Jump to content
Maestronet Forums

Marty Kasprzyk

Members
  • Posts

    3263
  • Joined

  • Last visited

Posts posted by Marty Kasprzyk

  1. On 7/26/2021 at 6:24 PM, Don Noon said:

    Presumably thise dB levels are the composite loudness as measured by a microphone.  To evaluate the loudness as perceived by the human ear, I think you'd have to take each harmonic component, adjust it by the ISO loudness curve, then recombine it all.  Then it doesn't really tell you whether the sound is generally desirable or not, which is something else entirely.

    Marty - re: 5 string viola with A0 at 196Hz... yes, you'd get some more roundness on the low G string notes.  However, that does other things.  On the low C string, the A0 is still too far away to help.  And looking at the next 3 overtones, the fall into response dips, which seems to me would make the low C string extremely weak. 

    I have taken the opposite approach on my viola, using relatively large F holes and small body to keep the A0 up around C, where it gives some reinforcement to the 1st overtone of the C string.  The size of the plates shifts the other resonant frequencies down relative to the violin, giving a tone that is distinctly different from the violin without getting to radical about things.

    I very much agree that reinforcing a small viola's 1st over tones on the C string with the A0 resonance is a good strategy.

    However listener tests on small violas have shown that a low A0 is preferred.  The Oberlin Violin Makers' "Obialto 2017 Project" (https://hampel-geigenbau.de/en/plus/obialto) designed a 16inch (406mm) viola and had a bunch of identical molds made by CNC machining.  These were given to  individuals the group and 26 violas were made with the same outline shape and size but with their own various personal choices of plate arch heights and shapes, thicknesses, f hole shapes, wood etc.

    These were all tested to find their frequency response curves.  About 50 listeners evaluated them when played by a good professional player.

    The group's average preference rating showed a general trend of preferring a low A0 frequency as shown in the attached graph.

    There also seems to be a strong preference for having light weight top plates as shown in another attached graph.

    I had mentioned in my previous posts that the A0 frequency is dependent upon the cavity volume and f hole but I forgot to say that a high cavity wall compliance (flexibility of the plates and ribs) also lowers the A0 frequency.

    I would like to see similar listening testing done on about 25 different size violas.  I would expect larger violas made with relatively thin plates would be preferred.  But they are not popular because of player injury problems--hence the Oberlin group chose to work on a small viola design.

     

    Screen Shot 2021-07-27 at 9.27.09 PM.png

    Screen Shot 2021-07-27 at 9.24.29 PM.png

  2. On 7/24/2021 at 8:40 AM, Muswell said:

    A set of Wittner violin pegs weighs 42g, before trimmming, compared with 22g for ebony pegs.  My wrist watch weighs 62g.  Use the Wittners and take off your wrist watch.

    I use the small diameter Wittner 1/2 violin size pegs to save some weight.  A set weighs about 28g.

  3. On 7/18/2021 at 8:16 PM, FiddleDoug said:

    "I am not a luthier and I could do a cello bridge "while you wait.""

    The big question is- what kind of quality is your "while you wait" cello bridge???

    It probably takes me about 45 min. to do a nice quality bridge for a violin. I suppose that you could call up a shop, and say "I want to reserve a luthier for an hour, to make a bridge, at 2pm on Tuesday" You could then give them your credit card info, so that if you don't show, they can charge you (like missed doctor's appointments). Rates are probably $70/hr or so.

    Looking back at this conversation, do you think we live in wrong part (western NY) of this country?

  4. 3 hours ago, FoxMitchell said:

    Heifetz could use a banana to play and we'd never know he's not playing a Strad!  ;)

     

    The guy who owns this Stroh recorded himself playing something Carnatic/Middle-Eastern and I think it works for that. That style isn't too concerned with complex timbre and overtones...

    I still couldn't handle the weight.

     

     

    Perhaps the horn should made with light weight carbon or kevlar fiber epoxy materials. 

