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Author Topic: Limiter help  (Read 6351 times)

Ivan Beaver

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Re: Limiter help
« Reply #10 on: September 30, 2016, 07:42:31 PM »

In a perfect world you could in theory power the subs at their continuous rating for nearly ever.

As an aside, many amps these days have the clip lights blink when audible distortion is occurring. Many times this is 3db before actual clipping occurs. So when the lights flicker, you still have 3db to go.
Sorry-but I disagree.

Loudspeakers are rated for a power using a specific test signal AND for a specified time period.

If you keep applying that signal, then they will just keep getting hotter and hotter until they fail.

When you apply a different signal (such as a sine wave-which occur quite often in EDM), the power rating will be quite a bit lower.

I also disagree about the lights coming on 3dB before clipping on amps.  This is kinda typical on consoles, but not amps.

I have found they are typically very close to actual clipping (less than a dB away).

Yes this can vary, but I would not agree that "generally" the leds come on 3dB early on amps.

Granted I have not measured all the amps out there, so specifics should be stated.

I also disagree that audible clipping occurs before actual clipping.

There can be quite a bit of actual clipping before we start to hear it.

There have been many tests of the years to prove that.

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Ivan Beaver
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Tim McCulloch

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Re: Limiter help
« Reply #11 on: September 30, 2016, 08:49:29 PM »

Sorry-but I disagree.

Loudspeakers are rated for a power using a specific test signal AND for a specified time period.

If you keep applying that signal, then they will just keep getting hotter and hotter until they fail.

When you apply a different signal (such as a sine wave-which occur quite often in EDM), the power rating will be quite a bit lower.

I also disagree about the lights coming on 3dB before clipping on amps.  This is kinda typical on consoles, but not amps.

I have found they are typically very close to actual clipping (less than a dB away).

Yes this can vary, but I would not agree that "generally" the leds come on 3dB early on amps.

Granted I have not measured all the amps out there, so specifics should be stated.

I also disagree that audible clipping occurs before actual clipping.

There can be quite a bit of actual clipping before we start to hear it.

There have been many tests of the years to prove that.

This is the correct response.

My near-destructive testing indicated that some program material should get much lower long term power limiting than manufacturer ratings would suggest.
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Ivan Beaver

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Re: Limiter help
« Reply #12 on: September 30, 2016, 10:00:01 PM »

This is the correct response.

My near-destructive testing indicated that some program material should get much lower long term power limiting than manufacturer ratings would suggest.
One thing that many people don't realize is that the test signals used by the manufacturers are "supposed" to mimic the levels of "music".

This includes rolling off the high AND the low freq.

THE PROBLEM is that the "music" that was standard when the signals were developed was very different in content (ESPECIALLY the low freq) than modern music.

Modern "music" puts much more of a strain on various parts of a loudspeaker-such as the voice coil and suspension systems.

But if somebody started using a test that was closer to modern music (whatever that is), the power ratings would have to be lower.

And then they would not sell as many.

So nobody wants to "venture out".

So it is up to the user to properly understand what a particular type of music "does" to their loudspeakers and set limiters properly.
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Ivan Beaver
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William Schnake

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Re: Limiter help
« Reply #13 on: September 30, 2016, 10:19:46 PM »

After reading this thread it occurs to me that I still, after 31 years of running sound and owning my own company, that I can still learn a lot from everyone on this board.  Thank you all for freely sharing your knowledge.

Bill
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Luke Geis

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Re: Limiter help
« Reply #14 on: September 30, 2016, 10:20:57 PM »

It almost sounds like we are in agreeance actually?

Look for the open ended nature of my statements.

In point A I state " nearly ever ", but not forever..... I didn't imply that you can in fact power a speaker as such indefinitely, but more that if the world was a perfect place, you could do it for a very long time. Longer than we would need it to be done for. In order for that number to even be created the DUT used to come up with it would still be under test. So OBVIOUSLY ( if you haven't already caught my jest about it ) the continuous rating is a VERY safe wattage that we can send to a speaker for a longer period of time than would be practical.

