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Theoretically I can raise Mode 5 by removing wood where?


fscotte

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Usually thinning down no matter where lowers the taptones. I never could raise taptones, at best one of the modes wouldn’t go down too much compared to others.

But you could also ask what is the purpose? I always recommend to make experiments on the assembled playable instrument in the white. If tap tones would be significant, wood removal in tap tone influencing areas on the assembled instrument should make clearly audible changes. It doesn’t. 

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9 hours ago, fscotte said:

So the pencil marks is where tea leaves showed mode 5 at 347 hz,

So the theory is that if I remove wood on the outside of the modal lines, top and bottom, mode 5 will actually go up?

 

20240211_200345.jpg

That is a very strange pattern for mode 5 particularly the way the lines move in towards the bass bar throough the C bout area 

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11 hours ago, Don Noon said:

 

7 hours ago, Andreas Preuss said:

Usually thinning down no matter where lowers the taptones. I never could raise taptones, at best one of the modes wouldn’t go down too much compared to others.

But you could also ask what is the purpose? I always recommend to make experiments on the assembled playable instrument in the white. If tap tones would be significant, wood removal in tap tone influencing areas on the assembled instrument should make clearly audible changes. It doesn’t. 

I also am sceptical thus why I thought about asking the question. I have yet to see Mode 5 (or Mode 2) go up by removing wood.  Modes "always* go down for me, or stay the same in the case of removing small amounts of wood.

 

 

 

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7 hours ago, Andreas Preuss said:

I never could raise taptones, at best one of the modes wouldn’t go down too much compared to others.

Most likely you were'nt pathologically focused on changing the taptone regardless of how stupid it was for the assembled instrument.

Out of morbid curiosity, I just took a scrap top (with bass bar) and raised the M5 from 316 Hz to 329 Hz by removing slightly less than .5g of wood from around the endblock area.

You could certainly raise the M5 more effectively by sawing off a few mm from the ends of the plate.

But I thought the idea was to make a good sounding violin, which I suspect is inversely related to manipulating free plate mode frequencies in bizarre manners. 

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15 minutes ago, Marty Kasprzyk said:

Does anybody have a list of the top plate M5 frequencies and weights of violins used by really good players?

While there is no guarantee that "really good players" actually think these are good violins, there's this:  https://josephcurtinstudios.com/wp-content/uploads/2017/06/taptones_vsapapers.pdf  I'm sure there is a lot more information somewhere.

My conclusion after looking into this stuff is that there's plenty of scatter such that good and bad instruments have a significant overlap in plate weights and taptones... although bad ones tend to occupy the high weight/taptone zone of the space (i.e. indicating poor wood properties).

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45 minutes ago, Don Noon said:

Most likely you were'nt pathologically focused on changing the taptone regardless of how stupid it was for the assembled instrument.

Out of morbid curiosity, I just took a scrap top (with bass bar) and raised the M5 from 316 Hz to 329 Hz by removing slightly less than .5g of wood from around the endblock area.

You could certainly raise the M5 more effectively by sawing off a few mm from the ends of the plate.

But I thought the idea was to make a good sounding violin, which I suspect is inversely related to manipulating free plate mode frequencies in bizarre manners. 

Interesting. 

.5 is not soo much material.

However I was always more concerned about the X mode (was that M2?) getting too low.

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3 hours ago, Don Noon said:

 

Out of morbid curiosity, I just took a scrap top (with bass bar) and raised the M5 from 316 Hz to 329 Hz by removing slightly less than .5g of wood from around the endblock area.

I suspect that had more to do with some other factor rather than a loss of weight.

I've never seen real evidence of any mode going up, when removing wood from the areas that aren't the edge.

But I have seen several places, and read some replies of those who say it can be done.

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5 hours ago, fscotte said:

I suspect that had more to do with some other factor rather than a loss of weight.

And what factor might that be?

I am confident that it is the mass reduction.  I removed wood as close to the edge as possible.  Since the edge moves the most in mode5 and contributes very little to the stiffness, removing weight there will logically (and does) make M5 frequency go up.  

This is an academic exercise only, and should never be used to "tune" a plate.  That's just silly.

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14 minutes ago, Don Noon said:

And what factor might that be?

I am confident that it is the mass reduction.  I removed wood as close to the edge as possible.  Since the edge moves the most in mode5 and contributes very little to the stiffness, removing weight there will logically (and does) make M5 frequency go up.  

This is an academic exercise only, and should never be used to "tune" a plate.  That's just silly.

When folks have suggested to remove wood outside the modal lines, I'm assuming they mean anywhere outside the modal lines.

Using the diagram below, it's suggested that if wood is removed from anywhere in the lower bout outside the line, (not the edge), then Mode 5 will go up.  

I never had this happen.  It will always go down as Andreas mentioned too.

 

Where_to_thin_a_belly-_Modes_2_-_5_V2.jpg

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2 hours ago, fscotte said:

When folks have suggested to remove wood outside the modal lines, I'm assuming they mean anywhere outside the modal lines.

