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Manufactures choice of strings on a guitar
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tri7/5
Posts: 570
Joined: May 5 2012
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 RE: Manufactures choice of strings ... (in reply to Tom Blackshear)
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quote:
ORIGINAL: Tom Blackshear
quote:
Probably if they put D'Addario Classic strings, i prob couldn't tell the difference. :)
Many factory guitar manufactures today do some sort of fine tuning on their guitars, since I began talking about it 46 years ago.
Spanish makers have been doing fine tuning for over a hundred years, and then left off for awhile, but took it back up when more knowledge was shared on the Internet.
Then factories started feeling pushed to add their share in it, due to being challenged to provide the best of guitar tone.
https://tomblackshearguitarbuilder.weebly.com/spanish-sound.html
You really think the large shop built flamenco/classicals in the Cordoba, Ramirez (not the custom shop), Alvarez, Saez etc. lines are really sitting there tuning their guitar tops by hand for a budget friendly guitar which is their primary market? Highly doubtful. I doubt even the small Valencia shops get into it i.e. Sanchis Lopez, Gravina, Atocha.
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Date Jun. 6 2020 23:48:50
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TonyGonzales84
Posts: 78
Joined: Apr. 23 2020
From: San Diego, CA
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RE: Manufactures choice of strings ... (in reply to cube_monkey)
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Good points, all, and much food for thought. Konstantin is correct with his 3.7% higher tension number for, as Tom and orsonw point out, a system consisting of a vibrating string attached to perfectly rigid supports at both ends. I will sketch some stuff, run a few numbers after digging around the internet for any applicable data on relative stiffnesses of the bridge and of the head, then get back to this. I'm guessing I'll end up needing to look at ranges of relative stiffnesses. I'm also guessing that whatever I can provide will best be discussed as a separate post, seeing as how it appears we've run far afield, relative to the OP's original question!
Echi and JasonM, I'm trying to wrap my head around your good, experience-based points. If I perform a thought experiment where I take a very short string, say a ukelele (on-line I can find a Pepe Romero at 432 mm), and compare how hard it feels compared to a very long string, say a 670 mm scale flamenca, I can't imagine the ukelele ever feeling harder than the flamenca, with both individual strings tuned to identical pitches. Granted, these are two extremes that I wouldn't expect anyone to compare playability on, but they do show where my mind is at. Of course the relative rotational stiffnesses of the respective bridges likely play a big part in this.
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Tony
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Date Jun. 8 2020 23:49:31
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kitarist
Posts: 1715
Joined: Dec. 4 2012
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RE: Manufactures choice of strings ... (in reply to Echi)
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quote:
yet at the same time you may feel a less stiff string under your fingers wit a longer scale;
But TonyG told us how it feels already - that the longer scale with the same strings feels as harder tension - I assume being plucked at the same place relative to the bridge. This is the opposite of what you say he may feel.
What you refer to can be more to do with changing other parameters like distance from bridge or different string material or even different bending stiffness from bulk stiffness.
As for Mimmo, you might be remembering his great point that the true tension after a string has stretched and stabilized is not what the label tension shows. Manufacturers provide the theoretical tension based on manufactured string thickness. On the label it usually looks like high-E string for example, and maybe B string, have quite a higher tension than the rest. But since the trebles and especially high-E is the string that stretches out the most before it stabilizes, the actual stable tension as strung on the guitar is less than on the package because the stable stretched-out string diameter is smaller. So in fact the stabilized tension profile across strings 1-6 is more uniform than it appears on the package. And this might be why the tension profile of unstretched strings was designed the way it was.
@TonyG84: Just a word of caution that the 3.7%, while estimated from an idealized model of the actual system, is a tension difference, not an absolute value. When you look for the effect on tension of adding more real features to the system, it is not likely(*) that the tension difference from adding that would change the 3.7% significantly (i.e. it will modify the actual tensions for both cases, but not likely the estimated tension difference).
(*)For example, 3.7% is the difference in tension, on the same guitar and the same strings, of raising or lowering the pitch by just 1/3 of a semitone. Which makes me skeptical, though open to proof otherwise, that it would make non-trivial change to the tension difference in the different-scales scenario.
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Konstantin
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Date Jun. 9 2020 1:33:48
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TonyGonzales84
Posts: 78
Joined: Apr. 23 2020
From: San Diego, CA
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RE: Manufactures choice of strings ... (in reply to cube_monkey)
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My apologies for the while it’s taken me to do this. I dug around a bit suspecting strongly that in the end I’d end up where I am, namely, the classical expression for the fundamental frequency of a stretched string is as good as I’ll be able to estimate the difference in required tensions at different scale lengths. Konstantin correctly stated this as 3.7% for a 662 mm scale vs a 650 scale guitar. I am including my results here, and not starting a new thread, because I do not wish to over-sell null results, often the yield of “research.”
This originally started with my comment on the relative perceived hardness of EJ-46 strings on a 662 mm scale guitar vs that on a different luthier’s 650 mm scale guitar. I believe it’s given that 1) Tom Blackshear is correct in stating that, the top’s torque response to the strings’ applied loads is the biggest driver in the perceived hardness (the important apples to apples requirement), and that 2) Konstantin correctly states the 3.7 % numerical value for the string tension difference resulting from the classically derived result for a stretched string’s fundamental frequency, and finally, 3) orsonw is correct that the vibrating system has to include the entire guitar. I also believe orsonw’s science philosophy comment, that guitars are secretive where revealing themselves to “reductionist measurement,” is probably currently true, for the method of attack I tried on the problem.
I am including a two page summary, scanned as pdf, of the results I obtained, that I would view as a sidebar or appendix, to be read only if it interests you, and with my apologies for my handwriting!
