Giuliano Nicoletti
Forum Replies Created
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Hello Robert,
I never been able to get consistent results from deflection measurements, and the dynamic test works so well, and easily. The only situation where you need to use a deflection test is when your samples are not of a regular shape. But then you cannot measure the damping, as I do with my TPC system.
Why this question, if I can ask?
Cheers,
Giuliano
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Hello Neil,
What you describe looks like a classic wolf note, caused by the interaction between the soundboard’s primary resonance (the monopole, around 164 Hz) and the fretted note, E3, at 164.8 Hz. And yes, when the mobility of the soundboard is high at that frequency, you can hear a buzzing noise, and it can be quite nasty.
However, this type of problem is not typically covered by a warranty, so the reply from Gibson is understandable.
Fortunately, reducing the wolf note is feasible. You could try reducing stiffness by scalloping the bracing (specifically, the two lower V-braces). Alternatively, you could increase mass by switching from plastic to bone pins or by gluing a small weight of 3–5 grams under the bridge. (In the latter case, you can easily test this by temporarily taping the weight to the outside of the bridge to avoid damaging the finish.)
Keep in mind that both of these methods will also slightly lower the frequency of the soundboard’s first mode.
If you want to explore the relationship between these primary modes, there’s software available for free download here: https://www.iuliusguitars.com/my-research/
I would also suggest using REW (Room EQ Wizard) to take frequency response measurements. Investigating wolf notes requires precision, and REW is an excellent and free tool for the job.
Cheers,
Giuliano
iuliusguitars.com
Explore luthier Giuliano Nicoletti's research into guitar acoustics. Download technical papers and innovative studies from Iulius Guitars and others.
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Already a lot of info there, what a great group!
I can add the link to my book, that will give a nice overview:
Cheers,
Giuliano
a.co
Mastering the sound of the acoustic guitar: Nicoletti, Giuliano: 9791041512539: Amazon.com: Books
Mastering the sound of the acoustic guitar [Nicoletti, Giuliano] on Amazon.com. *FREE* shipping on qualifying offers. Mastering the sound of the acoustic guitar
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Hello Jorge,
The behaviour of your guitar is normal, in Martin X braced guitars with the two asymmetric tonebars the two dipoles are very close in frequency around 350 Hertz, with the long dipole being usually the first to appear. If you’re interested, I had a talk on the group on this matter last weekend, it should be out soon…
Cheers,
Giuliano
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I agree with everything that has been said; there will be a difference, because there is always a difference, but of secondary vibroacoustic importance; usually you choose the best looking combination, that is generally accepted with tighter grains at the center.
Cheers,
Giuliano
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Great Max, thank you!
Giuliano
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Hi there,
In this thread:
https://dev.loothgroup.com/groups/new-builds/forum/topic/community-spread-sheet/
You will find a spreadsheet that comprises the formula to predict the top thickness, together with other features, in the PlatesPar tab. Of course you need to measure the main parameters of tonewood samples.
Cheers,
Giuliano
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Yes, the actual second revision of the book is sold-out; but I know that Trevor is working on a third revision, that should be coming soon…
Cheers,
Giuliano
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Hi everybody,
I found the time to add a first tab to the excel sheet, for general parameters of the instrument; the xls file is ready, where can I pin it?
Cheers,
Giuliano
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Hello!
I would say that between 10 and 15deg of headstock angle there won’t be any tonal difference. But as Anthony pointed out, with a different break-up angle you will change the orthogonal force exerted on the nut, therefore :
– the feeling of the string stiffness
– the smoothness of tuning
– the tendency to rub&buzz on the fret slots
I never made a direct comparison or an experimental check of this parameter, to assess the actual difference and impact. I use a 14deg angle on acoustic guitars, little less for classical one, and I am satisfied with the results. I cannot see how one could use this parameter to tweak the performances of a guitar, but I can be wrong on this one…
Cheers,
Giuliano
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Hi Paul,
Of course you can adapt the value of vibrational stiffness to your building style, or different types of sides. Generally speaking, it is mostly the density that’s affecting the decoupling of soundboard from sides; stiffness of sides is just shifting frequencies (of sides resonances), but not changing the boundary conditions of the soundboard. Keeping in mind that most probably the laminated sides are denser and heavier than traditional ones. That said, I suggest to try to measure these values and avoid comparing situations that are too different (classical and selmer styles guitars) without having solid references; it might be misleading. I hope this might be of any help.
Cheers,
Giuliano
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Hello everyone,
I see that already several of us are using the same software, and that’s a great facilitation for sharing data; I am just adding a quick reminder of guidelines for sharing graphs, to make more simple to read and compare curves;
– always use a log frq axis
– set limits to: 45-95 dB, 60-1500 Hz
– export the picture at 810 pixel, write details on the comment field
I know that at the beginning this procedure might seem boring and pretentious, but then again having beautifully formatted curves to compare will quickly pay back, trust me!
Here an example, and thanks for tolerating my obsessiveness (I am getting older…). 😇
Cheers,
Giuliano
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Hi Jonathan,
Sorry for the late reply, a very busy period. Sharing measurements is for sure one of the purposes of this space, I love to see that there’s already a lot of interest on the matter, let’s keep on rocking!
Cheers,
Giuliano
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hello Robbert,
Yes, a dynamic test, as described in the book, is performed through an impulse that excites in vibration the sample; acquired signal is then processed to get the mechanical parameters.
A deflection jig, at least part of it, can be used to measure the mobility of the monopole of soundboard and back.
Cheers,
Giuliano
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Hello Neil,
as you rightly pointed out, they are all in reasonable range for the species, but do not perfectly correlate (at least, not all of them). In my experience, the deflection method is is not very reliable, while the opposite is true for a dynamic test.
Did you try to repeat both test on the same sample to check dispersion?
Cheers,
Giuliano
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It’s a pleasure Jorge, dont hesitate if you need more help!
Cheers,
Giuliano
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Hello everyone
It’s a great idea Anthony; I would say that we can keep the DevTools sheet, and design together a generic acoustic guitar SpekSheet, that we can use to build a shared database.
If it’s OK with you guys I can propose a first draft of the SpekSheet;
Cheers,
Giuliano
