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Roger Hill

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Everything posted by Roger Hill

  1. The French polishing I have seen on guitars is typically opaque, and forms the surface of the wood. The back of this violin appears to have a clear layer over the wood, just what you would expect of ordinary varnish. Yet, it does have that "V" wear pattern (see here ). I hope that David, Jeffrey, Melvin or someone else who has seen lots of Cremonese varnish will tell me what I am looking at. Later: I'm having trouble getting the link to work, works fine with a copy and paste
  2. I asked her husband if she had any violins by contemporary makers. He said that she was given one by a current maker after she bought one from the same maker for her foundation, which provides violins to students. He didn't know who the maker was and said that she really plays only two violins, the del Gesu and a violin set -up for baroque.
  3. Have to echo everything skiingfiddler says. Heard Barton Pine do the Beethoven concerto this past Tuesday night in Colorado Springs. Unbelievable tone and technique. Rachel Barton Pine is that combination of talent and hard work that we reserve the word "genius" to describe. I sat in the mezzanine to her left, perhaps 75 feet away. She could always be heard above the orchestra, even though not straight on. If you have ever heard Rostropovich do the first Haydn cello concerto (only recording in my case) that Strad cello sounds as if it must look like the Tacoma Narrows bridge as it was resonating. You get the same feeling with the Soldat, which is, of course, sweeter than the cello being at higher frequencies. If she just touches the strings it produces powerful, woody tones. At the upper end, this violin and the "Kochanski" played by Aaron Rosand produce as sweet of highs as I have ever heard......lots of high frequency overtones. At intermission, she and her husband were selling her new CD of the Beethoven (which was released that day). As everyone else went back in, I skipped the first ten minutes of the "Emperor" concerto with Andre Watts, as her husband was kind enough to spend ten minutes allowing me to examine the Soldat. I was particularly interested in the arches which are low. Front appears to be about 14-15mm, with a long center flat section. Back is about the same height, maybe a mm higher and more peaked. To my eye, the peak of the back appeared to be at the sound post location. The cross arches do not have a lot of re-curve. The shape seems to be that of a straight line as the arch curve approaches the edge, work into tangency with bottom of the edge flute. The only apparent inflection is the edge flute curve. (I could certainly be wrong about this, I didn't touch the violin, but that is the way it looked to me) If you have the Kochanski poster, the cross arch curves of that violin are the complete antithesis of those on the Soldat. The Kochanski curves are the poster-child for the Curtate Cycloid arching, the Soldat for the catenary. I wish I could have my hands on that violin for about an hour in bright light to be sure of what my eyes told me. The other thing that struck me about that violin was the varnish.....seemingly flawless. There are a few black marks in front of the bridge. On the back, there is the usual "V" shaped area where the varnish is lighter in color. I don't know if that means that the varnish is missing there, but it surely didn't seem to be. All over, this violin has a sheen and glistening that to my untrained eye says all the varnish is there and it doesn't appear thick, only perfectly transparent. You may have guessed by now that I was really impressed by the first Cremonese violin I have ever seen up close, rather than from the audience. If you are in the market for some new CD's, rachelbartonpine.com has them all. I have the Brahm's concerto, Instrument of the devil and the Beethoven concerto. They are all wonderful. Plus she writes her own credenzas.
  4. Let me tell you an anecdote from the past: When I first got out of graduate school (1967) I went to work for Kaman Sciences here in Colorado Springs, which was a subsidiary of Kaman Corporation, a helicopter manufacturing firm in Connecticut. The founder of Kaman Corporation was one Charles Huron Kaman who was a guitar lover. He decided that since he had the (then) "worlds best team" of structure, flutter, vibration and composite materials analysts that he would have them create inexpensive guitars that would equal the sonics of the finest guitars available. He bought a series of such guitars and put the team to work, doing every conceivable measurement and analysis of said guitars. The result was the Ovation guitars, with round backs of carbon fiber cloth. They were noted for their powerful projection, but no one would buy them until he he paid Glen Campbell to use them on his TV show. Even then it was tough to get the market to accept them. The problem was not the aesthetics, but the acoustics which "duplicated" those of the great guitars. The problem in the market place resulted from the initial assumptions, i.e. that the acoustic properties of concern were the sounds as heard by the listener, which were a duplicate of the expensive guitars. Wrong, what the players wanted were the sounds that they heard, those in the side lobes of the radiation, which were not what the engineers duplicated. I think the lesson of this story is to make sure you focus on the right acoustical properties. Those detected by the player, which may be only weakly radiated, are equally important as those projected forward by the violin.
