2496, I have the X-over and outputs configured to tri-amp as my system runs three ways, tops, mids and subs. The system is wired up Mixer – EQ – DCX – Amps. I’ve read that a good method to setup a sound system is to calibrate the VU meter  levels of each device in the chain, for example if my mixer was reporting the output program is bouncing at about 0db than I’d adjust the input gain on my EQ & DCX to match this so everything is bouncing the same, I can understand the logic in doing this as if the mixer reports its not clipping then you know nothing else in the chain is either, but according the vu meters on the DCX it reports it goes to 0db then starts clipping at anything louder and the mixer/EQ has a +10db before they do, trying to put this in to logic terms does this mean I will have to always play my program material at 0db and no louder to prevent clipping or am I missing something here?  
 
Another thing I can’t get my head around is what to set the outputs levels of my DCX before going to the amps, they seem a lot lower than the input levels I presume this is because the signal is broken up into it separate frequency bands i.e tops, mids and bass, should I set the gain of the outputs db to match the input db so each of the amps is getting its maximum input level?
 
I would also like to set my system up so nobody can turn the increase the volume of the amps. I’ve read the best way to do this is to turn the volume on the amps to maximum and then set the output limiter up on the dcx, I’m aware on how to set the limiter up on the DCX but taking in the above to consideration would I set my limiter at the clip level or  much lower?  or would  I be better setting up some kind of dynamic eq to turn the volume down when the DJ goes into clipping? 
 
I would be very grateful of any answers or advise.
 
Kind Regards
Mark Biggus



Replies:
Posted By: JaKe
Date Posted: 29 September 2010 at 10:44am
The levels on the DCX are a little confusing 0dB on the DCX is actually +22dBu.
For overall protection look at a Drawmer SP2120 or an AVC2 as the DCX limiters will not protect against over enthusiastic DJ's etc.
Dynamic eq's may help but that isn't really what they were intended for  and use a lot of cpu. - why the &*@! they didn't build in a gain reduction option into the unit is beyond me.


Posted By: djyves
Date Posted: 29 September 2010 at 10:45am

The 0db on the vu meters of the dcx, are the limits of the dcx itself.

The input and output levels on your dcx:
Start with just 0db, then if there's anything missing, turn your subs, mids, highs up.
 
So you will need to set your limiters much lower than 0db (according to the vu on the dcx), connect your amps without speakers to your dcx. then turn the thereshold back until the clip lights of your amps go out, and then set it 0.5db or so lower, just for safety.
(Then connect your speakers and) drive your dcx in the limit and check if the limiters work.


-------------
"If brute force doesn't work, you're just not using enough!"


Posted By: djyves
Date Posted: 29 September 2010 at 10:47am
mmm... same time.
 
Like Jake said, the limiters on the dcx are not an good protection against some (enthousiast) dj's


-------------
"If brute force doesn't work, you're just not using enough!"


Posted By: Biggus
Date Posted: 29 September 2010 at 11:30am
Thanks for your replys its starting to make sense now.
 
Originally posted by JaKe JaKe wrote:

The levels on the DCX are a little confusing 0dB on the DCX is actually +22dBu.
As if I'm not confused enough already! This unit must clip high then as all my other equipment clips at +12db. Where would +10db be on the be on the dcx input vu so I have a idea if my inputs are bouncing OK.
Originally posted by djyves djyves wrote:

Start with just 0db, then if there's anything missing, turn your subs, mids, highs up.
Lol where is 0db on this DCX VU meter?
 
For the situation where I don't want people turning my amps up would I be right in saying that if I turn my amps to full and then reduce the gain on the dcx output channels on until the clip light just goes out or my prefared sound levels,  I just think this way nobody will be able to turn the amps up any louder and then just set limiter just above this volume so no idiot can try turning it up on the eq volume etc? would this be a sensible idea?
 


