(minimal) Set up for Chladni patterns

[Riccardo964]

Hello again,

I am curious to know your opinion about a minimum (and cheap) setup for testing the Chladni sound resonances (mode 5 and 2) in the violin I'm working.

Just out of curiosity, as I've noticed some different opinions on the matter (mostly from this old (2011) MaestroNet post).

It is not my intention to "fix" or "improve" anything - just curiosity.

I also read that a "small audio transducer (or a modified 3-inch speaker)" would work - so, technically speaking, for the maestro luthiers having such set ups, could you please disclose what you have?

Also on the Internets, there's mention to acquire a "small, punchy Bluetooth speaker."

I'm planning to use the Audacity app on the phone to generate the patterns.

 

Thanks in advance!

Riccardo964

[lorenzo fossati]

 You need:

-signal generator (not sure if audacity can generate a signal that can be modulated with a knob, which is very handy when it comes to sweep the frequency till the plate vibrates and pattern reveals); if the signal generator does not have a frequency display, you need to split the signal from it and send to a tester, so you know your freq (a lafayette multimeter has the option)

-amplifier (small 100w chinese ones work fine)

-speaker (I think 30w is enough, check impedence to match the one of the amp)

[Riccardo964]

Just now, lorenzo fossati said:

 You need:

-signal generator (not sure if audacity can generate a signal that can be modulated with a knob, which is very handy when it comes to sweep the frequency till the plate vibrates and pattern reveals); if the signal generator does not have a frequency display, you need to split the signal from it and send to a tester, so you know your freq (a lafayette multimeter has the option)

-amplifier (small 100w chinese ones work fine)

-speaker (I think 30w is enough, check impedence to match the one of the amp)

Thank you - I was trying to "make this work" with a cheap "bluetooth" speaker, to use it later as a radio/mp3 station  - I guess I'd still need the amplifier to make this work. Do you know any DIY schematics for this I could use?
I first saw this on this video: https://youtu.be/prkD9CBaRBY?t=862 - he shows/explains the modes, and how to use audacity to capture/analyse and then work on the Chladni patterns.

Thank you in advance,

Riccardo964

[lorenzo fossati]

26 minutes ago, Riccardo964 said:

Thank you - I was trying to "make this work" with a cheap "bluetooth" speaker, to use it later as a radio/mp3 station  - I guess I'd still need the amplifier to make this work. Do you know any DIY schematics for this I could use?
I first saw this on this video: https://youtu.be/prkD9CBaRBY?t=862 - he shows/explains the modes, and how to use audacity to capture/analyse and then work on the Chladni patterns.

Thank you in advance,

Riccardo964

I think his method works, but it is very time consuming to check the peaks each time before setting a frequency that eventually does not exactly match, just use a signal generator with 2 nice knobs: one for the rough sweep, and one for the fine tuning of the freq, then the method is the same, you just turn the knob "in the frequencies range" of the mode you try to reveal, and when the pattern starts to form, everything vibrates boldly, so you lower the volume output, and fine tune the freq where the plate vibrates the most, and that's what I consider the correct measure for the mode, quicker approach

this is the amp I have, works great, some time ago I thought it broke, so I bought another one, same model, but eventually I found out it was not the amp, but the speaker, the culprit, so I used a celestion 8 inches guitar speaker in place of the 4 inches that burnt (a monicor that was not supposed to break, but I suppose the small tea particles used in plate tuning make speakers prone to damage), it works best with 8 than with 4 inches, in my opinion, but as with the amp, going cheap is not an issue, just be sure to match the impedences

https://www.amazon.it/dp/B0753DQVK7

[Davide Sora]

1 hour ago, Riccardo964 said:

Thank you - I was trying to "make this work" with a cheap "bluetooth" speaker, to use it later as a radio/mp3 station  - I guess I'd still need the amplifier to make this work. Do you know any DIY schematics for this I could use?
I first saw this on this video: https://youtu.be/prkD9CBaRBY?t=862 - he shows/explains the modes, and how to use audacity to capture/analyse and then work on the Chladni patterns.

Thank you in advance,

Riccardo964

If your speakers are active (amplified) and powerful enough, you may not need anything else. The system of first detecting the mode frequency and setting the tone generator based on it works, although, as Lorenzo says, it's more time-consuming. But if you're just playing around with Chladni patterns, which is useful for differentiating the modes you hear and optimizing the grip and listening points for each mode, I wouldn't recommend spending too much money on these kinds of things.

