ctanzio

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About ctanzio

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  1. How Do the Best Violins Compare?

    Played back on my cheap computer speakers, I could not notice a difference. When I used a decent set of headphones, the difference was dramatic throughout the entire sound bite.
  2. Natural phenomena we can relate to, like sound waves, heat transfer, weather patterns, and those of a more esoteric sort, like quantum particle interactions and cosmic objects moving through gravitational fields governed by general relativity, can all have their interactions approximated by classes of functions called orthogonal functions. The approximation is a sum of the functions of the class. Each function is multiplied by its own unique number, called the coefficients. The method of determining these coefficients from the observed data is called a transform. The sine/cosine functions used in Fourier Transform form a class of orthogonal functions that are particularly useful when approximating phenomena that repeat in some fashion, but any class of orthogonal functions can be used to decompose the observed phenomena into a sum of the functions. When deciding what class of orthogonal functions to use, at least two questions are asked: 1. How many functions do I need to get the approximation to reasonably match the observation? This is the convergence question. The fewer number of functions one needs, the "better" in general. Although with the advent of readily available computing power to just about anyone who can afford a home computer, this had become less relevant. Let the computer use as many functions as it needs. 2. Do the functions of the class represent a solution to some mathematical model of the phenomenon? This is the question of relevance. Although any family of orthogonal functions can be used to model the phenomenon, a relevant family will almost always give some physical insight into what is happening, or suggest a useful way to manipulate the effects. TLDR: There are a great many transforms that can be used to mathematically fit functions to observations. The Fourier transform is especially useful for vibration phenomena because it quickly converges to the observations, and the functions form a natural solution to simple models of vibration.
  3. Thank you for these wonderful photographs! The scrolls on the Strads and the Andrea Amati's are my favorite. So beautifully proportioned but with just a hint of asymmetry that reminds one that these were created by hand.
  4. Attention to detail and stifled creativity?

    I think of this as a form versus function issue. To get something to function as desired, only enough attention to detail is needed to get it to perform as expected, and safely. I was a licensed PE for many years, and most projects did not require me to push the envelope on performance. The occasional high performance project that came through required slavish attention to detail with a comparable cost in both time and money. Form is a whole other issue, since so much of its value lies in the eye of the beholder. But for me, there is a direct correlation between mastery of detail and high art. To use a knitting example, I am reminded of my grandmothers. My maternal grandmother who could knit woolen vests like a machine. They were warm and durable and awful dull gray looking things. But functioned perfectly for seven of her own children and two orphans she took in off the streets, and all the grandchildren that followed. A vest from Grandmom Stunder was common but treasured, since we were all members of families of modest means and the winters in the northeast can be rough when you cannot afford to keep the house at a comfortable temperature. My paternal grandmother was an accomplished seamstress. She could knit lace table cloths that were astonishing in their complexity and the fineness and consistency of the stiches. A table or sideboard cloth from Grandmom Tanzio was rare and treasured as they were time consuming to make and time was something in short supply for a young widow with four children of her own. You can be remembered for creating lots of useful things, or a few beautiful things. I do not see the utility is valuing one more than the other.
  5. A VERY basic question about: Correct bridge setup

    Make sure the feet are sitting flush on the top. As David mentioned, tuning sometimes pulls the top of the bridge towards the fingerboard, If this it the case your situation, then adjusting the bridge so that the feet are flush to the top again will fix the visual slant of the bridge. If the feet are flush with the top then don't worry about it. There is a technical argument that can be but forth for making bridges with the side facing the tailpiece perpendicular to the top and the other side somewhat slanted, but unless the face slant or lean of the bridge are extreme, it will have no effect on tone or stability. If a line drawn from the center of the feet to the center of the bridge top is basically perpendicular to the top, you are good to go.
  6. Acoustic science

