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Old 10-01-2017, 04:52 AM   #1
Quiz
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Default JS: Master Limiter's Threshold confusion (

Hey folks,

I do have one question regarding the JS Mastering Limiter's way of working.

As far as I know a limiter is nothing more than a comp with an indefinite ratio and it can work in two ways:
- By setting a threshold, cutting everything above and finally rising the volume of the chopped-off wave up to the ceiling value.
- By increasing the input gain to a desired value and chopping off everything above a given ceiling value.

Because of the threshold slider in the JS plugin I assumed the plugin to be working like the first way.
I rendered a constant sine wave with a peak (and in this case = RMS) level of -15dB, set the threshold to -3dB for testing and expected nothing to happen - as the wave never crosses the threshold. Yet, the audio statistics plugin reveals that the level was risen by 3dB.

So...does anybody know how the plugin works or what I am missing?

Btw: I also tried out JB's Barricade Pro as it is supposed to be one of the best limiters out there, at least in the for-free-field. I thought about using it as a brickwall limiter but I can't find the ceiling value. Am I missing the obvious or is there no such possibility / is it always limiting at -0,16dB (the peak value I observed in an FX chain _after_ the Barricade Pro limiting an audio file with several heavy clippings)?

Thanks for your time and help!


EDIT:

I think I figured it out. It sort of works like way 1 but the volume is not risen to the ceiling level.
Everything above the threshold gets shopped off (in this case nothing) and the plugin has an auto makeup gain function, that is the hole wav is risen in volume by the threshold value (which is why it is 3dB louder without reaching the threshold). Finally, you can attenuate the volume with the limit setting (that was set to -0.1 which is why the volume gain actually is 2.9dB and not 3dB).

So for everyone who is confused by a limiter's workflow (way 1):
It's not: wav -> shopping off at threshold -> rising the whole wav's volume until chopped of peaks reach ceiling
But it's: wav -> shopping off at threshold -> rising the whole wav's volume by a given value (in JS Master Limiter plugin's case the threshold's value) -> attenuate the volume by a given amount (in JS Master Limiter plugin's case the limit; that actually is a trim function and for every part of the wav that exceeds 0dB it works as the ceiling)

---
The Barricade Pro - at least the wave/envelope section - works like way 2. You rise the gain (drive) until the wet signal reaches 0dB, then the limiter kicks in. Further rising the gain results in more parts of the signal reaching 0dB until it finally sounds like shit. Again, you can attenuate the volume by a desired amount using the ceiling (trim).

I hope I finally understood it and may bring some light in somebody else's head who may be troubled by the same confusion.

If my analysis is wrong I am happy to be corrected!

Last edited by Quiz; 10-01-2017 at 08:46 AM.
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Old 10-01-2017, 10:11 AM   #2
ashcat_lt
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You know that you can "pop the hood" on any JS plug and actually see how it works? You'd need to have some familiarity with coding and DSP, but it's all right there under the Edit button.

You're pretty much got it right here. It tries to keep anything from getting louder than the threshold, then adds gain to make up the difference between the threshold and the limit, and then hard clips anything louder than the limit.

You might think that's redundant, but there's that whole the "tries to" thing. That threshold based limiter has attack, release, hold, and lookahead, so its gain reduction is not always exactly right for the current sample. It's always moving toward the gain value that would bring the current sample down to the threshold, but there's no way to promise it'll actually get there when it needs to. So some peaks will still pop through. It clips those off hard at the limit.

So basically, you look at the input, where it peaks, and how much of that peak you want to knock down, and set your threshold based on that. Then you decide where you want the peaks to hit on your output, and set the limit to that value. In this case "limit" is what other plugs might call "ceiling".
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Old 10-07-2017, 02:51 PM   #3
Quiz
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Hey Ashcat,

I gave the edit button a shot but unfortunately I wasn't able to understand thec code. Thanks for the hint anyway.


Quote:
So basically, you look at the input, where it peaks, and how much of that peak you want to knock down, and set your threshold based on that. Then you decide where you want the peaks to hit on your output, and set the limit to that value. In this case "limit" is what other plugs might call "ceiling".
The bold part is the part that I do have trouble with. In my provided example I had a constant sine wave peaking(=RMSing) at -15dB and I'd like to use your explanation of the workflow to understand it correctly:

Quote:
So basically, you look at the input, where it peaks (-15dB), and how much of that peak you want to knock down (in my test setup nothing), and set your threshold based on that (-3dB). Then you decide where you want the peaks to hit on your output (for a testing purpose I would like to let it peak at -0.1dB but don't see a way to do so), and set the limit to that value (in my case to -0.1dB - but with a resulting peak(=RMS) of -12.1dB and not -0.1dB=Limit) In this case "limit" is what other plugs might call "ceiling".

I tried it out with another example (a clap sample) and turned the sample's volume up to let it peak at (+)5dB. I set the threshold at -0.1 (because I didn't want to compress it but just test what the limit does) and then but only then (I mean in a case where peaking is occuring) the limit works as a ceiling. So...are you completely sure that your described workflow is correct? If so, what am I missing?

I enhanced (hopefully) the workflow I assumed to be correct with the hints you gave and came up with this:
wav -> trying to shopp off at threshold -> rising the whole wav's volume by a given value (in JS Master Limiter plugin's case the threshold's value), in case of exceeding 0dB brickwall limiting to 0dB -> attenuate the volume by a given amount (in JS Master Limiter plugin's case the limit).

I look forward to your (or anybodys) reply. Sometimes it's the simple things that gives me the most troubles...
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Old 10-07-2017, 05:48 PM   #4
ashcat_lt
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Ok. Slightly different way to put it: It makes things that hit the threshold whatever level the limit is set at. In your test case, you'd have to set threshold to -15 to get what you're expecting.
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Old 10-08-2017, 06:59 AM   #5
Quiz
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Yeah, exactly, I also tried that out and it worked like expected.

I guess I got it now as I can explain/describe all test cases - that is including and not including clipping - with the workflow from my last post. Thanks for your guidance.
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