  5. "It's hard to make predictions--especially about the future."

     

    Some viola players like the sound, especially on the C string, of large violas that were traditionally used in the past.  Unfortunately these heavy and long violas are strenuous to hold and player injuries were common (https://www.sciandmed.com/mppa) so most players today often use shorter and lighter violas and accept the type of sound they produce.

    So my efforts have been to try to duplicate the sound of traditional large violas with a much lighter and shorter ergonomic one to reduce future injuries of players and to help the recovery of players who are already injured.

    Weight has been reduced through material substitutions and cavity shape redesigns that I've previously shown.  I'm trying to get viola's the A0 resonance frequency as low as possible with a high amplitude to get strong fundamentals on the lower notes which helps achieve a rich sound.

    A low A0 frequency can be achieved by having a small f hole area and a large internal cavity volume but  a small f hole area unfortunately also reduces the sound output.  It is therefore better to increase the cavity volume.  Attempts in the past to make a short violas with large volumes by using high rib heights and wide bout widths but these len to some holding difficulties for the player's left hand and chin placement.

    A better way of increasing the internal volume is to use a variable rib height where a high rib height doesn't interfere with holding such as at the lower bout right side and upper bout left side and a low rib height is used at the upper right side and lower bout left side.

    The twisted back plate mimics the curved shape of a shoulder rest to make the viola naturally easy to hold and it also reflects the author's mind set.  Attached is a photo of a styrofoam mock up of a viola now being built.

     

    I predict Carl won't like it.

     

     

    2021_07_26_0509.JPG

  6. 7 hours ago, Carl Stross said:

    I see. 

    Well, thank you very much for giving us the opportunity to have a listen -I always wondered how that "anti-violin/viola" of yours sounds.

    >

     

     

    Good traditional violins usually have a strong D note on the open D string because the that is where the A0 air resonance usually is at 294 Hz.  The B1-  body resonance peak is usually around 450Hz so the open string A note is also often strong.

    One tail of the A0 resonance extends to the left of the peak and one tail extends to the right.  Likewise for the B1- resonance.  These tails combine together to give a total output. But the A0 and the B1- resonances are out of phase so the combination of the two tails is low below the A0 peak and is high above the A0 peak.  This has been known for a long time and is shown in John Schelleng's 1962 graph shown below.

    The consequence of these two resonance tails being out of phase means the violin's open G string  and the next four notes are weak sounding because their fundamental harmonics are low amplitude.  This happens even with the best violins and this too has been known for a long time and is shown in Saunders' 1937 graph of the note loudness curves of five different Strad violins and their average is shown below.

    The first few notes also relatively weak on the E string of Stad violins. So Strad violins are strongly liked even though they have many weak notes. Players learn to adapt to these typically strong and weak notes and anything different requires new additional effort.  Hence players often can easily play new instruments that are similar to the ones they are used to.

    The large 5 string viola on the right in the student's video was played as a second violin for that composition and I would characterize its sound as more of an inverse or upside down version of a Strad violin sound.  Its lower notes on the G string show some strength because its A0 frequency is 196Hz.   The notes near the open E string are strong whereas its open A string is rather weak due to the locations of other resonance peaks. Its Saunders loudness curve, shown below, is superimposed upon a portion of the average Strad violin curve with the same scale.

    So you are right this is 5 string viola is sort of an anti-violin.

     

     

     

    Screen Shot 2021-07-25 at 7.21.09 PM.png

    828686181_ScreenShot2021-07-25at9_02_11AM.png

    Screen Shot 2021-07-25 at 7.49.08 PM.png

  7. 21 hours ago, Andreas Preuss said:

    No, but examination of dead horses gives doctors insight into the anatomy. For this the entire work of your experiments is very interesting. Besides do you have a sound clip somewhere available?

