Is arching a mid range booster?


Recommended Posts

Sorry if the question is a bit vague. I'm just trying to figure out how different arching heights affect the sound.

As I understand it, a low arching can have good low and high frequency response, but the mid range is weak. And maybe something similar happens with high arching.

Is this why 16mm is a prefered arching height? Also, it is true that Del Gesu generally made lower than this, and if so, how low is too low?

 

 

Link to post
Share on other sites

Extending your question, is arching height alone that valuable/predictive a variable?

 

I'm about a third of the way through building my first one, so I don't know anything, but it seems like you could have a host of different arching shapes with the same highest point.

Link to post
Share on other sites
2 hours ago, MMarsden said:

Extending your question, is arching height alone that valuable/predictive a variable?

 

I'm about a third of the way through building my first one, so I don't know anything, but it seems like you could have a host of different arching shapes with the same highest point.

As I understand it  if the internal arching of the belly is Xmm the arching height = X + 3mm 

As long as X isn't too low.

But how low is too low? 10mm?  11? 

 

 

 

Link to post
Share on other sites
9 hours ago, sospiri said:

Sorry if the question is a bit vague. I'm just trying to figure out how different arching heights affect the sound.

As I understand it, a low arching can have good low and high frequency response, but the mid range is weak. And maybe something similar happens with high arching.

Is this why 16mm is a prefered arching height? Also, it is true that Del Gesu generally made lower than this, and if so, how low is too low?

 

 

One dimension parameter tend not to have simple meaning by themselves on a violin.

Consider instead of just the height, the whole cup shaped area created by thw arching?  What area of the plate has been given an overall cohesive downward dome like shape, all concave on the inside?

This area can vary considerably. But it never depends just on the plate height.  It also depends on how quickly the long and cross arches come down.  Or, in a different but related way of thinking about it, the area depends on how wide the channels are, and where convextivity changes.

Few things exist in isolation on a violin.

Link to post
Share on other sites

Just an opinion based on some experiments and a tiny bit of theory:  higher arch => less midrange, all else being equal (which it never is).

Subject to revision.

Link to post
Share on other sites

Pure speculation on my part, but I think the ratio of convexity and concavity would be a significant factor. A long arch height difference of about 3 mm is quite a bit.

However, only planning and controlling the whole arching shape will lead to any understanding of what may or may not be most significant.

 

Link to post
Share on other sites
3 hours ago, Peter K-G said:

What's midrange

To me, it's the frequencies between the B1+ signature mode and the beginning of the bridge/body hill. About 700 - 1600 Hz.  

Other opinions may vary.

Link to post
Share on other sites

In my experience the midrange can be influenced by the weights of the f-hole wings, or as Martin Schleske once put it: "anything added in the vincinity of the f-holes and bridge" (if I recollect correctly). Many fine old instruments have repair patches above the f-holes, or below them. Often there are patches and/or cleats, or repairs, close to the bridge, f-holes and soundpost. Dünnwald noticed that many old instruments tend to have a weaker midrange than the factory and master built instruments (1980s). I speculate that this may be a repair related tonal trait, and not age or nation related per se. 

I found Erik V. Janssons article on a related topic where he, a bit bombastic, states a difference in the arching for old Italian instruments (flat long direction of arch) and French (rounded in long direction) and investigate a possible effect of that. The article is about the bridge/body hill which is a bit higher in frequency than the mid range.
I haven't read it fully yet. Just seeing that the first sentences do contain precise and useful information - and something new, makes me looking forward to reading further. Like: "A large number of wooden blanks was free for further experiments. It was planned to use the blanks to investigate the influence of material properties on the top plate of the violin. In introductory pilot experiments it turned out that the geometry influenced more than the material properties"
https://www.researchgate.net/publication/303444456_On_the_Violin_Bridge_Hill_-_Comparison_of_Experimental_Testing_and_FEM

Edited by Anders Buen
Added a reference
Link to post
Share on other sites
16 hours ago, Don Noon said:

Just an opinion based on some experiments and a tiny bit of theory:  higher arch => less midrange, all else being equal (which it never is).