Posted By: Tony Wilkes
Date Posted: 29 September 2010 at 12:11pm
I don't understand why you reckon the limiters are no good for stopping Idiot DJ's. They work perfectly if set right. The sound does degenerate badly if they are ragged senseless but the gear is protected and the DJ is shown for the Knob that he is.

Tony



-------------
www.forteaudio.eu - BMS - db-Mark Processors - Lexon (SAE)


Posted By: colinmono
Date Posted: 29 September 2010 at 5:01pm
Originally posted by Biggus Biggus wrote:

As if I'm not confused enough already! This unit must clip high then as all my other equipment clips at +12db. Where would +10db be on the be on the dcx input vu so I have a idea if my inputs are bouncing


As Jake said, full scale i.e. 0dB on the markings (0dBFS for short) on the Ultradrive = 22dBu. This is because it is a digital unit, meters on digital kit are often marked up like this, showing the dB relative to the "full scale" i.e. the maximum voltage the input can handle. It is very confusing when you've only used analogue kit before.

+10dBu = -12dBFS on the Ultradrive
0dBu = -22dBFS on the Ultradrive

For most analogue pro audio gear, 0dB on the VU meter equates to +4 dBu at the master output. This is not a hard and fast standard, but its a reasonable rule of thumb. The Vestax mixer I use measures about 4.5dBu when the 0dB VU LED's are lit. Another example - from the Allen & Heath Xone 62 Manual: "Meter ‘0’ represents +4dBu at the XLR outputs".

So...

0dB on Mixer = -18 dBFS on the Ultradrive
+10dB on Mixer = -8 dBFS on the Ultradrive

This calculator is useful in getting your head round dBV, dBu and VRMS:

http://www.sengpielaudio.com/calculator-db-volt.htm - http://www.sengpielaudio.com/calculator-db-volt.htm


Posted By: Biggus
Date Posted: 29 September 2010 at 5:17pm

@Colinmonro> Thanks for the info.

Just to make it clear if I was plugging in my analog mixer in to the ultradrive should I be bouncing about -12dBfs on on the VU meter before the analog signal goes into clip?
 
--- Don't want to make this even more confusing but if I was using a digital input would I bouncing right up to 0dbfs


Posted By: colinmono
Date Posted: 29 September 2010 at 5:33pm
Personally, I tend to come at it from the other end - look at what signal your amplifier needs to drive it to full output, and then set the limiter on the ultradrive so you don't go over that.

E.g.

If your amplifier input sensitivity = 1 VRMS = 0dBV = 2.2dBu
Set output limiter on Ultradrive to -19.8dBFS = 2.2dBu

Now, if you play your music so you are hitting -2dB on your mixer (0dB on analogue meters is usually +4dBu, so -2dB on the meter should correspond to +2dBu output), you should be just bouncing off the limiter (assuming the Ultradrive and EQ gain settings are at unity).

---

Re: digital input.... I'm not sure you really want to start thinking about that until you get your head round your current setup!


Posted By: colinmono
Date Posted: 29 September 2010 at 5:34pm
p.s. the name's Colin by the way, or colinmono if you prefer, not sure who this colinmonRo character is, perhaps my glamorous alter ego LOL


Posted By: Pirlo
Date Posted: 29 September 2010 at 11:56pm
JaKe, wich one would ya prefer (drawner or FS) and why!?
I´m searching for a 100%-secure-way to protect my stuff against the announced "enthusiastic DJ's", using a 336T as ls-management at the moment that have the same "protection-problem" then the berry (...or I´m unable to set it well, also possible, but think an additional protection could not be bad)
Ideally it should be absolutly inaudible in the signal-chain if it just "watch" and not protect.

Originally posted by JaKe JaKe wrote:

The levels on the DCX are a little confusing 0dB on the DCX is actually +22dBu.
For overall protection look at a Drawmer SP2120 or an AVC2 as the DCX limiters will not protect against over enthusiastic DJ's etc.





