Oded Kishony

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About Oded Kishony

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    Central Virginia, USA

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  1. Would your measurements reveal improved responsiveness? Did you check for that feature? OK
  2. I've tried various versions including an off center motorized twirling device clamped to a cello bridge. It made a huge roaring racket. Didn't seem to help the instrument very much (didn't hurt it either) I met a vioinmaker, years ago, who connected a violin to a radio via speaker driver with a stick glued to it, touching the side of the bridge. He claimed that when he first set it up he had to crank the volume all the way up to get any sound but over time he was able to reduce the volume setting significantly and the instrument worked very well as the 'cone for the speaker. Or you could try Micheal's gizmo. I don't think it matters too much what you play through the corpus (Limbaugh will ruin it though ;-) but this is something you could do that will not offend your wife since it will just be another audio device playing. Oded
  3. This photo illustrates how you can use this clamp to align a crack that has a 'step'. Notice on the right side of the crack is a narrow wedge that pushes against the screw shaft effectively pushing down that side of the crack. To glue the pillars in place I put a dab of thin hide glue with my fingertip on the surface, let it dry a bit and use ca glue on the pillars that are surfaced with paper (I use 3x5 card paper). Oded
  4. I use this flanged nylon knurled screw and a brass version with the corresponding tap. The lower screw is used to pull the clamp together, so the hole on the left is slightly oversized to allow for some degree of movement and the opposite side is drilled through and tapped. The upper part, drilled and tapped on one side, is used to spread the clamp.
  5. I've developed a clamp and procedure for this that works very well. The shop made clamps using hardware that costs apx $0.25/clamp plus scrap maple two drill bits and one tap. I use plastic covered rare earth magnets instead of clamps because they are light weight and clamping pressure is only vertical (no torquing from clamps). The plastic prevents scratching and glue does not adhere to it. Magnet clamps can be a little tricky to control. I 'park' the magnets alongside the cleat then slide them in place, lifting the one that goes over the cleat. If you get the magnets too close they tend to 'jump' out of control. I dry clamp everything, checking the alignment with a straight edge across the crack, glue the cleats in place then after the glue has dried apply glue to the warmed varnished side. Glad to answer any questions. Oded Kishony
  6. To discourage the bridge from warping after being straightened, I make a thin solution of aliphatic resin (wood) glue and soak the bridge for an hour or so after it's been straightened (using MD's method), I then wipe the bridge with a paper towel and buff on a piece of cloth or very fine abrasive.
  7. The same is true for some organic dyes such as madder, the purpurin fades immediately but after that the color is very stable.
  8. Those that know me are probably not too surprised to see me chime in on this topic. ;-) I have long (perhaps too long) advocated for the idea of voicing instruments before varnishing, (but perhaps after sealing) with the instrument 'in the white'. I've been developing a methodical system for accomplishing this which is based on the reciprocal or bi-directional relationship of the surface of the instrument and the strings. Simply put, the strings drive the surface in the same way that the surface drives the strings. In practice this means that when a string vibrates it creates various patterns of vibrations on the surface, if the surface is tapped, the strings will vibrate in response to the specific acoustic profile of that area that is being tapped. In this way acoustic 'targets' can be chosen and modified. Further, as an area is being modified other frequencies are also affected, this can also be observed. Any surface of the instrument is open to modification (think ribs). Individual strings and frequencies can be isolated by damping all but one string and/or tuning it to the desired pitch. The instrument can be then played and an assessment of the changed be determined. The changes are normally not huge, on the order of a sound post adjustment, but they are cumulative. Occasionally a dramatic change is heard, which I believe has to do with a psycho-acoustic phenomenon having to do with filling in missing harmonics. The lighter the instrument the more effective the adjustments. Because the scraping is done on the outside and, subtly and mostly imperceptibly alter the arching, some of the acoustic changes may survive regraduation. I usually combine the use of the reciprocating vibrating strings as well as a spectrum analyzer to make adjustments. This 'tuning' method is wholly compatible with the working methods of the Cremonese violin makers because they finished the instrument from the outside after it was assembled (see Roger Hargrave) Will all the acoustic changes survive the varnishing process? Remain intact forever? Make the instrument sound worse? Everything is possible but one must compare it to the alternative, where one is more or less stabbing in the dark and if luck is with you the instrument sounds fine. Admittedly after having finished an instrument and playing it in the white I've opted not to risk making any changes. But this approach does open otherwise unavailable options for the violin maker. Oded Kishony