Subject to revision.

Isn't this true of low arch too?

12 hours ago, Dennis J said:

Pure speculation on my part, but I think the ratio of convexity and concavity would be a significant factor. A long arch height difference of about 3 mm is quite a bit.

However, only planning and controlling the whole arching shape will lead to any understanding of what may or may not be most significant.

 

My 3mm number is the plate thickness around the bridge area.

So my X value is the internal arching height. How low is too low?

21 hours ago, Torbjörn Zethelius said:

I would probably not go less than 12.5mm external arch height. Up to that point I'd feel safe.

So I'm safe with as low as 10mm internal arching height?

 

15 hours ago, Peter K-G said:

1,What's midrange

2, Can I be the rivisor for the subject?

1,  I don't know, but some violins seem to be missing something in the middle.

2, What's a rivisor?

17 hours ago, David Beard said:

One dimension parameter tend not to have simple meaning by themselves on a violin.

Consider instead of just the height, the whole cup shaped area created by thw arching?  What area of the plate has been given an overall cohesive downward dome like shape, all concave on the inside?

This area can vary considerably. But it never depends just on the plate height.  It also depends on how quickly the long and cross arches come down.  Or, in a different but related way of thinking about it, the area depends on how wide the channels are, and where convextivity changes.

Few things exist in isolation on a violin.

Gimme a ballpark figure? 

 

8 hours ago, Anders Buen said:

In my experience the midrange can be influenced by the weights of the f-hole wings, or as Martin Schleske once put it: "anything added in the vincinity of the f-holes and bridge" (if I recollect correctly). Many fine old instruments have repair patches above the f-holes, or below them. Often there are patches and/or cleats, or repairs, close to the bridge, f-holes and soundpost. Dünnwald noticed that many old instruments tend to have a weaker midrange than the factory and master built instruments (1980s). I speculate that this may be a repair related tonal trait, and not age or nation related per se. 

I found Erik V. Janssons article on a related topic where he, a bit bombastic, states a difference in the arching for old Italian instruments (flat long direction of arch) and French (rounded in long direction) and investigate a possible effect of that. The article is about the bridge/body hill which is a bit higher in frequency than the mid range.
I haven't read it fully yet. Just seeing that the first sentences do contain precise and useful information - and something new, makes me looking forward to reading further. Like: "A large number of wooden blanks was free for further experiments. It was planned to use the blanks to investigate the influence of material properties on the top plate of the violin. In introductory pilot experiments it turned out that the geometry influenced more than the material properties"
https://www.researchgate.net/publication/303444456_On_the_Violin_Bridge_Hill_-_Comparison_of_Experimental_Testing_and_FEM

I believe Stradivari's longitudinal arching was just that, an arch, not a flat section in the middle, more of a gentle plateau that has sunk slightly in most cases, but is still visible in the best preserved examples.

What recommendations or observations did Schleske give for thickness in the wings?

Link to post
Share on other sites
20 minutes ago, sospiri said:

I believe Stradivari's longitudinal arching was just that, an arch, not a flat section in the middle, more of a gentle plateau that has sunk slightly in most cases, but is still visible in the best preserved examples.

What recommendations or observations did Schleske give for thickness in the wings?

According to Joe Curtins observations on instruments returning for service is that the arch tend to rise and that the plates becomes stiffer. Tap tones goes up as well. 

I did not ask him about that. I have used to thin the wings more than the rest in the ventre, until I got statistics for graduations from many Strads and del Gesus now from the literature. I also have something similar for Hardangerfiddles. I think the iwngs tend to be a little thicker than the centre, If I recall correctly. Maybe some have repair patches, cleats or something similar.

