curious1

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  1. Basic Acoustics Resource

    Yes, many Stradivari have had arching correction as have many fine bows. We expect some movement in wood under stress and I would not categorize it necessarily as a failure. I would say a breast patch is indicative of a structural failure though. In the Huberman case I would say the thinness of graduation (whether that is original or not is hard to say) lead to arch deformation. PS I don't think Stradivari made double hump camel back top arches.
  2. Basic Acoustics Resource

    Without being too contentious there are few premises that I would challenge here. First, the Gibson has clearly fallen over the edge of failure and that is why it required a patch and probably now may only be at the edge of failure and function better. Secondly, I don't hold that if it's lighter it's better. My singular example would be the Canon Guarneri del Gesu. At 444g it is grossly overbuilt yet it was considered by Paganini, arguably the greatest violinist of all time, as the greatest violin.
  3. Basic Acoustics Resource

    thanks Marty
  4. Basic Acoustics Resource

    Once I get the wood back in the workshop and it is time to make fiddles then I get very exacting but I'll know that all the wood is in the ranges that I prefer.
  5. Basic Acoustics Resource

    I guess it all depends on your perspective of precision. Personally I don't need to know exactly what something is but only approximately what it is. I follow the Goldilocks Rule. Is it hot, medium, or cold? My initial pass in the wood yard is all visual. Is the grain straight, is the split good, do. I like how it looks. The second sorting is more technical. With an iPhone, metric rule, and pocket calculator you can measure the speed of sound in under 30 seconds. In the lumber yard you can divide the wood into low, medium , and high speed of sound quite quickly. the same goes for density. If the wood is fairly uniformly cut you can get low, med, high very quickly.
  6. Basic Acoustics Resource

    Or develop techniques that allow you to sort wood quickly.
  7. Basic Acoustics Resource

    I guess, if you count a breast patch and arch reshaping 'holding its shape'.
  8. Basic Acoustics Resource

    If I take the cross section of the arch and combine it with the Young's modulus is that a section modulus?
  9. Basic Acoustics Resource

    I make no arguments about the sound but only point out that if we want a piece of wood to hold the shape we give to it we should be cognizant of the materials limitations.
  10. Basic Acoustics Resource

    Hi Davide, I give this fiddle as an example because it is so well known and archived. It shows how some very basic techniques can aid us in improving our work. my guess is that the arch was original a bit higher if we account for the sag in the middle. Perhaps 1 mm maybe more but probably solidly in the 15+mm range. This would certainly help hold up the arch but I think the principal culprit here is the thin graduations. Strength comes from a combination of arching and graduations. With .35g/cc anything less than 2.5mm is asking for trouble. changes in the arch shape do not change the speed of sound in the wood or the modulus of elasticity. Those qualities are inherent to the material and not shape. i believe they call the strength of the shape the 'section modulus' (?). (Can I get some help?) The language of science helps give a name to empiricism.
  11. Basic Acoustics Resource

  12. Basic Acoustics Resource

    If you went to the middle you'd have spruce .4g/cc, 5400m/s maple .65g/cc, 4000m/s i would then calculate the stiffness using this formula which incorporates the density and speed of sound speed of sound ^2 x density spruce 11,664 maple 10,400 stuff above those is going to be above average and stuff below that obviously below average if I was an amateur maker i would consider these to be average numbers that would accord well with these Top arch 15mm, thickness 2.7mm, weight ~68g w bar, pitch F-F# Back arch 14.5mm, 4.5mm in center, 2.3-2.5mm in lungs, weight ~100g, pitch E-F.
  13. Basic Acoustics Resource

    Warm and flexible is think how Sam Z. describes it. My point in bringing it up as an example is there is an interplay between the stiffness and arching/graduations. That the Gibson has strayed outside the norms (whether by the maker's intent or by over zealous regraduation we cannot know) is indicated by the bell patch and arch shape. And perhaps by the tone. The thread is titled Basic Acoustic Resources. I think measuring the modulus of the wood is a simple procedure that can benefit ones work when applied even in the most general of ways.
  14. Basic Acoustics Resource

    Spruce density .3-.5g/cc, speed of sound ~4800-6000m/s maple density ~.55-.75g/cc, speed of sound ~3500-4500m/s average would be for me right in the middle of those ranges.