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Roger Hill

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  1. if the violin, or anything else, is to be an efficient radiator of high frequencies with a pleasing power distribution, it must be a single, isolated vibrating surface, or an isolated portion of a larger surface, most of which is not vibrating at that frequency. We know that the high frequencies from the violin are radiated from the top. Look at the most common tweeter for high fidelity speakers: it is a 1" hemisphere. The characteristic size of the radiator must be comparable to the wavelength it is trying to radiate, this is true for both electromagnetic and acoustic waves. Midrange speaker drivers are about 4" in diameter. Bass drivers 10-15." In the case of acoustic radiators, the well designed radiator behaves as a piston, typically less than one wave length in diameter. If the characteristic size is several wavelengths long, then we have the radiator itself vibrating in its characteristic structural modes, ie several up and down areas. These produce pressure pockets and rarefactions that cancel each other when you get to the far field, and thus little energy is radiated. Next, consider a perfectly symmetric violin, one with a single string and the bridge and sound post in the middle(uniformly graduated, no bass bar). whatever happens on one side happens on the other. All the modes will will be symmetric about a vertical longitudinal plane. As one goes to high frequencies, the vibration will have several ups and downs across the top of the violin, and equal numbers of each on both sides. We will have (again) rarefactions and pressure pockets side by side, radiating out from the surface. We will also have a terrible cacophony of high frequency comb filtering (cancelation and reinforcement) that would render the sound unlistenable. Thus, when we get to frequencies that correspond to wavelengths considerably smaller than the length of the violin body, we need one principal area of the violin to be radiating at a given frequency. (There will be other principal areas radiating at the harmonics) How do we accomplish these requirements in building the violin? Well, we do some judicious thinning in front of the sound post, maybe on the f-hole wings, we put in a bass bar that doesn't move much at high frequency, etc. It is in no way mysterious that the violin must be asymmetric, given what we ask it to do. The luthiers art is simply to give it the best asymmetry. I plead ignorance as to how to do that.
  2. Happy Birthday, Dean. Give the wife a kiss, scratch the puppy's ears and enjoy the day. The important things help the recovery from anything. Roger Hill
  3. Hi Janito: Haven't forgotten, John's posts were the point of my question. I remember John's pictures on chatoyance, but, IIRC, John didn't tell us precisely what he used as a sealer, only that it was applied as an emulsion. To me, the results were truly impressive. Like you, given that it was John, I felt pretty sure that casein must be there somewhere. FC says that casein plus oil didn't look that good and that the combined (casein plus sugar plus oil) sealer looks better and is water resistant. Given how good John's samples look, my guess is now that he too is using something in addition to casein and oil. Gotta' take John's advice and start doing some experiments instead of just reading about the experiments of others.
  4. do you get a good looking sealer using either casein or sugar? are both necessary?
  5. Hi John: I think a quality of greater importance to chatoyance would be the wetting quality of whatever goes on the wood first. Incomplete wetting would leave microscopic air bubbles, RI = 1.0, from which light would reflect rather than reflecting from the wood. Perfect wetting would have the small discontinuity from RI differences between sealer and wood causing the reflection.
  6. another anecdote to add here: my second career was that of commercial real estate brokerage. I specialized in apartments, in 10 years I sold about 5500 units plus land for another 2000 units. Have owned apartments, I KNOW apartments. One of the worst headaches apartment owners deal with is Kool-Aid stains, never mind the color though red is especially bad. In a cleaning industry with a stain remover for everything, Kool-Aid stains are the absolute worst to get out of carpet. The most common remedy is to dye the carpet dark brown. The dominant ingredient in Kool-Aid, of course, is sugar.
  7. anybody remember this post? I suspect everyone thought him crazy........ "Step one: gently rub volcanic ash into the wood with the grain. Brush off any residue that didn't go into the pours of the wood. Step two: Blend an eggwhite, one teaspoon of whole milk and two tablespoons of pure honey (organic with no preservatives). Step three: Thin the mixture to a water like consistency with 100 proof grain alcohol. Let set overnight covered. Step four: apply the mixture with a fine sable brush against the grain. While the first coat is still damp, apply a second coat. Step five: while the second coat is still wet, ignite with a clear orange flame from a smokeless candle. Use appropriate fire proof clothing for this stage. Caution, do not do this indoors or outside. The flame will engulf the instrument and fuse the sugar and ash to the wood fibers. Do not let blacken! This in not for cajun music. Put out the flame with pure, screened, white sand. This is how the masters did it in Italy." as an anecdote, here in the very dry high desert, old time mechanics poured Karo syrup on car battery terminals. In low humidity, it dries to a clear resin that is all but waterproof, a real bear to get off. A little heat might do the same for a sugar resin in a humid environment. At the moment, I lack both the time and humidity to try it on wood. The quote is from this thread: http://www.maestronet.com/forum/index.php?showtopic=148035
  8. Glad you found that my elderly ears are still somewhat reliable. I am thoroughly enjoying Robin Ireland's Bach transcriptions. Beautiful playing, tone, all you could want. Now I've got to order another
  9. Did you save any of the shavings from the original parts of the back? If so, has anyone done any "scientific" evaluation of them? Thanks,
  10. Very nice work, Don. I really like the varnish. what pattern did you use for the outline/ff holes?
  11. Thanks, Ian. I've ordered that. Anxious to hear it. Hope you enjoy the Telemann/Hadelich
  12. Was recorded at St. John Chrysotom Church, Newmarket , Canada. The room, engineer, equipment, etc. are parts of every cd I own, but this one is really special, and only $7.00. I will check the other thread later.
  13. Good to know. His website says he now plays the above referenced violin. This cd was among my Christmas gifts from my wife, another being "the Miracle Makers." I found it quite interesting that among the Strads on those cd's, my favorites are the long patterns, which to my ears, have the low frequency character of the del Gesu violins. Thanks for the info. This violin (1683) is stunning in its tone.
  14. The single best recording of a solo violin I have ever heard. He plays a 1723 Strad. Absolutely stunning resolution of the sound and superb playing. http://www.arkivmusic.com/classical/Drilldown?name_id1=11975&name_role1=1&comp_id=18772&genre=70&bcorder=195&name_id=157367&name_role=2
  15. IIRC, Schleske has post-graduate training in physics. (I could be wrong, but if so, it will only be for the second time )
  16. Well, David, if you're calling the government every day then you're part of the problem. On the other hand, I've had to call tech support on software problems I couldn't find the fix to on Google perhaps three times in the last five years. All three times someone in India helped me and all three times they resolved the problem in short order. Maybe we want to hire Bill Gates to handle assistance calls for social security benefits. Boy, will that one cause a stink, what with Gates getting rich on the backs of laid off government clerks..........nah, never happen
  17. yes, and at lower levels, they are represented by one of the largest unions in the US. I'd be quite happy to replace a large fraction of them with off-shore workers at 10% of the price. Not exactly sure how we would do that once the TSA is unionized, but I'll continue thinking about the problem
  18. We've had union leaders negotiating for reduced productivity for decades and management giving in to that on the theory that the American people would buy whatever they sold. The union leaders have succeeded beyond their wildest dreams, we now have talented American workers who are more expensive per unit of output than ten unskilled foreign workers. The only industries in serious trouble are those that are unionized, and now they are seeking government bailouts for their health and pension programs. In my travels, I've seen plenty of guys wearing jackets that say "UAW" but none in jackets that say "Ford." Loyalty to ones employer rather than to the adversary of ones employer seems to work for most Americans, but not in the geographic areas in the greatest trouble. It really doesn't take any great genius to see the problem, but a great deal of suffering will be required to correct the problem. Union workers have my sympathy for they are the ones who will suffer the most as the problem is corrected, as the market place will force it to be. The solution is not to try to force the American consumer to pay more for what he buys, but to make the American worker more productive. That will require a great capital investment in new technologies and a tax structure that encourages investment. It will also require a lot of worker retraining to use those technologies and telling the truth to a lot of workers: they are going to have to re-train and/or relocate and/or accept a lower wage commensurate with the value they can produce. Trying to punish the rich who put up the investment for this to happen isn't going to help. I've got on my asbestos suit, go ahead and take your best shot............
  19. Roger Hill

