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Protective limiter with the Master Control Fader at 0dB?

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Protective limiter with the Master Control Fader at 0dB?

Postby Elephone » Tue Feb 05, 2019 7:21 pm

I just wanted to clarify a blind spot that's bugging me. For general protective use, for initial mixing, I was told to keep the master control fader at 0dB and place a limiter to prevent the significant peaks from overdrive.

But, I've never been too clear on the settings. What attack, hold, decay, threshold, ratio setting is ideal to prevent damage to transients?

(Most videos seem to focus on mastering, on how to make things sound louder, but I'm just talking about protection during mixing.)

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Re: Protective limiter with the Master Control Fader at 0dB?

Postby Elephone » Tue Feb 05, 2019 7:45 pm

Also, is it better to compress gently and frequently than rarely and heavily? I would think this might be true with very clean VST compressors, but less so with characterful compressors or emulations. (I mean, many of them have noise and distortions that might accumulate.)

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Re: Protective limiter with the Master Control Fader at 0dB?

Postby Jack Ruston » Tue Feb 05, 2019 8:05 pm

If you're clipping your mix bus, your gain structure may be too hot at the source level. To address that issue you could consider reducing the gain of the files themselves. But there's nothing wrong with pulling the master fader back a bit, or using a VCA type fader, or bus master fader (depending on your software) to reduce the level of the mix bus itself. Whatever, there should be no reason to apply dynamics processing to the mix for the purposes of protection. You may very well do so for sonic reasons, mixing into a compressor, using it as an envelope shaper, and in a way, an EQ.
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Re: Protective limiter with the Master Control Fader at 0dB?

Postby Sam Inglis » Tue Feb 05, 2019 9:44 pm

Elephone wrote:I've never been too clear on the settings. What attack, hold, decay, threshold, ratio setting is ideal to prevent damage to transients?

By definition a brick-wall limiter such as you'd use for peak protection has a fixed attack time of zero, a ratio of infinity to one, and wouldn't usually have adjustable hold or decay settings. The threshold is often called the ceiling and is set to the maximum peak level you want to pass down the chain (typically that would be something like -0.5dBFS in a mastering context).

Some limiters do have these additional controls, but they relate to a second stage of dynamic control that's sometimes useful for getting more level in a loudness maximisation context.
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Re: Protective limiter with the Master Control Fader at 0dB?

Postby James Perrett » Tue Feb 05, 2019 9:51 pm

The only time I do this is to prevent inter-sample overs on material that has supposedly been 'mastered'. Otherwise just pull the master fader down.

Of course this assumes that you are using a DAW and plug-ins that handle higher than 0dBFS signals properly - if you are using prefade plug-ins on your master bus that don't handle high level signals properly you'll need to attenuate the signal before the problem plug-in.

I'm currently using Reaper's JS Master Limiter as my main limiter and, as a default, have it set to 200us look ahead, 100us attack, 0 hold and 35ms release.
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Re: Protective limiter with the Master Control Fader at 0dB?

Postby Hugh Robjohns » Tue Feb 05, 2019 11:31 pm

Elephone wrote:For general protective use, for initial mixing, I was told to keep the master control fader at 0dB and place a limiter to prevent the significant peaks from overdrive.

Hmmmm.... The only reason for a 'protective limiter' is to prevent system overload... But system overload is only likely when working with uncontrolled sources and minimal headroom margins. It's a possibility in live broadcasting, and potentially in peak-normalised mastering, but it really shouldn't be in post-production mixing.

The implication of your concern is that you are mixing with very little headroom (hence the risk of overloads) and that's just bonkers in a world of 24-bit converters and floating point DAWs.

Rather than worry about a brick wall limiter, I'd suggest finding a Katz 'K-meter' metering plugin, and learn to mix using that as your levels reference, with the average sitting around the zero mark, and peaks maybe 10dB higher. If you use the K20 scale you'll have 20dB of headroom margin to play with and so shouldn't be troubled with peak overloads while you mix. I use the K20 scale for 'serious' music, and the k14 scale for pop/rock stuff. Alternatively, learn to mix using a LUFS meter with a target loudness of around -15LUFS. Both techniques encourage the sensible use of a generous headroom margin when mixing.

