I have always found this to be fascinating. But I have one question: How would one do this on an arched top or back? I see all these Chladni patterns on violin tops but I can't figure out how the medium stays on the arched plates. Doesn't gravity have anything to say about this? There is some rather serious angling going on in a violin top, how do they keep it from just falling down to the rim of the plate? I have never understood this. And that's annoying, I have several arched tops that I would like to do this on, but can't figure out quite how. Any suggestions?
I'd imagine it would depend on the type of material you use. I believe Cladni used iron filings, which may be rough enough to stick to sloped surfaces until vibrated off. I've tried several things that bounced right off a flat topped guitar. Thus my preference for course ground pepper. I'm guessing you'd have to ask a violin maker.
I don't know what it's ouput is. I did use a kill-a-watt meter (on the input) and at the highest volume it drew ~75 watts for the loudest frequency. I never use it at full volume. I set it about 1/2 way, although I don't know if it's linear or logarithmic.
I'm trying to understand why the nodes at resonance are some distance away from the sides of the body. I would've expected that there would be zero displacement (=node) where the top meets the sides. Any insight? (or perhaps my expectation was wrong?)
It is a bit odd on this particular instrument. I'm pretty sure that this is a result of the way I "squeezed" the X brace so that it is narrower than the standard angle. I also only used one finger brace on each side of the X. I have not seen the node line extend to where the top meets the sides on the fundamental frequency(s). It is usually 12-25 mm in from the sides, although that can very depending on the powder used and the amplitude and/or placement of the driver.The secondary harmonic that divides the top in two longitudinally usually gets much closer to the sides.
I use a frequency generator built by Don Bradley, who is unfortunately no longer with us. If you have a way to amplify sound from your phone to a speaker, check out the luthierlab app. It has a lot of great functionality including a frequency generator.
Cool stuff. I will eventually get into this as I progress, I suppose.
I have always found this to be fascinating. But I have one question: How would one do this on an arched top or back? I see all these Chladni patterns on violin tops but I can't figure out how the medium stays on the arched plates. Doesn't gravity have anything to say about this? There is some rather serious angling going on in a violin top, how do they keep it from just falling down to the rim of the plate? I have never understood this. And that's annoying, I have several arched tops that I would like to do this on, but can't figure out quite how. Any suggestions?
I'd imagine it would depend on the type of material you use. I believe Cladni used iron filings, which may be rough enough to stick to sloped surfaces until vibrated off. I've tried several things that bounced right off a flat topped guitar. Thus my preference for course ground pepper. I'm guessing you'd have to ask a violin maker.
Very interesting to see a monopole shape at such low freqs…
I've made guitars that show monopole, long and cross dipoles below 100 Hz as well. Those aren't showing here on this redwood top.
What is the power of you frequency generator set-up? Love you videos.
I don't know what it's ouput is. I did use a kill-a-watt meter (on the input) and at the highest volume it drew ~75 watts for the loudest frequency. I never use it at full volume. I set it about 1/2 way, although I don't know if it's linear or logarithmic.
I'm trying to understand why the nodes at resonance are some distance away from the sides of the body. I would've expected that there would be zero displacement (=node) where the top meets the sides. Any insight? (or perhaps my expectation was wrong?)
It is a bit odd on this particular instrument. I'm pretty sure that this is a result of the way I "squeezed" the X brace so that it is narrower than the standard angle. I also only used one finger brace on each side of the X.
I have not seen the node line extend to where the top meets the sides on the fundamental frequency(s). It is usually 12-25 mm in from the sides, although that can very depending on the powder used and the amplitude and/or placement of the driver.The secondary harmonic that divides the top in two longitudinally usually gets much closer to the sides.
What model frequency generator do you have in this video?
I recently decided to start testing my builds
I use a frequency generator built by Don Bradley, who is unfortunately no longer with us. If you have a way to amplify sound from your phone to a speaker, check out the luthierlab app. It has a lot of great functionality including a frequency generator.