    These are undergraduate students using three of my instruments at the Crane School of Music in Postdam NY  while playing Ellen Schwindt's 2019 composition "Trio for three friends".  Matt Grosso is on the right side playing a violin part on 5 string viola.

    Ellen Schwindt has made some interesting comparisons with music's progressions of harmonic overtone series and Mandlepbrot's fractals where smaller and smaller pieces retain the same form.  Sort of like me making sawdust out of large pieces of wood.

     

  8. On 7/23/2021 at 6:04 PM, jezzupe said:

     

    Most all violin, or violin like objects will produce and then reproduce overtones, we must choose how much, in what way and then really "why and how" also , and then ask how much time we want to put into finding that out vs being in the shop building 

    A bowed violin string produces all of the overtones of a note in a saw tooth wave form. But because it is so narrow it can't move much air when it vibrates so it produces very little sound.  Therefore the string is connected via a bridge to a much larger surface area violin body which can efficiently radiate sound.

    The bridge and the violin shell have many resonances which can increase or decrease the relative strengths of the string's harmonics produced thus they act as filters of the harmonics. They don't produce the harmonics.

    A

    ttached below is one of Colin Gough's diagrams of this sequence.

    711182422_ScreenShot2021-05-24at9_02_55PM.thumb.png.751aec9be1e5f78c84705c4f05e11f97.png

     

  9. The minimum bow force needed to prevent bow hair slipping can be lowered by using a slow bowing speed, playing far from the bridge, using a rosing that has a high static coefficient of friction and a low dynamic coefficient of friction, using light tension strings, and having a low admittance at the bridge (bridge and instrument body is hard to move).

    The last variable is expensive to play with if you like puns.

  10. 13 hours ago, Anders Buen said:

    Link to the article abstract. https://asa.scitation.org/doi/full/10.1121/10.0005587

    Perception of violin soundpost tightness through playing and listening tests

     
    The Journal of the Acoustical Society of America 150, 540 (2021); https://doi.org/10.1121/10.0005587

    ABSTRACT

    This study involved playing and listening (using recorded sounds) experiments to investigate how changes in soundpost length (for a fixed soundpost position) affect the perceptual qualities of the violin and what the threshold of change is below which players and luthiers do not perceive differences. A length-adjustable carbon fiber soundpost was employed. During the playing experiment, subjects played a provided violin on which the soundpost length was modified by the experimenter to find their optimal soundpost lengths. Then the experimenter varied the soundpost length randomly in ten trials within ±0.11 mm around their optimal lengths and asked subjects to always compare with the previous setting. The results showed that subjects' optimal soundpost lengths varied from 0.132 to 0.616 mm relative to the original length (53 mm), but subjects could not recognize length variation of 0.11 mm or less at above chance levels. During the listening experiment, subjects listened to 16 pairs of recordings through a computer interface and were asked, for each pair, whether the violin setup was the same or different. The results showed that subjects could differentiate soundpost lengths with a difference of about 0.198 mm at better than chance level.

    Dear Anders,

    I'm trying to sell my violins at very modest prices so I can afford to purchase these ASA violin research publications which hopefully will teach me something of value so I can raise my violin prices so I can buy more of these publications.

     

     

     

  11. 1 hour ago, Andreas Preuss said:

    Hmmm, really?

    Just in terms of mechanics the downforce on the bridge is only governed from the point at the neck heel and upper block making it much more unstable.

    Secondly Marty’s tailpiece setup does not allow a sideway  pivoting motion. This blocks more or less all the signature modes which need a rotation motion of the bridge. (though this doesn’t have anything to do with load path.)

     

    The bridge does rotate to give both horizontal and vertical movements.

    I use something similar to the ancient Welsh crwyth where the sound post goes through a hole in the top plate.  My treble bridge foot rests directly on the sound post and it doesn't touch the top plate at all and this reduces the string tension downward force on the top plate by about half.

    A very shallow string angle over the bridge also reduces the string tension downward load by another half so the total downward force on the top plate is only about 1/4 the normal amount.