Link to post
Share on other sites
19 hours ago, Don Noon said:

To me, it's the frequencies between the B1+ signature mode and the beginning of the bridge/body hill. About 700 - 1600 Hz.  

Other opinions may vary.

Ok = Transition hill?

We shouldn't invent new terms...

 

Link to post
Share on other sites
On 4/17/2021 at 1:37 AM, Don Noon said:

Just an opinion based on some experiments and a tiny bit of theory:  higher arch => less midrange, all else being equal (which it never is).

Subject to revision.

 

23 hours ago, Peter K-G said:

What's midrange

Can I be the rivisor for the subject?

 

7 hours ago, sospiri said:

2, What's a rivisor?

Don't know what the right word is.... 

Link to post
Share on other sites
19 hours ago, Anders Buen said:

According to Joe Curtins observations on instruments returning for service is that the arch tend to rise and that the plates becomes stiffer. Tap tones goes up as well. 

I did not ask him about that. I have used to thin the wings more than the rest in the ventre, until I got statistics for graduations from many Strads and del Gesus now from the literature. I also have something similar for Hardangerfiddles. I think the iwngs tend to be a little thicker than the centre, If I recall correctly. Maybe some have repair patches, cleats or something similar.

Isn't the arch more likely to fall slightly as the plates shrink across the grain?

And how much of this depends on the moisture content of the wood when the plate is glued to the garland?

Link to post
Share on other sites
13 minutes ago, sospiri said:

Isn't the arch more likely to fall slightly as the plates shrink across the grain?

And how much of this depends on the moisture content of the wood when the plate is glued to the garland?

I do not know the exact details there. My own experience is that the arching porobaly does drop a bit in the center, but that is mainly Hardangerfiddles with a flatter cross arch at and just above the f-holes. The humidity play a role, as well as the graduations arching shape, wood and setup. I would suppose that humidity at glueing time matters too. However, the whole instrument is probabably subjected to that, not only the top..

Hard to tell which direction it will go. And the changes are so small that is is bothersome to measure them, unless a good simple method could be outlined. Some things can be seen up against the light. If there are much changes the bridge should be adjusted. Some have controlled RH in their shops and remove that variation. 

I do not believe that wood shrinks more across grin (radial) than along its thickness e.g. (Tangential). Both these are larger than the along direction shrinking or swelling. These movements are reversible. I do not believe in the thought that Strads f-hole eyes are elliptical due to wood shrinkage over the years. Or I do not know that mechanism. It woold have to take an awful lot of wood shrinkage for it to be visible on a small hole like that.

Link to post
Share on other sites
On 4/17/2021 at 12:37 AM, Don Noon said:

Just an opinion based on some experiments and a tiny bit of theory:  higher arch => less midrange, all else being equal (which it never is).

Subject to revision.

I think I agree on this. I found a positive correlation between hich arch and high «ACD-B» frequency regions, following Dünnwald, in one of my studies. The B region is the mid range. CD is the body/bridge hill region and A is from 200-700Hz ish. More in A and CD is good, while B was weaker in the «Old Italian» group of his. There is a bit of dispute about this, «High B not being good».

I also have data on that on a semi large set of own instruments or repairs, sort of data mining. I need to look that up again. 

Edited by Anders Buen
Remembered new stuff on this older material
Link to post
Share on other sites
4 minutes ago, Anders Buen said:

I do not know the exact details there. My own experience is that the arching porobaly does drop a bit in the center, but that is mainly Hardangerfiddles with a flatter cross arch at and just above the f-holes. The humidity play a role, as well as the graduations arching shape, wood and setup. I would suppose that humidity at glueing time matters too. However, the whole instrument is probabably subjected to that, not only the top..

Hard to tell which direction it will go. And the changes are so small that is is bothersome to measure them, unless a good simple method could be outlined. Some things can be seen up against the light. If there are much changes the bridge should be adjusted. Some have controlled RH in their shops and remove that variation. 

