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Thomas Coleman

Arch height affect on sound

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At the VSA convention this last weekend they had a Jacob Stainer and a Peitro Guarneri of Mantua at the rare instrument table (amongst many others). Both beautiful instruments and highly arched. Stainer is obviously known for his highly arched instruments but the Pietro Guarneri of Mantua had a huge arch even when compared to the Stainer, just eye balling it I would guess it was well over 25mm.

Hi Mike,

 

I think those instruments were not selected for their tone but for their historical value. I recall hearing that the three earliest P.G. Mantua's have the highest arches and later models are lower. Can anyone check this?

 

it was great talking with you.

 

The other Mike

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Well one wouldn't want experience to stand in the way of a good theory, but I think the best way to predict how arching affects tonal content is to play thousands of violins with a range of archings and look for patterns.

 

Having done this, I would say that there is absolutely no correlation between arching and crude tonal characteristics. In other words, arching does not govern the amount of high frequency content or the amount of low frequency content, or the balance between the two.

However, high lateral arching which is gathered or which comes up suddenly from a flat edge (what might be called "pigeon  breast") certainly affects tonal colour in the upper midrange, and creates a vowel characteristic which is more "O" or "U" than "A". This is never ideal for a violin, since it seems to impose too specific a personality on the sound, and to restrict the way in which the player can sculpt it.

Very flat arching can take things too far in the other direction, creating a big wide and flabby sound that lacks articulation.

And therefore I would say that there's a narrow range of arching heights that are successful, though if you include the needs of trad or non-classical players that range is wider.

But I would re-iterate this has very little to do with the broad frequency content.

 

I'm afraid I find Wolfjk's and uncle duke's remarks nonsensical.

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Then could one say that the waves spread out as ripples do when a stone is dropped into a pool of water?

In a way, but only for the higher modes you can see such a pattern. 

 

I think of it as a LOT of stones, dropped in one-by-one at a specific interval.  A pattern will develop that is not spreading ripples, but a fixed pattern depending on the geometry of the pool and frequency with which the stones are dropped.  The first  few stones and spreading ripples would represent the start-up transient.

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I'm afraid I find Wolfjk's and uncle duke's remarks nonsensical.

I guess nonsensical means nonsense- I can live with that for the time being.  I'm just going to have to figure out how it [higher pigeon/arch} works by myself.  There has to be somethng better, I'll find it. 

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I think of it as a LOT of stones, dropped in one-by-one at a specific interval.  A pattern will develop that is not spreading ripples, but a fixed pattern depending on the geometry of the pool and frequency with which the stones are dropped.  The first  few stones and spreading ripples would represent the start-up transient.

I guess I was jumping in about the terminology in this discussion; John Masters objected to the word 'flow,' however at some point (where the string contacts the bridge) some oscillation or vibration happens and must travel, emanate, spread or flow from that point, and as Don here points out this does not happen only once but many times creating a complex pattern of reflections. And, as Peter K-G mentions these move the air so that we can hear them. The following is from a physics site: 

 

A standing wave pattern is a vibrational pattern created within a medium when the vibrational frequency of the source causes reflected waves from one end of the medium to interfere with incident waves from the source. This interference occurs in such a manner that specific points along the medium appear to be standing still. Because the observed wave pattern is characterized by points that appear to be standing still, the pattern is often called a standing wave pattern. Such patterns are only created within the medium at specific frequencies of vibration. These frequencies are known as harmonic frequencies, or merely harmonics. At any frequency other than a harmonic frequency, the interference of reflected and incident waves leads to a resulting disturbance of the medium that is irregular and non-repeating.

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I think of it as a LOT of stones, dropped in one-by-one at a specific interval.  A pattern will develop that is not spreading ripples, but a fixed pattern depending on the geometry of the pool and frequency with which the stones are dropped.  The first  few stones and spreading ripples would represent the start-up transient.

One thing to consider is that eigen modes and the vibraitions driven by strings and bow through the bridge is two different things. Thinking of how many "stones" are droped (all the harmonics that can be heard and their sub harmonics) from one prominant note/frequency, it is almost miraculous, because the violin body sends out all this from moving the air around.

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At the VSA convention this last weekend they had a Jacob Stainer and a Peitro Guarneri of Mantua at the rare instrument table (amongst many others). Both beautiful instruments and highly arched. Stainer is obviously known for his highly arched instruments but the Pietro Guarneri of Mantua had a huge arch even when compared to the Stainer, just eye balling it I would guess it was well over 25mm.

Are there any recordings around of high arched Stainers?

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Nope. I'm not going to do that. The entertainment value of your posts far outweighs their scientific ineptitude. You won't hear any criticism from me anymore, 

 

The math is straightforward.  It is not scientific it all.  It is about seperable solutions for linear equations.

 

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Thanks, that Stainer violin does have a really beautiful sound.  For $$$$ I could find out what it's actual dimensions and arch are, but by eyeballing it on my 23" mac display it seems, unfortunately,  to be around 14-15 mm.  Guess I have to make a trip to Austria, unless someone has already done this.