    Rotary Tools

    Are the carving (reciprocating) hand pieces of much use? Thanks,
  20. Beautiful work, Ben. Did del Gesu actually do such nice bee stings? Is that ff hole on your site so I can copy it?
  21. Very useful, Oded. Thank you for taking the time to do this. Will part 2 explain how to find the location of the anti-nodes on the surface and show the scraping process? I hope so.
  22. Good point, Melvin. Fry concentrates on Strads, which I believe have not been re-graduated to the same extent as the del Gesus. Now, if Cozio handed you a violin and told you to thin the plates, would the thinning be more or less uniform? which would tend to leave a tuning scheme in place? You tell me, I've never done it.
  23. I still find the precision we see in back bullseye patterns to be strong evidence that they could carve to any level of precision they desired. Did they always desire to get a very precise initial pattern? I don't think so .....I think they intended that later tuning of the top would be used to bring the instrument to the sound quality desired. my own opinion is that they had excellent ears and knew just where to scrape to get what they wanted. I also suspect, that just as Oded describes, at times they overshot and had to re-scrape other areas to bring the whole thing into balance. Kinda' like cutting off the legs of chairs to get it level........process doesn't always converge.
  24. at the risk of stirring up a propolis factory, it seems to me that Oded and Jack Fry are saying the precise same thing: very small changes in thickness at specific places can have dramatic effects on the timbre of the instrument. Fry adjusts his violins by scraping on the inside, Oded on the outside. The actual arch shape is the mid-curve between the inside and outside curves. For tiny adjustments it really shouldn't matter much which side you scrape to get the vibration you want. Oded locates his points to scrape through string reciprocity. Fry relies on his ear, experience, and knowledge of where to scrape HIS violins to affect particular frequency areas. I emphasize HIS violins because, to the best of my knowledge, Fry has settled on one particular Strad graduation scheme which he understands well and then adjusts to get a good sounding instrument. Note that Fry starts with an old violin and is stuck with its arching, wood, varnish, etc. He ends up with different schemes in a finished violin as dictated by what he starts with. We certainly see wide excursions in the graduation schemes depicted by Jeff Loen. With all due respect to Michael Darnton's differing opinion, it seems to me that the asymmetric graduation patterns of the Cremonese tops must be the result of a tuning scheme.
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