Ideally, the master fader should, indeed, remain at the 0dB mark, but if you need to pull it back a bit as the mix builds, so bit it. Better, though, to reduce the levels of the source tracks if you can.

I've never been too clear on the settings. What attack, hold, decay, threshold, ratio setting is ideal to prevent damage to transients?

As others have already said, A brickwall (protective) limiter will have an extremely fast attack (less than 1ms) and very fast release (below 50ms), so that only the transient itself is affected by the gain reduction. Some work with a look-ahead facility too, to preempt a transient's arrival. The ratio will be more than 20:1, the threshold just below the maximum acceptable level, and no hold or hysteresis.... But a proper brickwall limiter's dynamics settings are usually fixed internally, and only the threshold is adjustable.
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Re: Protective limiter with the Master Control Fader at 0dB?

Postby Elephone » Wed Feb 06, 2019 3:30 pm

Thanks for the replies. I was really just following advice from the Friedemann Tischmeyer DVDs that I have. In DVD 1 he advised to put a limiter on the master fader as a matter of habit. I found the part in the DVD last night:

"The master control fader should be set at 0dB with a limiter to prevent the significant peaks from overdrive. Set the working range of the limiter to 1-2dB counting down from 0dB full scale. This gentle limiting will not damage the transients."

I don't really understand why DAWs allow clipping by default, rather than automatically limiting where it becomes a problem. As long as you can override it, would most users be better off? Reaper just cuts out.

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Re: Protective limiter with the Master Control Fader at 0dB?

Postby Hugh Robjohns » Wed Feb 06, 2019 3:36 pm

Elephone wrote:I was really just following advice from the Friedemann Tischmeyer DVDs that I have. In DVD 1 he advised to put a limiter on the master fader as a matter of habit.

It's a rather antiquated notion based on the presumption that you're going to be mixing with minimal headroom, and therefore a strong likelihood of getting caught out by the occasional transient peak running into overload. In such circumstances, a protective peak limiter will minimise the embarrassment...

But a much better (and more modern) approach -- in my view -- is to mix with a generous headroom margin so that it is extremely unlikely that transients will clip the outputs... This replicates traditional analogue console mixing practice, too.

I don't really understand why DAWs allow clipping by default, rather than automatically limiting where it becomes a problem.

It's not the DAW that clips. It's the D-A converter sitting on the output. I see where you're coming from with the desire for automatic limiting, and there may be an argument for such behaviour in some situations, but personally I prefer to be in control of what happens, not the machine, and I work with headroom so that output clipping isn't an issue...

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Re: Protective limiter with the Master Control Fader at 0dB?

Postby Wonks » Wed Feb 06, 2019 3:43 pm

DAWs don't clip, as they can work with stupidly high digital signal levels over 0dBFS, but when you play back through a D/A converter, or export to a fixed bit-count wave file (e.g. 24-bit wav), then you get clipping.

So the DAW doesn't limit you by insisting everything must be under 0dBFS. You just have to realise that when you are about to export the mix that you need to check the output meter. It will tell you if you are going over 0dBFS, then you can either choose to drop the overall level, or use a limiter or compressor to reduce the peaks. Better still use the true peak meter to tell you when you are in danger of clipping.

The only way a DAW could limit to 0dBFS throughout is to clip every time once that point was reached, which would be rather stupid and not allow you to push the signal level creatively at times if you wanted to.

Keep the master output fader at 0dB when mixing etc. as the meters will then give you a reading on what the output levels are like, But if you like the way the mix sounds and don't want to add more compression or limiting and the output is a bit hot, then you can simply pull the master fader down to get the output below 0dBFS.
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Re: Protective limiter with the Master Control Fader at 0dB?

Postby Elephone » Wed Feb 06, 2019 4:10 pm

Hugh Robjohns wrote: Rather than worry about a brick wall limiter, I'd suggest finding a Katz 'K-meter' metering plugin, and learn to mix using that as your levels reference, with the average sitting around the zero mark, and peaks maybe 10dB higher.