Using the diagram below, it's suggested that if wood is removed from anywhere in the lower bout outside the line, (not the edge), then Mode 5 will go up.  

If you remove mass, and not stiffness, the frequency goes up. (and if you remove more stiffness the frequency drops) So, it’s very important where you remove the wood. If you are trying to raise the frequency, it is very important to not remove wood close to the nodal line. (And in general, since wood doesn’t weigh much, it’s much easier to remove more stiffness than mass, and drop the frequency.) 

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14 minutes ago, FiddleMkr said:

If you remove mass, and not stiffness, the frequency goes up. (and if you remove more stiffness the frequency drops) So, it’s very important where you remove the wood. If you are trying to raise the frequency, it is very important to not remove wood close to the nodal line.

The most important thing is that there's no evidence that the completed instrument is improved by mucking around with the graduation pattern to artificially raise or lower free plate mode frequencies.

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"Overthinking, overanalyzing, separates the body from the mind
Withering my intuition, leaving opportunities behind
Feed my will to feel this moment
Urging me to cross the line
Reaching out to embrace the random
Reaching out to embrace whatever may come"
 

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14 hours ago, Don Noon said:

Most likely you were'nt pathologically focused on changing the taptone regardless of how stupid it was for the assembled instrument.

Out of morbid curiosity, I just took a scrap top (with bass bar) and raised the M5 from 316 Hz to 329 Hz by removing slightly less than .5g of wood from around the endblock area.

You could certainly raise the M5 more effectively by sawing off a few mm from the ends of the plate.

But I thought the idea was to make a good sounding violin, which I suspect is inversely related to manipulating free plate mode frequencies in bizarre manners. 

Strangely, some of the best sounding violins make more of a *thud* when tapped as free plates to me. Like, there is some kind of dampening that's not being accounted for when making new instruments. It's almost like a certain band(s) of frequencies are being adulterated on the best sounding violins. The sound is usually more pure, and with less ringy white noise to the plate when free. 

I've been interested in dampening agents these days, rather than how the plate rings explicitly. 

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Making violins is like being one of the three bears who learned how to make their own porridge, they didn't have to leave it up to random chance to happen upon some bowls of porridge that may or may not be "just right"

Make your porridge, blow on it until it's just right and then eat it. You'll know when it's "just right" for "you"

You are going to have a much better time of it if you ditch your current line of reason which is based on a buncha gobbledygook you seem to have gleaned on the interwebs.

I'll make some suggestions that you may or may not wish to entertain that may or may not help you enter the realm reality faster then on your present course

These will be "Mr. Myagi" like "chores" or exercises that in my opinion are things that will help you achieve the type of personal refinement that "we" can tell you  are striving for. I won't really explain why this is important stuff, I'll just say I think it's way more important than some of the stuff your focusing on, as far as "becoming a better instrument maker"

1. not knowing where you are from, I will simply say take your local central bank backed coins, in the people's republic of America we use pennies, nickels, dimes and quarters, at any rate find the thickness of your coins so you have that thickness dimension in mind and simply spend lots of time training your fingers by keeping coins in your pocket and using them as calipers to really "feel" and train your fingers to accurately identify thickness by just pinching.

2. eventually make strips of wood and do the same with those, 1 mill, 1.5,2,2.5,3,3.5,4 and so on up to 5 or 6

3. now do the same "pinch training" with the wood strips, first by looking at them, and then work up to doing it blind by randomly picking them out of a box

4."Mechanical sympathy" training; take those strips of wood and bend them. really feel their flexibility levels, their ability to bend and twist, their recoil rates and if they want to return to flat or not. The more you can do this with different scrap woods of varying  sizes and shapes the more you see the differences of "piece to piece" board to board within the same species...this somewhat negates cookie cutter dimensions and "done that before" wisdom related to graduations. Peak arch heights/widths are however very important to many things.

for now just these simple "task" are enough to think about and practice for quite sometime...

become straw against the wind Grasshoper and learn to bend but not break...:)

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7 hours ago, FiddleMkr said:

If you remove mass, and not stiffness, the frequency goes up. (and if you remove more stiffness the frequency drops) So, it’s very important where you remove the wood. If you are trying to raise the frequency, it is very important to not remove wood close to the nodal line. (And in general, since wood doesn’t weigh much, it’s much easier to remove more stiffness than mass, and drop the frequency.) 

Right, that's the idea, but according to what I've read and seen, it is suggested that removing wood outside the modal lines will raise a frequency.  

Practically speaking though, it doesn't work unless you're very close to the edge.  But that isn't implied or suggested from those who claim it works by removing outside the modal lines.

If I'm wrong I'd love to see it performed on video.  I've yet to see that.

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17 minutes ago, fscotte said:

Right, that's the idea, but according to what I've read and seen, it is suggested that removing wood outside the modal lines will raise a frequency.  

Practically speaking though, it doesn't work unless you're very close to the edge.  But that isn't implied or suggested from those who claim it works by removing outside the modal lines.

If I'm wrong I'd love to see it performed on video.  I've yet to see that.

