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Peter K-G

Violin #5 - Strad Body modes

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After a lot of posts and interesting discussions in:

Body modes as violin sound equalizer

and other topics, it is time for some action :)

 

I visited a friend last night, who is professional violin maker and bought tone wood for two violins.

 

Top - two halves

 

MC < 6% (Meter showed 5 % in some places)

 

Half 1.

weight 330 g

dencity 0,423 g/cm3

longitudinal celerity ~ 6036 (Don Noon way: Ridiculously easy way to measure speed of sound)

 

Half 2.

weight 405 g

dencity 0,433 g/cm3

longitudinal celerity ~ 5928

 

 post-37356-0-04386700-1361795121_thumb.png   post-37356-0-27966700-1361795089_thumb.png

 

post-37356-0-91095800-1361793751_thumb.png

 

 

 

 

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You can download a very good program first developed by Oliver Rogers that measures density, stiffness along, across and diagonally on a plate. (top or back)

 

The link above is to Tom King's web site which has lots of useful information as well.

 

The density of your top seems on the high side. If the wood is extra stiff then it's probably ok, but if it's not then I would find a different piece.

 

Oded

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You can download a very good program first developed by Oliver Rogers that measures density, stiffness along, across and diagonally on a plate. (top or back)

 

The link above is to Tom King's web site which has lots of useful information as well.

 

The density of your top seems on the high side. If the wood is extra stiff then it's probably ok, but if it's not then I would find a different piece.

 

Oded

 

Thanks Oded,

 

Both top and back plate pieces are in the owen right now so their dencity should go down a little. The wood is relatively new ~2005.

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I was uncertain of the back plate wood so I decided to get another piece

It's probably the heating that caused the diffuse readings, I will save it for later tests.

 

Back plate (new)  1396 g < 6% MC

 

Half 1.

weight 719 g

dencity 0,61 g/cm3

longitudinal celerity ~ 4644

 

Half 2.

weight 677 g

dencity 0,59 g/cm3

longitudinal celerity ~ 4610

 

 

post-37356-0-74226700-1361902403_thumb.png  post-37356-0-27709600-1361902428_thumb.png

 

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Fresh from the owen, Medium rare;

 

Top

 

Half 1.

330 g -> 305 g; M5,  574 Hz -> 578 Hz

Half 2.

405 g -> 379 g; M5,  695 Hz -> 701 Hz

 

New back plate Wood

 

Back

 

Half 1.

719 g -> 684 g; M5, 514 Hz -> 518 Hz

Half 2.

677 g -> 643 g; M5, 468 Hz -> 471 Hz

 

I am very suprised that the M5 modes did not change more !!!!

(M5 is wrong term for the mode as Don pointed out)

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After a lot of posts and interesting discussions in:

Body modes as violin sound equalizer

and other topics, it is time for some action :)

 

I visited a friend last night, who is professional violin maker and bought tone wood for two violins.

 

Top - two halves

 

MC < 6% (Meter showed 5 % in some places)

 

Half 1.

weight 330 g

dencity 0,423 g/cm3

longitudinal celerity ~ 6036 (Don Noon way: Ridiculously easy way to measure speed of sound)

 

Half 2.

weight 405 g

dencity 0,433 g/cm3

longitudinal celerity ~ 5928

 

 attachicon.gifTopNotes1.png   attachicon.gifTopNotes2.png

 

attachicon.gifTop _C_Measure.png

For the first piece of spruce, the radiation ratio is 14.27 before putting in the oven. Don Noon can comment about whether this is high or low.

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Fresh from the owen, Medium rare;

 

I am very suprised that the M5 modes did not change more !!!!

For an uncarved hunk of wood, it's not really M5, but the first free-free longitudinal bending mode.  Picky huh.

 

If the wood stiffness (modulus) and dimensions remained unchanged after the bake, then the taptone would vary with the square root of the mass, not directly.  In addition, there is usually some structural stiffness loss, and (probably most influential) shrinkage of the thickness, all of which tend to keep the taptone low.

 

For the first piece of spruce, the radiation ratio is 14.27 before putting in the oven. Don Noon can comment about whether this is high or low.

It's a little on the low-ish side, if you like to look at radiation ratio numbers.  But so what?  That's about the same radiation ratio as my #8 fiddle, which placed quite high in the VMAAI tone competion.  I also got some offcuts from the first-place tone violin, and that measured out at a radiation ratio of 13.5.  

