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Power limiting approach
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Augusts View Drop Down
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    Posted: 28 January 2020 at 2:01pm
Hi

Could you share some insights about how you limit your speakers? Using longer attack time, release and hold and using treshold by speaker RMS rating, or using the shortest attack time and limiting the power by speaker Program Rating or in this case it would be called Peak power I guess - so that the limiter would not let any signal through the wall.

I understand that one value to be voice coil RMS and the other would be Xmax.
If you would use powersoft amps for example that would not be a problem.

I use a simple DSP and an amp that has variable Peak Power and RMS power.

I think the advantage of limiting by Peak is a controlled Xmax, as I build my own speakers, I know the value. The disadvantage would be a flat sound when reaching the limit and a danger of blowing the voice coil if the driver RMS rating is below the Xmax Power rating value.

Thanks
A
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Augusts View Drop Down
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I used the RMS standart approach but noticed that when pushing the limiter really hard, the woofers blurp. So I shortened the attack time from a recomended 16ms to 5ms.

I dont like long attack times because that lets through power that is of an uncontrolled amplitude until the limiter sets in.
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if your consistently hitting the limiters on the system in order to get the coverage you need, then best practice is to "bring more boxes".  

Edited by 4D - 28 January 2020 at 3:18pm
DMZ. "The bass was intense. Girls were literally running up to stand next to the subs"
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Points: 1083 		Post Options Post Options   Thanks (0) Thanks(0)   Quote fatfreddiescat Quote  Post ReplyReply Direct Link To This Post Posted: 28 January 2020 at 5:00pm
Your on the right track, take a look at this:

https://m-noise.org/

and also the powersoft limter setting guide, that should answer your questions.
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Augusts View Drop Down
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yes, I would love that but at first I have to be humble.
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Augusts View Drop Down
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Originally posted by 4D 4D wrote:

if your consistently hitting the limiters on the system in order to get the coverage you need, then best practice is to "bring more boxes".  

I meant to reply
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Augusts View Drop Down
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Even if I had more boxes, I would still have to limit them for times when someone got crazy with an eq for example.

The question is how to do it with a one level limiter to get out the maximum of the system and not damage the drivers.
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Elliot Thompson View Drop Down
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Originally posted by Augusts Augusts wrote:

Even if I had more boxes, I would still have to limit them for times when someone got crazy with an eq for example.

The question is how to do it with a one level limiter to get out the maximum of the system and not damage the drivers.


The last thing you want is the Attack Level of a compressor to be increased for it will increase the Dynamics/Transients. You want the Attack Level set to minimum. The same thing applies to the Release. The Release will determine how long the compressor will maintain the compressed signal on the program material before reverting back to a non-compressed signal. So minimum settings of the Release will focus on preventing all means of Dynamics/Transients from escaping the compressed signal at all times.

Minimum Settings: RMS Compression

Maximum Settings: Peak Compression

Minimum & Maximum Settings: Somewhere in between


You will have to drive your mixer to idiot levels, and configure the limiter from exceeding a certain amount of output voltage. Since I look at everything electrical based on volts and current only, the following is based from an electrician standpoint.


Pull out your multimeter and set the dial to AC Volts and, attach the probes to back of your LMS output channel.


Drive the mixer with music content to idiot levels into your LMS and measure the output voltage


Adjust the limiter on the LMS until the output voltage of the LMS does not exceed the input voltage of the amplifier with the input gains set to maximum. The manual of the amplifier will tell you what is the maximum input voltage required (with the input gains set to maximum) to achieve maximum output volts (watts).


Best Regards,


Elliot Thompson
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Points: 2544 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Conanski Quote  Post ReplyReply Direct Link To This Post Posted: 28 January 2020 at 10:40pm
Originally posted by Augusts Augusts wrote:

The question is how to do it with a one level limiter to get out the maximum of the system and not damage the drivers.


Not possible, you either risk damage with low crest factor material when using peak limiting or throw away a bunch of output with thermal/RMS limiting. If you are doing an event with a single known type of music you can adjust limiters to suite that event but if the system has to cover a wide range of music you are SOL.
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My preferred limiter is a 4ft stage leg triggered by me seeing the red lights on the mixer...
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ceharden View Drop Down
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Forgot to say, for a faster attack time, stand closer!
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the simple idea is to adjust the limiter so it acts purely to reduce gain without reducing the dynamics. IE fast attack and slow release (the release on an F/S PM80 for example could be set to around 20 seconds from memory). It's not rocket science. If the crest factor increases in limiting then it's set up as a compressor not a limiter.
A limiter should no more increase the power dissipated in the speakers than a big angry man with his fingers on your master fader who steadily pushes it down. If a DJ is determined to run the mixer up to the limit of its output voltage, then the limiter should be, by then, in such gain reduction with the high input levels that the amps are merely farting out a distorted noise at background levels, harming no one but the DJ's reputation.

The longer the release time, the longer the crowd will be able to appreciate his incompetence and the less he'll want to risk it.

Sometimes of course nothing short of a Sentry limiter tripping the amp contactors will convince a DJ to keep it in the green, but for live music one would hope the FOH engineer would be awake.

Formula Sound really are the units for speaker protection but a good LMS with limiter is next best.






Formula Sound
Kevin

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