Which limiters are good enough?

Re: Which limiters are good enough?

Richard Stringer said:
Thanks, I really apreciate all the help you guys have given me, any ideas on some pretty good limiter settings? I thought about these :

Attack Time : 1-5ms
Release Time : 100ms
Ratio : Infinity
Threshold : I turn that down until the amps stop clipping (when setting gain structure without a load connected to the amplifiers)
Output Gain : whatever number in db that the threshold has to be set to, so if the threshold is -10db (just an example) then the output gain would be set at 10db.

Is that right guys?
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If you want your limiters to actually protect your speakers, then you want your attack time as quick as possible. I like 0ms attack time personally. Release time depends on what you want your limiter to sound like. A longer release is going to pump more, while a short release time is going to be "choppy" sounding. My release time normally hovers around 80-90ms. Gets out of the way fast and sounds fairly transparent.

Output gain should be at 0. Adding 10dB of gain to your rig is going to completely change your gain structure and make your limiter setting completely useless. That 10dB(or whatever) of added gain is going to make your amps clip 10dB before your limiter even kicks in.




Evan
 
Re: Which limiters are good enough?

Bennett Prescott said:
The question is, does the red mean anything?

You're probably safe not tapping any amp limit/clip lights, but you may be throwing away a lot of potential system performance.
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+1

There has been a noticeable amount of increase in output/headroom since I switched to a DSP with 2 stage limiting with look ahead peak limiting. I can get more impact out of the rig and not worry about blowing stuff up. If you're running below clip all the time vs. right at or slightly into clip, especially with low frequency drivers, you're probably missing out on a few dB of extra umph. Maybe even more. Some people may poo poo 3dB. But in my experience, it's a noticeable amount of output. FWIW, I never allow my horns to clip at all. But they can easily outrun the rest of my rig even if the subs/15s/10s were into limiting and would be extremely painful in my venue if they ever got anywhere near clip ;)
 
Re: Which limiters are good enough?

Greg Cameron said:
+1

There has been a noticeable amount of increase in output/headroom since I switched to a DSP with 2 stage limiting with look ahead peak limiting. I can get more impact out of the rig and not worry about blowing stuff up. If you're running below clip all the time vs. right at or slightly into clip, especially with low frequency drivers, you're probably missing out on a few dB of extra umph. Maybe even more. Some people may poo poo 3dB. But in my experience, it's a noticeable amount of output. FWIW, I never allow my horns to clip at all. But they can easily outrun the rest of my rig even if the subs/15s/10s were into limiting and would be extremely painful in my venue if they ever got anywhere near clip ;)
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And, as I said before, if he's constantly into clip and he brickwall limits the signal just below clip, he's just going to decrease the dynamic range, increasing the heating capacity of the signal, blowing up his drivers that much faster. Unless, of course, the amplifiers' maximum continuous output is less than what would blow the drivers. In which case, no limiters are needed anyway!
 
Re: Which limiters are good enough?

If I managed to save up for a used XTADP426 would that provide me with near total protection? I know the DP series have RMS and Peak voltage limiting. Or is the only way really, to save up for as long as it takes to get used Crown I-Tech amps to power my system?
 
Re: Which limiters are good enough?

I'm from the UK thouhg and over here that kind of thing is extremely expensive, even used. A used Crown I-Tech4000 here sells for a minimum of £1,500 ($2,385) so the Lake would sell for easily over £2,000 I should think if they're about £3,000 new.
 
Re: Which limiters are good enough?

Evan Kirkendall said:
ASSuming you set your limiters right
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THAT is the key. RIGHT involves a bit more than keeping the amp out of clip. It ALSO involves keeping the driver from overheating-due to a higher average power. That is why knowing the point of power compression is important. That number is not so easy to come by.

One of the misunderstood aspects of limiting is NOT to use the limiter much. Let it be there just for the occosional "oops" that come along. a PROPER sized system is the answer.

I hear it all the time "but the amps never clipped!". YEAH-but the signal was buried in the limiter-therefore raising the AVERAGE-long term power-which means there is more HEAT going on-and therefore more possibility of failure.

As I said earlier-there are several different tyhpes of limiters-which do different things. They are all important-depending on what the "particular problem" is.

There are no magic bullets in audio. It depends-on a number of different factors.
 
Re: Which limiters are good enough?

Richard Stringer said:
I'm from the UK thouhg and over here that kind of thing is extremely expensive, even used. A used Crown I-Tech4000 here sells for a minimum of £1,500 ($2,385) so the Lake would sell for easily over £2,000 I should think if they're about £3,000 new.
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Hit up Aron at Audio Rent or Andy at Concert Sound and tell them I sent you. They'll hook you up.


Evan
 
Re: Which limiters are good enough?

Evan Kirkendall said:
Hit up Aron at Audio Rent or Andy at Concert Sound and tell them I sent you. They'll hook you up.