  5. Dean and Oded: That was exactly my interest. If you either slide or rotate the template to adjust arching or thickness you will introduce either a kink or flat spot in the center of a no longer precisely defined CC. Artistic license can certainly be used to smooth things together, you simply give up the mathematical precision of the curve, to which any but the most anal nit picker will say: "so what?" Slide the template far enough and you will end up with a flat-topped curve that resembles something drawn with an inhomogeneous.........oh, never mind
  6. Guess I need a little more explanation then. If the instrument is first put together, then the top finished, then the top adjusted to satisfy the EAR principle, how does the EAR principle adjustment maintain the curtate cycloid shapes carved from templates? or is the thinning done on the inside after assembly?
  7. Bill: I am distinctly non-religious, but to your comments I can say (quite assertively) Amen!
  8. Hi Oded: Does that argue against the cross-arching curves being curtate cycloids, formed from templates?
  9. "You haven't spent much time over at the audio foolery sites have you?? " Bill: Yes I have. I have really ruffled feathers there with my assertion that "C-37" theory is a large pile of B.S. We got enough to work to do without introducing bone density into the equations.
  10. To violins88: There is an interesting analogue to the violin that illustrates the coupling of different physical phenomena, and that is the loudspeaker in a vented box. Analysis begins with an equation for force on a moving coil in a magnetic field and induced voltage and current created thereby, proceeds to an electrical equation which is basically V = IR around a loop and then considers F =Ma for the mass of the speaker coil/cone and the air it moves , as well as the mass of air that moves into and out of the box. Damping arises from heating of the air in the box as well as resistance in the circuit. Finally, SPL is related to motion of the coil/speaker cone. Will take you about 15 minutes to read and get a feel for it. Highly recommended. http://www.silcom.com/~aludwig/Sysdes/Thie...ll_analysis.htm The input energy for the speaker system is electrical, that for the violin is mechanical. The easy part is that no one ever obsesses over the varnish on a loudspeaker
  11. Hi John: Where do you find the Bissinger paper? What were the conclusions you find unsurprising? I am also interested in the answer to David's question. Thanks,
  12. Thanks, everyone. Darren: I've tried to download those PDF's but they crash both Firefox and IE7. Anyone else have this problem? Ken and Michael: Is this the Richard Thomas program or the other cycloid program? Thanks, later: download now works fine. An Autocad type approach may be exactly what I am looking for. Hope to find something with an easier learning curve than Autocad, and preferably free.
  13. I would like to be able to scan the arching curves from Strad posters into my computer, read values into Excel and do some curve fits. Looking for suggestions for a cheap but useful scanner, software which will do the reading of the points on the curves, etc. Anyone done this, recommendations, etc.? Thanks,
  14. IIRC, in the book "violin maker", Zygmuntowicz is quoted as saying that he removes the asymmetry when making del Gesu copies.
  15. Several years ago, David Stimson mentioned a book by Roelof Weertman in which he described using Hyperbolic (catenary) arches and prescribed ratios of front-to-back stiffness. Mr. Stimson indicated that he had permission to distribute copies of that book. Anyone have any more information? I would certainly like to read the ideas. Thanks for any leads. Roger Hill
  16. Hi John: your stiffness result, as reflected in a spring constants for the top and back, is fascinating to me. Would you take a look at this thread and comment on whether you and Roleof Weertman are/were using the same basic consideration. Also, how are you measuring the frequency of thae plates? Thanks, Roger Hill http://www.maestronet.com/forum/index.php?...=194067&hl=
  17. I am sure he has made more than one. He has learned a lot since the mid-80's. What he does these days is take old ones, repair, add patches, etc. so that he can graduate to his schemes and try to get them into the hands of good students. I suspect that what he puts out today are well ahead of 20 years ago. He is a great guy. If you have any questions about what he does just call him in either Madison or Des Moines.
