Marty Kasprzyk

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Everything posted by Marty Kasprzyk

  1. Marty Kasprzyk

    machine made violins also CNC "Betts"

    How is a cnc better than a duplicator?
  2. Marty Kasprzyk

    Congrats to all!

    I didn't win anything at the VSA competition so I went to the hotel bar afterwards and drowned my sorrow in beer. But I couldn't stop thinking about where I went wrong. Next time I'll try amber ale color for my violins.
  3. Marty Kasprzyk

    'taptones' of a unstrung violin in the white

    I'm not sure about this. It might be correct or incorrect. I agree a high amount of damping lowers the peaks but it also raises the valleys. Since any violin note consists of many harmonics some of these will fall near or on peaks while others will fall in valleys by chance. If the loudness (power) of a note is determined by some sort of sum of the powers of all of the harmonics then it follows that sum of all these high and low amplitudes might remain nearly constant--the amount of damping doesn't change instrument's overall loudness a lot. Since most of the power of a bowed string note comes from the first few harmonics then a note's power is largely determined where these harmonics fall on the instrument's frequency response curve (FRC). Higher damping smooths out the FRC so the instrument's notes are likely to be more even in loudness. Sometimes increased damping happens simultaneously with increased mass like what might happen with real thick layers of varnish. I suspect that the decrease in sound power is a result of more mass rather than more damping. It might be possible that a wood might change over time by micro cracking which could increase its damping without increasing its mass. The wood might also actually decrease in density. So a benefit would be increased loudness with better note evenness. It also might be possible with special treatment or aging to decrease both the wood's damping and its density which would make the instrument louder but the notes might become less even. All of this is just speculation on my part.
  4. Marty Kasprzyk

    Plate Thickness/Overall Weight

    The instrument weight concern might be a regional question. Just out of curiosity, what does a full shovel full of snow weigh where you are out in Utah? Back here in Western NY the forecast is for some heavy mush. Maybe the instruments follow snow g/cc.
  5. Marty Kasprzyk

    Ray Chen plays a modern violin on the latest recording?

    The performer might use the new one for the recordings and the road and just mention the Strad in the program book.
  6. Marty Kasprzyk

    Another extreme arching experiment

    Hi Don, Will Your bass bar follow along parallel to the inside surface corner kink?
  7. Marty Kasprzyk

    Question for makers who work alone

    Does the ticket buying audience seated far away care about purfling worksmanship? Who are we trying to please?
  8. Marty Kasprzyk

    Another extreme arching experiment

    Yes but the flat top allows the bridge to easily slide and west when you do impact hammer tests on the bridge or when you bow hard which screws up the sound. So one purpose of the curved cross arch is to keep the bridge from moving around. I make my tops flat and I avoid this problem by gluing the bridge onto the top. I used to be traditional and used hide glue but now I use Gorilla glue. They always sound better after the bridge is glued and the frequency response curves show a higher output of some resonance peaks. While I'm at it--I believe the reason why good bridge fitting is so important is that a large contact surface allows good vibration transfer between the bridge and the top plate. You don't want to have air gaps between the mating surfaces giving large impedance mismatches. Using glue, which has properties more similar to wood than air, ensures this doesn't happen. Don't try this at home.
  9. Marty Kasprzyk

    Carbon back - huge difference?

    I recommend making more of them.
  10. Marty Kasprzyk

    top only or whole body?

    Most of the low frequency sound comes out of the f holes and is monopole -meaning it goes off equally in all directions. The higher frequencies are however directional and its possible for a beam of sound going out and missing the player. It's there but the player doesn't hear it much. The question is: what directions do you want the high frequency sound to go? If it comes off the cello's back it is probably going into the player's body or bouncing off the floor, then hitting other players or the back of the hall and eventually, with only little left unabsorbed, getting to the audience. So it makes sense to limit the amount coming off the back. This is done by making it stiff and heavy so it doesn't vibrate much while the top is made light and flexible so it can radiate sound easily. The ribs also radiate high frequency sound but I suspect their main contribution is to provide body flexibility needed to produce volume changes necessary for air flow thru the f holes to produce low frequency sounds. Hence the ribs are made thin. It is my guess that this is the reason why the single piece back and rib construction made from a carved out block for medieval fiddles was abandoned as a construction method. The newer separate thin bent ribs made the instrument cavity easier to expand and contract to produce lower frequencies. This in turn made for a richer and more liked sound.
  11. Marty Kasprzyk

    'taptones' of a unstrung violin in the white

    If you want a bright sounding viola then you should hit it with a hard hammer. If you want a mellow sounding viola then you should hit it with a soft rubber faced hammer. If nothing sounds good just hit your viola really hard.
  12. Marty Kasprzyk

    "Dutch Violin"