Posted By: jbinks
Date Posted: 30 September 2010 at 9:51am
Originally posted by Pirlo Pirlo wrote:

a 100%-secure-way to protect my stuff against the announced "enthusiastic DJ's"

Formula Sound AVC2
Bomb-proof.

Some people argue that they make it sound pants, but that's only after the DJ has cranked the level to (about) 22db ABOVE the limit. At that point the inputs on the AVC2 are clipping their stages and there's nothing that the unit can do about that.

I have AVC2s in every rack, they're brilliant! You simply can't "turn it up" past the level that the AVC2 is set to. If you do, it just turns it back down in sync. It has a series of red lights on the front that show it is attenuating and by how much you need to reduce the input. It also has a +10v output that you can use to drive a "reduce mixer output now, you stupid chump" light via a small relay/transistor.




As for the VU meters on the Ultradrive, I never see anything on them! Nobody does. Just ignore them! The only useful lights on the unit are the "clip" lights on the outputs. These come on at the point that you have set your limiter so you know it is affecting the output.

I did think about making some -20db pad/attenuation XLR-XLR cables at one point (one for each output) so that I could run the outputs with less/no attenuation in the DCX. That would bring the VU meters to life and make it look pretty, but I decided it was ultimately pointless and wouldn't actually achieve anything useful. It would also introduce the possibility of people playing with the cabling and swapping cables etc.


Posted By: Pirlo
Date Posted: 30 September 2010 at 12:20pm
Yeah, read about it before - I would use the +10v as relay-trigger-output for the 380v-DJ´s-balls-clip, that should be work! Wink LOL

The sound when in "protect" could be as bad as possible, together with the ball-clip, äh red-light, even the last idiot should recognize whats on!

Last questions here.
1.) do ya use it in the monitor-path as well!?
2.) Why companies like BSS built in things called "limiter" if they don´t work as a limiter should be!?
Would be "soft-limiter/watcher" not the better designation Confused




Posted By: toastyghost
Date Posted: 30 September 2010 at 12:55pm
Originally posted by jbinks jbinks wrote:

You simply can't "turn it up" past the level that the AVC2 is set to. If you do, it just turns it back down in sync.


This was my biggest issue with it really, if the DJ was stupid enough to not realise that pushing the mixer hard into the red is going to sound crap then they certainly didn't understand (or want to) that turning it up more made it go quieter until it eventually sounded a bit like a bad MP3.

Also, a lot of promoters seem not to care about the reason why the rig sounded weird and quiet for the headliner's set, just that it did and that can potentially cost you work.

A Drawmer SP2120 does the same job, with a cleaner effect to my ears, but keeps the volume at the same level rather than reducing it. That makes it more or less just a limiter, and one that you can leave wired in without having to take the time to explain to each DJ or the promoter how it works.


Posted By: massisoda
Date Posted: 30 September 2010 at 3:45pm
If my amplifier input sensitivity is 0,77 (like proline 3000) i have to set DCX2496 limiter to ?

thank you


-------------
Italian Sound


Posted By: Pirlo
Date Posted: 30 September 2010 at 4:02pm
Originally posted by toastyghost toastyghost wrote:

A Drawmer SP2120 does the same job, with a cleaner effect to my ears, but keeps the volume at the same level rather than reducing it. That makes it more or less just a limiter, and one that you can leave wired in without having to take the time to explain to each DJ or the promoter how it works.

Thats why I ask if ya put a second unit in the monitoring-path as well!?
I would set the second then a bit more "aggressive" then the main-one so se dj will notice (I hope so).

Finally the "better" the person behind the desk the better will be the sound at all but to many idiots outside these days! Angry


Posted By: colinmono
Date Posted: 30 September 2010 at 4:05pm
Originally posted by massisoda massisoda wrote:

If my amplifier input sensitivity is 0,77 (like proline 3000) i have to set DCX2496 limiter to ?


