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Roger Hill

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Everything posted by Roger Hill

  1. http://news.santacruz.com/2011/07/13/in_soquel_a_luthiers_mystery_solved
  2. AB = 1/3 pin length AC=0.866AB arc radius = 1/3AC The arcs are swung from the inner points of the F-hole wings
  3. see page 6 http://www.fiddleheadstrings.com/microsoft_word___for_the_strad_part_1_8_sept.pdf
  4. Thank you for doing this. I have only briefly scanned your article regarding Cremonese arches. I, and I suspect a number of others, would be very interested in seeing this analysis expanded to include having the circular arch terminated at the measured inflection point (rather than the nadir) and repeating the analysis for catenary arches, again terminated at the inflection point of the measured arch. I suspect there would be little to distinguish any of the curves if the termination of the analysis for the curves is at the inflection point rather than the nadir. Since I am being so free with your time ( ), there is a general acceptance on this forum of using the average of the treble and bass side arches in constructing what is thought to be a good approximation of the original (undistorted) arches. I think that too would be of great interest here and should be relatively easy to accomplish given that you have all the arches digitized. Again, thank you for this undertaking.
  5. I have to agree with Lyndon, her fingering is terrible. If you listen to the opening bars of the Bruch by Bell, Zukerman or any of a dozen other recordings you will easily recognize the off-key notes. She sounds like a great violinist who hasn't practiced eight hours a day for the past ten years or so. On the other hand, I do hope that that violin will be passed on to some young virtuoso and we will get to hear more of it. I find the sound spectacular.
  6. Oded, you are missing the point. Fry is also working with an assembled instrument. The objective for both of you is to get a great sounding violin. Fry is not a maker, he is simply trying to re-work old violins (which have stabilized varnish) to sound great and get them into the hands of young players at low prices. He begins with the physical principles (following a particular Stradivari scheme) of thicknessing that enhance the breathing and suppress the rocking modes of the top plate. With these principles in mind he re-graduates. After reassembly, he scrapes the interior to enhance frequency regimes that aren't yet satisfactory. How he discovers these is largely by ear and feel of the violin. He also adjusts the areas that affect very high frequencies to increase response if needed. He could discover areas needing adjustment with string reciprocity, surface transducers or a divining rod and it wouldn't matter, what is important is knowing where to scrape to get the response you want. I see no difference between that and what you are doing in enhancing certain vibration patterns, which you discover through reciprocity. The tongue of the top is certainly present in some of the Strad top plates, see particularly the 1703 Strad that Anders posted some time ago. Fry explains the function of the tongue and his explanation makes physical sense to me. That physical sense includes what the summaries show of the enhanced low frequencies, suppressed mids and again enhanced highs that appear in the plots we see here regularly. Could they be obtained in ways other than the one Strad graduation starting point? Of course, they in fact were. I don't see why that should keep him from trying a starting point that he knows works and adjusting from there. The bottom line may be that you both know the sound you want and what you want is, in fact, different from that that Fry wants. That you both know where to scrape to get what you want is admirable and what I consider the "art and quality" of the maker. I see no difference in scraping the inside or the outside. We are talking tenths of millimeters of wood removal, or less. The local vibration amplitude is first dependent upon the local stiffness of the plate which, we all know, varies as the cube of the thickness, i.e. is very sensitive to the thickness. The local arch height, being the central point between the top and bottom of the plate, is barely changing whichever side you scrape. A tenth of a millimeter reduction in thickness produces a twentieth of a millimeter change in arch height. I find Fry's explanation of the violin to be the most complete thing I have ever read about the violin and it is very surprising to me that, to the best of my knowledge, no big name maker has ever worked with him to build a new violin based upon his ideas. I do not think that the Fry explanation has covered all the facets that may ultimately come forth, e.g. John Waddle's measured discovery that the north-south centerline of the volume lies at the bridge. I suspect that also there is some "Cremonese method" of matching back and front plate stiffnesses (as opposed to mode frequencies). Still, I think that Fry has contributed a great deal and I certainly don't see why he is seemingly dismissed out of hand.
  7. That is one starting point if the violin he is working on will permit it. Recall that he is working only with existing old violins so that he is stuck with whatever wood, arching, thicknesses and varnish are already in place. He re-graduates, etc. and then works with Rosemary Harbison to "tune" the violin to his desired sound by scraping the inside. He can't really work the outside since he doesn't re-varnish. I've had several conversations with him about his approach and he will tell you, straight away, that the old masters tuned their violins by ear, in the case of Stradivari scraping the inside after the violin was "finished".
  8. Why wouldn't what Jack fry describes, i.e. scraping the inside through the F-holes, accomplish the same thing? What he does doesn't depend upon how you decide where to scrape.
  9. look here http://waddleviolins.com/downloads/Cremonese_Nov2003CASJournal.pdf
  10. [\quote] Do you have a printer ? yes. what I am hoping to avoid is hand digitizing, then summing, etc. (prior to doing fft) for a dozen different impulse curves
  11. I would like to be able to hang my violin with rubber bands, then tap it a dozen or so times in one spot and have the code sum the impulses and (as input from a microphone to sound card) then do the fft's. will require some logic to detect the peak at each pulse and then shift the individual pulses before summing. Can't find anything else that will let me do this, including my exotic loudspeaker software.
