Anders Buen

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About Anders Buen

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  • Birthday 06/03/1970

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    Oslo, Norway
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    Violin-, Hardanger- fiddle-, room- and architectural acoustics.

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  1. Looks nice with those flames. The summer wood look very wide in the four corners. Does the grainlines look _! to the clueing surface or are they at an angle? The crossgrain bending stiffness drops as the angle is changed from 90 degrees to say 80 or less. The grainlines in the centre are also pretty wide. I do not know this wood, but I would probaly not go to thin with it. Maybe the mode 2 frequency can say something about the crossgrain stiffness?
  2. Thanks for sharing the link to the youtube video. I have been looking at some of the data from that test. It is difficult to gat a good overview without taking part in the numerous tests, a real puzzle. However, the material part is fairly easy to get a grasp of. In general there are plenty of very clear correlations between the plate modes, the weight, the impedance formula and graduations. You can choose any you like to describe the plate. They are made of very similar wood, the same model etc to minimize that kind of variation. So the set will be more streamlined than most other sets of violin plate data. They have emphazised on the Davis formula for impedance as a tool. That may work well, maybe it is much faster just to do the weight, tap tones and graduations. It is just a way to make those numbers into one making it more abstract, which I think is not a good thing. There are many methodes that work well in making. I have seen one of the gratest do bending test of a plate I had at Oberlin, comment "stiff", which was correct. If you are trained at it you get good at it. If another tries it, it may not work. This kind of things depend on the training, skills and maybe a bit of talent. Not much kan beat the speed of tapping a plate and listening, having a control tuneable tuning fork near, the graduation meter or pounch a light source, a weight and a humidity meter.
  3. Samples are bent around a 25mm diameter rod. Sort of similar to the corner block regions, isn't it? The test samples used in the electron microsope is very small. Maybe they wanted to make sure they got useful results they could write about. It is a long way from bending skis or ship boards to bending a violin plate. Most likely a bent violin top will crack sideways unless the arch is low. Grandpa used bearclaw spruce for this.
  4. Link to Woodhouse and Barlows article on bent softwood. They used steam and ammonia, two different methodes, for softening the wood and bent test strips around a rod. http://www2.eng.cam.ac.uk/~jw12/JW PDFs/Bending.pdf
  5. The correlation between free plate frequencies and B1 modes may depend on the statistical material. Small datasets give higher correlations. In larger datasets, I think, it is around 33% and the correlation is significant. It is no doubt that there is a correlation there. It is not weak, the p-value is very low indicating that the correlation is significant. I know because I did the analysis. That is: some 67% of the variation are other factors. I think that is reasonable. This is across many different models. On the same insturment, like Schleskes master work violin the correlation becomes higher because the data comes from the same model, wood, etc. I think the highs are much more dependant on the quality of the set up. The reason many Strads have nice high frequencies are that they are set up and maintained by the best personal there are on this at budgets that makes it possible to do an optimal job. I do not think its the only factor. Less resonant insturments are easier to drive playing them. That is the minimum bowing force is lower. The resonant instruments have higher minimum bow force. I think the «speaks easily» is a loudness matter. The louder the instrument the easier it may feel tp be played. But in relaity they must have more bow force to speak and are more likely to have a wolf. I think most top modern makers do regraduate their insturments to some extent, either as a part of their regular building process, or as a part of the maintenance. I guess many have learnt quite a bit in e.g. 10 years seeing their instrument again. The instruments also do change somewhat, e.g. the archings, over time. Then a regraduation is a natural process, maybe, if the owner is happy with that.
