Andreas Preuss

Lowest possible arching for the top - does it work with any material?

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How low can the top arching be?

What would be the acoustic effect? 

(I remember reading somewhere that lower arches increase the intensity and the number of wolf notes.)

And most important in this context, what type of wood is needed? Or in other terms, I don't think that one can make an extremely low arching with wood of low rigidity, 

On the practical side, would it be enough to take the bending properties of a test strip as a guide line to form an idea of the arching height? (Something like: the stiffer the material the lower the arching) 

It would be interesting to know from MN followers how low was the lowest arch ever made? 

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Sorry, Andreas, I have not yet experimented with every possible combination.

Lowest arching height posted so far? Probably zero (or a little less), on flat-topped fiddles. Those I have played so far didn't "give me a stiffy";) , so I continue to make arched tops.

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23 minutes ago, David Burgess said:

Sorry, Andreas, I have not yet experimented with every possible combination.

Lowest arching height posted so far? Probably zero (or a little less), on flat-topped fiddles. Those I have played so far didn't "give me a stiffy";) , so I continue to make arched tops.

Wouldn't a flat top plate still technically have an 'arching height' of about 3 mm?

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43 minutes ago, Andreas Preuss said:

How low can the top arching be?

What would be the acoustic effect? 

(I remember reading somewhere that lower arches increase the intensity and the number of wolf notes.)

And most important in this context, what type of wood is needed? Or in other terms, I don't think that one can make an extremely low arching with wood of low rigidity, 

On the practical side, would it be enough to take the bending properties of a test strip as a guide line to form an idea of the arching height? (Something like: the stiffer the material the lower the arching) 

It would be interesting to know from MN followers how low was the lowest arch ever made? 

One consequence of low arches is that the bridge has to be correspondingly higher to maintain bowing clearances.  Increasing the bridge height H while maintaining standard foot width W increases the  bridge H/W ratio (like cello bridges have).  This increased lever-arm in turn increases the bridge's vibration forces on the top plate during bowing which simultaneously increases both loudness and worsens any wolf notes.

If you want to try lower arch heights I suggest either decreasing the C bout width to achieve good bow clearance and/or using wider bridge feet.

 

If you plotted top plate arch heights vs. construction year for Amati, Stainer, Strad, DG violins you might conclude that the plates should be pretty flat by now.  But fossils show evolution stopped about 200 years ago.

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In my experiments, it appears that lowering the top arch reduces the B1+ frequency, but not the B1-.  On my one beater fiddle, I made a top with 8.5mm arch (from gluing surface to top, so the actual curvature was more like 5mm).  It was bad.  The B1+ was so low that it merged with B1- to make one supermode.  Wolfy  and uneven.  At 13.5mm, I made a couple of tops that worked reasonably.  Not great, but certainly functional.  For all these experiments, I used very good, stiff, torrefied wood.  Normal wood might want a higher arch.

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On second think, there's the original "snakefiddle" that had dead-flat top and back, and the B modes were absolutely "normal", although the sound was extremely boxy and non-violiny. The ribs were extra-tall, which likely stiffened things up, and the plates were left quite thick.  Perhaps the matching of the back and top arch kept the B modes separated, whereas a flat top and arched back would lower the B1+ frequency relative to B1-

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1 hour ago, Marty Kasprzyk said:

If you plotted top plate arch heights vs. construction year for Amati, Stainer, Strad, DG violins you might conclude that the plates should be pretty flat by now.  But fossils show evolution stopped about 200 years ago.

Sorta like what the real fossil record shows for cockroaches, etc., on a vastly longer time scale.  Some things don't change past a certain point.  Once you've got it right, why mess with it?  :ph34r:

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3 minutes ago, Peter K-G said:

The whole shape of the arch is as important as height and if cross grain stiffness is low I would not make it low

Interesting. I played one fiddle where the cross-grain stiffness had been reduced by removing wood between the grains, and I thought it was pretty good. The fiddle was one of Joe Regh's experiments.

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4 minutes ago, David Burgess said:

Interesting. I played one fiddle where the cross-grain stiffness had been reduced by removing wood between the grains, and I thought it was pretty good. The fiddle was one of Joe Regh's experiments.

Don't they all (violins) sound awesome, would you make the arch low if you knew that it had low cross grain stiffness?

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3 hours ago, Peter K-G said:

The whole shape of the arch is as important as height and if cross grain stiffness is low I would not make it low

While I  do agree that the whole shape of the arch is important, I would be more uncertain about the idea of using a higher arch if crossgrain stiffness is low.  With a higher arch, the slope of the arch above and below the F holes becomes steeper, and with steeper arch the crossgrain becomes farther off-quarter, and the stiffness drops off a cliff.  There are competing factors and localized variations that could drive things in unknown directions.  As usual, it's complicated.

3 hours ago, David Burgess said:

Interesting. I played one fiddle where the cross-grain stiffness had been reduced by removing wood between the grains, and I thought it was pretty good. The fiddle was one of Joe Regh's experiments.

And there was my slab-top violin experiment, made to test low crossgrain stiffness.  It tied for 10th in tone (out of 44) at the VMAAI competition.

And then there was my viola that got a certificate for tone at VSA 2018, and it had abnormally low crossgrain stiffness.

From these (and others), it doesn't seem as if low crossgrain stiffness is too terrible.