Thanks. Apparently, it is possible to use K-metering in Reaper, by right-clicking on the master fader. The only thing is, I get the impression I have to calibrate my equipment (M1 - Alesis - Active MkII Monitors via Edirol FA-66 interface).
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Re: Protective limiter with the Master Control Fader at 0dB?

Postby Matt Houghton » Wed Feb 06, 2019 4:15 pm

Hugh Robjohns wrote:Hmmmm.... The only reason for a 'protective limiter' is to prevent system overload... But system overload is only likely when working with uncontrolled sources and minimal headroom margins. It's a possibility in live broadcasting, and potentially in peak-normalised mastering, but it really shouldn't be in post-production mixing.

What about the speakers, though? They (and your ears!) could still suffer if some rogue plug-in spews out full-scale digital noise or clicks, couldn't they? I'd always thought the old Cerberus Audio ICE9 plug-in (which is seemingly no more) was a good idea because of that... and a similar muting limiter is built into Reaper. (Not that it prevents problems caused by such sources outside the DAW, but the idea appealed in principle!)
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Re: Protective limiter with the Master Control Fader at 0dB?

Postby blinddrew » Wed Feb 06, 2019 4:58 pm

Matt Houghton wrote:a similar muting limiter is built into Reaper.
And very useful it is too, as I discovered by accident the other day. :oops:
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Re: Protective limiter with the Master Control Fader at 0dB?

Postby MOF » Wed Feb 06, 2019 5:00 pm

Get used to sub-grouping instruments and vocals, their faders will allow you to trim what’s going to the master fader. Also the groups with the most transients can be “limited” individually so that the output channel only needs a bit of compression, or none, according to taste or musical style.
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Re: Protective limiter with the Master Control Fader at 0dB?

Postby Hugh Robjohns » Wed Feb 06, 2019 5:12 pm

Elephone wrote: Apparently, it is possible to use K-metering in Reaper, by right-clicking on the master fader. The only thing is, I get the impression I have to calibrate my equipment.

There are two aspects to K-metering. One is the establishment of a nominal working or reference level with a suitable headroom margin for mixing -- and that's the part I think you would find helpful.

The other aspect is an electrical/acoustic calibration of the nominal working level to a specific acoustic reference level in the listening room. But while that's an important element in some applications, it's not particularly relevant to your situation at the moment and so there's no real need to concern yourself with the calibration at this stage.

Having said that... it is a good idea to establish a calibrated reference listening level in your particular room, because then you quickly train your ears to know when the mix is at the right kind of level, and when it's being too compressed for loudness etc.

The only potential for confusion is that Katz states that the K-meter reference 0dB point should always correspond to an acoustic reference of 83dBC, but while that makes perfect sense in a large professional mix room, it's way too loud for a typical amateur domestic/project studio! Somewhere between 74 and 79dBC SPL is probably a more sensible target.

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Re: Protective limiter with the Master Control Fader at 0dB?

Postby Hugh Robjohns » Wed Feb 06, 2019 5:17 pm

Matt Houghton wrote:What about the speakers, though? They (and your ears!) could still suffer if some rogue plug-in spews out full-scale digital noise or clicks, couldn't they?

Well, firstly any modern active speaker will have it's own built-in driver protection system anyway, and secondly, the protective limiter being discussed was only ever going to clamp the signal a smidge below full-scale digits, so it wouldn't be hugely protective of the speaker in the event of a DAW meltdown, anyway really...

Back in the olden days of analogue, it wasn't normal practice to strap a protective limiter across the (monitor) output of the console -- we maintained a headroom margin to make it unnecessary -- so why do it with the digital equivalent?

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Re: Protective limiter with the Master Control Fader at 0dB?

Postby Wonks » Wed Feb 06, 2019 5:26 pm

The main point about calibrating your monitors when using K-metering is that when swapping between different K-meter settings, say K-14 and K-20, then the 0dBFS point is the same listening volume on both scales.

So at K-14 you set the monitor volume knob at one position, and for K-20 you'd set it to a position that had 6dB more gain (as your working 0dB point is now 6dB lower).

