Jump to content
Maestronet Forums

Roger Hill

  • Posts

  • Joined

  • Last visited

Everything posted by Roger Hill

  1. Don and David: Fair enough. My biggest question about Fry's work is that there is clearly more than one way to come up with a great Strad or Del Gesu. Things like the tongue, the various holes, etc. that Fry identifies are not present in most of the famous violins for which graduation maps are available. The things he shows are sufficient but not necessary conditions to produce a selection of great violins so long as all the other features of a particular violin, great arches, wood, varnish are present and those may be the controlling features. I don't have any idea how to sort them down to a set of minimum essential features, if such a set exists.
  2. Hi Don: Have any of our respected makers ever tried to implement Fry's ideas? I am unaware of any such efforts if they do exist. Secondly, Jack never made a violin, his efforts were directed at providing good quality instruments to deserving youngsters. He always started with what he thought was a good prospect, repaired it, re-graduated it, tweaked it with his ideas, etc. to get the most out of it he could. Thus, his violins were made by someone else from wood he did not select, varnish he did not make or apply, arch shapes he didn't choose, etc. I think we really have never tried his ideas unless you know of examples I am unaware of. Also, like everyone else, I'm trying to figure out this whole violin sound production system. Could you give me a brief summary of ideas you think he has wrong? Thanks
  3. I sure don't expect much low frequency radiation from the ribs, the air is a direct sound source coming out of the sound box. Are you telling me that the disturbance from the small area of the ff holes is appreciable? With loudspeakers the radiation from the vent is usually well below the SPL from the cone.
  4. So you're thinking of direct radiation from the string as the third cone.............
  5. If you read the page I offered you will note that the assumption is that the speaker box has rigid walls. It is no great extension of the derivation to note that for the violin, at low frequencies the back also acts as a radiator, forming a dipole. Same derivation applies, only with two speakers oppositely directed. The rear speaker cone (usually on the back) as well as the front cone are driven mechanically instead of electrically as with the loudspeaker. The analysis of the air motion is unchanged. Now, I've got 2/3rds of the picture. Would you please grace us with your EXACT explanation for the final third? Inquiring minds want to know.........
  6. Carl: Would you please give me your explanation of the EXACT function of the bass bar and same for the working mechanism. I've always thought of the bass bar as something that makes the top a more rigid piston at bass frequencies, thereby enhancing low frequency radiation. Mechanism similar to that of a low frequency vented loudspeaker, described by the Thiele-Small equations, see http://www.silcom.com/~aludwig/Sysdes/Thiel_small_analysis.htm . Are your thoughts greatly different from mine?
  7. I have a lot more experience with balsa wood than with spruce and maple. When working with balsa for (say) a hand launched glider, a finish (usually nitrate dope) is applied which has the effect of hardening the surface and stiffening the balsa. I assume that the ground can do the same thing with spruce in particular. My question: do we try to stiffen the spruce with the sealer/ground? I've seen many cautions not to allow oil to soak deeply into the surface as it has a "rubberizing" effect that would damp vibration. Do we want the ground to enhance vibration? In particular for high frequencies which stiffening should enhance? Thanks
  8. Out of curiosity, why do we not build new violins with a thin (say) 1" diameter maple disk inlaid in the top cross grain covering the sound post area, or even harden the spruce with a series of pinholes filled with hide glue or (god forbid, cyanoacrylate)? Hope this isn't too far off track.
  9. Hi David: You're making my point. We don't even know what to measure to model, what is invariant across a spectrum of great violins, yet we have something carved from wood, easily picked up by a 10 year old child. It appears to be something only slightly more complicated than a soccer ball. As Sacconi noted, where are the secrets? Not in evidence, yet for all the apparent simplicity, we don't know the key ingredients that separate $100 dollar ebay violins from $10 million del Gesus. It isn't the cosmetics, the workmanship can be duplicated, the materials properties can be measured, the geometry can be precisely duplicated, material properties can be adjusted to render desired dynamic properties, but we still don't know, as you put it, what is invariant across the great violins. We produce perhaps a few dozen violins per year that are equivalent to the great ones in tonal qualities, and thousands that have workmanship comparable to the great ones. If there were a market for 1935 Rolls Royce automobiles, we could produce an exact equivalent, we know all the variables. For violins, we are either failing to consider and implement some essential physics that we already understand or we need to dig deeper to identify some physical principles that warrant further study before we can discover those invariant properties.
