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2 hours ago, Anders Buen said:

In my first article based on my master thesis work on vibration modes in violins we investiged a concept of violins made using thin laminated plates and a system for supporting the pressure and tensions. The inventor was Mikael Hagetrø from south Trøndelag (mid norway). An amateur maker and inventor. The maker made all his machines for the purpose. I think he patented the concept, as well as at least one earlier version.

The work I and the concert master from the Trondheim Symphony Orchestra: Sveinung Lillebjerka, was from 1993-94. Hagetrøs daughter later tried to run a business based on the idea. According to the late bass professor Knut Guettler, the violas did have a certain potential. They painted the flames on the back plates. 

My article for Stockholm Musical Acoustics Conference in 2003 on that work:
https://www.researchgate.net/publication/267848892_OPERATING_DEFLECTION_MODES_IN_FIVE_CONVENTIONAL_AND_TWO_UNCONVENTIONAL_VIOLINS

http://knutsacoustics.com/files/the-hagetro-violin.pdf

With no proof, I believe that the ‘sound shape’ we know from violins comes from the spruce top. Though it might be worth a shot to make a laminated top I don’t have the motivation to go into this kind of Endeavour at this moment. But I still think that a bent top might bring some benefits. For the moment I blame the wood quality for a not completely satisfying result. I need as well to correct the mould. So there is for the moment enough work.

 

Concerning f holes, I think it would be beneficial to develop a sort of system to adjust their length to the wood properties. For this asymmetric design is of great help. 
 

In the end many things look like this to me

 

the classical violin design evolved a concept with their tools and measuring devices leading for purely practical reasons to a model with intended symmetry (in reality the result was never perfect) and vertical ribs.

What I am thinking aloud here is

Must the violin be symmetric at all? 
 

Or saying the other way around: would asymmetric design make it absolutely impossible to build a functional violin?

My daring hypothesis is that asymmetric design enables us to build not only functional instruments but have more room to calibrate the sound result. And just on the side (though not the major goal any more) I think the whole structure can be built with less weight.

 

(hope the fight of my German speaking brain with the English language has a comprehensive result.)

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Well, I think it is really interesting.

 

I thought too that a bent top would be stiffer. This one is slightly weaker if you take tap tones as a parameter. However the carved plate was varnished the bent plate not and this factors in.

 

However this is not a good reason for me to abandon the idea of bending the top. First, 5he carved plate was split wood the bent plate not. I checked on the cutout leftovers how the wood split and it didn’t look too bad, but still was on a slight angle to the surface. But in the end I think this wood (actually a mandolin top) was not too good, though the relative weight around .38 seemed ok.

 

Regardless, playing this fiddle with the bent top, it sounds slightly better. The difference I can hear is the ‘overtone ring’ which I couldn’t get on the carved plate, no matter how I tried to adjust it. 

 

This is good enough reason for me to try a second bent plate test. 

 

Anyway after some adjustments the spectrum looked different and now there is the missing peak at 550Hz. Don’t ask me why. 
 

F9F5535C-3A65-4689-B7A3-A025D5A0D295.thumb.png.2fc650f8171ef4ebb280aad44cd3a089.png

 

For your second interpretation I don’t know. Could be possible because the top side of the rib garland has almost all the way around triple linings. (See picture in one of the previous posts)

 

In the end there is a chance that the new design does not need to follow the signature modes. 

 

I am thinking of making a quick experiment with another completely flat back to see how this alters the sound. Playing the violin I have a purely subjective impression that it might work better with less air volume, so a flat back should be enough to get some impression on this subject. Secondly I wanted to see if not the current back is too weak at the c bouts. So I am planning to thin out the flat back in the upper and lower bouts without touching the center.

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The latest spectrum shows a weak peak around the "normal" B1+ frequency, so it looks like my second interpretation was closer to correct, and you have an exceptionally powerful CBR sound output

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On 3/20/2021 at 6:10 PM, Anders Buen said:

Why does the A0 look so weak and broad? With such a low frequency B1- one would exspect the A0 to be much stronger. Is this a played spectrum (scales) or is it a bridge impact?

The spectrum comes from playing half note scale on all 4 strings up to b on the e string.

A0  could be broad and weak because of the light body which is in this condition only 286g. 
 

In the end I am much more interested in the overtone spectrum because it makes the quality of the sound.

————————————————————————-

Of course the violin is acoustically not symmetric. Just surprising that, as obvious as it is, we stick to optical symmetry and maybe nobody has a good explanation for that other than ,'this worked the past 500 years so there is no need to change it.’

though I think we can change the design, or to be more precise make a new variations on it, I wouldn’t touch basic principles like for example the underlying shape of an eight (8) with the waist in the middle.

—————————————————————-

thanks for forwarding the articles. I still need to re read the articles to completely understand the new concept with a new frame structure. In any case interesting!

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On 3/20/2021 at 12:55 PM, Don Noon said:

The latest spectrum shows a weak peak around the "normal" B1+ frequency, so it looks like my second interpretation was closer to correct, and you have an exceptionally powerful CBR sound output

Wherever those resonances land. I am just trying to ‘configure’ all parts to achieve a dense and full sound. 
 

