Loudness Contour Levels in DSP - How implement?

Hi. I want to implement “loudness correction” in my DSP engine. My intention is to improve sound quality during low volume levels. The effects should equal the “loudness button” of former analogue audio equipment (80s/90s).

Perhaps you have already read about the Fletcher-Munson Curve (The Mysterious Loudness Control: What Does It Do? | Extron) … and it would be very helpful whether you could show some screen shots of a well functioning “loudness correction” (higher lows and higher highs in DSP filter settings) to get a good starting point. Discussion and comments welcome. Thx so much!


Here you see my first attempts

As Richard III said: “Horse! Horse! My kingdom for a horse! " *) I will say: the kingdom for “Contour” correctly implemented in DSP

This is a basic function that should be implemented in any audio equipment. Because the physiology of hearing is inexorable, then every equipment would sound much better. But all audio equipment manufacturers avoid it like the plague. Why? Let the users’ ears decide - we can always turn it off, right?

By the way - could you please post the parameters of each band (frequency, gain and Q).

*) William Shakespeare


I have an rme-adi dac which has an output-dependent loudness function. It is the best feature I have ever had on a dac/pre-amp for evening listening etc. I think Roon could do the same, but as I understand it, it would require outputlevel-dependent dsp which I think would be a new, but very cool feature. Otherwise you would have to disable it at higher volumes.


I’d settle for just being able to adjust EQ without the Core needing to briefly mute the audio while the Core crunches the numbers and resends the stream to the Endpoint.


Agree. Would love to see a “output dependent loudness countour” functionality such as offered by my RME-ADI 2!

I don’t think I would be alone appreciating such a feature.

Anyone at ROON reading this thread, please take note. :slight_smile:


Can someone please tell me this is going to get done. I agree with others, loudness dependant EQ is the next step, and with regard to the loudness curve, seems pretty essential. We can’t all listen at reference levels all day.


I too like listening to music with volume dependent Loudness EQ/equalization enabled.

And so I too would ask Roon to consider adding a Virtual Loudness Control for use with systems and amplifiers that don’t have a physical Loudness EQ Button?

In the meantime, I came up with these settings to ~mimic the EQ curves shown in Michael_Christ’s screenshot above.

I moved the graph up to -3dB (instead of -9dB as shown by the horizontal purple line in Michael’s graph) to increase the output volume. I still have headroom management disabled, and so far I have not noticed any clipping.