  10. Why not go to the real mystery? What physics could we be missing? We know about vibration modes, we know about wood properties and materials properties, we know about cavity resonators. We can even produce exact physical replicas of any given violin now that we have CT scans. We have the ability to reproduce near perfect computer simulation of all of these issues at our disposal, yet we don't know how to combine our knowledge of the various phenomena, we haven't even been able to even decide what physical phenomena are truly fundamental so that we know what to model to examine the great violins. We have 300 year old violins that are in great demand in the market place but we can't seem to reverse engineer them, so what are we missing? If you gave me a Ferrari or satellite launch system and an adequate budget, I could reverse engineer that exactly, yet with half pound of wood and some simple steel strings in hand, we flounder while violinists everywhere crave a Strad and we can't seem to come up with anything great repeatedly. What could we possibly be missing? And of course we know, that Stradivari was missing it also for much of his output. Maybe black magic is the only explanation...........
  11. Don: I know what a cycloid looks like. You know what a cycloid looks like. We both know what a cycloid approximation to a violin arch looks like, with the low point at the minimum of the trough. I guess no nit is too fine to be left unpicked. You are not contributing to the understanding of the point I made for those who do not have the knowledge of mathematics that you and I have. You know very well from what I said that I meant the end of the arch shape curve as I defined it. You don't have to prove to me that you are smart, I know that. I've made my point, no good deed goes unpunished. I'll bow out now and move on to other things where I don't have to be harangued with pedantic bullshit. Roger Hill
  12. "What do you mean by "from any interior point along the line"?" A point on the arch shape curve that is not at either end. If you carve a perfect CC on the outside and use a uniform thickness for the top, both the arch shape curve and the parallel line along the inside surface of the plate will also be curtate cycloids to a close approximation. You will find a lot of clarification if you simply print out a transverse ct scan picture and draw the middle line of the top and look at what I am saying. If you are a windows user, open Windows accessories and find "snipping tool" to make this easy. "But then, I know nothing, and that is probably wrong." yup, its wrong. As you get closer to the end, the tangent becomes horizontal and not steeper.
  13. Could either of you provide a link to where "the other Roger" discusses this? I've missed it in my reading and would like to know what the great man said on the subject. Thanks
  14. Yes, of course. But you would have to do some very counter intuitive carving at the edge to do it any other way. Putting the minimum of the CC just inside the purfling will lead very naturally to the arch approaching the edge at a right angle.
  15. If you spend some time looking at the various CAT scans of the violins of the old masters, the most notable consistency is that the transverse arch approaches the rib at right angles. Darnton may have discovered the importance of this as the curtate cycloid enforces this automatically.
  16. Here is the rest of the story about my posting: In my first career I was a physicist and worked exclusively on defense problems. On one of my frequent trips to Washington, D.C. (perhaps '69-'70) my flight arrived early enough to go out to dinner. The restaurant I chose was in mid-rise hotel building near downtown and was supposed to be good. I got there at maybe 9:30pm and was the only customer in the place. They had an old violinist playing any request so I heard more than enough of my requests. Try coming up with enough requests for a solo violin when you haven't yet learned much about classical music (I was perhaps 26-28 at the time). Plus, even to my untrained ear the violinist wasn't particularly good and he certainly wasn't very enthusiastic about what he was doing. When the story of the Huberman came out (perhaps 30 years later) I learned from the story that the violinist was almost certainly Altman, who was definitely not Joshua Bell. A disguised Bell could, of course, open for a rolling stones concert and be enthusiastically received by the most tin-eared groupie in the hall. I did tip the violinist all I could reasonably afford, but did so mostly out of pity. He really wasn't much of a showman or musician.
  17. http://www.tampabay.com/things-to-do/stage/joshua-bell-heres-the-story-behind-my-very-famous-once-stolen-violin/2310865
  18. start here: http://straightrazorplace.com/srpwiki/index.php/Category:Honing
  19. Thanks, Davide. I shave with a straight razor (most of the time) so I have waterstones ranging from 225 grit to 20k grit. Will try this for a couple of new scrapers. Had always used the knife edge profile, but what you do sounds a lot quicker/easier and obviously works beautifully.
  20. Davide: very impressive skills. I love to watch you work. questions: how do you smooth the edge of the scraper prior to turning the burr? do you have different scrapers with different corner radii for various arching edge profiles? thanks,
  21. Those who do not know history are condemned to repeat it: http://www.maestronet.com/forum/index.php?/topic/317954-cremonese-arching-explained/ When I first started I thought I came up with something unique. I learned a lot from this. I think Michael Darnton learned a "little". What I learned is that when you are examining curves of very little curvature, a circle, catenary, spline, parabola, cosine, et cetera ad nauseum, will all fit the curve very well within the errors of carving accuracy, desired smoothness, etc. Occams Razor says use a circle as Michael advocates. I still think the inside first method I proposed (different from Torbjorn's but inspired by his ideas) will easily produce "Cremonese Arches" but so will any other method designed to do so, including appropriately calculated curtate cycloids.
  22. Thanks for taking and posting those pictures. Brings the instrument and cellist to life.
  23. This thread at The Straight Razor Place may be of interest............ http://straightrazorplace.com/hones/115250-auction-site.html#post1416066
  • Create New...