There are still many ideas for experimentation flipping around in my mind.

One could make by purpose some weak zones in the triple linings on the top side. There possibilities are numberless but maybe just a few well thought through variations can give answers on possible sound manipulation effects.

Another unexplored topic is ‘built in tensions’. We tend to focus on optical measurable dimensions, but tensions should in theory make some differences somewhere. I once made the experiment of closing a violin with a weight approximately equivalent to the downforce of the bridge. So I needed to adjust the ribs to the deformation of the top border glue surface. The violin was praised for its shining sound though I have of course no proof relating to the method of closing the box.

 

 

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23 minutes ago, Andreas Preuss said:

 tensions should in theory make some differences somewhere.

Acthally, structure theory says static tension/compression should NOT make a difference... to first order.

There is, however, a moderately long transient effect primarily on structure damping when static forces are changed, most obvious when a new violin is strung up for the first time.

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12 minutes ago, Don Noon said:

Acthally, structure theory says static tension/compression should NOT make a difference... to first order.

 

Sorry to ask: Where does structure theory come from and where is it used?

From restoration i know that squeezing the ribs to whatever position they ought to be when closing an instrument apparently doesn’t  have any negative effect. But if I would imagine the top like a banjo membrane with more or less stress this MUST have some effect. This can’t vibrate exactly the same way a plate without tension does. 

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1 hour ago, Andreas Preuss said:

The spectrum comes from playing half note scale on all 4 strings up to b on the e string.

A0  could be broad and weak because of the light body which is in this condition only 286g. 

A light and soft body would normally give a strong A0. Maybe you play it weakly?

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38 minutes ago, Don Noon said:

Acthally, structure theory says static tension/compression should NOT make a difference... to first order.

There is, however, a moderately long transient effect primarily on structure damping when static forces are changed, most obvious when a new violin is strung up for the first time.

There will be a slight change of the arching pattern when the instrument is strung up. There will also probaly be a time where the struture creeps a little over time, in addition to the regular shrinking or swelling doe to moisture exposure of different degree. All these facors influence the acoustics of the instrument body a little. 
The bridge may sink through the varnish, e.g. If the feet has not gotten solid ground underthem from the maker (varnish removed). Varnish thickness, and elasticity under the feet may also matter to the sound. 

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5 hours ago, Andreas Preuss said:

Sorry to ask: Where does structure theory come from and where is it used?

From restoration i know that squeezing the ribs to whatever position they ought to be when closing an instrument apparently doesn’t  have any negative effect. But if I would imagine the top like a banjo membrane with more or less stress this MUST have some effect. This can’t vibrate exactly the same way a plate without tension does. 

Basic examination of stress and dynamic vibration forces... there might be a summary treatment of it out there somewhere, but I haven't looked for it.

A membrane under tension is somewhat like a 3D string... everything is in straight lines and tension determines the natural frequencies.  For a curved structure or where bending stiffness dominates, the tension or compression is separate from the vibration benavior.  For a curved structure where the static forces change the geometry appreciably, then you can see some influence... but the static force don't directly influence the mode frequencies.

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On 3/20/2021 at 12:49 AM, Andreas Preuss said:

Though it might be worth a shot to make a laminated top I don’t have the motivation to go into this kind of Endeavour at this moment.

Has anyone ever made a laminated and pressed top ?

Maybe having thin laminates alternately angled rather than 90 degrees and press them into the mould shape while the glue is still wet ?

Almost like papier-mache.

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On 3/22/2021 at 3:17 PM, Delabo said:

Has anyone ever made a laminated and pressed top ?

Maybe having thin laminates alternately angled rather than 90 degrees and press them into the mould shape while the glue is still wet ?

Almost like papier-mache.

The violin type i refer to earlier in this thread is made like that. Martys violins are also probaly cross laminated, but do have an unconventinal shape, sort of 2D, rather than 3D.

The modes of a violin is both bending and stretching. E.g. For the mode 5 the mix is about 50% on each.

Anything changing the arching shape will also change the resonance frequencies. 

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On 3/22/2021 at 11:17 PM, Delabo said:

Has anyone ever made a laminated and pressed top ?

Maybe having thin laminates alternately angled rather than 90 degrees and press them into the mould shape while the glue is still wet ?

Almost like papier-mache.

If any laminating, the method you describe would be the most appropriate.

However.....

...I see there quite a few obstacles. 

  1. the wood panels must have very precise thickness
  2. The pressing is done with heat and moisture. Doing the glueing at the same time looks a bit tricky. Though if the panels are maybe only 0.5mm the moisture of the glue might be enough to make it bendable enough
  3. Biggest problem though is to have the positive and negative pressing moulds precise enough to guarantee pressure contact on the whole surface. If somewhere a glue layer is sandwiched in between both panels there might be a problem.
  4. if the top is done in two halves the joining could be difficult because the plane always runs on one half against the grain.
     

The main benefit would be certainly a top plate which will never crack. Thinking about acoustic advantages I am not sure if this would bring the desired result. I think the sound of a violin comes mostly from the top and its material. While different material for backs and ribs has proven to bring still very good results, instruments made from wood other than spruce always show problems for the sound.

