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Equal Loudness Contour ("Loudness") DSP for playback?

andreasmaaan

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#1
Does anyone know of a VST or plugin of some kind that allows the user to apply equalisation based on the equal loudness contours against a reference level? Something like what is available in the Adi-2 DAC/Pro, preferably a little more sophisticated? Ideally, this would be a plugin that could be placed in the output chain in Reaper or Foobar etc.

I've had a google and the closest I can find are dynamic EQs. I'm going to look into these further, but my understanding is that they respond dynamically to the input signal, which is useful for mixing but would be the wrong approach for playback. Really, for playback something that is controlled by the master level is needed.

I believe there's something like implemented in JRiver, but I'd prefer to find something that can be plugged in via Reaper or apply system-wide somehow.
 

Don Hills

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#3
... I've had a google and the closest I can find are dynamic EQs. I'm going to look into these further, but my understanding is that they respond dynamically to the input signal, which is useful for mixing but would be the wrong approach for playback. Really, for playback something that is controlled by the master level is needed. ...
I used to think a solution such as you proposed would be suitable, but after an extensive discussion the consensus was that dynamic equalisation is required on playback as well. See this thread:

https://hydrogenaud.io/index.php/topic,92822.0.html

"Woodinville" in that thread is "j_j" here. I don't know who "dc2bluelight" is but he's worth listening to as well.
 
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andreasmaaan

andreasmaaan

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Thread Starter #4
I used to think a solution such as you proposed would be suitable, but after an extensive discussion the consensus was that dynamic equalisation is required on playback as well. See this thread:

https://hydrogenaud.io/index.php/topic,92822.0.html

"Woodinville" in that thread is "j_j" here. I don't know who "dc2bluelight" is but he's worth listening to as well.
Very interesting thread, thanks.

Whether the EQ should be dynamic upon playback surely depends on how the track was mixed, I would have thought. I can imagine a situation in which dynamic equal loudness compensation EQ (or manual - perhaps even unconscious - compensation) is built into a piece of music by the mixing engineer, only to be doubled up by the listener on playback.

But reading all that at least sparks some more interesting in experimenting with dynamic EQ.
 
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RayDunzl

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#5
If the slope change/adjustment is tied to the playback level (volume control) I can see adjusting the curve, but if it is tied to the level of the music signal, I don't see it working as imagined.

In my case I'm not bothered by lack of bass at lower levels, have experimented with digital boost, and abandoned it, for the reason above.

I'm listening quietly right now, there's a string bass, seems like it is being reproduced properly.

---

20 min later... I'm watching the source RTA, I'm watching the in-room RTA, I'm hearing the low fundamentals... What's missing?
 
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pwjazz

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#6
I can imagine a situation in which dynamic equal loudness compensation EQ (or manual - perhaps even unconscious - compensation) is built into a piece of music by the mixing engineer
I would imagine that a lot of it simply depends on the level at which the engineer was listening when checking her work?
 
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andreasmaaan

andreasmaaan

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Thread Starter #7
I would imagine that a lot of it simply depends on the level at which the engineer was listening when checking her work?
Definitely. For a proper mixing or mastering studio, IME it's well understood that about 83dB RMS is correct, or slightly less for smaller rooms (essentially the same standards as for cinema). For amateurs, I'm sure that often tends to go out the window, but I'm happy to ignore the outliers. In general, I think it would be reasonable to generalise that all well-recorded music* was mixed at about 76-83dB RMS. Being conservative, one might set the equal loudness equalisation a little below the reference level, possibly at around 73dB RMS, and keep everything flat above that level. This is all off-the-top-of-my-head handwaving, however...

*EDIT: of the past couple of decades at least
 
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pkane

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#8
Definitely. For a proper mixing or mastering studio, IME it's well understood that about 83dB RMS is correct, or slightly less for smaller rooms (essentially the same standards as for cinema). For amateurs, I'm sure that often tends to go out the window, but I'm happy to ignore the outliers. In general, I think it would be reasonable to generalise that all well-recorded music was mixed at about 76-83dB RMS. Being conservative, one might set the equal loudness equalisation a little below the reference level, possibly at around 73dB RMS, and keep everything flat above that level. This is all off-the-top-of-my-head handwaving, however...
It should be fairly simple to make the reference level adjustable in DSP, so that the listener can shift it up and down the phon scale to produce the best tonal balance at a given volume for a given recording. The rest can be taken care of automatically by applying the F-M or equivalent curves to the signal, dynamically.