Evan
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Thanks Ivan fro that info, I really apreciate it. Evan, i'll have to see because i've added up import duty after contacting Customs And Exise and the price comes to well over £1,000 to get it to my door, and that's way more than I can afford for now, it'd take me 3 months to save up that much. But if I can manage somehow to save up that much i'll contact one of those guys you said about, and thank you for the help.
 
Re: Which limiters are good enough?

Ivan Beaver said:
THAT is the key. RIGHT involves a bit more than keeping the amp out of clip. It ALSO involves keeping the driver from overheating-due to a higher average power. That is why knowing the point of power compression is important. That number is not so easy to come by.

One of the misunderstood aspects of limiting is NOT to use the limiter much. Let it be there just for the occosional "oops" that come along. a PROPER sized system is the answer.

I hear it all the time "but the amps never clipped!". YEAH-but the signal was buried in the limiter-therefore raising the AVERAGE-long term power-which means there is more HEAT going on-and therefore more possibility of failure.

As I said earlier-there are several different tyhpes of limiters-which do different things. They are all important-depending on what the "particular problem" is.

There are no magic bullets in audio. It depends-on a number of different factors.
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Read this several times and then read it again. The bottom line is bring enough racks and stacks to do the job PERIOD. "Enough" is more than you need to do the job. Anything less is not "enough." If you are pushing the system you did not bring "enough." A limiter is for an "oops." It is not there so you can get your average level louder if you want your system to live a long and productive life. I went 10 years with a company as the chief engineer without 1 blown driver ever, and this was before the days of digital processing. I always brought 1.5 times the power that was specd and never saw the FOH meters hit the top ever, not even an occasional blink. I caught some flack from the owner in the beginning because of the extra labor involved but he soon figured out that not replacing even 1 JBL driver more than made up for any additional labor and truck space. We never even reconed a single driver for maintenance during that 10 years and we were out with alot of very loud Southern Rock bands. The other little tidbit for not blowing up speakers is use EQ as a cut only device as a general rule but that is for another thread.
 
Re: Which limiters are good enough?

Ivan Beaver said:
Just like building a bridge. Building a bridge to carry a specific load is pretty easy. Building it to "just barely" carry that load-is WAAYYYYYYY HARDER. Most people want to be able to run "right up to the edge" and not have a problem. That is very hard to do. So setting the limiter where it "kicks in" nice and early gives a better guarantee-but less overall output.

As will all things in audio-doing "really right" is often very hard. Kinda getting by-is much easier.
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Very good analogy. The best solution to prevent blowing up gear is to make sure you have enough that you're not driving it to the edge. If I EVER see a clip light during a show, that means I didn't bring enough.

I run DR260's on most of my rigs, and have the peak limiter in place just in case things go horribly wrong. But they aren't there to kick in during a show. i.e., bad cable, someone drops a mic, etc. My power amps are matched so that out of clip, the RMS power run for extended periods should not be a problem. You'd have to try REALLY hard to push it to the limit long enough to blow it.

Of course, running this way means bringing in more speaker to do the job than you could get by with if running to the edge, but if you bring in $1000 worth of speakers and end up blowing them up every couple years, or bring in $2000 worth of speakers and never blow a single one, which way are you going to come out ahead?
 
Re: Which limiters are good enough?

Hi Silas,

Silas Pradetto said:
Essentially nothing analog will work as a peak limiter to avoid blowing drivers, since to limit peaks the ability to 'look ahead' in time is required. Something analog could work if you don't mind limiting early, losing headroom.
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There's no shortage of analogue compressor/limiters where the limiter is a clipper that clips off the signal until the compressor has chance to ramp down the gain. If you integrate a delay you can, as you say, "look ahead" and start ramping down the gain early, so avoiding the clipping.

A regular compressor/limiter can't provide long-term power limiting, since they reduce the dynamic range of the signal (which increases average power) rather than reducing the overall signal (while preserving the dynamic range).
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This is a function of attack and release times. A compressor/limiter is essentially a fast-reacting hand on a fader: it ramps down the gain while the signal is over threshold and then ramps it back up again when the level drops below threshold. The appropriate attack time is usually a function of the lowest frequency within the bandpass (so it reacts quickly but doesn't audibly distort the waveform).

In fact, I don't know of any processor that implements a decent average power limiter, except maybe the Lake stuff. The only average power limiters I know of are the ones in DSP amps, which doesn't apply to you.
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I don't think there's a shortage of loudspeaker processors with RMS limiters as this is usually the primary requirement for loudspeaker protection. If you're lucky enough to be using an amplifier rated more than 3dB above the driver's power rating, you might consider a peak limiter as well.

BTW, I'd second Evan's recommendation of the DCX2496 as a budget loudspeaker processor. It includes a combined RMS and peak limiter.

Nick
 
Re: Which limiters are good enough?

