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A0 frequency for big violas


Marty Kasprzyk

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5 hours ago, Marty Kasprzyk said:

I mentioned before that my sound post goes through a hole in the top plate so the entire plate surface moves in the direction of the bass foot's motion which eliminates this phase cancellation which futher increases sound output in the low frequency range.

Removing the sound post connection with the top plate also reduces the stiffness of the plate and the entire instrument which lowers the A0 frequency and increases its amplitude which might be helpful for small violas.  

 

Marty, you know I already have one foot in the through-post dark side.

:D

Altho in my case the bass bar equivalent and top of the instrument are very thick and the bar is central and the strings are plain steel wire.

20231119_113435 (1).jpg

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Setting up and using the little accelerometers and force hammer is a fun thing to do. It's not essential but I think of it as similar to using a CRO and multimeter to look at electronic circuits. 

 

I am still assimilating the ideas in rhe Gough plate/shell modelling paper where he derives the motion in the various signature modes from first principles and also models how the whole body modes evolve from plate modes as soundpost, rib and bass bar strengths are increased, from go to whoah!

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  • 5 weeks later...

Marty,

A0 is what you hear when you blow in the f holes, isn't it? The 390mm viola I just glued together last weekend has a lower A0; the open G of a guitar; than the bigger ones I made. It is made of HD cedar decking, and mahogany. Someone on maestronet a few years ago said that he did that and it worked. I had some of each, and cut some to try it. 

A couple months ago, I wanted to do an experiment carving completely by scratching and tapping, like Peter Westerlund, so I decided to make a smaller viola with just an outline. It is the outline of a Storioni. It ended up being almost the same inside as my inside out method, on the belly with cross arches, and the back with long arches that come from the blocks, but only to the corners or bouts, leaving the center thick. That is what the tapping gave. The outside of the back is an arc, just like I do. The long arch  of the belly looks like a Montagnanga, but not so tall.

So the A0 is just under 200 for a smaller viola. Will it sound bigger? I have no clue. I have to finish it up. Noting outrageously light, 80 g for the belly, it is only cedar, and 120g for the back; I think it is like 3mm to 7mm, but it might have gone down to 6.5 or so, I don't remember. I haven't put the purfling in yet. I think I'll puts strings on it, and see what happens if I decide to tune the recurve now that it is glued up. The pitch goes up. toward the solid edge.

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1 hour ago, Ken_N said:

Marty,

A0 is what you hear when you blow in the f holes, isn't it? The 390mm viola I just glued together last weekend has a lower A0; the open G of a guitar; than the bigger ones I made. It is made of HD cedar decking, and mahogany. Someone on maestronet a few years ago said that he did that and it worked. I had some of each, and cut some to try it. 

A couple months ago, I wanted to do an experiment carving completely by scratching and tapping, like Peter Westerlund, so I decided to make a smaller viola with just an outline. It is the outline of a Storioni. It ended up being almost the same inside as my inside out method, on the belly with cross arches, and the back with long arches that come from the blocks, but only to the corners or bouts, leaving the center thick. That is what the tapping gave. The outside of the back is an arc, just like I do. The long arch  of the belly looks like a Montagnanga, but not so tall.

So the A0 is just under 200 for a smaller viola. Will it sound bigger? I have no clue. I have to finish it up. Noting outrageously light, 80 g for the belly, it is only cedar, and 120g for the back; I think it is like 3mm to 7mm, but it might have gone down to 6.5 or so, I don't remember. I haven't put the purfling in yet. I think I'll puts strings on it, and see what happens if I decide to tune the recurve now that it is glued up. The pitch goes up. toward the solid edge.

Interesting!

Will you put the strings on it and play it before and after you cut the purfling grooves in and then after the purfling is glued in?  

I use bowed glisandos on the C string to get a frequency response curve and the A0 frequency is easy to see and get an exact frequency with Audacity software (free on line).

I was never able to find the A0 with soft blowing agross the f holes because I'm a blowhard.

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2 hours ago, Ken_N said:

390mm viola...

So the A0 is just under 200 for a smaller viola. Will it sound bigger? I have no clue. I have to finish it up. 

Presumably you have no soundpost and it is not strung up, which will give a much lower A0 than the fully assembled one.  Unless you have extremely floppy plates or tiny F-holes, I think you'll end up around 270 Hz for A0.

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1 hour ago, Don Noon said:

Presumably you have no soundpost and it is not strung up, which will give a much lower A0 than the fully assembled one.  Unless you have extremely floppy plates or tiny F-holes, I think you'll end up around 270 Hz for A0.