    I too make my violins and violas with the bridge treble foot resting directly on a sound post that goes through a hole in the top like the ancient Crwth. I also glue every thing together-- the bridge to the sound post, and the sound post to the back. This arrangement has the advantage of eliminating endless bridge and sound post adjustments to fustrate those who never seem to be satisfied.
  13. Marty Kasprzyk

    thin back effect

    Can you use this stuff for the entire plate?
  14. Marty Kasprzyk

    thin back effect

    An old friend had a similar cheap violin which had great sentimental value. I made a large breast patch for the back to thicken it. It was a lot of work but it sounded much better and he was very appreciative. He's now deceased but I hope his violin lives on.
  15. Marty Kasprzyk

    slab cut - wide grain front

    Tops naturally come out made with the annual ringed closely perpendicular to the surfaces as a consequence of the wedge splitting and the length to width proportions of the violin were established long ago for the resulting longitudinal to cross grain elastic modulus ratio. If you wanted to keep the same sound character by keeping the same mode frequencies with off angle (45 degree example) low cross wise stiffness wood made by sawing it would be necessary to use narrower width bouts. While that might be able to work acoustically nobody would accept the skinny appearance hence it's not used. The opposite problem exists for plywood which has little stiffness difference in different directions. In this case the instruments should be made with wider proportions. But nobody likes a fat belly. Projection is important for violas too so you do want to have a long flight path.
  16. Marty Kasprzyk

    slab cut - wide grain front

    You could have used cross grain low stiffness for small violas where it might be beneficial to have low mode frequencies which are normally only seen on large ones. Model airplane gliders are similar to violas where you want a long time aloft before hitting the ground.
  17. Marty Kasprzyk

    An experimental pegbox and nut

    Now if the string is too long and bunches up against the peg box it will put an outward force on the peg which may cause it to loosen and slip. Be sure to cut your strings short enough to avoid this problem. Your original way of putting the string on the end opposite the handle was better (although confusing at first for a player) because a bunched up string would force the peg to become tighter.
  18. Marty Kasprzyk

    What does a (too) high air mode do to the sound of a violin?

    The Bissinger graph I presented was done with a stiff welded sheet aluminum body of violin size and shape ("La Empierre" in his references). The volume was changed by filling it up with various amounts of water. A real wood violin would be more flexible and would have the normal A0 frequency (~270Hz) however it apparently didn't seem like a good idea perhaps because of the hide glue. In any case, one interesting experiment was to add 200cc of water and hold the aluminum violin vertically with the lower bout at the bottom so the water leveled up there, then the experiment was reversed with the upper bout face downward, and then the experiment was repeated again with the body held horizontally (similar to using a low rib height). In each of the three cases the volume V remained constant (same amount of water fill) and the f hole area A wasn't changed yet the A0 frequency did change a lot---308, 329, 310Hz respectively. The classic Rayleigh equation predicts the A0 should have remained constant because the volume and the f hole area didn't change and their A/V ratio obviously stayed the same. Since the A0 frequency did change it meant that the Rayleigh equation (A/V)^0.5 was not correct for violin shaped cavities. The shape of the cavity has an affect not just its volume. But your point is still very correct--it take a huge change in f hole area or body volume to make much of a change. Tomorrow I'll take some photos of two of my experimental violas with greatly different f hole areas which proved to me that reading about other people's experiments was quicker and cheaper than doing my own. On the other hand "ignorance is bliss".
  19. Marty Kasprzyk

    What does a (too) high air mode do to the sound of a violin?

    Bissinger's graph shows the coupling effect of the upper and lower bout volumes and it was done with rigid walls of a full size body. Increasing the body stiffness or rigidity (decreasing the compliance) increases the A0 frequency. The A0 frequency increases about 10% when you insert the sound post which stiffens the body. Making the ribs thin and plates thin reduces it back down. There have been experiments with encasing the entire violin body in plaster to make it rigid to see how stiffness changes the A0 frequency.
  20. Marty Kasprzyk

    What does a (too) high air mode do to the sound of a violin?

