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How to Calibrate Loudness?

watchnerd

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#1
So the ADI-2 Pro has a variable, dynamic loudness control. You can configure both when it kicks in (in terms of -dB) and how much the treble and bass are boosted.

So given this is a psychoacoustic compensation, and not something microphones "hear", what's the best way to empirically calibrate it?
 

Blumlein 88

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#3
I am assuming you read the manual for details of how it works. I have a Tact Room EQ with a similar function which can be engaged. You get to select "loudness curves" for each level below a reference. Default was using the F-M curves like Amir has posted above.

Looks like RME wishes for you to pick your lowest gain setting as a starting point, and suggests it be -20db from your normal max listening position on the gain. You plug in your adjustments at the low reference level and each db gain increase will reduce the bass and treble compensation. The manual (unless I missed it) didn't specify over what range it operates for bass and for treble.

In the Tact I found this feature worthwhile for listening. I found the equal loudness contours (red in Amir's graph) to work better than F-M curves in the bass.

I would probably throw some white noise thru the unit in a loopback and see exactly how those controls effect the resulting curve of frequency response. Just a guess, since they picked a default of 7 db on bass and treble, I am guessing they picked the F-M curves for 80 db SPL. Probably working more like conventional bass which shelves at 50 hz and treble shelving at 10 khz relative to 1 khz. Just a guess though. Run some white noise thru it and an FFT will show you what happens.
 
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watchnerd

watchnerd

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Thread Starter #5
I am assuming you read the manual for details of how it works. I have a Tact Room EQ with a similar function which can be engaged. You get to select "loudness curves" for each level below a reference. Default was using the F-M curves like Amir has posted above.

Looks like RME wishes for you to pick your lowest gain setting as a starting point, and suggests it be -20db from your normal max listening position on the gain. You plug in your adjustments at the low reference level and each db gain increase will reduce the bass and treble compensation. The manual (unless I missed it) didn't specify over what range it operates for bass and for treble.
This is the graph from the manual:

Screen Shot 2017-12-16 at 21.17.37.png


The loudness is configurable for a Low Vol Ref, ranging from -90dB to -20dB. The default is -30dB.

Treble and bass gain can be set from +1-10dB, default is +7.

But given that the loudness needs to be calibrated to sounds at my listening position, over my monitors / cans, with both the level at which it kicks in and the amount of EQ configurable, I'm struggling with a good method.
 

Blumlein 88

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#6
I would suggest -20 db pink noise set to about 85 db spl. This gain setting becomes the zero level in the graph. Gives you a good loud listening level with headroom for music. Reducing volume from here engages the loudness once you set the lower level parameters appropriately.
 

Cosmik

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#7
They didn't calibrate it themselves???

The starting point would be the Fletcher-Munson curves:
But nothing short of meta information provided with the recording can take into account the 'correct' level for playing back the recording.

If the recording is of a quiet 'event' then even though it is quiet, you *shouldn't* boost the bass and treble when listening to it at a realistic (yet non-neighbour upsetting) volume. Only if the recording is of something loud and you are playing it quietly should you boost the bass and treble.

But the volume control setting can't help you. If the recording features just an acoustic guitar, they are not going to metaphorically cut it on the metaphorical disc at the same gain as a full blown symphony - it will be 'cut' at a different gain.

Nor can the recording's content be automatically analysed to tell you whether to boost bass and treble for a particular recording unless your algorithm can deduce the absolute 'correct' volume from content. I presume it is also accepted that you don't want to boost bass and treble dynamically with content - yuk!

Unless a recording is supplied with information about the absolute level it should be played at, there is no scientific way to do it. Without this information there is no "calibration" possible. It must always remain a subjective guess.

And even if such information was supplied, how would they take into account all the deviations from 'raw', including dynamic compression that is changing the recording's position on the Fletcher Munson curves all the time? (one of the reasons why dynamic compression is evil!).
 
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Fitzcaraldo215

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#8
Agreed, because there are no agreed, absolute standards in loudness for music recordings.

It is a little different for BD movie playback, where there is a loudness standard in production. I am not an Audyssey fan or user any longer, but they did implement something different and potentially useful - Dynamic EQ. During calibration, all channels are level trimmed to the standard output level with zero dB on the master volume control equal to the industry standard level. Then on playback, the amount of boost to bass and treble was increased proportionally per the built in loudness contours based on how far the Master control was turned down from 0 dB by the listener. So, loudness compensation was not based on and did not vary with instantaneous levels of the signal itself.

I never used it, but I thought it an interesting idea. But, other faults of Audyssey and access to better tools made me jump ship.

Also, the movie loudness standard does not seem to prevent movie theaters from varying loudness all over the map.
 
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watchnerd

watchnerd

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Thread Starter #9
But nothing short of meta information provided with the recording can take into account the 'correct' level for playing back the recording.

If the recording is of a quiet 'event' then even though it is quiet, you *shouldn't* boost the bass and treble when listening to it at a realistic (yet non-neighbour upsetting) volume. Only if the recording is of something loud and you are playing it quietly should you boost the bass and treble.

But the volume control setting can't help you. If the recording features just an acoustic guitar, they are not going to metaphorically cut it on the metaphorical disc at the same gain as a full blown symphony - it will be 'cut' at a different gain.

Nor can the recording's content be automatically analysed to tell you whether to boost bass and treble for a particular recording unless your algorithm can deduce the absolute 'correct' volume from content. I presume it is also accepted that you don't want to boost bass and treble dynamically with content - yuk!

Unless a recording is supplied with information about the absolute level it should be played at, there is no scientific way to do it. Without this information there is no "calibration" possible. It must always remain a subjective guess.