It's interesting, weird and I have no idea of the significance, that the supposed A0 pitch again has 1/4 wavelength approx the same as the body length. 

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Yes Marty, I'll finish getting the outline even with the ribs, then make a tailpiece and string it up. I always wanted to do that, but then just want to get varnish on and be done with it!

I never check the modes and all that. I just got Audacity to work a while back. I was looking for the controls on the page it brings up, and NOT on the very top line, that I consider to be the computer, not the ap. So I gave up on it. Yes, I am not tech savvy at all. It doesn't make sense to me.

I think the 16.5" viola has the same A0 as the 15" 5 string. 175, F or so.  They seem pretty similar. I have no clue what is what, I do think the A0 is the 175 peak though. That's where the body starts bouncing.

largeviola.thumb.png.38097c09eadce437308a9c955d4d5cf7.png

 

5strin.thumb.png.d7413b09f3d1f57d64c62ee4d8c86224.png

 

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28 minutes ago, Ken_N said:

I think the 16.5" viola has the same A0 as the 15" 5 string. 175, F or so.  They seem pretty similar. I have no clue what is what, I do think the A0 is the 175 peak though.

Unless you have a radical Kasprzykian design, I highly doubt you will have A0 at 175 Hz on a 15" viola.  It's one of the easiest things to find on Audacity:  just tap the bridge (or over the bass bar if unstrung) with the eraser end of a pencil. You need a soundpost installed in order to get in the right ballpark, and without strings/bridge it will be off too, but not as much.

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Ok Don, I didn't know about that. Tapping on the bridge over the bass bar, and muting the strings, they both are about A-A#. 225 on the viola, and 233 on the 5 string? What are the other peaks? (5 string on top). 5string.thumb.png.68de3c1580b01e8e5c1471e68b9ede1a.png

viola.thumb.png.d327f52b24417610b653c58fdfe9d57c.png

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Clarity of the resonance peaks depends a lot on the technique of tapping and recording, but generally you should find the B1- peak a bit below 400 Hz and the B1+ around 440 for a small-ish viola, and maybe 10 or 20 Hz less for a larger one.  There could also be a CBR peak between the A0 and B1-. maybe around 330 Hz.

But it's not always clear what's what, particularly for violas, which are more variable than violins.

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Marty,

In have an idea for your A-0 journey.

A group of my compadre's and I preformed an experiment on some violas.' (all who have since passed away, oh how time fly's)

I like to always experiment with groups, a singe result means nothing to me, a half a dozen is what I like, this time we only had three but it seems that the results were significant.

,,,We took 3, 15" violas, made by the same gentleman, all the same model and arching, all sounded very similar, so we used them and did some experimenting. They sounded like good 15" violas to begin with, but lacked that large viola openness and bigness. We checked them with audacity till blue in the face, could not find any evidence of A-1 or any other harmonics of relevance, just A-0 and some other low HZ  rumblings.

I took them apart, and installed a plastic bottle attached to the neck block.

2 holes were drilled into the block and 2 bamboo sticks were glued in place, in the plane of the ribs, left and right. they were spaced to accommodate the plastic bottle in between them. The bottle was rectangular with the screw threads cut off of the top of the bottle to leave a smooth straight edge. The finished size was approx. 50mm x 125 mm. The open end of the bottle was positioned about 25-30mm away from the neck block. It was held in place with string wrapped around the bottle in 2 places enclosing the sticks. One at the open end, one a bit more than halfway down the side of the bottle. The string was then saturated with super glue, along with the contact points between the bottle and the bamboo to prevent any rattles.

These were done one at a time for comparisons with the remaining instruments.

Previously they had been played a lot to compare and get used to the sound. After the bottle was installed there was an immediate and audible difference. The sound became much clearer, the notes had a distinctive clarity and edge to them, not so fuzzy and veiled, it sounded larger, it was quicker more open and transparent. It definitely changed the sound, and all for the better.

The A-0 did not move at all, but now the A-1 was found just above the f-holes, along with a series of harmonics. It made the A-0 audible and the viola sounded much larger.

The other two were done, one at a time, and the results were the same.

We now knew for certain that before using small violas for snow shoes, this should be done first, so in the event of being buried by an avalanche, the rescue crew will be able to hear your whereabouts.

And, as a survival tool, A little bonus is the extra BTU'S you get when the fire reaches the plastic.

 

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2 hours ago, Evan Smith said:

Marty,

In have an idea for your A-0 journey.