When I was doing this (many years ago), I used a chromatic analog tuner as my tone generator, and a guitar amplifier I already owned (a Marshall 50W). However, the two 12" speakers that the Marshall was equipped with were too big and could not be directed to a precise point, so I had to build an external speaker with a chipboard panel on which I placed the plates supported on four foam blocks. You need to place the speaker in a motion area of the mode you are testing (anti-nodal area) and place the four foam blocks on the outline at the nodal lines of that mode.

I used this setup when I first started making cellos, because correctly identifying which modes you're hearing isn't as easy as with violins or violas, and identifying them via the nodal lines helped me avoid misunderstandings. Otherwise, it's not very useful.

[Don Noon]

7 hours ago, lorenzo fossati said:

 You need:

- Earplugs.  And deaf neighbors.

I made a testing table several years ago with a 3" speaker I salvaged from somewhere, and the 20W amp I was using for my shop stereo.  And a free tone generator app (there are several) on my phone.  It was sufficient to get rough patterns of the major plate modes, but for more clarity I think you'd want more power.

Totally pointless, IMO, but if you must...

[lorenzo fossati]

10 minutes ago, Don Noon said:

- Earplugs.  And deaf neighbors.

I made a testing table several years ago with a 3" speaker I salvaged from somewhere, and the 20W amp I was using for my shop stereo.  And a free tone generator app (there are several) on my phone.  It was sufficient to get rough patterns of the major plate modes, but for more clarity I think you'd want more power.

Totally pointless, IMO, but if you must...

 very good ear covers are mandatory, as well as get to get rid of your neighbours

probably 30w amplifier is enough even for a cello, I am more picky on the ease of use of a nice vintage signal generator, especially when come the times (sometimes happens, not too often luckily) that I decide to do "session testing", so i make a grid of like 14x6 on the plate, and start compulsively removing as low as 0.15 grams of wood, and measure the modes variations, for each single square, even if I know that accuracy with such small amounts, goes to hell, the big knobs of the generator comes handy

[Riccardo964]

2 hours ago, Don Noon said:

Totally pointless

I'm almost giving this up entirely, really, as it seems the gains are minimum, to say the least.

8 hours ago, Davide Sora said:

I wouldn't recommend spending too much money on these kinds of things.

Yes - I am verging towards this idea of not wasting money altogether.

 

All in all, thank you all for the answers!!!

Cheerios,

Riccardo964

[Marty Kasprzyk]

I used to weigh myself often but I never lost any weight so I my scale was a waste of money.

[Don Noon]

1 hour ago, Marty Kasprzyk said:

I used to weigh myself often but I never lost any weight so I my scale was a waste of money.

But if you didn't have the scale, you'd never know if you were losing or gaining weight.

[Riccardo964]

5 hours ago, Marty Kasprzyk said:

I used to weigh myself often but I never lost any weight so I my scale was a waste of money.

 you're certainly right - in this analogy, knowing "I'm fat" and not being able to change it (shave here and there on sweets and colas) because I don't know how, would invariably result in the same outcome: "I'm fat" (I sound bad).

Riccardo964

[Edward Byler]

Recently my tone generator quit working. It was an old amp and speaker hooked to a sweep tone generator for tuning radios. I needed something to just finish the plates I was making and this worked ok though the app on my phone is not a sweep tone generator and a bit unhandy. I often only listen with my ear to hear the tone but want to verify that it is truly Mode 5 or 2 because there are others that one can confuse. After confirming that,yes, it is the mode 5 shape I continue by ear. I’m glad to hear Davide Sora believes at least a bit in tap tones.  I take a compromise between weight, tap tone of mode 5, and the thickness. It doesn’t probably do more than make my plates more consistent from one violin to the next giving me similar results. 

 

[Don Noon]

50 minutes ago, Edward Byler said:

I’m glad to hear Davide Sora believes at least a bit in tap tones.  I take a compromise between weight, tap tone of mode 5, and the thickness. It doesn’t probably do more than make my plates more consistent from one violin to the next giving me similar results. 

It is OK to believe in taptones... but another thing to worship them 

I too take into consideration weight, M5, and thickness in deciding where to stop.  With wood that's different (they all are, to some degree), you can't make everything the same.  At least we can hope for something still good, even though not the same as last time.  Or maybe it will be better; you never know.

