Hi Richard, In fact what was stated in the "5 lectures" was the same that what I said : excerpt from the five lectures : "It turns out that at a certain dynamic level, about mezzo forte, the key reaches its bottom position at the same moment as the hammer strikes the string, while at other dynamic levels this synchrony is dissolved" "The relation between the moments of key bottom contact and hammer-string contact shows a smooth progression with dynamic level (see Fig. 5). At a soft level (piano) the bottom contact is delayed compared to the hammer-string contact, and at louder levels, the contact is advanced - at forte it occurs even before the hammer strikes the string(s)." I guess we took a too fast lecture of the text as a truth (was ready to believe it myself before I think twice) Checking moment was not tested, I see no experiments stating that checking occur always after key bottom. Then, by evidence the hammer does not catch before or during string contact !!! The more I think of the energy that is transmitted to the hammer (or robbed from it) via the hammer center pin, the more I am persuaded that any bump transmitted to the action stack, is playing a non negligible role, in regard of hammer string time contact. The contact being more than one time evenement (the hammer being in contact, more than once at time of stroke in part of the piano ), any bump arriving at this moment could modify the hammer string interaction more than we can imagine, may be as Bernhard state also for phase reasons (?). This is part of the front punching effect , to me. (???) Not talking of synchronicity key/backchecks there. An adequate energy acting on the hammer center at the good moment can very certainly lengthen the hammer/string contact duration, fighting the shortening of that moment that occur with higher force of play and reinforcing the low frequencies then. (I'd state that this is one of the reasons very low shoulder needling add lower frequencies, while at the same time limits the high spectra) it cut in the fundamental non linear properties of the hammer, because it break the stiffening chain low, at a place where it acts mostly under heavy playing. Too bad Askenfelt, did not experiment with different stiffness of parts, shanks, punching, nor check the synchronism of drop letoff as a parameter to be used for the tests. I believe that the braking induced by jack rubbing on roller, and regulating button, drop screw on button and augmented by the shank flex, is modifying the synchronization of the different events a lot . I recall Askenfelt and friends used very precise sensors to determine moments of contact or bottoming, but those sensors where fixed so no way to see the changes induced with regulation or different punching. A study about the results of those events (based on the shocks waves only) should prove interesting. the device they used could not measure acceleration (speed) of parts alone. For instance when they analyze the staccato note, we don't know if the finger accelerate the key to the bottom, or if the key is thrown and goes down with its own inertia, yet slowing to produce the note. In that case they notice the hammer hit the string, then goes in check, then the key bottoms. I still believe that some technicians and pianists are more able to understand (or suspect) the action function than engineers , as usual, engineering can see some events, while the artist and the technician have learn to use the result of these events and perceive them in a different way. For instance a friend of mine which studied a lot acoustic in regard of the piano said me that never made him a better voicer or tuner. I have to go, I'll like to hear more on the subject of the way the hammer center can be made firmer or more floating with other impact. I thought also that this 2 mm dimension is a mean to keep some "parallel" between the system having a drop dimension of around 2 mm (we are more in the metaphysics than physics there !) Have a nice day Isaac OLEG -----Message d'origine----- De : Richard Brekne [mailto:Richard.Brekne@grieg.uib.no] Envoyé : mercredi 18 août 2004 10:19 À : oleg-i@noos.fr; Pianotech Objet : Re: back check, a magical mystery tour. Isaac OLEG wrote: >Because of the key and the system flex , I believe that "synchronism" >, or a very short follow-up is very well possible, assuming the hammer >hit the string and is back in check in a very short moment, and the >key did not bottom yet, for instance. > > As Ed Foote reminds us... Askenfelt shows that the key bottoms out before the hammer hits the strings above soft play. That said we are talking nano seconds here... or something like that :)... That said again... how the 2mm spacing can affect any of this in the way Bernhard suggests seems unlikely... but hey... who knows ? >Another possibility is that the key bottom first and the hammer is in >check before the wave travel of the key is yet passed... > >The hammer impact also is generating a bump, (one in the string and >one in the hammer pin) so we are yet there with 4 bumps in a very >short time.) > >And so on, I will probably not dream of that tonight, so no chance I >see the light since tomorrow ! > >The idea of these serial of bump reinforcing a wave going toward the >tail of the piano pleases me a tad also. > > > This affect of impact noises on the tone and sustain of the piano is one of the things I've been on about for about 5 years now. These noises definantly do travel through the system, and can have a positive affect on the sound the strings impart as they vibrate, can help to increase the effective sustain, or can contribute negatively as well. Sorting hammer shanks for their resonant frequencies is an example of some manufacturers trying to take advantage of this. Indeed... Steinway philosophy would have it the the entire instrument should be seen as sound bearing, and sound producing in some sense of the or another... and as such each element should contribute what it does in a positive fashion. (which in the end is part of the reasonment for the famous magic circle of sound... which of course seems greatly overstated from most technicians perspectives) In the end... such things are just another little cog in the entire sound making machine. Some technicians of course take the tact that much of these are in reality unwanted noise... and we get past talking exclusively about impact noises here immediately and get into all kinds of things.... but it seems to me quite obvious that the discussion about what is or isnt noise in these regards is purely a subjective one... even taken to extremes when it comes down to it... and really has no place in discussion as a justification for objective criticisms of any particular manufacturers design. >A similar effect partially occur on vertical pianos , seem to me (or >part of the aforementioned) > > no doubt... for that matter any instrument. >Isaac OLEG > > > Cheers RicB
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