BillFitzmaurice.info

I'm running a Driverack 260 in my B rig now and having an issue with the limiter.

I have the attack, hold, and release, set to minimal settings (what I had my DCX set to).

I set the Threshold to stop my amp at 60V (where I need it for my T48's)

Peakstop Off
Auto Off
Overshoot 0

When I run the gains up on my mixer the limiter holds the gain and my amp stays at 60V, no clipping, everything is good.

The problem is if I quickly snap the gain up to max the limiter doesn't drop the signal fast enough and the amp clips the voltage peaks up. If I knock the Threshold back a few DB I lose a ton of voltage on the amp side (from 60V to 40-42V), but the clipping stops.

I'm running the latest firmware and everything else is running correctly, but I can't seem to figure out why the limiter isn't grabbing the signal fast enough to keep the amp from over volting. My DCX did it no problem.

Anybody see this?

You want peakstop ON, not off... that's the feature that is supposed prevents this from happening.

Hey Brent,

I believe I tried it with that on, and it didn't help. I'll have some time to mess with that amp rack tomorrow and will report back.

Thanks!

Alright here's a screenshot of the limiter for the subs (even though this happens on all the limiters)

Peak stop is on, but isn't doing anything to help stop the sudden inrush that's clipping the amps. (The amp's clip lights come and the signal is clipped). So if I had a drummer slamming the kick to the beat, the amp would be clipped everytime he hits it. But if bass is sent through it brings the peak down and maintains that gain until the signal stops for a moment and then comes back. I've tried messing with all the settings. Best I can come up with is the processor isn't catching the signal fast enough.

Ideas? I'm ready to eBay it.

I might be on the wrong track, so apologies if that's the case.
I'm just trying to get some more info, in case it's not necessarily the 260 that's the issue.

With your mixer;
Did you set it up so the channel fader and master faders are at max, then adjust channel strip gain to just below clipping?
If you didn't, then if you bump any of the faders hard up, of course you will get clipping at the mixer, which always goes through the chain.

I'm assuming this is live sound rather than DJing because you're saying "if I had a drummer... etc", you can't just take one channel in the mix into account.
If every channel strip has a gain structure set up to just below clipping (with the channel fader to max), the resultant mix (usually demonstrated in masters PFL) will be often be clipping.

So, using your example, while setting that kick channel, you turn down channel strip gain (but leave the faders at max), so that it doesn't matter if the drummer is trying to put his beater through the head, it never clips. If he doesn't play that hard in some songs, level stays lower. You could bump the level in that case, but it may well be the drummer is simply trying to play with some dynamics.

The same applies if you are DJing, (ie inputing multiple CD's or MP3 players etc) and some songs have a higher gain compared to others. Just because the input channels aren't clipping doesn't mean the masters aren't. Songs with higher gain might be causing clipping as well.

Also, did you adjust input and output gains on the 260?

Grant,

Thanks for your response. Just to give you a little background, I've got quite a bit of experience with system processors and configuring things.

I'm pretty good with a sound board and the system is setup correctly. In my first post I mention that the processor is limiting to the correct voltage, but is not limiting fast enough to stop a pulsing audio signal (like a kick drum).

I'm setting the limiter similar to how you describe, if I swap a DCX2496 in this DriveRack's place, set it the same way, the problem is solved. Changing the input/output gains on the DR only changes just that, the gain. It may lower or increase the audio but it's not preventing a sudden jump in signal from clipping the amps.


I'm stumped.

With attack of .01, transients will still get through. How far over the desired limit is the signal peaking?

It's all good, wasn't doubting what you know

I'm hoping Brent is getting closer to solving your problem...

Brent,

Raising the attack doesn't help. It's limited to 60V. My DMM is catching about 78-80V but that number varies and may not be totally accurate because my DMM isn't all that quick. That's from switching a 80hz tone on/off.


Grant,

Any and all help is appreciated and sometimes we all have a "duhh" moment, so your post is right on point with trying to debug something like this.

Didn't get out the manual, so this is off the top of my head from my less than stellar memory.......

Based on the pic of the settings, it looks like OverEasy is engaged. If I remember right, that will allow it to go past the limit and bring it down easy....as in the name.

I think you want that set to off.