Eric Cagle said:
Read this several times and then read it again. The bottom line is bring enough racks and stacks to do the job PERIOD. "Enough" is more than you need to do the job. Anything less is not "enough." If you are pushing the system you did not bring "enough." A limiter is for an "oops." It is not there so you can get your average level louder if you want your system to live a long and productive life. I went 10 years with a company as the chief engineer without 1 blown driver ever, and this was before the days of digital processing. I always brought 1.5 times the power that was specd and never saw the FOH meters hit the top ever, not even an occasional blink. I caught some flack from the owner in the beginning because of the extra labor involved but he soon figured out that not replacing even 1 JBL driver more than made up for any additional labor and truck space. We never even reconed a single driver for maintenance during that 10 years and we were out with alot of very loud Southern Rock bands. The other little tidbit for not blowing up speakers is use EQ as a cut only device as a general rule but that is for another thread.
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This needs to find a way into the wiki, there is wisdom in Ivan's post and Eric's experienced response.

My little tirade: "system protection" limiting is a frequent flyer on multiple forums. The "been there, do that for a living" guys know that there are no "right on, magic bullet" answers for the implied needs of those who do not bring Enough Rig for the Gig®. Reducing dynamic range even further puts even more thermal stress on every component. Continuously operating a system on the edge of transducer or amplifier thermal limits is certain to fail and almost assuredly during a critical show. From a 'drive' standpoint, there is so much gain ahead of the amp outputs that an "oops" or "oh SHIT" moment might be just the amount of stress needed to push a thermally saturated voice coil over the edge. The limiter can't save you in this circumstance.

Also consider that "system protection" limiting is something that the Junior Varsity did without for a very long time. When I was a "guy with a van load of PA", I paid for some recones and diaphragms, some amp output stages and other repairs. It was tuition at the Ye Olde Skool of Harde Knox. I learned what stressed components sound like and learned the art of manual control. And I bought more rig.
 
Re: Which limiters are good enough?

There have been some truly masterful responses here but when DO you set limiters in live sound? Personally I have lots built in to both analog and digital possessors and for live work I just leave them off. I feel my active rigs have enough protection built in already and my passive rigs are powered to my liking.

Am i right in thinking this is for and occasion when you have vastly more headroom then you could ever use and need to put the handcuffs on a potentially out of control band engineer?
 
Re: Which limiters are good enough?

I find limiters to really come in handy personally. There's 2 things that I find them useful for:

1. On my personal rigs- I keep my DSP's at FOH. When the limit light comes on, it's a stop sign for whoever is mixing. I tell my engineers when you see the red lights flashing, that's all she's got and don't turn it up anymore. It's a good way to know where you are without having to watch the amps.

2. On my touring rigs- It's hard to know in advance how hard you're going to be hitting a PA. We always try to bring in as much as possible, but sometimes that just isn't enough(weight limitations, height limitations, ect). When those "oh shit" moments occur, the limiters allow me to get the absolute most out of the system. IMO, all of the Clair rigs I take out sound their absolute best when you're just starting to tap the limiters. I know the lake limiters will keep the rig safe, and I know Clair has them dialed in to a point, where I can ride them lightly and it actually sounds really damn good. But, just a little too far and it goes to shit. It's all about knowing the limitations of the box, and keeping it within those limitations. Limiters will help you stay there, but ultimately, it comes down to using your ears.

As far as the whole "limiting an out of control engineer," I wouldn't do that either. A truly ignorant engineer will just push further into those limiters you're trying to set to keep him quiet, and you'll end up sending a higher power average to your speakers, and could do more damage than just letting him suck out loud. If anything, turn him down on the DSP and let him run out of headroom on the console.



Evan
 
Re: Which limiters are good enough?

Guys, it sounds like you're getting annoyed with me thinking I run my system menacingly hard, the fact is, I do run my system on full, but I don't take it to the very edge of what it can do. Also, I CAN'T AFFORD ANYMORE SYSTEM, SO CAN'T BRING MORE THAN I NEED. But, if I see a red light I personally ALWAYS turn it down, straight away, I see red clip lights as bad, I don't see clip lights as a sign of everything being near the limit but being ok to be pushed harder. That's why in 17 years of doing small dance events and working with speaker systems (on an amateur level on and off) i've never blown a single driver, EVER. I'm not a professional sound engineer and can't afford the absolute best equipment, but i'm intelligent enough to know how hard my system can run safely, so that it'll last me years. I'm gonna keep hiring out the XTA DP226 until i've saved enough money to get myself one of them Lake speaker management systems, this one in fact :

XTA DP 226 - Dolby Lake Contour DSP 2 x 6 DSP with AES EBU digital inputs | eBay
 
Re: Which limiters are good enough?

Richard Stringer said:
That's why in 17 years of doing small dance events and working with speaker systems (on an amateur level on and off) i've never blown a single driver, EVER. I'm not a professional sound engineer and can't afford the absolute best equipment, but i'm intelligent enough to know how hard my system can run safely, so that it'll last me years.
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17 years and no blown drivers, working with whatever you have at hand........ My friend you ARE a professional engineer.
 
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