    I wonder if he is using the term "intonation" in a way that is understood differently in the violin world. Unless the vbracing dynamically changes the fixed fretting as the strings are plucked, there isn't anything the bracing can do to change the intonation. You stop the string, its length is fixed, its intonation is fixed. Of course, there are things one can do with the fingers to tweak the intonation, like bend the string or finger the string over the fret itself to subtly change the stopped string length. Assuming by power he means loudness, then sustain and power are always and forever opposing each other. Think of it like this: the total energy you can put into a plucked string is basically how much you stretch it before releasing. If there is no energy loss, i.e., all the energy remains in the string, it will vibrate forever: infinite sustain and zero loudness. No bracing effect here. Strings have internal damping, which means as the string vibrates a percentage of the energy is converted to heat. The sustain is now limited as the energy in the vibration is systematically converted to heat, but you still have zero loudness. Still no bracing effect. The vibrating string will move some of the air. So some of the energy of vibration is passed to the air to generate pressure waves. Not a whole much. Sustain again drops but you get a teensy bit of loudness. Bracing still has no effect. The bridge is connected to the flexible top. So some of the vibrating string energy is continuously passed onto the guitar body. The string sustain drops even more, but now you have the energy passed to the body as vibration. So now you have sustain and loudness to consider for the vibrating top. A flexible top means its vibrating body energy can be passed onto the air as stronger pressure waves, i.e., more loudness. But that means the energy of the body vibration decays quicker, or less sustain. Bracing can most definitely affect this, but it cannot increase both. The only way to increase both sustain and loudness is to reduce energy loss from internal effects, like damping. If he means vbracing allows them to use materials with much lower internal damping so they can drive the air harder without reducing sustain below acceptable levels, then fair enough. Otherwise, the only thing he is affecting is the response spectrum of the guitar body. So it is not changing intonation as much as it is changing timbre.
  7. Varnish

    Red lets the cello play faster. Well, I know it works for cars so why not cellos?
  8. Restore your very own Amati!

    After staring at the full-sized photos, I have to ask the question: How much of the original wood has to be replaced before it ceases to be represented as a genuine Amati?
  9. As far as I can tell, the height of the bridge foot at the edges is a non-issue for tonal performance. The fit of the foot to the surface is the critical dimension. But structurally, making the foot "too thin" towards the outer edges will dramatically increase the local pressure on the varnish and cause it to compress and deform over time, and sometimes to flake off. The outer edges of the foot will bear progressively less of the string pressure than the center as the edges are thinned. In the structural engineering world, considerable research has been done on the design on these "bearing surfaces". So when there is metal-on-metal or wood-on-wood contact, one can look in a manual of standard practices and it will tell you how thick the footing should be to prevent permanent deformation of the surface. The challenge in the violin world is to apply it to the variety of varnishes one encounters.
  10. Bridge Rocking Motion and Leverage

    That video is a good demonstration of how moving waves can combine to give the appearance of a "standing" wave at a natural mode of vibration, i.e., stationary nodes where no wave action appears to be happening, and antinodes where peak oscillations seemed to be fixed. But there are wave-like disturbances constantly propagating through the plate.
  11. Bridge Rocking Motion and Leverage

    Marty's equation is a good approximation for many materials. The more precise equation also accounts for a material property called the Poisson's Ratio. What might be helpful for a builder is how it predicts the frequency changes of plate modes as one changes different parameters. The equation can be transformed into the following: f = K x t x C / L^2 Here, f = frequency of the mode t = thickness of the plate C = longitudinal sound speed L = distance between "boundaries" of the violin K = some proportionality constant Suppose you are looking at a breathing mode which is an asymmetric rocking up and down between the two f holes. You can raise the frequency of this mode by making the plate thicker or lower it by making it thinner, mostly in the sections where it shows the most movement. You can change the characteristic length of the mode, basically some dimension across the violin's width, by adjusting the plate thickness as one approaches the edges. Making that area thicker will make the length appear smaller, and vice versa. Making the length "smaller" rapidly increases the frequency. Of course, this assumes some sort of plate tuning approach is a useful thing, which is a topic which has been covered many times in this forum.
  12. Bridge Rocking Motion and Leverage