My hope had been that I could find some quantification of the guitar’s effective mass and stiffness, that I could then incorporate in my glorified back-of-the-envelope analysis, but I found nothing like that (probably because no one’s needed to set up a test lab to measure said quantities!). I did find a (surprisingly to me) large number of finite element modeling of various types of guitars – classical, steel-string, carbon construction, etc, performed at various universities, world wide. These tend to focus on frequency response analyses, showing mode shapes and deformations. I did not know there is so much work being done here!
Echi, I would be very interested in seeing design guide formulae used by various luthiers, especially if they are of similar form at the different shops. I do understand that these are the types of guidelines that would be closely held and guarded.
 Attachment (2)
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Tony
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Date Jun. 25 2020 0:25:44
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Richard Jernigan
Posts: 3430
Joined: Jan. 20 2004
From: Austin, Texas USA
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RE: Manufactures choice of strings ... (in reply to kitarist)
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I add some anecdotal empirical info. As Tom Blackshear recommends I use high tension D'Addario EJ-46s on two guitars he made, #325 (April 2016) and #329. The label is on #329 is dated 2/12/2019, but I first saw and heard it on 11/10/2019. I think Tom had done some fine tuning on it until nearly that time.
The guitars are quite different. #325 is a cedar/Indian "Rodriguez" model. Tom described it as a classical guitar, and I agree. #329 is a spruce/Indian "1987 Reyes" model flamenca negra.
Both are powerful and brilliant. #325 has more sustain, slightly stronger basses. While the trebles are brilliant, they are less brilliant than #329, with a fuller, more classical sound. Sounding one string on #325 excites a strong sympathetic resonance with one or more other strings, while this effect is not particularly noticeable on #329.
The setups are slightly different. #325 is 2.4mm on the 6th, 1.4mm on the 1st at the 12th fret (capo on I). #329 is a very low 1.7mm on both 6th and 1st. #325 doesn't buzz playing classical, the basses on #329 can be made to buzz, but are quite practical for classical playing.
The scale lengths are the same. Despite the very slightly higher trebles of #329, D'Addario EJ-46s have a slightly softer pulsacion than the same strings on #325.
I use medium tension D'Addario EJ-45s on two classicals: a spruce/Brazilian 2006 Abel Garcia, and Jose Romanillos #407, a 1973 spruce/Indian. They are set up at about 4mm on the 6th, 2.5mm on the 1st. The Garcia feels harder on the left hand, softer on the right than Tom's guitars. The Romanillos feels stiffer for both hands, but played just right it pours out beautiful tone and great tonal variety.
Ricardo's son recorded him playing the Arcangel on a cellphone, in an acoustically dead hotel room--thick carpet, drapes, bedclothes, upholstered furniture. Despite having played the guitar myself for nearly 20 years, I doubt that I would have recognized it by the sound of the recording, though Ricardo made it sound great.
RNJ
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Date Jul. 7 2020 22:46:55
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TonyGonzales84
Posts: 78
Joined: Apr. 23 2020
From: San Diego, CA
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RE: Manufactures choice of strings ... (in reply to cube_monkey)
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Konstantin,
Thanks for your reply. Yeah, this is one of the many idealizations I considered in attacking the problem, but in the end, the one that I showed in the summary pdf, I chose because of its relative simplicity, i.e., the non-string part of the guitar I modeled as one equivalent mass-spring system. I could not find any publicly available, online quantification of any part of the guitar's masses or spring rates (understandably, again, because no one's ever required such values). Relative to the one I finally performed, the main difference in a Rayleigh-Ritz analysis using an idealization such as that in your post, would be the inclusion of the respective additional springs and masses in the quotient's respective numerator and denominator.
I settled on a Rayleigh-Ritz attack because I was only interested in the frequencies, and not in the mode shapes, which won't be representative (I hesitate to say "correct") with any form of lumped-mass modeling (meaning, one will never be able to compare lumped-mass analyses with, say, Chladni diagrams, which should be possible with the finite element analyses I did find online).
The Rayleigh-Ritz plan of attack removes the necessity of taking on the full equations of motion, solving the full eigenproblem, finally obtaining the frequencies. Given that I was only searching for the forms of expression of the string length versus string tension, a Rayleigh-Ritz attack should yield the correct form, because the resulting somewhat high leading quantity (guaranteed in this type of analysis) will algebraically cancel out in the comparison of one scale length versus any other scale length. Again, I was interested in the string length-tension expression incorporating the effects of the non-string guitar -- including the air in the body, etc.
This is a very interesting problem that, over time, will lead to many brain farts. I've even wondered if it would be of any value to run a matrix analysis including discretizing a guitar top, etc...but I doubt I'll be "looking for something to do" to that extent... 
Cheers!
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Tony
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Date Jul. 7 2020 23:49:44
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TonyGonzales84
Posts: 78
Joined: Apr. 23 2020
From: San Diego, CA
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RE: Manufactures choice of strings ... (in reply to cube_monkey)
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Thanks for the info, Richard. I downloaded, and quickly (!!!) glanced at Mr. Carruth's 17 page pdf, seeing PSD looking plots, etc (welcome to Fourier Transform world in order to back out data in time space -- more online searching for data eating software). I'll now skim his note to see what kinds of data I might glean from it.
I will also dig around for publicly available FEA software. It'd be easier than setting up a hand-run matrix structural analysis model, and have much more rapid turnaround time in running what ifs. Basically, my nebulous thinking runs along the lines of modeling a stiffened top, with some sort of Boundary Condition(s) (BCs) along the joint of the top-to-sides. I would use orthotropic elements for the top and everything "stiffening" the top.
Anything I have to report or ask I will do here. I will start a new thread so as not to completely hijack the OP's. Please feel free to add any inputs, suggestions, ridicule... 
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Tony
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Date Jul. 8 2020 5:54:59
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