Use http://www.sengpielaudio.com/calculator-db-volt.htm - http://www.sengpielaudio.com/calculator-db-volt.htm

To convert input sensitivity (VRMS) to dBu, and use that to answer your question... post again if you are still stuck!


Posted By: massisoda
Date Posted: 30 September 2010 at 4:12pm
If your amplifier input sensitivity = 0.77 VRMS = -2.27 dBV = -0.052 dBu

Correct?

How to convert this -0.052 dBu in dBFS for set the limiter in DCX2496?

-19.8dBFS : 2.2dBu = x : 0.052 dBu

I have to find the X?

Thank you


-------------
Italian Sound


Posted By: colinmono
Date Posted: 30 September 2010 at 4:29pm
Originally posted by massisoda massisoda wrote:

If your amplifier input sensitivity = 0.77 VRMS = -2.27 dBV = -0.052 dBu

Correct?

How to convert this -0.052 dBu in dBFS for set the limiter in DCX2496?

-19.8dBFS : 2.2dBu = x : 0.052 dBu

I have to find the X?

Thank you


You are nearly there.

Once you have the sensitivity in dBu, just remember that 0dBFS on the Ultradrive = +22dBu.

The equation to give you the answer:

(Amp Sensitivity in dBu) - 22 = (Meter Reading on Ultradrive in dBFS)

So...

0.052dBu - 22 = -21.948dBFS




Posted By: massisoda
Date Posted: 30 September 2010 at 7:46pm
Ah ok,perfect!

I have to set to -21.95 the limiter on the DCX2496 correct?

thank you


-------------
Italian Sound


Posted By: kedwardsleisure
Date Posted: 30 September 2010 at 7:52pm
Quote the limiters on the dcx are not an good protection against some (enthousiast) dj's


They should be, thats what they're designed for. We've had this discussion before.

Probably fair to limit the DCX well before the amp clip so you get a bit of headroom for the poor amps. DJ's tend to 'ride' limiters meaning the amp will spend all night just below clip.



-------------
Kevin

North Staffordshire



Posted By: Dom
Date Posted: 30 September 2010 at 8:35pm
The limiters on the dcx also often don't go low enough...

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"It sounded like a million fire engines chasing ten million ambulances through a war zone and it was played at a volume that made the empty chair beside me bleed."


Posted By: colinmono
Date Posted: 30 September 2010 at 9:21pm
Originally posted by massisoda massisoda wrote:

Ah ok,perfect!

I have to set to -21.95 the limiter on the DCX2496 correct?

thank you


Yep that's right. For maximum safety use the maximum release time. Shorter release times will make the limiter behave like a compressor. The long term average level will increase if the system is driven hard into the limiters.

For live music you'd be ok with a shorter release time.


Posted By: massisoda
Date Posted: 21 October 2010 at 3:57pm
Originally posted by colinmono colinmono wrote:


Yep that's right. For maximum safety use the maximum release time.


Maximum release time is 4000 ms,is not too much?

thank you Tongue


-------------
Italian Sound


Posted By: colinmono
Date Posted: 21 October 2010 at 4:22pm
Originally posted by massisoda massisoda wrote:

Originally posted by colinmono colinmono wrote:


Yep that's right. For maximum safety use the maximum release time.


Maximum release time is 4000 ms,is not too much?

thank you Tongue


All depends on the program material, and the person driving the input to the DCX.


Posted By: chilli
Date Posted: 21 October 2010 at 5:20pm
i originally thought that the berry limiters wouldnt do the job, but i was wrong.

Set up correctly i've had a dj spank the living daylights out of a mixer with the limit lights on solidly for hours and provided you've set the limiters correctly nothing gets toasted. ok it sounds a bit crap when being abused so heavily, but you just cant tell some people.

i know how to set the limit for the system its running, and its absolutely fine.


-------------
Money can't buy you happiness, but it can allow you to be miserable in comfort.