In point B I state that many amps, not all have this sort of function. In the case of many ( again not all ) Crown amplifiers, they use a comparator circuit between the input and output. It will trigger the Clip light when the two signals no longer match within a certain spec. Crown's manuals state that the light will flicker at the onset of audible distortion. Many QSC amps will flicker a yellow light when you are within 1% of full power and then red when actual clipping is occurring within the amp. Other amps also utilize the red clip light to indicate that limiting is occurring. What is the limiter setting at? Roughly round -3db? Without quantifying the math or power in the statement, I would say that the clip light in most any amp is not exactly the most accurate indicator, but more an operational guideline. The rules are simple, DO NOT operate the amp for prolonged periods of time with the clip light on. If you see the RED LED flickering you need to turn down till it is not. Now as to whether flickering, or solid red lights is any different, I do not know for certain. I can say that to make a clip light go from flickering to actually fully illuminated does usually require more drive signal. So again when the red light is flickering is the amp clipped? One could argue that when the clip light is fully illuminated, there is no doubt as to the condition of the amps output signal.

In the OP's case I don't think he will need a lot of protection for the speakers. If he operates the amps correctly ( as in no red lights ) he cannot hurt the speakers and no limiting would be needed. From a thermal standpoint I would bet that he will not have -3db crest factor music being played at full tilt boogie for 10's of hours on end. There are a lot of points in EDM and music in general, where there are spatial bridges, breakdowns, into / outro's and filter sweeps. EDM being an extreme in the sense of crest factor, it is still realistically higher than -3db. Most ( that word again ) commercial music is now sitting around a -5db crest factor.

This is all of course moot if you have designed a system that exceeds the need. If you have a system that is running as needed at near idle, then heat and limiting is the least of the worry.
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eric lenasbunt

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Re: Limiter help
« Reply #15 on: October 01, 2016, 12:22:01 AM »

Thanks for the help guys! I used Ivan's suggestions and it is working great. I actually lowered the engaging level a bit to keep it out of clip. Rock show for 1000 indoors and rarely clipped the amp. Plenty of gas.

Thanks!
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Jeff Bankston

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Re: Limiter help
« Reply #16 on: October 01, 2016, 04:11:51 AM »

I can kick my bass drums hard enough to increase the spl a lot and freeze the woofer cones right out of the frames almost. I did it a long time ago and started using a limiter on my bass drums. If you ever need your woofers blode up just call on me and I'll come kickin'. Blode up real good !

http://www.youtube.com/watch?v=R4FfNYjw6qU
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Ivan Beaver

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Re: Limiter help
« Reply #17 on: October 01, 2016, 10:49:19 AM »

I can kick my bass drums hard enough to increase the spl a lot and freeze the woofer cones right out of the frames almost. I did it a long time ago and started using a limiter on my bass drums. If you ever need your woofers blode up just call on me and I'll come kickin'. Blode up real good !

http://www.youtube.com/watch?v=R4FfNYjw6qU
It does not matter how hard or light you kick your kicks.

How far the drivers move is solely based on how much signal level is going to the drivers.Y

You could take a "light kicker" and drive any loudspeaker where the cone will jump out of the frame.

Case in point.  At a large stadium install, we got called because the high powered subs we sold were not working anymore-right after the University choir sang before a football game.

I went there and sure enough- most of the cones were completely destroyed-with a number of them having the voice coils that jumped through the dust caps.

After a little bit of "probing", this is what i found.

The contractor used 2 Itech 9000s, mono bridged into each speaker cabinet.  They had NO limiters and NO high pass.

The choir was singing (outside) and the wind was blowing pretty strong.

They were using condenser mics with NO windscreen.

The console operator had no NO highpass on the mics.

The wooferswe re around 150' in the air.  One of the system guys said he could hear the cones going "flap-flap flap" during the choir performance. 

Because of the wind blowing into the mics and NOTHING to keep it out of the subs.

So yeah- even a small choir can cause lots of woofer damage.
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

ProSoundWeb Community

Re: Limiter help
« Reply #17 on: October 01, 2016, 10:49:19 AM »


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