Edit.....now that I look at it again - it may be set to off. I don't know if you have to move the fader all the way over for it to be off or not. Anyway, check that out.

It's been a while since I set one of these up, so I went back and read through the manual. To start with, the 260 is not a brickwall limiter per se. However, with Peakstop, the manual does indicate that you should be able to achieve the desired functionality.

It looks like you have to turn Peakstop on, then lower your threshold by the number of db that you have set as your overshoot. In other words, if you want to limit to 60v and a +6dbu threshold does do that except for peaks, you should lower that to +4, with Overshoot of 2. That will keep you 2db below your limit normally, and "clamp" the peaks that the 0.01ms attack causes at the real voltage limit. All this makes sense for what you're measuring. If +6 is a 60 volt RMS limit, you'd have to double the power to 84v to achieve a 3db difference... given that you're getting 70-80v peaks, that's in line with 2db overshoot.

If it works, this should end up sounding better than a standard brickwall limiter which just squares off the wave and distorts. If it doesn't work exactly as it claims, then it probably isn't a suitable limiter for horn subs.

Brent,

Thanks for the help, I did as you describe but the results are the same. I think you're right, this thing is useless. I can't run this with DJ's

Anybody want to buy a Driverack 260??

Are you doing all the programming in the PC in System Architect? Have you tried manipulating the values on the device itself, or at least made sure that they are changing when you change them in SA?

I have had devices that responded sporadically to SA input. They work fine when you force update or do it from the control panel.

I had a strange, almost similar problem with my Driverack 260 when setting limiters for Osses quadstack of T30´s. We ran a 60hz testtone through the djmixer, and we couldnt get a stable voltagereading when we were adjusting the limiter to bring it down from my normal 55-56V to 50V for the T30s, and we just couldnt figure it out, Osse even left the place to and get his DR PA+ after we had isolated the issue to my 260. (stable voltage when we sent the signal from the mixer directly to the amps)

And then for some reason I got the idea to check the dynamics section, finding that the feedback eliminator was activated, and that when I deactivated it, we had a nice perfectly stable signal to the amp:) The feedback eliminator saw the 60hz testtone as a feedback and clamped the output, and ramped it back up moments later, to then clamp it down again and repeat.. I think it was on this board that I saw someone having a similar problem when running dubstep or some other lowbass electronic music.

So even if i dont think the feedback eliminator is causing this problem with the limiters that the OP has, it could perhaps be something similar..

At that gig I also found that if you set the limiter to, say 10db, with the gain at 0db, and then increase the gain, the output will also increase. I dont actually remember if it was input gain, crossover gain or the output gain (i belive there is an output gain?) But I remember that we were very surprised by it, we felt that all gain functions should be before the output limiter (anything else is f*ing stupid) and so should only make the limiter engage earlier, not increase the output! But I could be wrong, and perhaps all DSPs have their output gain after the limiter.

I also found that the manual says that you can set the Limiter attack time to 0,01ms, but that in reality the lowest value I can set on my 260 is 0,1ms..

It should be mentioned that mine is from like 2006, I bought it used, and I dont know if the firmware has been updated, I´ll check that tomorrow.

But, I have run my 2 T48s pretty hard, almost allways wide open amp (Lab 1600), almost allways with djs, and never had a problem, have not destroyed a woofer yet But, I think that the cliplimter in the amp actually stops the output at 55-56 volts, I havent tried without cliplimiter engaged, but will when I have time. But have not been able to provoke a higher output then 56V with the limiter in the DR 260 engaged, not even when setting it for 50V.

Feels a bit sad that an expensive DSP like the 260 can be outperformed be cheap behringer unit in some aspects though;)
And to be really frank, my 260 also has a problem with output 4, sometimes it simply doesnt work. Sometimes there is no signal on output 4 at startup, and a reboot fixes it, but if you connect or disconnect an xlr, no matter which one, out 4 turns of, and one time it turned of mid gig, and a reboot didnt fix it, that one could have been overheating.. But something is wrong with that unit.. Now I´ve simply routed the signals so that I dont use out 4, monosummed bass on out 3, and using the other 4 for bi-amping the tops.

Well, if the Driverack 260 is not good enough, what processors are??

//Robin

Robin_Larsson wrote: Well, if the Driverack 260 is not good enough, what processors are??

//Robin

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