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A0 mode: What is more important air mass or frequency?


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There is a correlation between A0 without a soundpost and A1.

This may give some thoughts back to the old Hutchin's theses about A1 relation to B1 modes...

It might be A1 to B1- that is important. Quite often they have about the same frequency 

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4 hours ago, Andreas Preuss said:

Not that I doubt what you are saying;), but this makes me scratch my head, because if not the air mass, what caused the tonal change after the first rib height reduction...... (?) (And somehow quite clear change for the better in the sense that a permanently exisiting sound problem of this particular instrument could be solved)

I am thinking on a very simplified model that the air is a kind of bumper. So this would mean to me that 'mass' in absolute weight does maybe not have such a big influence. This means reducing air mass by filling whatever material around the rib inside does not have a big effect. (It doesn't as I had seen in one of my first experiments) But what about the thickness of this 'air cushion'? Something like 'the thinner the harder it gets'?

 

It is impossible to separate the effect of the A0 level and frequency, as they are related to other modes and thus each other. For small perturbations these are rather small, thoug. Having said that, for the A0 mode alone, the volume per se does not influence the A0 level in a violin, but the frequency. So the effects you hear are mainly driven by the frequency changes..

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4 hours ago, Peter K-G said:

There is a correlation between A0 without a soundpost and A1.

This may give some thoughts back to the old Hutchin's theses about A1 relation to B1 modes...

It might be A1 to B1- that is important. Quite often they have about the same frequency 

Well the A0 follows the volume^0,3 and the A1 as the length of the body linearly, so there is a medium correlation there. The A1 to B1- delta is also linearly dependant on the B1- frequency which do say something about the top plate stiffness, mainly. In general Hutchins violins were too stiff as the B1- modes ended up at 480 Hz ish. And the central part of the top was very stiff to make fulfil the Bi-Tri actave tuning. Some hardangerfiddles have thick bridge irland region because they may have long f-holes, a flat arch across the central top and, sometimes, very thin «longues» in the plates. One Norwegian maker has had some sucess using her system, but I think he has left that many years ago.  

She measured insturment modes inside and the A1 was probably a bit of reference there as it does not move much between instruments. She made many larger insturments that are more difficult to measure in a room. In the acoustics system of a violin the A1 is of rather limited influence, although it problably isn’t nil.

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Yes, we all know that Hutchin's tuning suggestions are practically impossible. I made my two first violins 25 years ago, to learn that it was bull...t.

Still there is some usefull insights from that time.

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26 minutes ago, Peter K-G said:

Yes, we all know that Hutchin's tuning suggestions are practically impossible. I made my two first violins 25 years ago, to learn that it was bull...t.

Still there is some usefull insights from that time.

Isn't it all bull? Chasing your tail?

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28 minutes ago, Peter K-G said:

But sospiri, I told you it's okay now! You can play with the other kids as long as you are nice to them.

I'm a little dissapointed, we agreed on this! :huh:

Who agreed on what exactly? That the overtone series is too wild to be tamed?

 

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20 hours ago, Peter K-G said:

Yes, we all know that Hutchin's tuning suggestions are practically impossible. I made my two first violins 25 years ago, to learn that it was bull...t.

Still there is some usefull insights from that time.

Plotting the graduations of top and back plates of documented fine violins show a trend: If the tops are thickish the backs are too and the other way around. It could indicate systematic graduation measurement problem. Maybe it indicates regraduation practice or that the instruments were built that way. Or they could have been built that way. If so, there should also be a correlation between the free plate frequencies. 

Her tuning advice in the 60ties was to use higher tap tones for the back plate than the top. They had data from a fine Strad, the top was low though 315 Hz ish for mode 5 top and 350 Hz for the back plate. If you build violins after that someone is going to tell you that the top need a bit more stiffness. Later in the early 80ties she recommended the same note for top and back and tops at 180Hz for mode 2 and 360Hz for mode 5, I think. The 180 Hz advice for the top mode 2 makes the top thick in the centre to push that mode up, I think. Some help is gained from the «Sacconi plateus» in the ends too. 

She worked much with other type of instruments, like their Octet. Maybe some of these ideas suit these better than violins. I do not think she made many violins. She was a viola player, and devoted herself to the octet later in her career which may not be as interesting to write about in Science or Nature as the violin. 

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1 hour ago, Anders Buen said:

Plotting the graduations of top and back plates of documented fine violins show a trend: If the tops are thickish the backs are too and the other way around. It could indicate systematic graduation measurement problem. Maybe it indicates regraduation practice or that the instruments were built that way. Or they could have been built that way. If so, there should also be a correlation between the free plate frequencies. 

Her tuning advice in the 60ties was to use higher tap tones for the back plate than the top. They had data from a fine Strad, the top was low though 315 Hz ish for mode 5 top and 350 Hz for the back plate. If you build violins after that someone is going to tell you that the top need a bit more stiffness. Later in the early 80ties she recommended the same note for top and back and tops at 180Hz for mode 2 and 360Hz for mode 5, I think. The 180 Hz advice for the top mode 2 makes the top thick in the centre to push that mode up, I think. Some help is gained from the «Sacconi plateus» in the ends too. 