 

For spruce at C=6000 m/s, that is about as high as I have seen so far.  For maple, the highest I've measured was C=4500m/s, so 4900 is pretty stiff stuff.  I have not explored high speed of sound wood yet (that will be my next one).

 

 

Peter... as yet the title of the thread is sortof hanging there.  Presumably you intend to try to match some Strad's signature modes with the violin you plan to build with this wood?

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Matching the frequencies is nearly meaningless  unless you can also match their relative amplitude.

 

And, by the way, a spectrum chart is only a snapshot of a small percentage of what is going on in a violin. If you run a live FFT (continuous) you will see that mode frequencies and amplitudes are far from 'steady state' they shift with every nuance of every bow stroke. The peaks may rise and fall at different rates and the directionality, a very important constituent of sound quality, is not represented at all.

 

That's not to say that spectrum output is meaningless, but IMHO it gets far more attention than necessary

 

I've been thinking of looking at spectrum analysis much the same way as I look at photos of varnish. You can make a mediocre varnish look quite good to the innocent eye and a grand varnish can look very unimpressive in less than ideal lighting conditions.

 

Oded

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That's not to say that spectrum output is meaningless, but IMHO it gets far more attention than necessary

The problem is that there aren't objective ways to measure tone that seem to be any better.  And subjective opinions are, um, subject to opinion. 

 

I agree that signature mode frequencies mean very little without considering amplitude, and I'll also add my view that the signature modes and amplitudes are only a minor part of the picture. 

 

I still use impact spectra a lot, because it's quick and easy.  However, I'm trying to look more into bowed response, as that is the real story, and there are some differences with the bowed vs. impact response.

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The problem is that there aren't objective ways to measure tone that seem to be any better.  And subjective opinions are, um, subject to opinion. 

 

I agree that signature mode frequencies mean very little without considering amplitude, and I'll also add my view that the signature modes and amplitudes are only a minor part of the picture. 

 

I still use impact spectra a lot, because it's quick and easy.  However, I'm trying to look more into bowed response, as that is the real story, and there are some differences with the bowed vs. impact response.

 

 

Yes, to someone with a hammer everything looks like a nail. That's why I get very skeptical with discussions that are too focused only on spectra without acknowledging (or possibly fully understanding) the limitations.

 

Oded

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Is that a common way to write velocity in Finland to use the word "celerity"?

 

No, it's from Patrick's book. I speak Swedish by the way, I'm not even good at the Finnish language.

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For an uncarved hunk of wood, it's not really M5, but the first free-free longitudinal bending mode.  Picky huh.

 

If the wood stiffness (modulus) and dimensions remained unchanged after the bake, then the taptone would vary with the square root of the mass, not directly.  In addition, there is usually some structural stiffness loss, and (probably most influential) shrinkage of the thickness, all of which tend to keep the taptone low.

 

It's a little on the low-ish side, if you like to look at radiation ratio numbers.  But so what?  That's about the same radiation ratio as my #8 fiddle, which placed quite high in the VMAAI tone competion.  I also got some offcuts from the first-place tone violin, and that measured out at a radiation ratio of 13.5.  

 

For spruce at C=6000 m/s, that is about as high as I have seen so far.  For maple, the highest I've measured was C=4500m/s, so 4900 is pretty stiff stuff.  I have not explored high speed of sound wood yet (that will be my next one).

 

 

Peter... as yet the title of the thread is sortof hanging there.  Presumably you intend to try to match some Strad's signature modes with the violin you plan to build with this wood?

 

Thanks Don,

 

Yes I plan to match a Strad's signature modes. Does anyone know the Soil Stradivari's :)

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And, by the way, a spectrum chart is only a snapshot of a small percentage of what is going on in a violin. If you run a live FFT (continuous) you will see that mode frequencies and amplitudes are far from 'steady state' they shift with every nuance of every bow stroke. The peaks may rise and fall at different rates and the directionality, a very important constituent of sound quality, is not represented at all.

 

That's not to say that spectrum output is meaningless, but IMHO it gets far more attention than necessary

 

I mostly run live FFT on an Ipad - Audiotools by Studio Six Digital. The only measurable way I know of is spectrum analyzes, but I agree that you can't know exactly how the violin sounds by looking at the spectrum. Maybe one could say that it's the violins KPI (Key Performance Indicatior)

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Exactly my point in Body modes as violin sound equalizer, so when we also know how to match their relative amplitude we might be pritty close ?