I do not believe that wood shrinks more across grin (radial) than along its thickness e.g. (Tangential). Both these are larger than the along direction shrinking or swelling. These movements are reversible. I do not believe in the thought that Strads f-hole eyes are elliptical due to wood shrinkage over the years. Or I do not know that mechanism. It woold have to take an awful lot of wood shrinkage for it to be visible on a small hole like that.

I'm wondering if there is a right and a wrong time to glue the plates on, depending on the weather?

I see old board in furniture and pannelling that have shrunk across the grain and other old boards that haven't shrunk. Was the wood not seasoned long enough?

Link to post
Share on other sites
52 minutes ago, sospiri said:

I'm wondering if there is a right and a wrong time to glue the plates on, depending on the weather?

I see old board in furniture and pannelling that have shrunk across the grain and other old boards that haven't shrunk. Was the wood not seasoned long enough?

How do you know that a table has shrunk or not?

The drying part of wood after cutting is a process I do not know well. There is free water in the cells and the bound water in the cell walls. As long as there are free water in the wood, that will feed the cell walls with bound water in addition to the diffusion going on. The RH in the air within green wood will be higher than in wood that has reached EMC.

CLT buildings are coming now in the «green revolution». I have looked into the effects of building in outdoor climate and then the dry time comes indoor. Some days are under 10% RH here in late winter time. I think these effects are measureable on sound insulation and impact noise. It will be best just after closing the building and worsen a little as the building dries out.

Link to post
Share on other sites
2 hours ago, Anders Buen said:

I do not believe that wood shrinks more across grin (radial) than along its thickness e.g. (Tangential). 

I believe it's the opposite, if torrefying data can be inferred to be a similar trend in natural aging.  My spruce measurements show a shrinkage of .9% average crossgrain (radial) and 1.9% in thickness (tangential), or about double.  Longitudinal shrinkage is negligible.  A 1.9% loss of thickness (~.06mm) might not be noticed, but a .9% crossgrain loss (\~1.8mm) would.

1 hour ago, Anders Buen said:

The B region is the mid range. CD is the body/bridge hill region and A is from 200-700Hz ish. More in A and CD is good, while B was weaker in the «Old Italian» group of his. There is a bit of dispute about this, «High B not being good».

I see a clear trend like this as well, particularly in the Strads I have been able to measure.  Very low strength in the B range... or midrange, or transition hill.  While "high B" might not be good, it's really an aesthetic judgement.  Too low = gutless (but many might prefer the refined tone), while higher B = louder and more aggressive.  The low B in Cremonese is often too gutless for my taste as a player. The major issue I think is getting a moderate B range without having big peaks and dips (uneven and colored).  There aren't a lot of modes to work with there.

Link to post
Share on other sites
28 minutes ago, Don Noon said:

I believe it's the opposite, if torrefying data can be inferred to be a similar trend in natural aging.  My spruce measurements show a shrinkage of .9% average crossgrain (radial) and 1.9% in thickness (tangential), or about double.  Longitudinal shrinkage is negligible.  A 1.9% loss of thickness (~.06mm) might not be noticed, but a .9% crossgrain loss (\~1.8mm) would.

I see a clear trend like this as well, particularly in the Strads I have been able to measure.  Very low strength in the B range... or midrange, or transition hill.  While "high B" might not be good, it's really an aesthetic judgement.  Too low = gutless (but many might prefer the refined tone), while higher B = louder and more aggressive.  The low B in Cremonese is often too gutless for my taste as a player. The major issue I think is getting a moderate B range without having big peaks and dips (uneven and colored).  There aren't a lot of modes to work with there.

Doesn't every note on every musical instrument have a degree of resonant consonance and dissonance? 

This is well recognised amongst trumpet players and the degree of "lipping in" required to make the note sound as good as possible.

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
  • Recently Browsing   0 members

    No registered users viewing this page.