  12. I left my FFT at the office when I retired, and I didn't use it then. I developed a routine based upon the quadrature formulas of Filon, which give much more accurate results for Fourier integrals which must cover functions of widely varying time scales, such as characterized by summed pulses of nano second and microsecond duration. I was never infatuated with the normal modes analysis for anything but the simplest analyses. I preferred to simply set up the difference equations and do things in the time domain if it was at all sensible to do so. If you have the computing horsepower and the time domain equations, it just makes life easier. So that is how I tend to visualize things, with a time clock in the upper right hand corner. I also watch swinging balls in the time domain, but that is just a personal preference.
  13. Well, I suppose it is odd. Looking at 15 balls in a regular motion I understand and seeing the apparent complexity of the motion of the set of them. Somehow it reminded me that I could next do the same length pendula with more or less rigid shafts and get the same thing to happen. Then my thought process said I could weakly couple them together at only one point from each shaft to the adjacent one and try to understand that motion. Then I thought, good heavens, I could put a different mass at the end of each and really have something to analyze and I could even throw in some damping just to make it interesting. And the next thing that occurred to me was that the coupling springs could all be different too. And them, Shazam! instead of different masses, I could break those pendulum shafts down into a series of unequal lumped masses, each connected to the adjacent ones with springs again. And then let them move in three dimensions. And all of that would still be described by the same simple equations of the coupled harmonic oscillator. And, best of all, if the east -west springs were made much weaker than the north-south springs, but they were all still different, and there were varying numbers of lumped masses in each direction, I could create a system analogous to a violin plate. But then I thought, hey, this gets better: I could also connect all those little masses with damped torsion springs so that they would resist twisting motion and everything would still be described by the harmonic oscillator equations. And then I thought, "well I'll be a son of a b*tch, if I could solve all those simple equations and figure out what all the masses and spring constants should be, I'd really understand the violin." And then it hit me, "Roger, the resulting motion is too big a problem for your simple mind." So after all that, the next thought that came to mind was that, "you know, the flow equations aren't aren't really any more complicated than the equations of the coupled harmonic oscillators in three dimensions, yet they contain all that chaotic turbulence." So in the end, you're right. Such a thought process that connects simple harmonic oscillator equations with something that is truly chaotic is clearly that of a sub-human intellect that has no business rubbing shoulders with the real intellects here.
  14. We have reached the point where no words from me would convince you. Lets leave it at that.
  15. I trust that both of you noted that I merely said that the apparent complexity "reminds" me of the chaotic motion inherent in the seemingly simple flow equations, not that the oscillatory motion is, in fact, chaotic. Torbjörn: if the vibrations take care of themselves, i.e. are under the sole control of the player, why is there such demand for violins that the virtuosos perceive as vibrating differently?
  16. Duplicate deleted. Don't know what is causing duplicates to post.
  17. Well, yes. And given the complexity that is exhibited by such a simple system, one that we can all look at and understand how it works, does this not provide a good demonstration of why the violin is so damned difficult to understand? I see myself in your response to something that to me is quite elegant. Most everyone here regards, varnish, scrolls, corners, purfling, etc. as elegant art. To me they are mundane details that don't affect the sound one bit and are, hence, of very little interest and certainly nothing to get exercised about. I'm inferring something here, and may be totally wrong, but I suspect your reaction to these vibrations is very much akin to my reaction to scrolls
  18. you're certainly correct in all you say, Brad. I could write that program right now. Now, tell us the truth........as the video started and you first saw the apparatus, did your mind's eye have any inkling of what would evolve? I am well trained in physics, lots of experience with oscillating systems, and I had no inkling that the evolution of what I was about to see when the prof dropped the board would be anything so complex. As I think about what will happen, my mind does not anticipate the system of the relative separations of the balls, which is what makes the patterns interesting. Now take your mind to the next level, where you decompose longitudinal fibers into (say) 25 segments along the length of the fibers and couple those segments with springs. Can you visualize how the motion will evolve from such a system if you tap one of the fibers at some given location? Again, this is a system of simple equations that those same physicists and engineers can write down and solve with computers. Compared to a violin top surface, we are still talking about something that is very simple compared to a violin. As you say, the violin is much more complex. Which was my whole point in posting this.
  19. if I knew what you are talking about I am sure I would have some deep, insightful reply...........
  20. My bet is that the ornithopter will not get off the ground, let alone be controllable, without the top wing. Entertaining none the less. But then, perhaps I am easily entertained
  21. What you must look for is how adjacent longitudinal fibers of different length vibrate at different frequencies after a simple stimulus. Different length can be defined as the length between substantial changes in thickness. The complexity of how the vibration evolves between adjacent fibers is mind boggling, and based upon very simple physics. Reminds me of the chaos intrinsic in the equations describing the movement of gas in the atmosphere.........A butterfly flapping its wings in Brazil causes a hurricane in Florida, or something to that effect. That the simple harmonic oscillator equations contain this, for a series of adjacent oscillators, is really remarkable to me. Perhaps I'm just easily entertained............
  22. http://sciencedemonstrations.fas.harvard.edu/icb/icb.do?keyword=k16940&pageid=icb.page80863&pageContentId=icb.pagecontent341734&state=maximize&view=view.do&viewParam_name=indepth.html#a_icb_pagecontent341734
  23. Hi Anders: The whole point of my first post was that the efficient high frequency radiation, for any given frequency, comes from some small isolated area, (not a half-dozen areas) so that comb filtering will not become an issue.
  24. If that is what violins are, different people listening to the same concerto in the same row would say that the strad sounded awful, wonderful, sonorous, cacophonous, screechy, silky, etc. They would all be listening to very different high frequency content in the music. I'll get right to work on the acoustic weapon. I'll have my wife help. I'm certain that she can hear 25kHz, as the minute I put a violin solo on the stereo she runs from the room........
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