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Thanks, that Stainer violin does have a really beautiful sound.  For $$$$ I could find out what it's actual dimensions and arch are, but by eyeballing it on my 23" mac display it seems, unfortunately,  to be around 14-15 mm.  Guess I have to make a trip to Austria, unless someone has already done this.

The numbers I have for the NMM Stainer violin are back: 16.95mm, front 16.5mm

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But it seems to do the opposite, in my limited experience with bent archings.

Well, you know what happens when you bend a piece of wood; you squize out some air, therefore there is less left in the wood to resonate!

In my limited experience it is the air in the reeds and the structure of their walls that give the spruce/fir tonewood the resonance.

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Well, you know what happens when you bend a piece of wood; you squize out some air, therefore there is less left in the wood to resonate!

In my limited experience it is the air in the reeds and the structure of their walls that give the spruce/fir tonewood the resonance.

If your view is that the function of the soundpost is to "stop" the grain of the wood in the way that a finger might stop a string and divide it into two portions, thus creating higher frequencies than the unstopped string, why don't you try replacing the soundpost with a little G clamp attached through the f-hole to the table only (the kind that we use for repairing f-hole cracks).

Please report back with results.

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"Well, you know what happens when you bend a piece of wood; you squize out some air, therefore there is less left in the wood to resonate!
In my limited experience it is the air in the reeds and the structure of their walls that give the spruce/fir tonewood the resonance."

 

But as the compressed cells become smaller on one side of the bent piece, aren't the cells on the other side getting stretched and bigger, cancelling out the effect?  :unsure:

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"Well, you know what happens when you bend a piece of wood; you squize out some air, therefore there is less left in the wood to resonate!

In my limited experience it is the air in the reeds and the structure of their walls that give the spruce/fir tonewood the resonance."

 

But as the compressed cells become smaller on one side of the bent piece, aren't the cells on the other side getting stretched and bigger, cancelling out the effect?  :unsure:

Actually I think that because wood is stronger in tension than compression we would find the inside wood more affected by bending.

Wolfjk . Did you bother doing any of the math associated with frequency to resonance chamber size proportions proposed the last time you brought this subject up? It really is the simplest form of acoustic math and goes a long way helping to understand how sound is produced.

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The common mistake is to think that mass is flowing along a vibrating string or violin surface. As John points out, any mass movement is highly localized.

 

But it is very useful to think of energy as flowing along a string or plate surface. It travels with a distinct velocity and maintains a distinct spatial shape (wave shape ) over time until reflected, absorbed or severely damped. And when it reaches a discontinuity, like the rib, f-hole edge or a sound post, the energy will reflect in predictable ways.

 

For example, you can find high speed videos of plucked strings. The whole string is not vibrating at once, but rather a distinct, localized position displacement is observed as the energy passes down the string. After it passes, the string will actually be almost stationary until the energy bounces off a fixed end and flows back the other way.

 

As the string sticks and then slips off the bow hairs, bursts of kinetic energy travel away from the bow towards the bridge and the nut. They ravel back and forth along the string and eventually decay, but the bow refreshes the energy packets. So the bridge is seeing a periodic series of energy impulses as the waves travel back and forth along the string. The impulses reach the feet of the bridge. The impulses then travel outwards from the feet and along the plane of the table in all directions.

 

To the extent that the energy pulses travel along the "plane" of the violin table, Uncle Duke is right in thinking that a more severe arch at the sound post will affect how the energy will reflect around, away and down a sound post. The angle between the direction the energy pulse is traveling and the sound post is altered.

 

Is that a good or a bad thing? >shrug<

 

So if you want to visualize something flowing, think packets of strain energy.

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I guess I was jumping in about the terminology in this discussion; John Masters objected to the word 'flow,' however at some point (where the string contacts the bridge) some oscillation or vibration happens and must travel, emanate, spread or flow from that point, and as Don here points out this does not happen only once but many times creating a complex pattern of reflections. And, as Peter K-G mentions these move the air so that we can hear them. The following is from a physics site: 

 

A standing wave pattern is a vibrational pattern created within a medium when the vibrational frequency of the source causes reflected waves from one end of the medium to interfere with incident waves from the source. This interference occurs in such a manner that specific points along the medium appear to be standing still. Because the observed wave pattern is characterized by points that appear to be standing still, the pattern is often called a standing wave pattern. Such patterns are only created within the medium at specific frequencies of vibration. These frequencies are known as harmonic frequencies, or merely harmonics. At any frequency other than a harmonic frequency, the interference of reflected and incident waves leads to a resulting disturbance of the medium that is irregular and non-repeating.

 

Yes,  the specific frequencies are the ones associated with the normal modes.