The theory works in theory, that is, if you consider a flat rectangular plate with two parallel and horizontal nodal lines for the M5 and two parallel and vertical lines for the M2. In this case, if you remove inside the nodal lines (the part that flexes) the frequency will go down, if you remove outside the nodal lines (therefore removing moving mass and not stiffness) the frequency will go up. This is indisputably true. But violin plates with their strange shape and arching are much more complicated, so don't expect the theory to apply by the letter.

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13 hours ago, fscotte said:

When folks have suggested to remove wood outside the modal lines, I'm assuming they mean anywhere outside the modal lines.

Using the diagram below, it's suggested that if wood is removed from anywhere in the lower bout outside the line, (not the edge), then Mode 5 will go up.  

I never had this happen.  It will always go down as Andreas mentioned too.

 

Where_to_thin_a_belly-_Modes_2_-_5_V2.jpg

I would recommend to use average Strad or del Gesu thicknesses and wood similar to theirs instead of guiding the graduations from an idea of having certain relations between the free plate modes. One reason for not using ideas like the one shown in the figure is that the assembled violin body moves different from the free plate. Free plates "flap" a lot along the border, while the plates tend to move more in the centre and "the lungs" in the assembled body. The sensitivities to changes in thicknesses are somewhat different. 

You do not want to have a too thick central part of the top plate. In cremonese violin types the central part is rather thin, sonmething Jeff Loen called "Reverse graduation". Building a violin like this takes more skills and abilities in getting a good high frequncy response. It is easier to get this by using a thicker central part.
I have looked a lot at graduation charts and calculated average plots and have used average graduation as mentioned above with a certain degree of success. 
 

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13 hours ago, fscotte said:

When folks have suggested to remove wood outside the modal lines, I'm assuming they mean anywhere outside the modal lines.

Using the diagram below, it's suggested that if wood is removed from anywhere in the lower bout outside the line, (not the edge), then Mode 5 will go up.  

I never had this happen.  It will always go down as Andreas mentioned too.

 

Where_to_thin_a_belly-_Modes_2_-_5_V2.jpg

This diagram ignores completely the influence of the arching and wood quality. Which means it suggests that you can achieve specific mode frequencies with any wood and any arching height and pattern. 
 

In my view this is very questionable.

 

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3 hours ago, fscotte said:

Right, that's the idea, but according to what I've read and seen, it is suggested that removing wood outside the modal lines will raise a frequency.  

Practically speaking though, it doesn't work unless you're very close to the edge.  But that isn't implied or suggested from those who claim it works by removing outside the modal lines.

If I'm wrong I'd love to see it performed on video.  I've yet to see that.

"Who are you going to believe, me or your own eyes?   Groucho Marx

Oliver Rogers used theoretical computer finite element analysis to show how the various vibration mode frequencies changed with wood removal in different areas of the top and back free plates. He found the plate edge areas are quite sensitive to wood removal.  

Three of his papers are in the CAT journals which are attached.

I found similar results in my plate thinning efforts.  But rather than believing others it might be more believable to do your own experiments.  Remove wood in a small area and see if there is a change in frequency for the various modes.  Try different areas and make a map of the results. Keep good records and enjoy the resulting arguments.

Newton's third law:  "For every physicist there is an equal and opposite physicist"

May 1990.pdf Nov1991 pdf.pdf May 1993pdf.pdf

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Last week I took a 390 long viola back from 184g to 125g, and the ring mode went from F on my guitar, to 316 on audacity. The lower 2 tones dropped to 107, and 160. The middle tone always was about an octave lower. I have no idea why it didn't drop more. I didn't check it on audacity until I was done. 

The upper end opened up with lots of peaks to 1,000 showing on the graph.

I didn't check the belly either until it was done. It seemed to be around E for almost all the time too. But the graph shows that it is about 280, and on the guitar, I do place it something between C# and D on the guitar. I was hoping that they would be the same. 

I wouldn't have a clue about how to drop it down. I'm not going to try. The back feels a little stiff, but the belly doesn't, so it might need the stiffness.

The belly has a low ring that I hear at an octave lower than C#, about 70hz. A blip showed up at 80 before I put the bass bar in, but I hear it at C#. Ears do funny things.

 

Screenshot2024-01-31at8_58_09AM.thumb.png.c99b903cc44923383ad5f1e67a16ff29.png

 

Cedarviolawithbassbar80grams.thumb.png.76534e7d091d9cd645249f575a565b7b.png

 

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On 2/11/2024 at 8:08 PM, fscotte said:

So the pencil marks is where tea leaves showed mode 5 at 347 hz,

So the theory is that if I remove wood on the outside of the modal lines, top and bottom, mode 5 will actually go up?

I've run into a number of people who seemed to get good results by mode frequency tuning. However, I don't recall that any of them tried to raise these mode frequencies back up after getting them too low, using wood removal in selected areas (not that it can't be done), and I would question the efficacy of doing so just to get a number.

My current opinion is that "good" violin sound and playing properties are contingent upon getting stiffness-to-mass ratios "right" everywhere on a violin, and not just those affecting the lower plate modes.

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