Posted By: kedwardsleisure
Date Posted: 21 October 2010 at 7:05pm
Quote The limiters on the dcx also often don't go low enough


If you bring the channel gains up on the input section then the signal will be at a higher level where it enters the limiter, meaning the threshold can be set effectively. If the DCX output is then too strong for the amp, turn the output channel gains down.



-------------
Kevin

North Staffordshire



Posted By: massisoda
Date Posted: 21 October 2010 at 7:23pm
Originally posted by chilli chilli wrote:

i originally thought that the berry limiters wouldnt do the job, but i was wrong.

Set up correctly i've had a dj spank the living daylights out of a mixer with the limit lights on solidly for hours and provided you've set the limiters correctly nothing gets toasted. ok it sounds a bit crap when being abused so heavily, but you just cant tell some people.

i know how to set the limit for the system its running, and its absolutely fine.


how do you set it?


-------------
Italian Sound


Posted By: massisoda
Date Posted: 21 October 2010 at 7:27pm
Originally posted by colinmono colinmono wrote:

Originally posted by massisoda massisoda wrote:

Originally posted by colinmono colinmono wrote:


Yep that's right. For maximum safety use the maximum release time.


Maximum release time is 4000 ms,is not too much?

thank you Tongue


All depends on the program material, and the person driving the input to the DCX.


We play music of every type for party(dance,pop,rock,techno,house ecc ecc).we use
a pc for source connected to a usb mixer(Proel m8 usb).After the mixer a DBX 266Xl,then a digital equalizer connected to te pc a Alto Digan 2.30,and then two dcx2496(the system is a four way,before we have two cx3400)....


-------------
Italian Sound


Posted By: kedwardsleisure
Date Posted: 21 October 2010 at 9:51pm
The 4000mS for system protection is ideal. You dont want it much shorter or it'll come out of gain reduction before the thing that triggered it has gone! The unwanted result would be dynamic compression or system pumping which could stress the sound system more, not less.





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Kevin

North Staffordshire



Posted By: LionsPaw
Date Posted: 18 January 2011 at 10:25pm
Originally posted by kedwardsleisure kedwardsleisure wrote:

Quote The limiters on the dcx also often don't go low enough


If you bring the channel gains up on the input section then the signal will be at a higher level where it enters the limiter, meaning the threshold can be set effectively. If the DCX output is then too strong for the amp, turn the output channel gains down.



Are you sure? I've just tried to set the limiters and find that the amp clips before the limiters come on, even set at a minmium threshold. 
 Using what you said and turning the input gain up and the output gain down, it appears that turning down the output gain down stops the limiter from coming on at all.


Posted By: jerronimo
Date Posted: 19 January 2011 at 7:13pm

Im also new to all of this, but should it not be the other way around?

The signal reaches the output gain first and then the xover,eq limiter etc. at least thats what the manual says.
So I think a higher output gain would be more beneficial to let the limiter cut the signal.


Posted By: kedwardsleisure
Date Posted: 19 January 2011 at 7:33pm
Quote turning down the output gain down stops the limiter from coming on at all.


In my V1.1 manual on disc it shows the output gain as being before the limiter in the block diagram, so what you say happens I'd agree with. But I've played to my hearts content with a couple here and in installs and the output gain hasn't altered the level that drives the limiter. Maybe there are different firmware versions around?

-------------
Kevin

North Staffordshire



Posted By: jerronimo
Date Posted: 19 January 2011 at 7:44pm
Latest firmware is 1.6


Posted By: jacethebase
Date Posted: 19 January 2011 at 9:54pm
We have 2 DCX's and the limiters are fine better if set correct. Nothing is better than good old fashion standing behind the foh console turning it down tho IMHO.
Before I have put a note on the decks saying if you red line it hard I will turn the monitors off, Turn them off and watch the level come down!

Jace


-------------
www.wedding-production.co.uk

www.stage2sound.com



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