[Riccardo964]

@Edward Byler: this is more or less what I meant in the original post, a very simple set up: a cardbox, a bluetooth device, a phone app, and that's it, just for fun. Thank you!

10 minutes ago, Don Noon said:

It is OK to believe in taptones... but another thing to worship them 

 the list of worshipping keeps becoming bigger and bigger then:

• the use of sandpaper and the sanctity of not using;
• "best sharpening" opinions;
• use of machinery in violin making;
• no experimentation on new things;
• shaving 0.1mm here and there and expect any change;
• the weight of each plate within 0.1g (give or take) from the masters;

and now,

• tap tones using one's ear;

I'm sure I'm forgetting a lot of things in the list though.

Cheerios!

Riccardo964

[Jay Higgs]

On 7/6/2026 at 11:45 PM, Riccardo964 said:

the list of worshipping keeps becoming bigger and bigger then:

As a retired hobby maker, I can afford the time to enjoy getting side-tracked by the many issues you list. I had a lot of fun learning Chladni patterns of my first and only cello and comparing those with tap tones.  A friend with a guitar speaker and green glitter helped me set up.  Online tone generators are available for the computer.  Audacity was great for tap tones and body resonances.  I kept records of it all.  I didn't use any of that to modify my cello, but it turned out to (?accidentally) have a good tone, so if I do make another one I will probably use these tools compare the new to the old.  You can see and hear that cello in the white in the contemporary makers' gallery.

 

[Riccardo964]

14 hours ago, Jay Higgs said:

As a retired hobby maker, I can afford the time to enjoy getting side-tracked by the many issues you list.

Yes, that's my general feel about all this.

Each part of the process brings new challenges, and new things to ponder, etc. I find it an almost perfect hobby, despite the blisters, the mistakes, and it all. It's very gratifying indeed.

I "was" satisfied with my 145g for the back plate, until I learned (using a very simplistic setup for the chladni patterns) that unless I remove about 30g in material (give or take), I won't resonate well in the "right frequencies", which then led me to rethink the whole approach, which is nice.

Thanks for sharing your setup, I'm working on a similar one (with a simpler amplifier though).

Question: do you think anything would change if instead of wood (below the plate) you used something 'softer' like foam/etc?

Best,

Riccardo964

[Don Noon]

2 minutes ago, Riccardo964 said:

I "was" satisfied with my 145g for the back plate, until I learned (using a very simplistic setup for the chladni patterns) that unless I remove about 30g in material (give or take), I won't resonate well in the "right frequencies", which then led me to rethink the whole approach, which is nice.

You don't need chladni patterns to tell you that.  

[Riccardo964]

5 minutes ago, Don Noon said:

You don't need chladni patterns to tell you that.  

(  sadly, I know... ) I was just thinking "it was done"  

At least now I own a bluetooth speaker to put in the shop - wife's not happy with yet another useless expense

Best,

Riccardo964

[Davide Sora]

3 hours ago, Riccardo964 said:

I "was" satisfied with my 145g for the back plate, until I learned (using a very simplistic setup for the chladni patterns) that unless I remove about 30g in material (give or take), I won't resonate well in the "right frequencies", which then led me to rethink the whole approach, which is nice.

Question: do you think anything would change if instead of wood (below the plate) you used something 'softer' like foam/etc?

Using four foam blocks to be placed at the nodal lines should be the correct method, so as not to create constraints and leave the plate free to vibrate. But I don't know how much of a difference it makes if you use other materials (like wood), and with the higher mass cello plate, the difference could be smaller. But an elastic support seems the most appropriate; the most technologically advanced people who do modal analysis today use an elastic net to support the plate, without having to change the position of the four blocks depending on the mode being visualized.

A vague utility of Chladni patterns is that when the plate is very stiff, the nodal lines are thick (wide), indicating a smaller active surface area. As flexibility increases, the mode lines become thinner and better defined, and the active areas become larger. This might seem very useful, but in reality, it's a rather rough guideline that can be obtained even without this system. Furthermore, thin nodal lines don't guarantee an accurate thickness distribution, so they can be misleading.

[Jay Higgs]

On 7/9/2026 at 12:12 AM, Riccardo964 said:

Question: do you think anything would change if instead of wood (below the plate) you used something 'softer' like foam/etc?

