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Makers Survey, one-piece fronts grain orientation


Ratcliffiddles
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If we stay within the realm of the known, it's quite straightforward to demonstrate that wide grain does not correspond to better low frequency response and vice versa.

While wood density might have some bearing on overall frequency response, we see plenty of violins with uniformly wide grain with excellent high frequency content, and plenty of violins with uniformly narrow grain with excellent low frequency content.

I would also, like many others who have already posted, question whether the handling of different parts of the register is really "divided up" by the table in a "left side = bass, right side = treble" sort of way. 

 

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There is a large body of literature on experimental and theoretical vibration modes for the low frequencies of a violin.

My take-away from these works is that treble-side deflections of the upper and lower table bouts are as significant as any bass-side deflections. The lowest frequencies tend to have most of the top along the bass bar and extending into the upper treble-side and bass-side bouts moving in one direction, and the treble-side lower bout moving in the other.

The mode shapes of the back show very little distinction between treble and bass sides. Both contribute substantially to the vibration of the violin.

 

 

 

 

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16 hours ago, Dwight Brown said:

I was thinking of this in terms of Hi Fi speakers. (perhaps a poor model) The tweeters have far less movement in terms of excursion compared to the woofers.  I always think of the top sort of like the cone of a speaker and the back and ribs as the enclosure.  This is kind of an incomplete idea however.

 

DLB

 

The physical principal behind the high end loudspeaker enclosure is quite different from that of the violin body. Loudspeaker enclosures must be rigid, with zero vibration resulting from the driver excursion, so not to contribute to coloration or impulse response. They must also have zero outer surface diffraction so no to reflect acoustic waves and cause redirection or phase canceling. The main function is to add a air load mass that results in a linearization of the low end spectrum. All manufacturers struggle with these problems because they tend to result in heavy and bulky boxes which add to cost and handling issues.

There are also some issues regarding the lower end that might benefit from diffraction on the front baffle, at the cost of coloration and directionality, but not at all related to friction instruments.

However, as the violin body, the drivers do suffer from the same bending modes phenomenon. In the drivers case these bending modes are also to be avoided but it's extremely more difficult than just making them thicker. The added mass would result in lower frequency response and efficiency. So they go with harder materials.

Attached one of the best examples of cone deformation. Valid for all types of loudspeakers in all kind of fluids.

Notice the similarities to the violin body as being the cone (or dome) and suspension,  and the bridge as being the voice coil

PLS2011PAPERFINAL.pdf

The ones: http://www.bowers-wilkins.com/Speakers/Home_Audio/Nautilus

 

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19 minutes ago, Luis Martins said:

The physical principal behind the high end loudspeaker enclosure is quite different from that of the violin body. Loudspeaker enclosures must be rigid, with zero vibration resulting from the driver excursion, so not to contribute to coloration or impulse response. They must also have zero outer surface diffraction so no to reflect acoustic waves and cause redirection or phase canceling. The main function is to add a air load mass that results in a linearization of the low end spectrum. All manufacturers struggle with these problems because they tend to result in heavy and bulky boxes which add to cost and handling issues.

There are also some issues regarding the lower end that might benefit from diffraction on the front baffle, at the cost of coloration and directionality, but not at all related to friction instruments.

However, as the violin body, the drivers do suffer from the same bending modes phenomenon. In the drivers case these bending modes are also to be avoided but it's extremely more difficult than just making them thicker. The added mass would result in lower frequency response and efficiency. So they go with harder materials.

Attached one of the best examples of cone deformation. Valid for all types of loudspeakers in all kind of fluids.

Notice the similarities to the violin body as being the cone (or dome) and suspension,  and the bridge as being the voice coil

PLS2011PAPERFINAL.pdf

I was thinking the same thing about my loudspeaker model.  Not at all at your level however! I read the paper and I was surprized I was able to follow it at least a little bit.  Now back to displaying my ignorance :-) 

This is kind of a basic question but I have always been under the impression that the soundpost functions (amoung other things) to couple the back of the instrument to the top and force it to vibrate in phase with it to increase the amplitude of the sound generated.  If it wasn't used the back might have a tendency to vibrate out of phase and cancel some of the energy.

