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Well, i don't know if it's my CA-63 which is buggy or if it's a problem for everyone (and maybe also a ca-93 problem ?), but still...
lately, i've noticed that when pressing a key very softly (<=>trying not to make any sound), keeping it pressed, and then pressing the key which is 5 notes higher, then, instead of hearing the 1st key (sympathetic resonance) where it was, i hear the 1st key, but 2 octaves higher ! strange, no ?
for example, pressing a C1 very softly, and then pressing a F1 will trigger the bug... and i'll hear the F1 and the C3 instead of F1 and C1...

and, talking about bugs, sometimes, when i play very loudly (with the damper pedal), there also may be one key that leave as if i were playing with the sostenuto pedal (i mean that when i release the damper pedal, if i press this key, it resonates, whereas all other keys don't)...

ah yes, and i tried to do a factory reset and to re-update to 1.07, but nothing changed...

Thank you for your help !!

I believe that's normal Resonance does not work just with fundamental notes but with all harmonics. The first harmonic of F1 is F2, but the third is C3. The harmonic series of C1 is C1-C2-G2-C3.. Since they both share C3, when you hit F1 you make the string of C1 vibrate at the frequency of C3.

Strings actually oscillate at all those frequencies of the harmonic series at the same time, but they're different frequencies playing together. In your case you shouldn't hear C1 since you're not generating that frequency, but only C3 (and some more, higher). The string of the note C1 is able to oscillate at those different frequencies, but you only "push" C3 so to speak, so that's the one you hear. Try with an acoustic piano if you can and hear by yourself!

However, now you mention it, besides the bug I explained in https://www.pianoworld.com/forum/ubb...Another%20CA63%20review.html#Post1639579, I do think there's something odd with sympathetic resonance. In particular when I hold F1 down and hit Bb2, its third harmonic (Bb2-Bb3-F4) should make F4 sound, but it does not. At first I thought they might not be modeled because of the great distance, but then I hit F4 and indeed made F4 sound with a sustained vibration because of F1 being held. Interesting



I've had that behaviour when I hit keys while the piano is busy doing stuff, for example reading the USB. It kinda "locks" those strings and makes the virtual dampers act weird. I reported it and they said it's in the list of stuff they have to update. However I haven't had this while playing normally yet.

edit: I misunderstood your post at first

I tried, and i effectively heard a C3... it's funny lol


i found another but similar bug today
immediately after playing very loudly (as always ) (with the damper pedal), and after releasing the pedal (so i wasn't hearing anything), i depressed again the damper pedal, and i heard the resonance of the keys that i were pressing before releasing it.... like if i didn't released it meantime...


i also think it's the main cause of the bug.... when the piano is busy (like reading USB, or playing fast and loud xD), that may trigger one of these bugs.. let's hope they'll be fixed in the next firmware update

This behaviour is normal acoustic piano behaviour and very much desired by DP owners since it is an essential function required for many playing styles.

this is not what i was saying :P
if i release the damper pedal, i shouldn't hear anything (because the dampers are on the strings), but if i depressed it again after, i still shouldn't hear anything, because i'm not pressing any keys !

This digital piano behaviour is very much valued by acoustic piano owners because it reminds them how lucky they are to be able to play on a real acoustic instrument!

Michael R, what you're describing is not a bug. That's real piano behavior and it's one of the points dewster included in his DPBSD tests after my request. I would strongly encourage you to read the physical explanations in his thread in order not reporting bugs which are in fact desired features.



How unlucky for theJourney waiting for a new Kawai bug to make laugh of which now shows his real nature.

The harmonics of F1 and their shift from the equal temperament frequencies:
F1, F2, C3 (+2 cents), F3, A3 (-15 cents), C4 (+2 cents), Eb4 (-31 cents), F4 (0 cents)

For Bb2:
Bb2, Bb3, F4 (+2 cents), .....

As you can see, the "F4 harmonic" as a part of F1 (its eighth harmonic) has a pure frequency (F4 in the ET) and as a part of Bb2 (its third harmonic) has a frequency which is 2 cents higher than that. They differ in frequency and therefore are not mutually excitable.

However the fundamental F4 can excite the pure eighth harmonic F4, so you can hear it.

In conclusion, it's not a bug, everything is correct. theJourney should not exult

Look at the following article in Wikipedia: Harmonic series (music) - Harmonics and tuning . It explains the variance in cents for each harmonic.

Hi Cybergene. I was already aware of the differences, but thanks for the link as it's an interesting reference to have at hand, for me and everybody else.

I have to admit that I haven't considered in detail the actual frequencies nor have I tried that on an acoustic piano (yet) but Bb2 in fact excites F4 if you hold that key down despite the -let's say- round-off errors of the equal temperament, and F4 is in theory an exact multiple of F1. So it's not that clear.

Now, I'm oversimplifying and not taking stretched tuning into consideration, which even between octaves makes differences of several cents show up - yet you will still hear sympathetic resonance between such notes several octaves appart. This is because coupled oscillators (or, in this case, strings) can be excited not just with exact frequency ratios but approximations as well: it's just the coupling is weaker the further these frequencies are appart, until no oscillation happens.

I'm not 100% sure the example I mentioned should happen in an "real" piano because I'm no expert in acoustics (I'll try it as soon as I have the chance) but believe me on the previous paragraph (I'm an electrical engineer and I've designed quite a few electronic oscillators ;))

edit: bad typos :|

Indeed you are right, despite the difference in frequencies they should be excitable to some lesser degree. I believe Kawai have decided to not implement such a sophisticated emulation with harmonic resonances of differing amplitudes but it may as well be a bug. I am not sure if their CPU would allow that. Hopefully Kawai James can bring some light although I believe that's the least important issue in Japan right now... It would be interesting though to hear how is that implemented on Roland and Yamaha models supporting string resonance.

I don't know any DP that implements that behaviour. It's kind of neglectible.

I've just been trying an old (slightly out of tone) acoustic upright piano and the coupling between strings in this case was very clear.

I don't think they should bother modeling the intensity of this coupling depending on the exact frequencies involved, but simply allow them with a fixed value based on the harmonic numbers (and then of course modified by the strength of the key strike). It's how it works already; it's just it doesn't for some harmonic combinations.

Anyway, I agree with mucci's post in that it's a very very subtle effect to complain about. And my opinion about this piano hasn't changed: the sound quality is superb.



Absolutely



Or even between models within a same family. When I started reading about digital pianos I was suprised to learn that even relatively low budget ones implemented these effects even if just to a limited degree. I think it's overall a very important feature specially in certain styles (a couple slow romantic and impressionist pieces with very intense use of sustain pedal come to mind right now), and it would be another useful parameter to evaluate the complexity of the emulation done by different DPs.

yeah, i'm 100% with you that the problem of sympathetic resonance isn't a bug, but i wasn't talking about the same bug
i was talking about this one :

i recorded the bug i you wanna listen :
http://www.mirorii.com/fichier/69/391192/bug-zip.html
it doesn't happen always, (approximatively 10-20% of the time (and only if i play fast & loud ))
so in the zip, there's one record without bug and 2 with it (one of them being more noticeable)

Yeah this doesn't sound good at all. Very interesting, I'll try to reproduce it when I get home to try to figure out when it happens exactly.

Merci beaucoup

edit: nope, I've been unable to make that happen. Good for me I guess? Confusing tho