She worked much with other type of instruments, like their Octet. Maybe some of these ideas suit these better than violins. I do not think she made many violins. She was a viola player, and devoted herself to the octet later in her career which may not be as interesting to write about in Science or Nature as the violin. 

Thanks, for answering!

Whatever the reason for trend of thickness relations between these documented violins, we can only speculate. To find some correlations based on data, it would require as you have said many times, a lot of data. Quantitative research by nature (think about guessing skittles in a jar, if enough amount of guesses it gets close)

I don't trust numbers from old documented modes to be even close to comparable, in case of Qualitative research.

To be more specific about what I meant by bull..t. I was thinking about how she (or anyone) can suggest tuning frequencies in general for plates.

This I learned from the first two I made, because the second violins back would have been left 130 g if leaving M5 at ~360 Hz and the first one's top would be out of wood trying to bring it down to ~360 Hz (later I destroyed it by doing so)

When the arching is done you get what you get, for the wood you have picked.

Anyway this is old stuff, we have discussed 1K times, no point of getting deeper....

I think Hutchins gave some good contributions, but also mislead things in the wrong direction for decades. I'm also old enough to remember the 80's, how the culture was with tech starting to grow and one observation to another with equipment lead to false facts. (Like AI today in the Business software industry, everyone sells it but it doesn't exist yet in ERP/BI systems)

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On 5/14/2021 at 12:53 PM, Peter K-G said:

You might be jumping into conclutions about the "changes" after a modification?

My experience is that modifications made, that you observe as an immediate impact, many times goes back to the original state, after  some days or even weeks.

 

On 5/15/2021 at 5:23 AM, Andreas Preuss said:

I mentioned I think several times that I wait for conclusions after a 'stretch-in' time for the instrument. At least one day.

 

Andreas, here is a different approach to experimental research:

I mention I'm making 10 Soil copies, this is the first one made 2014:

https://photos.google.com/share/AF1QipOviCTZBCJy5LTCZdBKTB1LlWmtrLQK08oHh3yHm8Jxjnoh46fQude7Hj0INSibeg?key=TnR0a0lpUXBrZE94ZTVseFB0NmtLQXhJVGdYWkx3

I have tuned it up and after about 2-3 weeks of playing it is now in its "equilibrium" state when it peak performs.

A0 is stronger (too strong) and 5-8 Hz lower than when it was made, it's  at C (~264 Hz)

B1- has decreased ~10 Hz (~435 Hz)  and B1+ increased 5 Hz (528 Hz) - At this specific humidity level. A0 and B1+ combination makes it nearly unplayable at any C:s.

I measure all my violins every second month or so over years, then carefully document and make decisions on what to do.

 

The Soil 2014 is now going to be opened and get a new BB and the top side ribs after c-bouts are going to be trimmed.

A0 will be ~275 Hz and B1- ~450 Hz, B1+ unchanged..

After it is ready to be the violin I will play this summer.

 

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1 hour ago, Peter K-G said:

Thanks, for answering!

Whatever the reason for trend of thickness relations between these documented violins, we can only speculate. To find some correlations based on data, it would require as you have said many times, a lot of data. Quantitative research by nature (think about guessing skittles in a jar, if enough amount of guesses it gets close)

I do have data for some 70 Strads and 50 del Gesus from different sources, so it is a substantial number. Some new Strad posters have arrived since I last upDated, and I see that there are avilable some data on several hundred Strads at a rather stiff price. For those who may want do dig that deep, it is possible. (Who knows how much graduation data there are)

There are enough data to conclude on the matter, I think. The correlations are significant. 

Edited by Anders Buen
Corrected spelling errors and clarified.
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1 hour ago, Anders Buen said:

I do have data for some 70 Strads and 50 del Gesus from different sources, so it is a substantial number. Some new Strad posters have arrived since I last upDated, and I see that there are avilable some data on several hundred Strads at a rather stiff price. For those who may want do dig that deep, it is possible. (Who knows how much graduation data there are)

There are enough data to conclude on the matter, I think. The correlations are significant. 

Wow, tempting to say share,share, share. But I understand, not everything is public, I know you share a lot of other stuff, so thanks for that...

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50 minutes ago, Peter K-G said:

Wow, tempting to say share,share, share. But I understand, not everything is public, I know you share a lot of other stuff, so thanks for that...

These data have been shared here on MN, either as average del Gesu and Strad graduation plots or as point clouds, probably before you became active here. 

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A plot of average del Gesu and Strads along with data from Otto Möckels maker book from 1930 (1st edition and fewer data points). This was from a talk on Hardangerfiddles so I chose to plot all in the same colour for comparison to HF data from my familiys workshop journal which show an opposite trend (not shown here). 