And even if such information was supplied, how would they take into account all the deviations from 'raw', including dynamic compression that is changing the recording's position on the Fletcher Munson curves all the time? (one of the reasons why dynamic compression is evil!).
I'm pretty much coming to the same conclusions....this is a real chicken and egg problem.
 

mitchco

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#12
I would suggest -20 db pink noise set to about 85 db spl. This gain setting becomes the zero level in the graph. Gives you a good loud listening level with headroom for music. Reducing volume from here engages the loudness once you set the lower level parameters appropriately.
Agree with Blumlein 88 - been doing this for years. One unofficial guide: https://www.digido.com/portfolio-item/level-practices-part-2/ If using JRiver: https://yabb.jriver.com/interact/index.php?topic=76608.0
 
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watchnerd

watchnerd

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Thread Starter #13
Well, I already calibrated my monitors to 83dB without loudness in the picture.

I set the output at +19 dBU, which at -19 dBFS gives me 83 dB, and at 0 dBFS gives me 105 dB at 1m, which is within 1 dB of the max SPL of the speakers (5" Dynaudio LYD 5).

But I don't understand how this tells me to calibrate the loudness level and EQ curve...

I'm a n00b to loudness. Never had a product with the feature before.
 

Blumlein 88

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#14
Well, I already calibrated my monitors to 83dB without loudness in the picture.

I set the output at +19 dBU, which at -19 dBFS gives me 83 dB, and at 0 dBFS gives me 105 dB at 1m, which is within 1 dB of the max SPL of the speakers (5" Dynaudio LYD 5).

But I don't understand how this tells me to calibrate the loudness level and EQ curve...

I'm a n00b to loudness. Never had a product with the feature before.
As I understand it the loudness won't dynamically alter the signal as the signal level fluctuates. It will apply the bass and treble lift as the gain setting is reduced by you. The effect on treble and bass is fixed for each gain setting.

So -19 dbfs with +19dbu gives you 83 dbspl from your speaker. So you want Low Reference level for loudness set 20 db lower at -39 dbfs in the settings menu. Does this make sense? The manual says the Low Reference level is 20 db lower than regular listening levels.
 
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watchnerd

watchnerd

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Thread Starter #15
As I understand it the loudness won't dynamically alter the signal as the signal level fluctuates. It will apply the bass and treble lift as the gain setting is reduced by you. The effect on treble and bass is fixed for each gain setting.

So -19 dbfs with +19dbu gives you 83 dbspl from your speaker. So you want Low Reference level for loudness set 20 db lower at -39 dbfs in the settings menu. Does this make sense? The manual says the Low Reference level is 20 db lower than regular listening levels.
That's different from how I understand it to work.

To quote the manual:

"
Low Vol Ref

Reference level for highest Bass/Treble amplification, referenced to the Volume set in dB.

Available range is -90 dB to -20 dB. Default: -30 dB. A volume setting below this point will have

maximum Bass/Treble gain, all volume settings above this point will have lower Bass/Treble

gain. 20 dB above the Low Vol Ref setting the Bass/Treble gain will be zero."

So as you increase the gain, the loudness goes down.

If you set the Low Vol Ref to -30dB, then at -10dB it's "off".
 
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watchnerd

watchnerd

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Thread Starter #16
So -19 dbfs with +19dbu gives you 83 dbspl from your speaker. So you want Low Reference level for loudness set 20 db lower at -39 dbfs in the settings menu. Does this make sense? The manual says the Low Reference level is 20 db lower than regular listening levels.
This assumes I want the Loudness to be zero at 83 db SPL.

How is that determined to be the case? Because it's the reference level, and therefore should have no alterations?
 

Blumlein 88

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#17
That's different from how I understand it to work.

To quote the manual:

"
Low Vol Ref

Reference level for highest Bass/Treble amplification, referenced to the Volume set in dB.

Available range is -90 dB to -20 dB. Default: -30 dB. A volume setting below this point will have

maximum Bass/Treble gain, all volume settings above this point will have lower Bass/Treble

gain. 20 dB above the Low Vol Ref setting the Bass/Treble gain will be zero."

So as you increase the gain, the loudness goes down.

If you set the Low Vol Ref to -30dB, then at -10dB it's "off".
Well, as I read what you wrote it is the same thing I am saying. Other than setting Low Vol Ref to -39 db. Yes this is so at and above a room SPL of 83 db you have no Loudness effect.
 

Blumlein 88

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#18
This assumes I want the Loudness to be zero at 83 db SPL.

How is that determined to be the case? Because it's the reference level, and therefore should have no alterations?
Yes, that is presumably about where you would listen to music. A comfortably high level with some headroom. As you drop volume below this level is where you want Loudness to compensate for the dropping sound level.

Music doesn't have the agreed upon standards as film, but this should be a reasonable level.
 
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watchnerd

watchnerd

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Thread Starter #19
Yes, that is presumably about where you would listen to music. A comfortably high level with some headroom. As you drop volume below this level is where you want Loudness to compensate for the dropping sound level.

Music doesn't have the agreed upon standards as film, but this should be a reasonable level.
Okay, now it makes sense, in theory.

In practice, here's the rub:

1. Setting it at -39 dBFS means the loudness boost is in full effect at ~66-67 dB SPL, and lower. I don't usually do recreational listening quite that softly. Maybe background level.

2. Stupid variability in how hot various music is mixed leaves things all over the map...
 

Blumlein 88

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#20
I hear you on the variability of mix hotness. Set it - 39 dbFS and live with a few days. You can always adjust that up or down a few db till it suits you best.

I don't want music playback to end up like movies where there have to be a couple dozen proprietary formats on the AVR to watch anything with sound. Some basic level stabilization would pay some dividends however.
 
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