# Seeking Specific DSP Programs



## TheNivek (Nov 9, 2013)

As many in this forum, I am in search of the best sounding audio I can achieve within financial reason – 80% solution at 20% cost. I have used room absorbers and EQ’ed the room in which I will be the only listener – and am almost there. As this is probably a perpetual process, the advancements in programmable digital electronics are extremely exciting and leave me wanting more towards this goal – however I do not buy into hype and use my ear as the final determinant. So with the large knowledge base in this forum, I have a couple questions that I hope someone can help me with:

1) Onkyo incorporates a dynamic loudness that, in my opinion, is extremely effective – it may be part of the Audysses system. This adjusts the bass and treble according to the volume music is played at. Is there an add-on solution that anyone knows of that can be applied to an older 2.1 channel system? … an add-on that follows the “Loudness vs Frequency” curves on page 46 (Fig. 4-6) in the 5th ed. of Master Handbook of Acoustics, for example? I would think it relatively straight forward to implement.

2) Samsung/Android has an app for its “Music Player” called “Adapt Sound.” The app goes through a routine that adjusts the frequency response of the headphone output to your hearing by asking if you hear various tones in either ear. I find that this is also extremely effective and I am wondering if this kind of thing is offered in a standalone DSP – MiniDSP for example?

Any help would be greatly appreciated!


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## AudiocRaver (Jun 6, 2012)

TheNivek said:


> Is there an add-on solution that anyone knows of that can be applied to an older 2.1 channel system? … an add-on that follows the “Loudness vs Frequency” curves on page 46 (Fig. 4-6) in the 5th ed. of Master Handbook of Acoustics, for example? I would think it relatively straight forward to implement.


I am not sure which set of curves is referred to above, the older Fletcher-Munson curves, or a more recent iteration like the ISO 226:2003 Equal Loudness Contours which are supposedly more accurate and have higher bass levels. That might not be super critical. The implementation could be quite involved, with

a frequency response curve that is constantly changing with level
gain constantly changing with level
attack, sustain, and decay time constants
Sounds doable but fairly involved. I have not heard of a DSP with a developer's toolkit for those functions, although there could be something out there.



> Samsung/Android has an app for its “Music Player” called “Adapt Sound.” The app goes through a routine that adjusts the frequency response of the headphone output to your hearing by asking if you hear various tones in either ear. I find that this is also extremely effective and I am wondering if this kind of thing is offered in a standalone DSP – MiniDSP for example?


I have seen the apps. They work at the hearing threshold, and regular listening level involves a different curve, does it not? Wouldn't that cause some inaccuracy? Again, maybe not super critical for what you are trying to accomplish. Have seen nothing for a DSP, though.


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## TheNivek (Nov 9, 2013)

AudiocRaver, thanks for your response. The set of curves I am referring to come from (according to the bibliography in the Master Handbook: Robinson, D. W. and R. S. Dadson, “A Re-Determination of the Equal-Loudness Relations for Pure Tones,” British J. Appl. Psychology, 7, pp. 166-181, 1956.). They are similar to the Fletcher-Munson curves you point out, but not the same (http://www.sengpielaudio.com/Fletcher-MunsonIsNotRobinson-Dadson.pdf). Any of them, including the ISO you mention, would surely make low volume listening sound better.

I think what you are discussing is more complex than I imagined. In what I am looking for, the curve would change according to the state of the volume knob, for example (or some long time averaged output, or equivalent) – it is not a compression scheme. I am not sure how the system in the Onkyo’s are implemented, but I would guess it is somewhere between a simple loudness button and what I discuss.

Thus, I would think it straight forward to implement – simply different equalization according to the quasi-static output level or volume knob. – probably nothing more than a firmware routine for the MiniDSP.

The Adapt Sound would be similar, and it would truly personalize the audio (for 1 listener anyway). As a person ages, it can be readjusted according to their hearing change. This is something that should be incorporated in hearing aids btw so that a user can adjust it (not going any deeper into that can of worms ).


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## AudiocRaver (Jun 6, 2012)

TheNivek said:


> AudiocRaver, thanks for your response. The set of curves I am referring to come from (according to the bibliography in the Master Handbook: Robinson, D. W. and R. S. Dadson, “A Re-Determination of the Equal-Loudness Relations for Pure Tones,” British J. Appl. Psychology, 7, pp. 166-181, 1956.). They are similar to the Fletcher-Munson curves you point out, but not the same (http://www.sengpielaudio.com/Fletcher-MunsonIsNotRobinson-Dadson.pdf). Any of them, including the ISO you mention, would surely make low volume listening sound better.
> 
> I think what you are discussing is more complex than I imagined. In what I am looking for, the curve would change according to the state of the volume knob, for example (or some long time averaged output, or equivalent) – it is not a compression scheme. I am not sure how the system in the Onkyo’s are implemented, but I would guess it is somewhere between a simple loudness button and what I discuss.


Leave it to me to think of the most complex possible approach. What you are suggesting would be far more practical, and might be approximated with a number of parametric filters, commonly available with DSP units. Maybe four or five approximated curves, selected to cover a volume range. How to activate/select is the remaining question.

You might look at REW's target curve function as a way to generate filter values, see what it comes up with.



> Thus, I would think it straight forward to implement – simply different equalization according to the quasi-static output level or volume knob. – probably nothing more than a firmware routine for the MiniDSP.
> 
> The Adapt Sound would be similar, and it would truly personalize the audio (for 1 listener anyway). As a person ages, it can be readjusted according to their hearing change. This is something that should be incorporated in hearing aids btw so that a user can adjust it (not going any deeper into that can of worms ).


Interesting idea.


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## TheNivek (Nov 9, 2013)

Great! I have not found the target curve function in REW – only “target settings” in the EQ section which might be too limiting – no way to add gain in the bass/treble or cut midrange. Am I missing it?

I don’t have a MiniDSP but might get one soon – do you know if the software is open architecture? I might write something myself but I don’t want to reinvent the hardware wheel. Apparently it has a digital volume access point which could be utilized as the control.

As far as I am concerned, over thinking a problem is an optimization process which is always a good thing 



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## AudiocRaver (Jun 6, 2012)

Oops, meant to say House Curve. It is on the House Curve tab under Preferences. There are instructions for file format on that page. You will need a fake measurement to apply correction to. Import a saved measurement file into an Excel spreadsheet, and change all of the SPL values to the same number, say 80 dB, or whatever, all phase to 0 deg. Then you can generate filters for that curve and the House Curve will be applied.


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## TheNivek (Nov 9, 2013)

Excellent idea AudiocRaver! Thanks for the details - got it – and also the original measurement file has to be exported as a text file from REW instead of saved. I will play around with this a bit and see where it leads.


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## AudiocRaver (Jun 6, 2012)

TheNivek said:


> ...and also the original measurement file has to be exported as a text file from REW instead of saved.


Ah, yes, those all-important details.

Good luck!


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