So for the moment I think bending the plate is good enough followed with torrefication to stabilize it against humidity.

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Guitars have been made with laminated tops for decades, and as far as I know no really good ones are made that way.  But they are flat, and easy to laminate.  The arches of a violin would make things far trickier, and the laminations would be prone to wrinkle and fold.  Wood can be bent, but it isn't very stretchy.  I think Joseph Curtin has done some work with laminated tops, with no earthshaking results that I'm aware of.

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6 hours ago, Don Noon said:

Guitars have been made with laminated tops for decades, and as far as I know no really good ones are made that way.  But they are flat, and easy to laminate.  The arches of a violin would make things far trickier, and the laminations would be prone to wrinkle and fold.  Wood can be bent, but it isn't very stretchy.  I think Joseph Curtin has done some work with laminated tops, with no earthshaking results that I'm aware of.

The only thing I can think of is the Classical guitars by Matthias Dammann of Germany, his guitars have two thin tops glued together with a nomex core inside. Probably not the kind of lamination you are referring to exactly, but he has been very successful with this and his guitars are highly regarded and expensive. I have my own thoughts on this construction technique but I will keep them to myself ha ha.

I have heard a few Dammann guitars played by top conservatoire guitarists and they are powerful, clear and sound wonderful.

I believe his guitars cost about 25,000 Euros each.

https://www.classicguitar.com/the-origin-and-development-of-the-double-top-guitar/

 

 

 

 

 

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12 hours ago, Andreas Preuss said:
  1. the wood panels must have very precise thickness

I think the sheets needs to be very thin. I saw Hagetrø's press, some 30 years ago. It was made of a stiff frame with some tube rubber screwed densely to it. It was probably a vacuum press, and he used white glue for the job. Cascol wood glue, I believe. The plates were so thin that you could bend them by finger pressure on the violins. Very ackward. 

There are also a workshop in Norway that has developed a method for glueing in maple patches in back plates using hide glue and large pressure. Many Hardanger fiddles, from some makers, do have thin backs. And some of these have been patched up. The patches are laid along the wood grain, so not rally cross laminated.

My grandpa used spruce patches both in the tops and backs if he wanted more wood. 

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11 hours ago, Andreas Preuss said:

@Don Noon   @Anders Buen   @Delabo   @Shelbow

you can make your prediction on the sound with a flat and graduated walnut back (weight c. 120g) thickest zone between the c bouts.

Hard to say... but it should be less awful than a flat top.  I will guess that there will be more power in the range above the B1+ resonance up to about 1200 Hz.  A more boxy sound.

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On 4/1/2021 at 4:40 PM, Andreas Preuss said:

@Don Noon   @Anders Buen   @Delabo   @Shelbow

you can make your prediction on the sound with a flat and graduated walnut back (weight c. 120g) thickest zone between the c bouts.

I think we may expect a larger distance than normal between the B1- and B1+ frequencies. The A0 probaly becomes weaker. The C4 mode above the B1+ frequency will be weak and have a rather high frequency. Besides that I do not know what may happen. I am a bit out of shape regarding this. I would count on Dons assumption. 

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3 hours ago, Anders Buen said:

I think we may expect a larger distance than normal between the B1- and B1+ frequencies. 

I would also expect this, but didn't think it was terribly important.

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On 2/7/2021 at 6:10 PM, Andreas Preuss said:

So now there are the latest changes.

I installed an x shaped bass bar and reduced the thickness of the top slightly in the upper half which reduced the weight of the plate from 61g to 56g. Then I made a second cross bar below the f-hole.

IMG_7833.thumb.JPG.4008399fde9d15440bbcb175a88a0dc2.JPG

The overall impression is that the sound became louder and crispier. If there was any negative effect the overall response became a little less. This means in my personal impression the instrument is a little harder to play and more attention is needed on bow speed, arm weight and location on the string. 

No changes in the general setup. weight didn't change either 300g now. (this means the second cross bar equals the weight reduction of the top.

I am planning to kick out the cross bars on the assembled instrument next to see if there is any effect.

Right now I am very happy about the sound. It is crisp has depth and can be played with a heavy bow arm. 

The graph before making the changes:

NCV44.thumb.jpg.52305d9b4fb913e3e339dec77247078d.jpg

and 2 days after the changes were made

1562102308_NCV45(2daysafterstringingup).thumb.jpg.b0930fa8e4d92085c801b684163329a5.jpg

Your split bassbar reminds me a bit of Falcate Bracing which is used by some modern guitar makers.

https://www.youtube.com/watch?v=6YCBJQ3MF5Q

 

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On 4/19/2021 at 4:07 PM, avandesande said:

Your split bassbar reminds me a bit of Falcate Bracing which is used by some modern guitar makers.

https://www.youtube.com/watch?v=6YCBJQ3MF5Q

 

Quite interesting, though my inspiration didn’t come from there. 
 

My idea came from the thought that the bass bar has to enlarge the vibration on a larger surface and at the same time give the top lengthwise strength. To do this with minimal weight I thought it is a good idea to curve the bar in both directions. And it works.

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