 

When the bow is drawn across the string the first few milliseconds produce transients this initial sound is critical, it is the sound that the ear/brain uses to identify the source. If you take the recording of a violin and remove the transients, the first few milliseconds of sound, most people cannot identify what it is. Is it a tuba, a fog horn, a trumpet?

 

At the next point the resonances start to define themselves, but they don't all emerge simultaneously, some become louder than others more quickly. This will also affect the perception of the sound quality. Then following that some resonances may fluctuate.

 

For a given resonance if it is supported by harmonics (in the musical sense octaves, 5ths 3rds etc) then those resonances will change their timbre depending on the harmonics and what key the piece of music you're playing! That's why in developing a program to analyze and understand violins it is important to know which resonances are harmonically supported and the musical notes associated with those harmonics

 

 see screenshot below

 

In this early version of the analyzer I've been developing with my colleague Bob Hoffman. You can see the history of each resonance, the size of the dot indicates amplitude and each resonance is identified by frequency as well as musical note (on left)

 

The other part of the analyzer allows for user defined spectrum band display and identifying the location of the sample taken on a violin

 

 

(still under development)

Oded 

post-95-0-59236300-1361889837_thumb.jpg

post-95-0-05665300-1361890238_thumb.jpg

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Back plate 1345 g < 6% MC

 

Half 1.

weight 640 g

dencity 0,612 g/cm3

longitudinal celerity ~ 4985

Error Reading !! C ~ 3800

Half 2.

weight 704 g

dencity 0,623 g/cm3

longitudinal celerity ~ 4980

Error Reading !! C ~ 3800

 

Probably not suitable for back plate

Edited

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When the bow is drawn across the string the first few milliseconds produce transients this initial sound is critical, it is the sound that the ear/brain uses to identify the source. If you take the recording of a violin and remove the transients, the first few milliseconds of sound, most people cannot identify what it is. Is it a tuba, a fog horn, a trumpet?

 

At the next point the resonances start to define themselves, but they don't all emerge simultaneously, some become louder than others more quickly. This will also affect the perception of the sound quality. Then following that some resonances may fluctuate.

 

For a given resonance if it is supported by harmonics (in the musical sense octaves, 5ths 3rds etc) then those resonances will change their timbre depending on the harmonics and what key the piece of music you're playing! That's why in developing a program to analyze and understand violins it is important to know which resonances are harmonically supported and the musical notes associated with those harmonics

 

 see screenshot

https://plus.google.com/photos/106576171087568832231/albums/5849228392557800033/5849230936716622162

 

 (sorry can't upload image)

 

 

In this early version of the analyzer I've been developing with my colleague Bob Hoffman. You can see the history of each resonance, the size of the dot indicates amplitude and each resonance is identified by frequency as well as musical note (on left)

 

The other part of the analyzer allows for user defined spectrum band display and identifying the location of the sample taken on a violin

 

https://plus.google.com/photos/106576171087568832231/albums/5849237221920652481/5849237235724550354

Oded 

 

Very interesting! I can't open the links though.

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Very interesting! I can't open the links though.

 

 

screen capture on right below....

In this early version of the analyzer I've been developing with my colleague Bob Hoffman. You can see the history of each resonance, the size of the dot indicates amplitude and each resonance is identified by frequency as well as musical note (on left)

 

screen capture on left below...

The other part of the analyzer allows for user defined spectrum band display and identifying the location of the sample taken on a violin

 

Oded

post-95-0-03666700-1361890790_thumb.jpg

post-95-0-56570600-1361890823_thumb.jpg

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Busy week, not much time for violin making. Scroll and pegbox is beginning to take shape, scroll still too big but has the right shape. Hope I can finnish this weekend. Great thing is that I can allready hear how wounderful the violin is going to sound :)

 

Here is the targets for my next Strad sounding violin:

 

Violin5_Targets_09032013.pdf

 

 

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and here's my target for my next Strad sounding violin:

post-25192-0-75436900-1362842338_thumb.jpg

 

The plan is to copy the archings and grads very closely, and see what happens.  (I might un-distort the archings a bit).

 

Ex-Jackson Strad, by the way.

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First target acheived, edges still need some finishing but i'm happy with the shape.

 

Neck: Target 70 g --> now 71 g, will be ~68 g when finnished

 

post-37356-0-29037000-1362846626_thumb.jpg   post-37356-0-45515700-1362848105_thumb.jpg

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