4610460C-6475-43CF-89D6-F10D74648168.jpeg

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3 hours ago, Peter K-G said:

 

 

Andreas, here is a different approach to experimental research:

I mention I'm making 10 Soil copies, this is the first one made 2014:

https://photos.google.com/share/AF1QipOviCTZBCJy5LTCZdBKTB1LlWmtrLQK08oHh3yHm8Jxjnoh46fQude7Hj0INSibeg?key=TnR0a0lpUXBrZE94ZTVseFB0NmtLQXhJVGdYWkx3

I have tuned it up and after about 2-3 weeks of playing it is now in its "equilibrium" state when it peak performs.

A0 is stronger (too strong) and 5-8 Hz lower than when it was made, it's  at C (~264 Hz)

B1- has decreased ~10 Hz (~435 Hz)  and B1+ increased 5 Hz (528 Hz) - At this specific humidity level. A0 and B1+ combination makes it nearly unplayable at any C:s.

I measure all my violins every second month or so over years, then carefully document and make decisions on what to do.

 

The Soil 2014 is now going to be opened and get a new BB and the top side ribs after c-bouts are going to be trimmed.

A0 will be ~275 Hz and B1- ~450 Hz, B1+ unchanged..

After it is ready to be the violin I will play this summer.

 

Peter,

I see a lot of pictures. At the beginning you seem to take data of the wood logs. In between a graph.

Hmmm, trying to puzzle together what you meant with 'different approach'.

--------------------

For making violins, though this doesn't give the impression right now from my posts, I try to get away from any 'data driven' method.

Maybe I can crystallize it to 'make a functioning arched membrane and adjust the rest to it'

Or

Procedure oriented sound Calibration

-------------------

The only thing I take granted from classical Cremonese violin making is that they didn't make a box to insert the neck. And maybe from doing differently we must run into many complicated problems.

4 hours ago, Peter K-G said:

Blow into the f-holes of many violins and compare

This gives me the pitch not so much the amplitude.

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1 hour ago, Anders Buen said:

A plot of average del Gesu and Strads along with data from Otto Möckels maker book from 1930 (1st edition and fewer data points). This was from a talk on Hardangerfiddles so I chose to plot all in the same colour for comparison to HF data from my familiys workshop journal which show an opposite trend (not shown here). 

4610460C-6475-43CF-89D6-F10D74648168.jpeg

Since I can' read Norwegian, I suppose this represents the relation of tops to backs.

looks pretty convincing. Do you have also a figure for an deviation value?

Considering the possible measuring prescision one might wonder how makers in the past achieved it. I once looked into weight systems in the 17th century and found that this was better than a 1/10g scale using plant grains. I think in theory it is possible to work with a reference thickness in combination with weight and arrive at the same or similar distribution pattern.

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6 minutes ago, Andreas Preuss said:

Peter,

Hmmm, trying to puzzle together what you meant with 'different approach'.

------------------

This gives me the pitch not so much the amplitude.

Yes, my post was too long...

By different approach I meant

Making non-experimental violins as good as I can and observe over several years and make "micro" changes. The Soil 2014 has been under research for 6 years. 

 

If you blow and compare you also learn the amplitude

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26 minutes ago, Andreas Preuss said:

Since I can' read Norwegian, I suppose this represents the relation of tops to backs.

looks pretty convincing. Do you have also a figure for an deviation value?

Considering the possible measuring prescision one might wonder how makers in the past achieved it. I once looked into weight systems in the 17th century and found that this was better than a 1/10g scale using plant grains. I think in theory it is possible to work with a reference thickness in combination with weight and arrive at the same or similar distribution pattern.

Right axis is the back plate average thickness the y axis is the average of the. The dots are averages over about 25 measured positions, like those in Biddulphs et als book on del Gesus. 

I do not understand what a deviation figure is. The spread is given in the R^2 and can be translated to the percentage explained by the other parameter. 

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13 minutes ago, Anders Buen said:

Right axis is the back plate average thickness the y axis is the average of the. The dots are averages over about 25 measured positions, like those in Biddulphs et als book on del Gesus. 

I do not understand what a deviation figure is. The spread is given in the R^2 and can be translated to the percentage explained by the other parameter. 

I meant how far this can be away from the medium line. Maybe that is what you meant with spread? 

Would be interesting to know if there is another relation to the air resonance.

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12 minutes ago, Andreas Preuss said:

I meant how far this can be away from the medium line. Maybe that is what you meant with spread?

Yes, the correlation coefficient is a measure of that deviation. The method is called least squared deviation method or something like that. The sum of the deviations squared is minimized to make the line. 

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7 hours ago, Peter K-G said:

Anyway this is old stuff, we have discussed 1K times, no point of getting deeper....

After noticing your 45 sg. Soil belly example that you are planning to take apart I must ask are any of the other nine what one could call exceptional to where you wouldn't want to change anything?

The reason I'm asking is if there happens to be an exceptional example we could apply the " MK plate hz correction formula " to the violins that need to be adjusted and make them the same or as close to the exceptional example as possible. 

It would be nice to have plate weights and free plate hz information in advance assuming all wood for back and bellies are the same spec wise.  

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