A group of my compadre's and I preformed an experiment on some violas.' (all who have since passed away, oh how time fly's)

I like to always experiment with groups, a singe result means nothing to me, a half a dozen is what I like, this time we only had three but it seems that the results were significant.

,,,We took 3, 15" violas, made by the same gentleman, all the same model and arching, all sounded very similar, so we used them and did some experimenting. They sounded like good 15" violas to begin with, but lacked that large viola openness and bigness. We checked them with audacity till blue in the face, could not find any evidence of A-1 or any other harmonics of relevance, just A-0 and some other low HZ  rumblings.

I took them apart, and installed a plastic bottle attached to the neck block.

2 holes were drilled into the block and 2 bamboo sticks were glued in place, in the plane of the ribs, left and right. they were spaced to accommodate the plastic bottle in between them. The bottle was rectangular with the screw threads cut off of the top of the bottle to leave a smooth straight edge. The finished size was approx. 50mm x 125 mm. The open end of the bottle was positioned about 25-30mm away from the neck block. It was held in place with string wrapped around the bottle in 2 places enclosing the sticks. One at the open end, one a bit more than halfway down the side of the bottle. The string was then saturated with super glue, along with the contact points between the bottle and the bamboo to prevent any rattles.

These were done one at a time for comparisons with the remaining instruments.

Previously they had been played a lot to compare and get used to the sound. After the bottle was installed there was an immediate and audible difference. The sound became much clearer, the notes had a distinctive clarity and edge to them, not so fuzzy and veiled, it sounded larger, it was quicker more open and transparent. It definitely changed the sound, and all for the better.

The A-0 did not move at all, but now the A-1 was found just above the f-holes, along with a series of harmonics. It made the A-0 audible and the viola sounded much larger.

The other two were done, one at a time, and the results were the same.

We now knew for certain that before using small violas for snow shoes, this should be done first, so in the event of being buried by an avalanche, the rescue crew will be able to hear your whereabouts.

And, as a survival tool, A little bonus is the extra BTU'S you get when the fire reaches the plastic.

 

It is so subversive to hide all that inside your viola.

 

My favourite ad-hoc resonator is a piece of brass hobbitube in 1/4 wave format which has input end open other end plugged up. You can get good resonance effects with these down to 1.5 to 2mm id tubing since when you hit resonance the input impedance is very high ( or antiresonance =low)  and you can bend them around a bit.   

Why hide them away? Just drill little holes to stick them in and turn your viola into a hedgehog. 

But now you have me thinking of making runs of  interior baffles... 

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1 minute ago, LCF said:

It is so subversive to hide all that inside your viola.

 

My favourite ad-hoc resonator is a piece of brass hobbitube in 1/4 wave format which has input end open other end plugged up. You can get good resonance effects with these down to 1.5 to 2mm id tubing since when you hit resonance the input impedance is very high ( or antiresonance =low)  and you can bend them around a bit.   

Why hide them away? Just drill little holes to stick them in and turn your viola into a hedgehog. 

But now you have me thinking of making runs of  interior baffles... 

The idea of a curled horn had come up decades ago, but when looking at function, a lot of the surface area is too open and the effect wanted is wasted,,, too much unused surface area.. The idea of a simple container placed in reverse seemed more functional. It actually took up negligible space, yet added more volume in a sneaky sort of way.

Crazy man CRAZY!:D

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2 hours ago, Evan Smith said:

The idea of a curled horn had come up decades ago, but when looking at function, a lot of the surface area is too open and the effect wanted is wasted,,, too much unused surface area.. The idea of a simple container placed in reverse seemed more functional. It actually took up negligible space, yet added more volume in a sneaky sort of way.

Crazy man CRAZY!:D

Not really crazy. 

Was the neck of the bottle attached to the block sealed off? If so I'm thinking you have added a 1/4 wave res much like my favourites but which has it's inlet in such a place as to extend A0 but also add its own harmonics, these are odd# in 1/4 wave Z system. 

I suggest a simpler and less intrusive approach would be to make an end pin which is bored through as large as poss so a piece of tube can be inserted, tube blocked at outside end. Length can be varied outside, trombone fashion. Inner position of tube end ditto, probably close to neck block? It won't give the volume blocking and shifting arrangement of yer inner plastic bottle through the mid section. I'm suggesting a resonant viola spike arrangement instead. 

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  • 2 weeks later...
On 1/8/2024 at 11:52 PM, Marty Kasprzyk said:

I screwed up.  Hope this one works.  Also attached is Schelleng's fig 4. from the paper.