    I very much agree that you have to make huge changes in the f hole area or violin volume to see an affect on the A0 frequency but I don't fully understand what affects the A0 amplitude. There are several reasons why the A0 frequency doesn't follow the classical Rayleigh square root of 1/volume. or 0.5 exponent. Rayleigh's equations are for rigid cavity walls whereas the violin walls have some compliance. Rayleigh's assumptions also used a simple shape (a bottle is a typical example used in experimental work where you fill it up with different levels to change the volume). The violin cavity on the other hand can be modeled as two cavities (upper and lower bouts) joined by a narrow portion (C bout). The longitudinal A1 air mode is influenced by the relative volumes of these two cavities. Since A1 is coupled with A0 the shape of the violin cavity has an affect in addition to its simple volume. George Bissinger has done many A0 experiments and he's shown the A0 frequency closely follows a 1/volume exponent of 0.25 and an exponent of 0.27 is even better. Attached is one of his experimental plots. The classic rigid cavity exponent of 0.5 is a poor fit for violin shape cavities which is shown with the blue line. 1. G. Bissinger, "Acoustic normal modes below 4 kHz for a rigid, closed violin-shaped cavity", J. Acoust. Soc. Am.100, 1835-1840 (1996). 5. G. Bissinger, ‘‘Semiempirical relationships for A0 and A1 cavity mode frequencies for bowed string instruments of the violin, viola and cello family,’’ Catgut Acoust. Soc. J. 2 (1), (Series II), 8–12 (1992). 8. G. Bissinger, ‘‘The effect of violin cavity volume (height) changes on the cavity modes below 2 kHz,’’ Catgut Acoust. Soc. J. 2(#2) Series II, 18–21 (1992). 11. G. Bissinger, “ Effect of f-hole shape, area, and position on violin cavity modes below 2 kHz” Catgut Acoustical Soc. J. vol 2, #2, 12-17(1992) 15. G. Bissinger, "Wall compliance and violin cavity modes", J. Acoust. Soc. Am. 113,
  21. Marty Kasprzyk

    What does a (too) high air mode do to the sound of a violin?

    The A0 frequency for a violin shaped cavity is more closely proportional to (1/V)^0.25 instead of the square root, (1/V)^0.5
  22. Marty Kasprzyk

    What does a (too) high air mode do to the sound of a violin?

    I try to follow standard string length, spacing, height over the fingerboard, bridge curvature, fingerboard curvature, neck length etc. that affect the player's fingering and bowing interactions. But all the other construction details (geometry and woods used) are completely different from Strad's or any other Old Italian instruments because we already know those designs are perfect so there's no sense in beating a dead horse. I do however meet the requirement that the instrument cases fit in the overhead bins of airplanes.
  23. Marty Kasprzyk

    What does a (too) high air mode do to the sound of a violin?

    Hi Andreas, Yes, all these data points are from my experimental light violas and violins. No. 22 violin had rich and loud low notes due to its low A0 frequency which I and many others liked however others thought it sound too different from a normal violin. My later experiments were attempts to get closer to normal violins. I often use an old fashioned Saunders loudness test to compare my violins. This test measures the loudness of each bowed note of a chromatic scale. I use Audacity for recording the notes and for measuring their loudness and I plot the results in Excel. The attached graph shows how No. 22 compares with No. 29. I've also included on the graph the average of 5 Strad violins measured by Fredric Saunders about 60 years ago. The vertical loudness scale in dB was fudged so that Saunders' amplitudes and mine are similar so the loudness is arbitrary and my loudness measurements can't be compared with his. But the important information is the overall shape of the plots. No. 22 had very strong low notes and weak high ones compared the Strad average which was pretty much the opposite--weak low notes and strong high ones. No. 29 was closer to the Strad ave. I should point out that my No. 22 and No. 29 plots look quite jagged. Individual Strad violins are also quite jagged but when you average 5 of them together the envelope looks smoother. It is my belief that you should try to minimize the loudness difference between the notes to make it easier for the player to adjust his bowing--you don't want to have overly strong or weak notes. My last just completed violin, No. 31 was played for the first time today by a good player. He said "it sounded like a violin" which was a novelty for me.
  24. Marty Kasprzyk

    An experimental pegbox and nut

    It,s much stronger than a usual hollow peg box. The only negative thing I can imagine is that the pegs directions are reversed--it might take a player a little time to get used to them.
  25. Marty Kasprzyk

    What does a (too) high air mode do to the sound of a violin?

    If your starting volume is 2000cm^3 with a 30mm rib height I estimate with a 20mm rib height the new volume will be about 1550cm^3. From George Bissinger's violin volume experiments (I'll provide references in a day or two) this should produce about 20Hz increase in the A0 frequency. If your starting frequency was a rather typical 270Hz ( C is 261.6 and C# is 277.2 like Don mentioned) then the new A0 frequency would be 290Hz which is near an open D note at 293.7Hz which is a just a little higher. Some people might like the higher A0 frequency while others might not. But as Don often points out changes often aren't generally well accepted. If you want to keep the original low A0 frequency with a lower rib height it will be necessary to decrease your f hole area. There are equations which predict what the new f hole size should be which brings up and interesting question: What works better- a large violin cavity volume with big f holes or a smaller cavity with smaller f holes? I've been able to argue both ways which is an indication of mental disorders (Gollum in Lord of the Rings) Another variable affecting the A0 frequency is the flexibility of the cavity walls (ribs and plates) with stiff walls increasing the frequency. Since my instruments are constructed so differently from traditional ones I try to adjust the A0 frequency from one experimental instrument to the next to get close to typical frequencies. So I play with these above variables all the time. Attached is a graph showing how the A0 of my last 5 violins and 6 violas has been adjusted trying to converge on typical 270Hz and 220Hz frequencies respectively.