  6. In general, yes. But the B1 modes are also influenced by factors like the soundpost position, the type, weight and position of chinrest, every now and then the tailpiece or the fingerboard can have an influence. The size of the model also play a role, as well as the arching height. Larger implies lower frequencies. The arching height should not be too high, lower arches in simple terms means stronger B1 modes. Higher arches supresses or stiffens the plates, and it makes the instrument more sensitive to humidity changes. TYhe arch shape probaly also has an influence on the overall frequency response of an instrument, although this has never been proven with clear correlated measurements. Arching is very difficult to document in a few numbers. The plate stiffness depend on the thickness, the arching height, the wood properties and to some extent the climate it is measured in. Wood with higher moisture content is softer and heavier. It will also be a little more damped. The ring will last a bit shorter while tapping them. Thinner instruments will in general lead to a stronger low frequency response, usually at the expense of loosing some of the highs. Strings are important too. So the violin voice may depend on the choice there too, as well as the type of rosin. Not only the string gauge, but also their damping influences the tone balance. I am not a practical expert in this, but learnt from Güettlers research in this regarding the bowed string. I think it is difficult to predict the voice of an instreument from the properties of the free plates. But some broad lines can be drawn. Your suggestion is a very good idea. Will give you increased experience, and maybe it answers some of your questions. It is always good to control this process yourself.
  7. No, because the amplitude also has to be known. It is very difficult to predict if there will be a wolf or not. It is related to the complex dynamics of the bowed string, and the buildup of the Helmhoz kink motion of the bowed string. The string gauge also matters. In general stronger resonances and thicker string gauges will increase the risk of getting a wolf. An instrument may also have a varying response with the climate, how humid or dry the environment is. More humid will lead to somewhat lower frequencies of the signature modes and a weaker response due to a little more damping. There are tools out there to do calculations of the likelihood of getting a wolf, or more precisely: Calculating the minimum bow force to get the Helmholz motion going. That is: to get a reasonable sound while bowing, not noise. For a soloist instrument they try to get absolutely as much power as possible with strong well distributed resonances in the singature region and strong output around the 1 kHz region and 2 kHz bridge hill. I think it is most usual to get wolf notes around the B1+ mode, often by playing c-c# on the g-string. I think it is a tendency for many fine new or some old to have a strong B1+ in relation to the B1+. I think a solution with balanced B1- and B1+ in amplitude is a better solution in relation to wolf notes and tonal balance in general. I do also think that it matters where these resonances are in frequency and level. It is something requred, but not suffcient for making a great instrument. Players expect to find power in the insturment within fairly narrow regions. And the high frequency part has to be good, or the instrument is doomed. If the mode frequencies are odd, it will usually be a sign of something out of order. But for a fiddler, as I am to some extent, many more combinations can work nicely or great even modes way outside the usual region. I think the violin acoustics communiioty are too monomane on thir violin research. Why do they not compare baroque instruments to violins? Investigate what is grat toen for a fiddler, etc. It is a political choice of VSA to not do so. This limits the insights! It is not only the VSA (Colin Gough has been positive). The KTH music acoustics group are not interested in folk music instruments like the Nyckelharpa either. There is a snobbery in this violin acoustics business. I hate that part.
  8. What is the relative humidity around the plate? The weight, and the plate tones are to some extent dependant on the moisture content of the plate. Usually higher density wood implies stronger wood. That is you need to go thinner than normal to get a reasonable result. It is probably wise to cut the f-holes and bar before preceeding thinning. The central region is probably too thick, except for the post area. The borders are also thick, but this is a regaion that influences the plate modes quite much, I think. While thinning there probably does not influence the assembled instrument so much.
  9. Some trees do get a bend as they grow. It has been workmanship practice to utilize that for spoons, walking sticks, boat parts etc. I think the cell walls will buckle no matter which method is ued to bend the wood. Something has to give and it does.
  10. Bending violin plates is a theme or article in at least one of the CAS Journals. I remember that the blanks were bent before glueing using wedges and a hammer, I guess.I assume they steam heated or boiled the blanks before this. Woodhouse and Barlow have investigated bent and normal wood in an electron microscope. Bent wood get buckled cells. We do have some fiddles after grandpa with bent plates. He used bearclaw wood and a suitable arching. The instruments are still in use, but are not among the main ones, partly because they are not traditionally decorated hardangerfiddles, and possibly because they look a little experimental. He heated the plates to about 180 degrees C in the cooking oven and bent them gradually, I guess, by clamping pressure. I have seen a mold but not the process. I would believe one gets unseen cracks and bucklin of cells. Microscopically it does probably not look good. Why not try naturally bent wood?