While I've played with dynamic EQ in UltraCurve 2496, I didn't find it to do much for playback, and finally turned it off. Maybe it's just not doing the same thing or is not implemented correctly, or maybe I just didn't figure it out :)
 
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andreasmaaan

andreasmaaan

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Thread Starter #9
It should be fairly simple to make the reference level adjustable in DSP, so that the listener can shift it up and down the phon scale to produce the best tonal balance at a given volume for a given recording. The rest can be taken care of automatically by applying the F-M or equivalent curves to the signal, dynamically.

While I've played with dynamic EQ in UltraCurve 2496, I didn't find it to do much for playback, and finally turned it off. Maybe it's just not doing the same thing or is not implemented correctly, or maybe I just didn't figure it out :)
I just had a play with a dynamic EQ designed for mixing/mastering called TDR Nova. Did it with headphones in a DAW, setting the "reference level" by ear (40/100 on my Windows volume control) and based on the Fletcher-Munson curves, with the 80 phon curve as the arbitrary standard.

It wasn't so satisfactory. This particular EQ allows for a lower threshold (which I set as -40dB and EQ'd corresponding to the F-M curve for 60 phon), but doesn't allow for an upper threshold beyond which no EQ is applied. That's something essential for this application IMO, since you don't want EQ to take effect whenever the signal is below 0dBfs (i.e. all the time). So, ideally IMO you'd find a dynamic EQ that had both a lower and an upper threshold. If 100dB was the loudest you ever listened, you would then (for example) set the upper threshold at -25 or -30dBfs to correspond to the 80 phon curve, with a lower threshold 40dB below that corresponding to the 40 phon curve.

I'm going to keep searching for a dynamic EQ that might be able to be set up this way...
 

Eurasian

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#10
I'm very interested in this topic as well -- please keep us posted.

In the mean time I will explore the dynamic eq options that may lurk within my Venu360.

Best wishes for the new year to all!
 

Blumlein 88

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#11
The later Tact gear had this option. I found I preferred it with almost all recordings.

It's possible Lyngdorf gear still has it. A plugins version would be great.
 

Don Hills

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#13
That's for a different purpose. Foobar measures the loudness or volume - how loud it appears to you - and sets the replaygain value accordingly. On playback, very quiet tracks are "turned up" slightly and very loud tracks are "turned" down". The intent is to provide a more consistent listening experience when tracks of differing loudness are played sequentially, such as in a shuffle playlist.
 

pkane

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#14
That's for a different purpose. Foobar measures the loudness or volume - how loud it appears to you - and sets the replaygain value accordingly. On playback, very quiet tracks are "turned up" slightly and very loud tracks are "turned" down". The intent is to provide a more consistent listening experience when tracks of differing loudness are played sequentially, such as in a shuffle playlist.
I find it easier to visualize equal loudness curves on a 3-D chart. Here's the ISO 226 set of equal loudness curves. Vertical axis is the relative perceived dB difference from 1KHz, horizontal axis is the frequency.

1546399583805.png
 

Guermantes

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#15
I did a quick google and found that someone has tried using ReaFIR (which is free in Reaper): https://www.reddit.com/r/Reaper/comments/44unfn
However, this is not dynamically adjustable in the way that you want. The Dynamic EQ plug-ins I have used all seem to work with the one threshold as you have mentioned. Then there are multiband compressors which will give you separate thresholds for each band, but once again, probably not what you are envisaging. The Adaptive Spectral Inverse Filter in Salient Sciences' Cardinal suite is a little different but I don't see any way to conveniently switch between equalisation curves.

Decades ago, a friend of mine joked about designing an amplifier that would do exactly what you want: apply equal loudness compensation based on volume level. He called it "The Flat Amp". At the time the closest thing on the market was probably Yamaha's dial-in loudness control.
 

Jose Hidalgo

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#19
Just jumping in too. I'd like to implement this dynamic loudness EQ thing in my Windows PC (unless some inexpensive DACs like the E30 or so have it already, which I doubt). It could be either in my player (foobar2000) or somewhere along the audio path.

So far I've found this thread on Hydrogenaudio with some potentially working solutions: https://hydrogenaud.io/index.php?topic=119730
I'm just wondering if there's anything better and more refined. After all JRiver has been having it for a long time already.
 
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