  18. He doesn't make violins. he takes old violins (typically pre-1900) that he buys for low $, repairs them, and then tries to improve them. The reason he does this is that he wants something for which wood and varnish are stabilized. He is limited by the raw material he starts with. If he has changed his modus operandi please correct me.
  19. Wow! That is beautiful work, Melvin. Particularly like the arches. They look just like....well, never mind
  20. Actually, Jacob, that standard of measurement here in the U.S. is kept in an environmentally controlled and isolated bunker at the National Bureau of Standards, just up the road in Boulder,Colorado (home of 95% of the remaining communists in the world), along with various atomic clocks, Meter Sticks, etc. We refer to it here as a "Gnats A$$, with the emphasis on the first $. Newbie violin makers tend to work in larger, less precise units, such as "elbows" because the carving requirements are less refined, as are the accuracy standards for curve fitting and recognition
  21. Ben: any chance that you will publish any of your working drawings? Very nice work that I would certainly buy.
  22. Ken: Calculated them down to a gnats elbow with my bureau of standards calibrated MK I eyeball. In other words, no. But since I can cover any of the long arch lines with a 2-3 mm chain, they seem reasonable enough for government work. Please understand that the last Kruse curve is not a different fit, just another photo from an overhead view to make the line position more visible. Note that the tag ends of the chains point inwards, indicating viewing from above. BTW, I hope you are looking only at the long arches, not the cross arches.
  23. Jacob: very useful comments, and I too am pleased to see you back. Thank you for telling me what you learned. Oded: bite your tongue
  24. Hi Ken: Good advice. But I will have to carefully consider which one. I know that Michael has a very good eye and has been very generous to the community in sharing his knowledge. While I appreciate very much his processing the Strad back outline, I think his complaints about my eye are rather petty. I was, after all, able to look at curves and see their mathematical structure, something I haven't seen claimed before. As for the chains I use, I am not going to spend a few hundred bucks to get something in gold that is 16" long and 1mm. My chains are 2mm and 3mm and cost about $3.00 each. Further, there is substantial runout in one of the 2mm chains, i.e. it hangs in a natural twist of about one complete turn per three inches. That is the least stressed condition for that chain. A few more words about the curves: on the del Gesu long arches it took me 45 minutes to hang the long arch alone. I started by attempting to use a constant offset from the poster curves to make the line more visible. What I pictured was the best I could do at locating the pins. In the configuration I pictured, taking one link of slack out of the chain would move the center portion of the catenary above the line, even though I was trying to hang the whole thing about 1/8" below the line. On the Kruse poster I started by placing the pins very close to the line so that producing the photos wouldn't take me all night. It is still very difficult to get the pins in place and tension adjusted to leave any of the line visible, as I attempted to do. Look carefully at my later photo of the Kruse curves. You can do a much better job of overlaying the chains on the curves with your index fingers, but then you have to take a picture through you back with your other two hands. I haven't yet acquired those skills. Finally, suppose you have a new theory of something, doesn't matter what, and you send me to the lab to measure what you have predicted. If I came back with results that were better than with +/- 1 over a mean of about 10, maximum of 15, for (say) 360 different measurements, you would be very proud of your theory and I would be very proud of my measurements. Well, the accuracy of what I propose is even better than that. It is not valid to say that any discrepancy prevents one from saying that the theory seems correct. Further to the point, if you say that there must be much greater accuracy than what is shown, it is perfectly pointless to pursue "how did they do it" questions. There is not a set of data accurate enough, or consistent enough to draw any conclusion if your standards are that high. Then we are left to say only, "its magic."
  25. Oded and Ken: not taking either of your comments as buckshot. Please go to the other forum and read Michael's comments again. Feels like I imagine buckshot in the butt would feel. Oded: I certainly respect your experience, knowledge and arguments. Your arguments are very good ones and I acknowledge that they may very well be correct. Can you acknowledge that the longitudinal arch curves I propose may be correct? Ken: "I am persuaded" (am I repeating myself ) that the CC's are probably what was used. And I think that starting with an interior catenary is a (good, plausible, feasible pick one) way to get there. How you get there, of course, depend upon your starting point. There seems to be some disagreement as to where that may be Bill: I'm working on my first one right now. I have some access to violinists in the Colorado Springs Philharmonic and I will report their comments when it is done. This work is simply the result of my studies of arching as I try to understand the beast.
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