DLB

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1 minute ago, Dwight Brown said:

I was thinking the same thing about my loudspeaker model.  Not at all at your level however! I read the paper and I was surprized I was able to follow it at least a little bit.  Now back to displaying my ignorance :-) 

This is kind of a basic question but I have always been under the impression that the soundpost functions (amoung other things) to couple the back of the instrument to the top and force it to vibrate in phase with it to increase the amplitude of the sound generated.  If it wasn't used the back might have a tendency to vibrate out of phase and cancel some of the energy.

DLB

Check the Nautilus link, they go a long way to uncouple the back portion of the drivers sound. Not at all the violin case.

Don should have better explanation for the violin, I'm on the ignorant side too :wacko:

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For the low frequency modes, the soundpost does help get the plates moving in opposite directions, creating a volume change which is necessary for producing sound at those low frequencies.  However, the soundpost also is involved in defining higher modes too... it's a structural element, coupling the masses and stiffnesses of the plates in various ways to influence the mode shapes and frequencies of the whole structure, and thereby also affect the impedence at the treble bridge foot.  Moving the soundpost around doesn't change the low frequency action very much, but it has a significant effect on the higher modes.

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3 minutes ago, Don Noon said:

For the low frequency modes, the soundpost does help get the plates moving in opposite directions, creating a volume change which is necessary for producing sound at those low frequencies.  However, the soundpost also is involved in defining higher modes too... it's a structural element, coupling the masses and stiffnesses of the plates in various ways to influence the mode shapes and frequencies of the whole structure, and thereby also affect the impedence at the treble bridge foot.  Moving the soundpost around doesn't change the low frequency action very much, but it has a significant effect on the higher modes.

It gets the plates moving in or out of phase?  Sorry Don, you are about 5 Parsecs past my ability :-)

DLB

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23 minutes ago, Dwight Brown said:

It gets the plates moving in or out of phase?  Sorry Don, you are about 5 Parsecs past my ability :-)

DLB

I guess you'd call it "out of phase" if the average areas are moving in opposite directions.  Again, this only has meaning for the lowest frequencies, where the plates have fairly simple movements.  When you go up in frequency, the plates start having lots of antinodes in different phases, and the plates have different mode patterns.  Talking about the plates being in or out of phase no longer has any meaning.

The things that are simplest to understand seem to be the least important to performance, while the most important stuff is impossible to understand.

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What I'm hearing in this thread is:

"We don't know a good theoretical reason to prefer associating wider grain with bass", so "let's sat it doesn't matter", and "there is a known historical preference to make this association", but "we see no reason to honor it".

 

Why not instead say:  

"We don't know a good theoretical reason to prefer associating wider grain with bass", so "let's say we don't know", and "there is a known historical preference to make this association", and "we see no reason to dishonor it".

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David, I like your version fine!

The violin is a construction/construct whose form was established definitively 3-400 years ago. Personally, I think the choice of grain is more likely aesthetic than sonic, since my own experience of historic instruments tells me that anything goes, provided you know what to do with any given piece of wood. 

But some associations are so culturally ingrained that no-one questions them. For example, we think that low notes are somehow low, rather than notes whose waveform has less frequency. Similarly we think in terms of a keyboard, that low notes are somehow on the left and high notes on the right. These are completely arbitrary associations.

I think it's healthy to understand that many of our patterns of thought are metaphorical rather than logical. 

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Hi Martin,

I can see that as a good general point.

The rub here though is that we really aren't sure the reason is only cultural.  On this forum, we often seem to jump from 'we lack a theoretic understand of X' to 'therefore X isn't true'.  But to be rigorously logical and scientific, 'we lack an understand of X' does not earn you any kind of conclusion at all.