    Hardly "standing". The term "standing wave" is a classic misnomer. Pick a point, any point, on the violin plate. The displacement at that point is not standing still but rather changing constantly, only in a cyclical fashion. Mass is being displaced in a very localized way that causes a change in the stress and displacement fields to "travel" through the plate. It can be convenient to think of it as a wave of kinetic energy. For a standing wave, it simply means that the energy reflects off the ends of the violin in a cyclical fashion that causes the displacement of any point to vary in a regular pattern. This is no different than tapping the end of a beam and measuring the longitudinal sound speed. Mass displaces in a very localized way that causes the pressure (stress) to change in a way that appears to move through the beam. It can reflect off an end and return to the original end that was tapped. It continues back forth until the energy is dissipated by several different mechanisms. This is also a "standing" wave in every sense of the term's technical usage. The SHAPE of the wave is just different from the violin plate only because of the way the energy was fed into the system. In terms of complexity, the violin is a rather simple vibrating system compared to the systems that have been successfully analyzed using experimental, theoretical and computer analysis. Why such analysis doesn't seem to add anything to understanding the violin is because there is no quantitative standard that defines a "good sounding violin". If you ever figure that out, finding an Applied Physicist to help you design a violin to that standard would be easy.
  13. Bridge Rocking Motion and Leverage

    Strictly speaking, concepts of leverage are more appropriately applied to static and uniform motion problems. So some caution is needed when trying to use the leverage concept for energy transfer from a vibrating string to the top plate via the bridge. For most of the frequency range of the violin, the method of transferring energy from the strings through the bridge results in wave lengths much larger than the dimensions of the bridge. The bridge essentially acts as a rigid body until one approaches the first prominent harmonic of the bridge which is around 3kHz. The top plate operates differently. Because it is transferring energy along primarily as bending waves, it exhibits a phenomenon known as dispersion: the speed of the wave is a strong function of the frequency of the wave. This is called the group or phase velocity. This is much slower than the longitudinal or shear sound velocities. Roughly speaking, a 200hz bending wave in a spruce plate might travel around 75m/s with a wavelength about equal to length of the violin. So at any point in time, one would see peaks and valleys associated with such a wave. A 800hz wave would travel at roughly double the velocity of a 200hz wave and have half the wavelength. You can verify this for yourself by considering some of the mode animations posted by David. Find one that has a single peak and valley at any snapshot. Look up the frequency corresponding to that mode. Now estimate the wave speed as the frequency times the length of the violin. Edited for clarity.
  14. Cleat Dimensions for Post Crack

    The left side of the picture is supposed to be a cross-grained pillar. Maybe the camera perspective is confusing. The bottom of the picture is the end of the pillar and you can see the grain running horizontally across the face. The cleats I glued in last spring also had the grain going across the crack, but I glued them slab side down. The web site referenced in an earlier post seemed, to me, to say the grain side should be glued to the plate with the grain going across the crack. Did I misunderstand their directions? I encountered something unexpected when setting up the edge clamps prior to gluing the crack. The plate as it came off the violins did not have the edges sitting flat on a surface. The plate was splayed, like someone had grabbed the outer edges and permanently curled them up. As I applied the edge clamps to secure the plate to a 1" thick piece of plywood, the crack closed naturally so that it took what was probably its original shape as it was originally carved. There was a non-trivial amount of clamp pressure needed to get the edges to sit flush to the plywood. I left the plate clamped in a cool, dry room for about 72 hours. When I removed the clamps, I expected the crack to open and the plate to curl out-of-shape again. But the plate shape did not change. The edges now sat flush to the table while unclamped and the crack barely opened. It is as if all the deformation in the plate had been reversed by leaving it clamped to a flat surface for 3 days.
  15. Cleat Dimensions for Post Crack

    Caution expressed about rubbing mating surfaces together has been noted. I will check the fit after trimming the saddle then reconsider my options. I prepped a cleat stick and counter form as per the Triangle Strings reference. Slab cut spruce to 1/4" (6.4mm) thickness. Trim to a width of 1/2" (12.7mm). Angled width edges to 30degress to make a parallelogram shape. Drew a line on either side 1/4" in from edge to act as a guide to align the cleat with the crack. Made a counter form to keep the cleat edges snug with the plate while glue dried.