 

Hi Marty   I'm so behind with my reading that I'm only now reading through this CAS issue in depth. In the Bissinger esay is a mention of the close coupling between A0 and A1 driven by plate compliance, then onwards to A2 and A4 Then there's the Jansson article on the higher air modes to contemplate. Time to be getting a little microphone inside on of these viola things to sniff around a bit!

I had an idea about note and mode sniffing for a quick and dirty modal mapping for a single mode by using a parametric equalizer after the microphone preamp set to the frequency of interest. Then one could just tap around all over the place and measure the response at the selected frequency with a cro or an audio voltmeter etc. 

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Too nasty to retain.  I'm not at all happy with taking a maker's output and using them for experiments, if that's what was done, but certainly there's a better way to express the same idea - my apologies to Mr. Smith.

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6 hours ago, Dr. Mark said:

You sound like someone who would rip del Gesus and Strads apart, drill holes in them and slice them up if given half a chance.  Or maybe the maker volunteered them or something...?  Why not use factory violas instead of, as you seem to be saying, some maker's hand-made violas?  Have I misunderstood what you've done?

Hopefully you can reference people who will verify these results or have reproduced them (hopefully with their own or factory instruments), or are they all dead now?

Oh yes, as you said.  Fugit inreparabile tempus.  It's not just some gentleman's hand-built violas that passed away, but your witnesses.  Is anyone else available to verify your results or can I continue to indulge in assuming the worst? 

Seriously, claims are cheap.  Is there any kind of --> consensus <-- that you actually achieved something significant rather than just made some kind of tooter, or worse, ruined some violas?

 

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On 2/21/2024 at 3:53 PM, Evan Smith said:

Marty,

In have an idea for your A-0 journey.

>

I took them apart, and installed a plastic bottle attached to the neck block.

>

The A-0 did not move at all, but now the A-1 was found just above the f-holes, along with a series of harmonics. It made the A-0 audible and the viola sounded much larger.

The other two were done, one at a time, and the results were the same.

We now knew for certain that before using small violas for snow shoes, this should be done first, so in the event of being buried by an avalanche, the rescue crew will be able to hear your whereabouts.

And, as a survival tool, A little bonus is the extra BTU'S you get when the fire reaches the plastic.

 

The Nov. 1996 CASJ issue (attached below) has an article by John Miles " Tuning the A1 mode without changing the body size of an instrument" where a plastic bottle attached on the inside of a test viola with the bottle's opening near the upper block.  This increases a longitudinal air wave's travel length which lowers its A1 resonance frequency which could make a small viola sound more similar to a large one.

He mentioned that the frequency of A1 and others can be adjusted by changing the volume of the bottle. This could be very useful for avoiding wolf notes, correcting weak or overly loud ones and changing the instruments sound character.

This is not a new concept-- the volume and shape of a person's voice track is very moldable and this why the human voices can be so unique and expressive. 

Some come to mind.image.thumb.png.657ba391b5bba54bc155f0e6502f6911.png

CAS_yj455sn6422.pdf

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1 hour ago, Marty Kasprzyk said:

The Nov. 1996 CASJ issue (attached below) has an article by John Miles " Tuning the A1 mode without changing the body size of an instrument" where a plastic bottle attached on the inside of a test viola with the bottle's opening near the upper block.

The more I think about this the more difficult it seems to determine whether there's a practical benefit.  I suppose a blind test would be run with both 15 in. and larger violas to determine an audience's ability to choose between them (I don't know what to do about the player-side problem. maybe a violin-playing machine).  Given that the test audience could group the 15 inchers seperately from the others there would be a basis for evaluating whether modified 15 inchers are similarly distinguishable.  It may require an intermediate test with another group of instruments.  The ideal outcome would be that the modified violas would not be distinguishable from the others i.e. grouping by the audience would be random or correlated with other factors than viola size.  Otherwise there are the other claims - even if the modified violas can still be distinguished from larger unmodified ones their tone may have improved or degraded.  I've been casting around for articles describing something like the above and will continue to do so for awhile.

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2 hours ago, Marty Kasprzyk said:

This increases a longitudinal air wave's travel length which lowers its A1 resonance frequency which could make a small viola sound more similar to a large one.

 

51 minutes ago, Dr. Mark said:

The more I think about this the more difficult it seems to determine whether there's a practical benefit. 