  11. Hi, The plates are heavy and stiff like some mass produced chinese instruments. I have regraduated a few of these as part of a «research program». Octave tuning is not a good idea because you end up with too thick central parts of the top and probaly also the back plate. I would look more on mode 2 than any of the other and get the top plate weight below 70 g, even down to 65 g or lower without the varnish, and with bar and ffs. I would varnish the insturment before the last «plate tuning». I would aim for a mode 2 frequency around 145 Hz and I would remove the platforms in the ends of the plate which makes the mode 2 frequency too high in relation to mode 5. In normal instruments the relation between the mode5/mode2 frequenciues are around 2,2 to 2,3 with average Strad or del Gesu graduations, pretty even in the tops. I think the back plate could work better around 100g or even a little lower with the varnish on. I agree that the back can have a little higher tap tones than the top. I think graduations and the weight is more important than the mode frequencies. There are of course also other factors that matters as arching, wood peroperties etc. There is no evidence I know of in the violin acoustics literature or research that support the idea of using octave tuned plates. A double bass professor friend liked the violin octet double bass, though. Maybe it works better for violas. Hutchins played the viola.
  12. Thanks back Don, I follow your updates and appreciate your comments and input very much.
  13. Statistically R^2 = 1 would mean that all variation in the frequency of B1- (?) could be explained by the variation in the M5 top plate frequency. We know that e.g. adding a chinrest in general will move the B1 frequencies a bit, sometimes quite a lot. Now, the variation in the top plate can´t explain that and 100% prediction from the top plate M5 frequency is not possible. We can dig up other examples too. From my large dataset about 30% of the variation maybe is reasonable. One need to do multiple regression or maybe some other type of statistics mining technique to figure out this. The input data need to be of high quality. Patrick Kreits book claim very high prediction power like that, but by looking at the data proivided there, and having experience with violin acoustic datasets, one can tell that they are likely to be model predictions and are not real measured data. I think I have explained where I think the fault is in that model too, somewhere here on MN. The problem with Dons and Bissingers datasets is that they are not large enough. And sets with data from before and after regraduation are probably better. Using models from statistics, like this, probably also works better for predicting the perturbations, the expected changes, from regraduation than for a new build of a given model.
  14. Regarding Dünnwalds Sound parameters I have done a few years research in trying to figure out what influences these. The level of the A0 in relation to the mid frequency response is called the L parameter. Lower top plate weights and low Mode 1 frequencies go with stronger L-values. This affects the stiffness of the box. Lower stiffness gives a stronger A0 response. We have also seen some traits of weakening the midfrequency response from adding mass close to or at the f-hole upper wings. A typical patch and repair position. Furthermore higher arching and thinner border region of the back plates seem to go with higher values of the ACD-B (see Figure). The most difficult part is the higher frequencies. DE-F, bass, bridge and setup may be crucial. I have also seen that high values of Dünnwalds parameters does correlate with a lower overall SPL. A «Dünnwaldian» violin may have a certain sound characeristics but may not carry as well. D´Addarios old Naepolitan violin is an example of that, sweet sound but not particularly powerful. (If you attend the VSA Oberlin Violin Acoustics Workshop you will probaly hear or even play it). However some violins have both Have high scores of DW parameters and high SPL. An example is the de Diable del Gesu on the Miracle makers, at least it is like that in the recording. Later research have shown that the nomenclature used by DW for «nasailty» etc was not well founded. Also the frequency regions for different classifications are disputed. But to be honest, I have not been able to understand the contant of this, not from reading it nor from hearing the presentations. I am not going to do the work over. I do think that good violins can have a strong mid frequency response, e.g. Boosting the fundamentals of one or some notes on the E-string. The winner of the VSA 2016 competition was one such instrument. Strong E string instruments are fun to play. How do we measure «fun factor»? Or just let it be?