    The longitudinal string tension buckling compressive force on the top plate is eliminated by having the strings attached to the tailpiece extension of the fingerboard instead of the usual end pin /saddle.

    These reductions of loads on the top plate allows the use of a thin flat plate made from low density (0.28g/cc) Pawlonia wood which reduces the plate's weight.  The elimination of the arching reduces the plate's stiffness and the combination of these two effects increases the plate's admittance which increases the instrument's sound output.

    The reduction of plate stiffness also increases the modal density which means there are more resonance peaks in the frequency response curve which in turn makes the various notes in a scale more even in loudness.

    Other body shape and material changes further make the frequency response curves quite different and therefore sound quite different from the usual "old Italian" character--

    There's no sense in beating a dead horse.

     

    2021_07_23_0503.JPG

  12. 1 minute ago, Andreas Preuss said:

    FYI I tried plywood not so long ago. For this purpose I glued 3 boards of 1mm birch plywood together. The sound was too dull. 

    Do you think your birch plywood bridge had too much damping or was it too heavy or something else?

  13. On 7/14/2021 at 8:35 AM, Marty Kasprzyk said:

    I used to glue a 20mm diameter round disk about of craft paper on the inside surface of the top plate at the sound post location to strengthen the wood and prevent cracking without adding much weight.

     

    I should have added that I first thoroughly soak the kraft paper in hide glue.  When it is dried it is very hard and strong.  I also put these kraft paper patches above and below the f-hole eyes to prevent cracks there.

  14. Remove  the bridge and bow one of the strings.  The pitch will be lower because the string length is longer but the note will still have all its harmonics present: 1f, 2f, 3f, 4f.... where f is the fundamental frequency.  The sound produced will be due to longitudinal tension changes in the string for each harmonic.

    This sound produced is superimposed over the sound produced when a bridge is present.

    The string's longitudinal tension changes also cause the bridge to vibrate back and forth towards the nut and saddle and to twist because the string is off center on the bridge.  This also produces a small amount of additional sound.  If you tap the bridge in a direction parallel to the strings you get a generally similar frequency response curve as a horizontal or vertical tap.

  15. Force transducers have been placed under the bridge feet to show their up and down vibrations for a bowed note but I've never seen any tests done using a force transducer on the tail chord to show the longitudinal tension vibrations.

    We know the static string tension causes the top plate to buckle downward at the bridge and upward  in the upper and lower bouts with the whole instrument bending. The amount of downward force on the bridge is dependent upon the string angle hence the resultant amount of deformation is also dependent upon the string angle

    The tension vibrations are superimposed upon the static tension load so the bridge area and the bout areas would go up and down thus producing sound.  This effect is  also be dependent upon the string angle.  Thus the top plate arch height and bridge height are likely to have some effect.

    I would expect to see a small amplitude at 2x frequency contribution for each of the note's harmonics.  For example a A note at 220 Hz (1st harmonic) has higher harmonics at 440 (2nd), 660 (3rd), 880 (4th)...So we should see small amplitude boosts at the 440, 880, 1320, 1760Hz... frequencies.

  16. On 7/9/2021 at 6:09 AM, David Beard said:

    Don't underestimate 'mindless' tradition.

    >

    We don't need more 'improved' or 'inventive' violins.   We need more that are 'as good' as 'good' violins have been.

    If your goal is to make good violins then it is reasonable to closely adapt tradition and don't make any changes to it.  It is unreasonable that you can make any improvements.

    “Reasonable people adapt themselves to the world. Unreasonable people attempt to adapt the world to themselves. All progress, therefore, depends on unreasonable people.”


     George Bernard Shaw

  17. On 7/9/2021 at 6:56 PM, Don Noon said:

    >

    One other thing:  Andreas, it looks like you have in mind that longitudinal string tension variations are a big thing in creating sound.  I'm quite sure that's not the case, and lateral vibrations at the bridge are what we need to think about.

