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Arching deformation and break in


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Since hearing about the Betts project at Oberlin I have wondered about the benefits of carving arching deformation into the arching.  I wonder if the asymmetry caused by natural deformation of the arch over time is part of the 'broken in' sound.  My understanding is that the cnc model was an exact copy from the CT scans and did not correct for deformation.  

 

My first thought was that you would have more run out around the soundpost area because it would be deformed upward, and the section of the top that would normally have less runout would be fundamentally different.  Perhaps this makes little to no difference, however, my next thought was that you could do an arching correction and produce a top and back with the corrected arch, then have a counter form of the exact arch.  

 

If you broke in the instrument for a certain period of time (6 - 12 months?), then tested it before pressing the arch in the counter form you could hear something of the difference between the arch pre and post deformation.  Perhaps this could even be done by a large number of Oberlin attendees and do the test, arch press, and retest at Oberlin as a crowd sourced project.  It wouldn't solve the question of whether to carve some deformation into the top from the start, but I think it would be interesting.  Any thoughts on this?

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I often use an arching system Feng Jiang came up with-- shown to me initially by Felix Krafft-- that tries to plan an arch that will deform in ways that will bring the arches to resemble those of the old greats. This is interesting to me. I think cycloid-created arches are also great, though I haven't done one in a while.

I've done tons of carving-it-the-way-the-damn-thing-looks, and seeing those instruments six or seven years later, if the post has been replaced tighter once or twice, the arches really do start to deform. As much as antiqued instruments are my bread-and-butter currently, I grow to respect building to resist the passage of time more as my eye gets better, and my mouth opens less...

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My neighbor and person who got me into this frustrating hobby, Roelof Weertmann, had access to many great inst's  that he copied and to correct for the distortion in the sound post area would flip the arch and average a line from the two lines. How can you improve something worth millions by altering it.

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My neighbor and person who got me into this frustrating hobby, Roelof Weertmann, had access to many great inst's  that he copied and to correct for the distortion in the sound post area would flip the arch and average a line from the two lines. How can you improve something worth millions by altering it.

Altering it by trying to conform to the original concept (trying to subtract known distortion tendencies which have occurred in the interim), or altering it by trying to conform to the distorted shapes which have come with time and numerous restorations? Or altering it in anticipation of the distortions which come with time, in an attempt to keep the arching close to the original(?) concept, after several hundred years have passed?

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Altering in anticipation would be my choice. A rounder cross arch at the peak of the arching-- the 'sausage' of the long arch, as Big P Prier used to point out, will help. I think new arches are sometimes carved too sloped at their ends-- some of the springing slope we see on old instruments seems to be an artifact of age and repair to me. Anyone have thoughts?

The best is to see where arches bulge and flatten with time, hoping the Morel-school of post-setting isn't pushed too far. I've been surprised by a few Engelmann tops' changes-- one of the reasons I started patching and reinforcing the softer tops.

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Since hearing about the Betts project at Oberlin I have wondered about the benefits of carving arching deformation into the arching.  I wonder if the asymmetry caused by natural deformation of the arch over time is part of the 'broken in' sound.  My understanding is that the cnc model was an exact copy from the CT scans and did not correct for deformation.  

 

From what I have heard, the exact copies didn't have the "broken in" sound.  And, from what I know of that sound, I don't see it as being a result of distorted arching.

 

While I would certainly admit that changes in arching most likely would cause some change to the modes and therefore sound, I also see no reason to think that these distortions would lead to a consistently better sound, just a little different from what it was.  The bass bar and soundpost already put in massive asymmetry in the structure, so distortion is not a question of symmetry vs. asymmetry.

 

If I was in the buisness of making an exact bench copy of a specific instrument, I might copy the distortions.  Since I'm not, I don't.

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A few months back, I had a chance to play one of these CNC cut Betts.  The instrument had been in the hands of an orchestra player for a while, so presumably as played in as it will get.

 

Sadly, the instrument had the stiff and boxy sound associated with much 19th century factory work, and many French fiddles.   Not a wonderful instrument (at least in my book).

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I did not mean to suggest that those instruments sounded more broken in.  I only ever heard one in a blind testing and I have no idea which one it was, so I have no opinion on it.  I think it's hard to make any sort of assumption based on a single instrument anyways.

 

I've generally tried to correct arching templates to the way I think the instrument may have been made.  Sounds like there are other ways that are successful as well.  Part of the reason that I think the asymmetry may help with break in is that there seems to be a benefit to a soundpost being in an unsetup instrument for some time before being played.  It seems like there can be a little pre-stretching of the plates that helps with break in.  Not suggesting that you hold off setting up an instrument, just that you may as well have a soundpost in it even before you set the neck and varnish it.  Maybe that has more to do with changes to the wood in some way, not the shape of the arch, but that's the question that I'm considering.