  9. It may be possible to remove excess iron by chelation. Oxalic acid would be a reasonable choice. https://en.wikipedia.org/wiki/Oxalic_acid Oded
  10. The deleted section was a discussion of the effect of aging on the instrument, the possibility that playing an instrument over a long time period enhances and increases the amplitude of the harmonics. OK
  11. I would like to add my two pennies to this discussion. Scraping or removing wood from the surface of the instrument in some random way, even if it is an 'educated' guess, and hoping for a positive outcome is like putting your elbows on a piano keyboard and expecting to hear a Bach fugue-not likely. The timbre of an instrument or a string is dependent on the harmonic structure of the sound, the brain re-arranges the sound to produce the timbre. A well-documented example of this is that the violin produces a very weak signal at 196 Hz (open G string) the listener assembles the harmonics which produce the effect of 'open G' ie 196Hz. If some component of the harmonic structure is missing or is weak the character of the sound (timbre) will change. If, for instance the higher harmonics are missing the sound may seem to be dull. If on the other hand, lower harmonics are weak but higher ones have a greater amplitude the sound may seem to be harsh or too bright. Even though we talk about discreet modes, the modes (areas of vibrations) don't function separately under playing conditions. When an instrument is played, any frequency generated by the strings or bow that 'finds' a friendly spot on the surface of the instrument will be amplified. However, most of the vibrations on the surface do not get projected into the far field (apx 3ft) because of 'phase cancelation', which works the same way as sound canceling headphones (see google for details). When any given area of the violin is thinned it will affect a great many frequencies at the same time, so selecting where to thin is tricky and in my experience often requires some compromises. For instance, if I have a too bright G string I may tap the surface until I hear a clear G fundamental vibrating, then while scraping that area I listen for changes because as you scrape, the tonal landscape is changing under your scraper. I often find myself 'chasing' a note or harmonic around the surface. In addition, you should keep in mind that on a violin, all frequencies below ~ 1kHz are produced by the whole corpus, which is why scraping the ribs can produce dramatic changes in the sound (see caveat above re psychoacoustics). If you are computer fluent you can explore this by sampling the surface of an instrument with a simple computer mic or a contact mic. just tap the surface of the instrument with the microphone while running an FFT spectrum analyzer on 'continuous' with 'peak hold'. You will see the frequency spectra are completely unique for any spot on the instrument. (dampen the strings) What I find exciting is this can be done without using a computer, because the information embedded on the surface is transferred to the strings, when the surface is tapped or being scraped. You can hear when you're thinning an area that affects the harmonic of the string because the string starts to vibrate at that harmonic frequency. Oded Kishony PS entire sections of material that I've written seem to erase automatically when I post here. Am I doing something wrong or is there a glitch in this program? Never had this issue before on Maestronet.
  12. Can you remove some wood from the perimeter? I would just try it in the white and see how it sounds.
  13. Seems to me that the writer is a very inexperienced player/maker who is very ernest but has not thought through his ideas. He is mostly 'shooting from the hip' . I considered replying to this post but got tired just trying to sort out all the misconceptions. To point out just one: every violin has a unique voice, just like a finger print. That is because every piece of wood is unique. If you try to 'normalize' the wood I think you would discover that the result would be a supremely boring instrument. Oded
  14. One photo that has made an impression on me is an endoscope image of the interior of the Del Geu Cannone. it shows drip marks from the F holes of a thin colored liquid which I’m assuming is from Del Gesu’s hand. https://www.google.com/search?q=il+cannone+endoscope&rlz=1C9BKJA_enUS786US787&oq=il+cannone+endoscope&aqs=chrome..69i57.15392j1j4&hl=en-US&sourceid=chrome-mobile&ie=UTF-8#imgrc=YMAJkdCLqJ0QRM: oded