In that light, I think it foolish to go from "we know there is a historical preference, but we don't understand a reason" to "since we don't understand a reason, it's only cultural or aesthetic".   We haven't actually earned dismissing the possibility that there might actually be a reason that we just don't understand yet. 

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10 hours ago, Don Noon said:

For the low frequency modes, the soundpost does help get the plates moving in opposite directions, creating a volume change which is necessary for producing sound at those low frequencies.  However, the soundpost also is involved in defining higher modes too... it's a structural element, coupling the masses and stiffnesses of the plates in various ways to influence the mode shapes and frequencies of the whole structure, and thereby also affect the impedence at the treble bridge foot.  Moving the soundpost around doesn't change the low frequency action very much, but it has a significant effect on the higher modes.

I'm am a bit surprised at some people not understanding what is happening when a violin is set in motion  by  being played! I can see clearly that the motion is caused by the sound waves exiting the reeds. The movements are more pronounced at the end grain- F-hole wings and  where the arching is steep and exposes more reed endings.

The movements are also effected by the way the plate was finished; a sharp knife or plane causes less chaotic movement than sanding or dull blade. The varnish layer, grain filler. and accumulation of dirt and wear also has an effect on the movement.

The transfer of sound waves from the bridge to the plate is also a critical factor, so is the sound post stpping/restricting the reeds. Perhaps watching the movements of of the plate in slow motion my be more informative?

 

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4 hours ago, Wolfjk said:

I can see clearly that the motion is caused by the sound waves exiting the reeds.

You seem to be the only one, and intent on establishing this alternative fact by constant repetition.  Please find some way to prove this, or cite some other research to support this notion.

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9 hours ago, David Beard said:

Hi Martin,

I can see that as a good general point.

The rub here though is that we really aren't sure the reason is only cultural.  On this forum, we often seem to jump from 'we lack a theoretic understand of X' to 'therefore X isn't true'.  But to be rigorously logical and scientific, 'we lack an understand of X' does not earn you any kind of conclusion at all.

In that light, I think it foolish to go from "we know there is a historical preference, but we don't understand a reason" to "since we don't understand a reason, it's only cultural or aesthetic".   We haven't actually earned dismissing the possibility that there might actually be a reason that we just don't understand yet. 

Can't disagree!

But that is true in a wider sense of all phenomena, even the ones that science has (for now) "fully understood".

It comes down to a question of whether violin design should be developed on an experimental basis or whether it is complete and not in need of development.

With reference to this thread, much of the discussion seemed to be predicated on two assumptions ...

1. the bass side of a violin handles lower frequencies and the treble side handles higher frequencies

2. wider grain favours low frequencies and tighter grain favours high frequencies

Since both assumptions can easily be shown to be just that (ie. false assumptions) then if there is a reason for putting wide grain to the left on one-piece tops, it can't be connected to either of these false assumptions. 

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In my opinion we need:

i) Determine if there is sufficient variations in the young's modulus of the wood piece that might lead to significant variation on the speed of sound. It may have some influence in the radial direction due to wider ring ratio when compared the left and right sides.

ii) Determine if there is enough rigidity variation on the sample that might influence the longevity of the assembly. (including sound post contact point wear)

iii) Determine the influence of the absent traditional top glued joint in frequency response and mechanical stability.

iv) Determine if the asymmetry produced by the sample will result in significant expansion/contraction variations over time due to moisture variation, with consequent response impairment.

v) Determine if any of these variables might be carved/shaped out.

I'm inclined to say no to all except (v) but it's just an (semi)educated guess.... Thought anyone? 

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3 hours ago, martin swan said:

... if there is a reason for putting wide grain to the left on one-piece tops, it can't be connected to either of these false assumptions. 

If there is wider grain on a 1-pc top, it has to go one way or the other.  With absolutely no knowledge of frequency or vibrations, I'd put it on the left because it would look better behind the fatter strings.

50 minutes ago, Luis Martins said:

Thought anyone? 

Far too much thinking.:)

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