You probably won't need to do this in a home studio if you always make the same type of music, but if you work on differnt styles of music for commercial release, then it's something worth doing.
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Re: Protective limiter with the Master Control Fader at 0dB?

Postby The Elf » Wed Feb 06, 2019 6:19 pm

If any of your source tracks are peaking over -10dBFS then gain them down right from the start. You shouldn't be going anywhere near clipping once that's done.
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Re: Protective limiter with the Master Control Fader at 0dB?

Postby Matt Houghton » Wed Feb 06, 2019 7:00 pm

Hugh Robjohns wrote:Well, firstly any modern active speaker will have it's own built-in driver protection system

True. But we haven't all upgraded to 'modern active speakers'.

Hugh Robjohns wrote: the protective limiter being discussed was only ever going to clamp the signal a smidge below full-scale digits, so it wouldn't be hugely protective of the speaker in the event of a DAW meltdown, anyway really...

I hadn't read it like that. Master fader at 0dB could mean lots of things. I took it to mean leaving the fader at unity gain. Not to have the master stereo bus meter hitting 0dBFS. And the limiter is described as a 'protective' limiter, hence my thought about ears/speakers. This could surely have a threshold set where you want, in which case it could be as protective as you chose to make it. But perhaps I just misunderstood the OP...

Hugh Robjohns wrote:Back in the olden days of analogue, it wasn't normal practice to strap a protective limiter across the (monitor) output of the console -- we maintained a headroom margin to make it unnecessary -- so why do it with the digital equivalent?

It's precisely because you (sensibly) leave lots of headroom in the digital domain that full-scale noise can be so bloomin' loud in the real world when it happens by accident! And I have a hunch that full-scale digital noise was less of an issue in the (g)olden days of analogue :headbang:
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Re: Protective limiter with the Master Control Fader at 0dB?

Postby Jack Ruston » Wed Feb 06, 2019 7:12 pm

Matt Houghton wrote:I hadn't read it like that. Master fader at 0dB could mean lots of things. I took it to mean leaving the fader at unity gain. Not to have the master stereo bus meter hitting 0dBFS. And the limiter is described as a 'protective' limiter, hence my thought about ears/speakers. This could surely have a threshold set where you want, in which case it could be as protective as you chose to make it. But perhaps I just misunderstood the OP...


I think the point is that the OP is trying to prevent clipping on the mix bus...therefore, regardless of the position of the master fader, the signal would be full scale.

As mentioned above, there's a nice pref in Reaper, which cuts the signal if a channel exceeds full scale for a given period of time. It's handy if something freaks out!
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Re: Protective limiter with the Master Control Fader at 0dB?

Postby Hugh Robjohns » Wed Feb 06, 2019 7:18 pm

Matt Houghton wrote:But we haven't all upgraded to 'modern active speakers'.

Yes, fair point. If converter overload is likely and could create damaging levels to the speaker it might indeed be wise to introduce some form of external protection... But something appropriate in the analogue domain would make much more sense than peak limiter in the DAW... And I'd still argue that working with a generous headroom margin obviates the need anyway.

Master fader at 0dB could mean lots of things. I took it to mean leaving the fader at unity gain.

Me too! And I think that was the intention. I read the need for a protective limiter as something to avoid clipping the DAW mix bus or converter outputs, presumably because of mixing with minimal headroom. ...but I may have misunderstood too. But if that was the real concern, mixing with headroom avoids the problem and has other benefits too...

It's precisely because you (sensibly) leave lots of headroom in the digital domain that full-scale noise can be so bloomin' loud in the real world when it happens by accident! And I have a hunch that full-scale digital noise was less of an issue in the (g)olden days of analogue :headbang:

:lol: Yeah, okay... You got me there -- although full amplitude +24dBu analogue howl rounds were/are still possible! But if damage from full-scale noise is the over-riding concern, a limiter in the DAW will only be a help if the DAW remains functional, and could give a rather false sense of security. If the computer or interface freaks out -- which are as likely if not more so -- the DAW limiter won't help at all -- hence really needing a protective limiter in the analogue feed to the speaker/amp where it will always be functional.

Whichever way you look at it, a 'protective limiter' in the DAW is a bit of a chocolate fire guard!

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