 

I suppose the other problem with trying to press the distortion in is that the instrument would probably change so much in disassembly as well as a new soundpost and possibly new bassbar if you couldn't press the shape with the bar installed.  Neither my first nor my last thought that leads to a dead end.  Thanks everyone for the input anyways.

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Part of the reason that I think the asymmetry may help with break in is that there seems to be a benefit to a soundpost being in an unsetup instrument for some time before being played. 

 

How did you determine that?  It seems like it would be an awfully difficult thing to verify.

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With regard to the original question which is a good one...NO! But on the other hand luthiers should be very conscious of the distortion process you mention.  In the 1990's Sam Zyg presented a paper at the Dartington conference when he described how he had monitored the archings of his violins changing as they 'settled in' with the belly rising and narrowing etc...( should be compulsory text)..In my opinion there is no benefit to be had by copying existing distortions for sound etc but there is certainly a benefit to understanding how they happened so that a maker can reverse engineer an arching to be correct in 300 years time. The truth is that new violins distort a lot. Good makers who have a handle on this try to keep finished instruments as long as possible before handing to a client....The same is similar with old violins that have been taken apart and put together..even they need some time to settle in. ( one of the ironies of violin making competitions is that they generally ban violins old enough to have settled in) Readers here who try to make looking at arching profiles on Strad posters or the wonderful Biddulph Guarneri book need to be aware that these arching profiles were taken from distorted ribs...best thing is to try to interpret the grammar rather than the measurements..

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It seems like there is a consensus that the deformation doesn't matter much, although I'm puzzled as to how people came to that opinion.  Even though there aren't very many comments I take it as a hint when well established makers (particularly with different backgrounds) are all saying the same thing.  I guess that means I should keep doing what I'm doing, but I am still fascinated by the notion of the proposed experiment on a large enough sample size that you could actually determine some difference.  I can't imagine being able to tell anything of value from one or two.  I suppose it's a lot to ask for people to take part in such a thing if the consensus is that it isn't important.  

 

How did you determine that?  It seems like it would be an awfully difficult thing to verify.

 

I regret to answer that question with my least favorite answer.  That's what my teacher told me.  I have nothing of substance to offer in defense since I've always done it the same way.  I will give what circumstantial evidence I do have.  My last instrument waited from Fall to mid winter before varnish was completed, and started with a post that was probably a little too tight.  By the time I was doing the first setup the post was too loose.  The new post was almost 1/2mm taller than the old one.  Certainly some stretching going on, but I can't prove that there's any 'breaking in' going on.  When it was finally set up it didn't sound like a violin that had been breaking in for 3 months, it still needed to be played.  Another violin of mine was met with surprised responses by luthiers who were hearing it's first notes because they thought it should have sounded a bit stiffer right out of the gate.  I have no idea if those luthiers adhere to the same method regarding early soundpost installation.  In my day job I occasionally have factory instruments come unsetup without a standing soundpost.  It's easy to convince myself that those instruments take a little more breaking in, since I have a preconceived notion that is as you say, difficult to verify.  I won't advocate one way or the other, but I'll keep standing posts up as soon as possible just in case.  Is that sufficiently vague and unsubstantiated of an answer to count as 'traditional'?

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I hope I understand the topic enough for my contribution to be relevant, I am only a player. But here goes:

 

I think that deformation of the arch, or of the instrument as a whole, but especially of the back is a great factor in the phenomena known as breaking in. It has especially large influence on the string response, more than on sound. I believe, maybe erronously, that the deformation of especially the back of instruments makes the whole structure stiffer (provided sound posts of the proper length are installed), less flexible (makes it resonate at higher frequencies?). Imagine a plank of wood, like a springboard, from which a weight large weight is hung for a very long time. The spring board will change shape, curve downward, and intuitively I think, lose some of its springyness.

 

In cellos, which is the instrument I have personal experience with, the deformation of the back has a great influence on playability of the upper two strings. I have a cello that had a very problematic a string for years. Slowly but surely, the back, which is relatively thin, has deformed, the deepest point moving toward the sound post, and with this process the problematic string response of the a string dissipated. I am assuming that the back is least flexible at its deepest point or very close to the ribs and is most flexible in the middle between the deepest point and the ribs, which is where the sound post usually is placed. I am suspecting the better response of the a string has to do with a changed way of resonating of the back; a resonance that is no longer interfering with the a string. I must say that over time this cello has had several new sound posts installed, and I think arch distortion of the top is really fairly small if at all existant; I cannot detect it by eye, the f holes do not show any sagging of the arch at all. So I believe that, with cellos, it is beneficial if a top retains its arch as much as possible, but for backs that in some cases, when that back is too flexible, a distortion can be beneficial to string response. I can imagine the opposite case too: that for particular instruments the deformation of the back is not good.

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