    The longitudinal string tension variations have frequencies twice that of the strings bowing frequencies.

    Starting at a zero starting position with zero longitudinal variable tension the string is stuck to the bow hair and is dragged to one side (left side for example) which increases the longitudinal string tension. The string eventually slips off of the bow hair and flies back in the opposite direction to the right to its starting position with zero additional tension.

    The string continues to move in the right hand direction which again increases its longitudinal tension for the second time until it stops and begins to move left back to its starting position with zero additional tension again. This completes one total cycle of the string.

    So during this one string vibration cycle the tension has hit two two peaks and two zeros hence the longitudinal tension has twice the frequency of the bowed string.

    Thus the longitudinal tension vibrations always contribute to the violin's high frequency range.  But a question is how much?  It can be shown (1) that the longitudinal tension variation is dependent upon how close to the bridge the bowing occurs--playing close to the bridge increases it which explains why playing close to the bridge increases the loudness of the note's higher harmonics thereby making the note sound brighter.

     

    1.  N. Fletcher, T. Rossing,  "The Physics of Musical Instruments" 2nd ed.  Springer, 1997,  Chapter 9.3 Force Exerted by the String

  18. On 7/9/2021 at 2:20 PM, Violadamore said:

    In all seriousness, the problem is that modern physics and engineering in all their glory do not yet have the physical or mathematical tools to untangle what these silly little wooden boxes do when you play them, because too many functions in too many variables are involved, and the supercomputer hasn't been built that can calculate all those paths at once.  :huh:

    This being known to the assembled multitude (a lot of us on MN have messed with this), don't be surprised if they expect that your attempts are doomed.   

    Welcome to MN.  :)

    1.  Modern physics and engineering haven't bothered with violins because there's no money in it because the market for good violins is piddly-ass small.

    2. Violin players don't agree on what they like so engineering specifications can't be established.  If you can't define what a violin is supposed to do there is no sense in giving it any attention.

     

     

     

  19. On 7/11/2021 at 12:04 AM, RobertL said:

    Thank you for the warm welcome. Im going to go down your list and make a few of everything. Though I did make a scraper last night out of stainless. It's not professional grade but it wasn't useless it didn't make any dust or leave any nicks so I call it somewhat useful? I made a few knives.  I have a few chisels but no gouges. I have a bandsaw and the heavier side of things. I was just curious about where others got started. I'm not going to start from scratch right away but it was surprising to me how relatively cheap wood was compared to my other hobby balsa model airplanes. For the money I have in my 1/3 scale pitts I can make a "moderate" to "high end" violin. I am skilled at wood working but I have never tried the task of actually carving anything yet though. I have some idea of what I'm getting into but I have no idea where to start. I thought start small start with something I know or something easy. Im not going to build the best sounding violin ever my first attempt or even my second or 3rd attempt. But eventually my goal is to be as proficient at violin making as I am a model airplane building. And to have a nice sound violin or two to show for it. I've been studying a lot and it seems pretty obvious to start with the plates so wanted to aquire those tools first. In my curiosity I got more into it and now I've decided to make a tool every night until I feel comfortable starting an actual build. You mentioned a heating iron or just using water. My thoughts were confusion. Everyone I've seen uses an iron. In the model world we use water or ammonia. Ammonia works wonders if you've never tried it. Anyway is there any reasoning to use the iron over water or vice-versa? From my experience with water and wood eventually something is going to change im not sure I like that. Is the iron just more widely used because its faster? I mean so much emphasis on naturally dried wood just to use a hot iron on it doesn't make much sense to me either.  I'm positive both ways give good results or is it to each their own type thing? Another thing was plate tuning and plate thickness. Wood density.... but I suppose that for a different conversation. Anyway thanks for the advice and any more information or tips would be greatly appreciated.

    I suggest using shorter paragraphs with spaces in-between to make things easier to read.

×
×
  • Create New...