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I've read several del Gesus described as having "gentle" arching (I think Il Cannone and the Kreisler), and that Dilworth described some of dG's later arches as being "reduced to a shallow minimum". Assuming that these are pertinent to the OP's question, does anyone have measurements?

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6 hours ago, Don Noon said:

And there was my slab-top violin experiment, made to test low crossgrain stiffness.  It tied for 10th in tone (out of 44) at the VMAAI competition.

I would expect a slab to have a higher crossgrain / longgrain stiffness ratio than a quarter from the same log. (With decreased overall stiffness). Am I wrong?

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Quite a long time ago, over 40 years, I made a copy of a Michael Angelo  Bergonzi and the top wood given me to do it gave a maximum arch of 12 mm.  I remember it sounded quite good.  The top wood I used was high quality European and quite stiff, with a hard winter grain.  I don't remember the fiddle's dimensions, but I suspect it may have had a narrower chest than what we consider optimum.  I would not normally make one that low, but sometimes wood will dictate what you need to do.

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And some more examples that they all (violins) sound great, countless of "odd" examples that are awesome.

- low arch, high arch, low dens, high dens, bad wood, slab cut, tuning, no tuning, graduation schema (whatever that is), fungus treatment, removing wood between grains etc etc...

and surprise, surprise great sound ;)

(except maybe for David, who seems to have heard some bad ones?)

 

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26 minutes ago, Peter K-G said:

And some more examples that they all (violins) sound great, countless of "odd" examples that are awesome.

- low arch, high arch, low dens, high dens, bad wood, slab cut, tuning, no tuning, graduation schema (whatever that is), fungus treatment, removing wood between grains etc etc...

and surprise, surprise great sound ;)

(except maybe for David, who seems to have heard some bad ones?)

 

I think we need to add horrid Ebay rot boxes to this list, which also sound like angels singing (but only to the ears of the winning bidder) :D

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10 hours ago, Don Noon said:

While I  do agree that the whole shape of the arch is important, I would be more uncertain about the idea of using a higher arch if crossgrain stiffness is low.  With a higher arch, the slope of the arch above and below the F holes becomes steeper, and with steeper arch the crossgrain becomes farther off-quarter, and the stiffness drops off a cliff.  There are competing factors and localized variations that could drive things in unknown directions.  As usual, it's complicated.

And there was my slab-top violin experiment, made to test low crossgrain stiffness.  It tied for 10th in tone (out of 44) at the VMAAI competition.

And then there was my viola that got a certificate for tone at VSA 2018, and it had abnormally low crossgrain stiffness.

From these (and others), it doesn't seem as if low crossgrain stiffness is too terrible.

Maybe cross grain stiffness for the top in violas needs to be low but not on violins. 

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51 minutes ago, Bill Merkel said:

Could I ask why what the lowest possible arching is is important?

Just had an Andaldo Poggi violin in my shop with an incredible low arch. Something like 13mm and this instrument had a pretty penetrating sound. The arch looked like as if avoiding at all cost  narrow curvatures. So it made me wonder...

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5 minutes ago, Andreas Preuss said:

Just had an Andaldo Poggi violin in my shop with an incredible low arch. Something like 13mm and this instrument had a pretty penetrating sound. The arch looked like as if avoiding at all cost  narrow curvatures. So it made me wonder...

And Limburger cheese has a "pretty penetrating" smell.  :lol:  Are you describing the sound positively, or negatively?  :huh:

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Thinking of Don Noon's posts, and David Burgess' admission that he hasn't tried every possibility, yet, reminds me of how many variables are being juggled by violin makers and how many lifetimes it would take to actually try all the possible combinations of arching, thickness, wood stiffness, mass etc. In the end, we gather as much anecdotal information as we can and fiddle around at the edges of the things we've found that work, don't we?

My little anecdote to add to the pile, for whatever it's worth, is that last year I made a fiddle with a 12mm arch that prompted me to post some questions about overstand/neck projection compromises on low-arched violins, as sticking with a standard overstand gave me a disturbingly flat string break angle, and while the violin had a pleasant sound, it was darker than I liked. After a little experiment to see what increased string break might do (involving tying down the tailpiece) I decided to re-set the neck to get a 158-160° angle (though that gave me quite a high bridge). That improved the tone considerably, and made the violin usable in a pro setting to my ears, at least for tone quality and projection. Unfortunately, it turned out to be a wolf-monster! I'm used to playing some fine fiddles with wolves, and having to avoid c5 on the g-string is a small compromise if the rest of the fiddle sounds great, but on this fiddle, ALL the c5's would wolf, d-string and a-string, and even  the c6 on the e-string a little bit!

I made a new top for it last January, with a 17mm arch, and the violin's doing fine, today. I've been thinking of course that with a different piece of wood, that 12mm arch might have worked better, or with different thicknesses, or a different profile descending towards the edge, but again, so many variables! As I admitted in my post about the overstand/projection question, that low arch was a bit of an improvisation after a bit of over-zealous roughing out, not a reasoned experiment, but the experience doesn't make me too impatient to try it again when my usual arching height/profile gives me fairly predictable results.

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I think if the ffs were really short, large bass bar, soundpost near the bridge foot, meeting a strong back, that one could achieve a flat plate of thickness 3mm. Soundwise it would probably sound like stringing up a book of some sort. 

Those are my thoughts. 

 

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