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Purdy Offline OP
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Hang with me here.

I have a digital piano that allows adjusting the volume and tuning for each key.

I noticed some keys seemed louder.

So I hooked up an app and measured the sound pressure for each key when struck at its maximum velocity.

I ended up with this adjustment curve, see bottom graph below.

Is there a better way to do this? Should I approach this a different way?

[Linked Image]


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How does it sound when played normally after all of those adjustments?

Ron Koval


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my piano videos:
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Interesting. I understand that the bottom graph is amplitude versus note number. Is that the case for the top graph? If so, it would imply that you prefer a slightly more stretched tuning than the default tuning already provides.

How did you measure sound pressure? A microphone, or a line-out ?

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The other question to be asked is: Before you made adjustments, did some notes sound louder through the speakers and/or through the headphones?

On my acoustic piano, some notes sound louder depending on where I turn my head, whether or not I have the music desk raised or lowered or removed, whether or not the lid is fully closed, partially open, on half stick or on full stick.

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Purdy Offline OP
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I used the usb audio out straight into an iPad. No speakers or microphones involved.

And yes, as I mentioned some keys did sound louder. What I didn’t expect because I didn’t notice is some keys were softer. Sometimes groups of loud next to a soft key.

Overall I would call it an improvement to my ears.

I originally tried to normalize the sound at the fundamental frequency but that left the bass too loud as a lot of the energy is in the harmonics.

It is interesting that the adjusted volumes generally decline until it reaches the high notes and then goes up. That has me somewhat questioning my approach.

I used a trial version of piano scope and it calculated out a new stretch tuning curve. I had to tweak the values by hand as it appears the underlying model is not perfect.

Roland doesn’t build the stretch tuning into the model and you can actually see it. Here is the default stretch tuning curve.

[Linked Image]

Last edited by Purdy; 12/01/21 07:59 PM.

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Again, very interesting. Thanks for the response. How did you play the notes to achieve maximum velocity? Could that be the issue? The sensors might not all respond equally to equally applied velocity, which would be unfortunate, though not all that far off from an acoustic piano.

The normal stretch for a grand piano is around -25 cents at A0 to about +30 or more at C8. These numbers can vary drastically.

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Purdy Offline OP
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You can set the key velocity from 0 to 100

0 is full on with a key press regardless of velocity. An organ essentially.

That is what I used. In spite of that there is some variation that occurs I believe because of the resonance modeling.

I used multiple key presses especially for values that were quite different

I believe the stretch tuning values are in line with acoustic grands.

The calculated retuned curve is slightly flatter in the upper mid section.

I’ve read at least one review that says Roland is too sharp by default in that region. That would tend to agree with the results.

Last edited by Purdy; 12/01/21 08:20 PM.

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curiouser and curiouser.

Another question: When using multiple presses on the same note, did the output amplitude change?

You could send me a .wav or.mp3 file of the usb port output, including examples of multiple presses of the same notes that vary. I will do an DFFT analysis to look at the waveforms. I am interested to see if the modelling includes randomized variables. PM me for an email address.

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I've posted some results of research I conducted on a .wav file sent to me by Purdy. The data is in the Piano Photo Gallery.

My take on the data is that the FP-90X is very consistent in simulating the normal behaviour of a typical grand piano.

For a consistent key velocity the overall power output is the same for a given key when repeated.

The power curve vs. note number follows the expected pattern. More energy is emitted by lower pitch notes than higher ones.

The amplitude curves vs. actual frequency also follow the predicted pattern. Mid frequency partials (C4 area) show the highest amplitude for a given note.

We should keep in mind that the human ear is most sensitive to frequencies in the 1000-4000 Hz range.

Cheers,

prout

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Purdy Offline OP
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Thanks that was a lot of work on your part.


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