Yes, we did have foam supporting the plate, not visible in my pic.  

[Marty Kasprzyk]

On 7/9/2026 at 5:11 AM, Davide Sora said:

Using four foam blocks to be placed at the nodal lines should be the correct method, so as not to create constraints and leave the plate free to vibrate. But I don't know how much of a difference it makes if you use other materials (like wood), and with the higher mass cello plate, the difference could be smaller. But an elastic support seems the most appropriate; the most technologically advanced people who do modal analysis today use an elastic net to support the plate, without having to change the position of the four blocks depending on the mode being visualized.

A vague utility of Chladni patterns is that when the plate is very stiff, the nodal lines are thick (wide), indicating a smaller active surface area. As flexibility increases, the mode lines become thinner and better defined, and the active areas become larger. This might seem very useful, but in reality, it's a rather rough guideline that can be obtained even without this system. Furthermore, thin nodal lines don't guarantee an accurate thickness distribution, so they can be misleading.

The late Robert Spear used to claim sharp and narrow node node lines was important.

He also thought achieving a high bounce height of his glitter particles at an antinode was important because it was indicated the plate was vibrating a lot which produced more sound output.

The sharp node lines and high glitter bounce happened at the same time.

Spear thinned his plates to get a high glitter bounce rather than hitting any particular mode frequency targets.

When some people do tap tests to determine mode frequencies they fail to notice the loudness of the tap sound is important.

 

[Don Noon]

45 minutes ago, Marty Kasprzyk said:

When some people do tap tests to determine mode frequencies they fail to notice the loudness of the tap sound is important.

If you're playing the free plates, maybe so.  

As yet, I see no evidence or logic that this has anything to do with the quality of the assembled instrument... other than perhaps if the plate is waaay to thick, it doesn't vibrate as much.

I would like to see a competition of instruments made with Chladni patterns vs. no Chladni patterns to see if it makes a difference.

[Marty Kasprzyk]

16 minutes ago, Don Noon said:

If you're playing the free plates, maybe so.  

As yet, I see no evidence or logic that this has anything to do with the quality of the assembled instrument... other than perhaps if the plate is waaay to thick, it doesn't vibrate as much.

I would like to see a competition of instruments made with Chladni patterns vs. no Chladni patterns to see if it makes a difference.

Chladni patterns physically exist regardless if they are observed or not.

I tried to lose weight years ago but nothing happened so trying to lose weight is a useless effort for everybody.

 

[Davide Sora]

1 hour ago, Marty Kasprzyk said:

The late Robert Spear used to claim sharp and narrow node node lines was important.

He also thought achieving a high bounce height of his glitter particles at an antinode was important because it was indicated the plate was vibrating a lot which produced more sound output.

The sharp node lines and high glitter bounce happened at the same time.

Spear thinned his plates to get a high glitter bounce rather than hitting any particular mode frequency targets.

When some people do tap tests to determine mode frequencies they fail to notice the loudness of the tap sound is important.

 

With sufficient practice and a trained ear, it's not difficult to make the same assessments. As the plate becomes thinner, you'll clearly feel the increase in volume, and, with your fingers, you'll easily notice that the gripping point gradually becomes more and more localized in smaller areas (along the thinner nodal lines), while precise positioning is less critical at first. It is also easy to understand the path of the nodal lines precisely and, if you want, draw them.

Of course, with the glitter test, even those who don't have a sensitive and trained ear can visually get the same things, which is why I said it's still an interesting (and fun) experience for beginners.

The problem is that, in both cases, you understand when you've reached the maximum amplitude of the vibration when you've already passed it, that is, when you notice that it no longer increases and begins to decrease. In the meantime, you've probably thinned the thicknesses too much. That's why I said it can provide rather rough indications.

[Riccardo964]

48 minutes ago, Marty Kasprzyk said:

I tried to lose weight years ago but nothing happened so trying to lose weight is a useless effort for everybody.

 I love that all your examples are about weighting and measuring one's weight, and so on  keep'em coming, sir. You're not wrong!

36 minutes ago, Davide Sora said:

which is why I said it's still an interesting (and fun) experience for beginners

And at the point I'm currently am (in terms of skills) this is exactly why I did it -  There's fun in the things we do, don't we agree??

Cheers,

Riccardo964