 

I did allow for transients,  these need to be pointed out.  In a violin,  at typical pitch frequencies,  a standing wave can be established in a couple of cycles perhaps,  a couple of milliseconds.  What rate of response do you want in a violin?  Transients to establish standing waves would be OK at less than (perhaps) 1/100 second.  Heifetz's recording of Moto Perpetuo (1917) clocks out at 18 notes per second.  I think a 1/100 second rise time would be more than adequate for a really responsive violin.

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The common mistake is to think that mass is flowing along a vibrating string or violin surface. As John points out, any mass movement is highly localized.

 

But it is very useful to think of energy as flowing along a string or plate surface. It travels with a distinct velocity and maintains a distinct spatial shape (wave shape ) over time until reflected, absorbed or severely damped. And when it reaches a discontinuity, like the rib, f-hole edge or a sound post, the energy will reflect in predictable ways.

 

For example, you can find high speed videos of plucked strings. The whole string is not vibrating at once, but rather a distinct, localized position displacement is observed as the energy passes down the string. After it passes, the string will actually be almost stationary until the energy bounces off a fixed end and flows back the other way.

 

As the string sticks and then slips off the bow hairs, bursts of kinetic energy travel away from the bow towards the bridge and the nut. They ravel back and forth along the string and eventually decay, but the bow refreshes the energy packets. So the bridge is seeing a periodic series of energy impulses as the waves travel back and forth along the string. The impulses reach the feet of the bridge. The impulses then travel outwards from the feet and along the plane of the table in all directions.

 

To the extent that the energy pulses travel along the "plane" of the violin table, Uncle Duke is right in thinking that a more severe arch at the sound post will affect how the energy will reflect around, away and down a sound post. The angle between the direction the energy pulse is traveling and the sound post is altered.

 

Is that a good or a bad thing? >shrug<

 

So if you want to visualize something flowing, think packets of strain energy.

Yes,  energy goes in.  And is dissipated or radiated.   The flopping string video can (I am sure) still be decomposed as a linear combination of all modes. 

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Actually I think that because wood is stronger in tension than compression we would find the inside wood more affected by bending.

Wolfjk . Did you bother doing any of the math associated with frequency to resonance chamber size proportions proposed the last time you brought this subject up? It really is the simplest form of acoustic math and goes a long way helping to understand how sound is produced.

My dear Jones,

Whatever maths you use, you can't get away from the fact that 75% of the volume of the spruce top is air. The important factors are the air inside the reeds and the structur of the cell walls that make the tonewood. Apart from that the seasoning of the wood is important. Experience with working with wood also help.

Maths help with working out the economic side and acoustics of the auditorium and building the workshop.

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It's one thing to say that the air contained in spruce is crucial to the tone of a fiddle - no-one would deny that.

It's another thing to say that the frequency response is a function of the length of the grains - I think you're on your own there. If you have any experience of 367mm Magginis or Vuillaumes, or 349mm Rogeris, you will know that this is a false premise. There are many opinions here which are better argued, better observed, and based on greater experience. However, as David Burgess said before, if it helps as a way of visualizing your way into making great-sounding violins, knock yourself out. 

 

There's been enough debate about this to know that you won't change your mind.

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 The important factors are the air inside the reeds...

There's been enough debate about this to know that you won't change your mind.

 

And there is enough evidence to conclude that the air in the reeds has been a red herring from day 1, and there is no point in bringing it up or discussing it again.

 

Similar to Facebook's "like" button, perhaps we need to get a "BS" button to indicate posts that are worthy of it.

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My dear Jones,

Whatever maths you use, you can't get away from the fact that 75% of the volume of the spruce top is air. The important factors are the air inside the reeds and the structur of the cell walls that make the tonewood. Apart from that the seasoning of the wood is important. Experience with working with wood also help.

Maths help with working out the economic side and acoustics of the auditorium and building the workshop.

Just noticed this little debate.  They aren't reeds at all, they are sealed compartments.  Any sliced ones on the surfaces have the wrong parameters to resonate as part of the larger system. Any air is trapped like the bubbles in a foam, contributing a compressibility and a decease in density.

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I'll agree with the camp that calls the "air in the reeds" bs. The real difference between a carved arch vs a bent one will be a difference of internal stress and how that relates to something being pre-tensioned or not. I mean, I suppose by all accounts we should treat the plate as if it were a washed out Hollywood actress injecting botox, in that technically sound travels 4 times faster in water than it does air, yet we always associate "liquid" with dampening. And yet somehow if we could induce 100% saturation without catastrophic failure, I don' think the violin would sound "better" because we now have a material that has a radiation increase x4, even if we had "light" water that did not increase weight I still don't think that would help. I would venture to say the solid "matter: components of the material and the way its shape along with the  STIFFNESS/FLEXIBILITY/ELASTICITY of the "matter" part of wood is what dictates "tone" not the air space in between. The air space or lack thereof only effects density and weight Air might matter if the interior of the wood was a concert hall where we were listening to "notes", but I don't think they make violins that small.

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