Look at the full picture of what makes something sound the way it does.  This is an impact spectrum of one of my small (40cm) violas.  What we're talking about here is taking that one lowest resonance and shoving it a few tens of Hz to the left, with all those other gazillion resonances left as-is.  And that one resonance only shows up as a fullness characteristic of a couple of notes on the first position of the G string, nothing else affected.  It ain't gonna sound like a big viola if you only move that one peak.

32200821.jpg.2b1909a65176a6bc515484d19750e654.jpg

(edit:  I notice I've made this basic point 2 moths ago in this topic, but I forgot,. And it seems to be mostly ignored.)

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37 minutes ago, Don Noon said:

Look at the full picture of what makes something sound the way it does.  This is an impact spectrum of one of my small (40cm) violas.  What we're talking about here is taking that one lowest resonance and shoving it a few tens of Hz to the left, with all those other gazillion resonances left as-is.  And that one resonance only shows up as a fullness characteristic of a couple of notes on the first position of the G string, nothing else affected.  It ain't gonna sound like a big viola if you only move that one peak.

32200821.jpg.2b1909a65176a6bc515484d19750e654.jpg

(edit:  I notice I've made this basic point 2 moths ago in this topic, but I forgot,. And it seems to be mostly ignored.)

It's a moot point as to whether modifying or introducing one air resonance might have effects on the others. See the Bissinger intro as I mentioned earlier.  There are strong interactions between all the air modes mediated by the compliance of the plates.  Introducing a 1/4 wave resonator gives you more than one resonance to spice things up. There are f, 3f, 5f resonance peaks plus 2f, 4f, 6f antiresonance peaks. All sorts of potentials there. 

Also one need not lift the lid to test the idea. A suitable sniffer of flexible pipe can be wrangled through an ff hole or via modified end pin. 

 

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Quick back of an envelope calculation: a 1/4 wave tube resonating at a C 523 wolf note ( or thereabouts) would be ~155mm long. That would be an interesting thing to try. Damping in a tube can be introduced by loosely packing with wool or etc. 

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1 hour ago, Don Noon said:

I notice I've made this basic point 2 moths ago in this topic, but I forgot,. And it seems to be mostly ignored.)

Yeah sorry - there's a lot floating around and it's difficult to know what's going to matter a few weeks down the road.

48 minutes ago, LCF said:

There are strong interactions between all the air modes mediated by the compliance of the plates.  Introducing a 1/4 wave resonator gives you more than one resonance to spice things up. There are f, 3f, 5f resonance peaks plus 2f, 4f, 6f antiresonance peaks. All sorts of potentials there.

There's some discussion of this in the CAS paper Mr. Kasprzyk attached above :

'Jansson (1973) reported on the higher
air modes of violins. His paper showed
the nodes of the first seven higher air
modes. The same air mode system will
presumably exist in violas. Examina-
tion of Jansson's Figure 3 shows how
the higher air modes can be tuned using
method similar to the above methods
for tuning the Al mode. For a start,
since modes 3 and 5 have nodes at posi-
tions X and Y of Figure 1 [these are points on the centerline  near the lower and upper blocks respectively], it is clear that these modes will be affected by the cavities used to tune the Al mode. ...etc.'

I respect Mr. Noon's insight and experience -it may be that there are no other audible effects up the scale despite an expectation of real physical effects based on general principles or theory - and in light of claims and open questions I still contend both that a well-designed experiment is needed to settle some of these issues, and that there are some significant difficulties in experimental design.  Also, it would be interesting to add a mass to a test article equivalent to the mass and dimension of the resonator to identify effects other than those of the resonant cavity per se.

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2 hours ago, Dr. Mark said:

...etc.'

I respect Mr. Noon's insight and experience -it may be that there are no other audible effects up the scale despite an expectation of real physical effects based on general principles or theory - and in light of claims and open questions I still contend both that a well-designed experiment is needed to settle some of these issues, and that there are some significant difficulties in experimental design.  

 

I respect everyone's experience but I believe that Evan's observations are most relevant here.

 

Quoting Evan Smith:

"These were done one at a time for comparisons with the remaining instruments.

Previously they had been played a lot to compare and get used to the sound. After the bottle was installed there was an immediate and audible difference. The sound became much clearer, the notes had a distinctive clarity and edge to them, not so fuzzy and veiled, it sounded larger, it was quicker more open and transparent. It definitely changed the sound, and all for the better.

The A-0 did not move at all, but now the A-1 was found just above the f-holes, along with a series of harmonics. It made the A-0 audible and the viola sounded much larger.

The other two were done, one at a time, and the results were the same."

 

 

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