Official Luthiers Forum!

The pictures show my shameless knock-off of StewMac's Body Board. Given the ease of making it, my guess is that many people have done the same thing, long before me. The initial plan was to buy one, but my reservations were that there would be too much movement of the board and the vertical threaded rod. I keep a good selection of wood and plastic sheet goods on hand, so I tried to bend some Baltic birch and plywood 6" and larger widths, and at the 30" mark they did bend for me. And I don't even hang out at the gym. Also, it saved me $143 for less than an hour's work, and I did not have to spend eternity in a big-box lumber store. For me, I need holding fixtures to be rock solid. And, StewMac's might be, I just did not want to try it. As to the threaded rod, my experience has been that using threaded rod in a slot is never as solid as a putting it in a tight-fitting hole. Also, I only build classical guitars, so I don't think a sliding rest is necessary, but I could be back here, tail between my legs with an update.

My fixture is made with 1⅛" sub-floor plywood, 30" long, and 8" wide (which I use for most of my substitute table fixtures), and two ¾" threaded rods, that were left over from a go-bar deck. My base did bend. All I added was a foot (which cured the bending), attached with the threaded bracket used on tables, where the legs are screwed into the underside of the table. A foot (or maybe more accurately, a leg) adds a huge amount of solidity to any hang-off-the-bench fixture like this.

BTW, cutting the 3/4" in threaded rod was a breeze since I got one of those small Chinese horizontal metal band saws on Amazon, for about $160. It cuts through the rod, literally, in seconds. The cut is clean to the point that I don't need to mess with the edge so the nut can be threaded, as is the case (at least for me) when using a hack saw. Like almost anything, once the thing is in the shop, all kinds of tasks are solved by the new thing. I got it initially for cutting metal for side mass loading weights, since it takes lots of trys.

The holes in the StewMac base were unnecessary, because of the proximity to my workbench. The next one will have the following modification: The hole in the middle of the base pushes the vise opening (in my case) to the left. What happens is that the guitar is not centered on the base's center line. I thought the extra 2" would mitigate that issue, but it didn't (I should have measured it first). So the next one will be in the shape of a small "L", by making the area where the vise is attached wider (maybe 12" wide) so the vise can be centered to the board, and the guitar will be centered to everything.

In use, for example, sonic testing of a guitar, I can easily damp the top or back, by loosening the vise and pushing the guitar onto, or off of the pad, which is very convenient. It is solid for cutting binding/purfling slots, hammering, and I've only had it for a week.

Nice. got to make one.
Can I ask what software you are using for the frequency analysis?
And I'm wondering if you notice a difference in response between using the guitar on it's side touching the board and hanging it from your hand by the neck?
I'm new to this and trying to follow Julius Guitar's book, Mastering the sound of the acoustic guitar.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

[quote="Colin Can I ask what software you are using for the frequency analysis?
And I'm wondering if you notice a difference in response between using the guitar on it's side touching the board and hanging it from your hand by the neck?
I'm new to this and trying to follow Julius Guitar's book, Mastering the sound of the acoustic guitar.[/quote]

Hi Colin - Thank you. I'm using Visual Analyzer 9.0.6, which is the one recommended by Trevor Gore. I have my old Dell XP laptop, and with it, I get some features that are lost running it on Win 10.

As to the difference between sideways and pointing up, the I'm not sure because I did not record that pattern and frequency. I drafted a guitar outline, scanned it, and then printed the pdf printing it with 9 on a page function. That is how I record my info. But I was trying all kinds of things with my new toy, and forgot to record it. However, like you, I suspected there would be some difference since the neck has an effect on the guitar. Also, I was only able to play with it for two days, when my function generator died. When I am back in action I want to continue my checking things things out, to make sure I am able to make apples to apples comparisons.

Yesterday, I read somewhere about Julius, or iuliusguitars. Never heard of him before, but I went to his home page; but he seems to be doing amazing things.

I'm also curious about StewMac's body board - whether I'm wrong, and it is truly rock solid. Inquiring minds want to know. Tom

I've tried the Gore Book and VA, but TBH it took me ages and some help from an ANZLF member to sort out a spreadsheet for plate thickness.
He "encourages" you to work stuff out for yourself, spreadsheets, etc etc. I had enough problems understanding the material in the book!
Maybe I have a short attention span (or like my wife says, just ADHD)
Mr Nicolletti supplies QR codes to link to spreadsheets (several) and it includes measuring the SRF (sound radiation Coefficient) and the possibility of measuring damping factor, so I'm in the process of wrapping my head around his book (He's Italian and was helped by AI to write in English)
Also I'm gathering/making equipment for Chandli patterns and possibly Q measurement attempts.
He uses REW software (Room EQ Wizard, which is also free), which seems very powerful, has lots of stuff I'll never use.
I'm still exploring the possibilities.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Yes, I still recommend Visual Analyser 9.0.6. I run it on Win 10 and it still has all the required functionality with greatest simplicity. Instructions on how to set it up are on my website here, (a dowloadable .pdf). There's lots of other helpful information on the ANZ Luthier's Forum, though access has been restricted in some parts of the world due to the hammering it gets from AI bots from those locations.


Indeed. My objective has been to try to bring understanding, rather than quick fixes, so writing your own spreadsheets encourages that and hopefully encourages people to do their own spreadsheets on other guitar related stuff that is of particular interest to them.

Various versions of spreadsheets and similar are available, some just shameless copies of mine that I issue at my Modal Tuning Courses, others offering different formats. However, Robbie O'Brien, Rick Malloy and I are offering a free tool set that eclipses everything currently out there, with brace sizing apps, plate thicknessing calculations, the 4-DOF model and more; all run through graphical interfaces. Working previews of this tool set are available here. Over time, other tools will be added.

At the upcoming Timber to Tunes Modal Tuning Course at La Conner in August we'll be going through the workings of this toolset, but for those who can't make it there, we're doing a live stream next week covering this subject. Keep an eye on the O'Brien Guitars Youtube channel for details of when and how to join the livestream.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Hi Trevor,

My post was reflecting a personal view of using your book, not a criticism, and i have recommended it to many. And I still use it.
My foray into Mr Nicolletti's book was actually after a reluctance to send (even a little) cash to someone who basically advertised on Facebook and who didn't reply when I asked if he had acknowledged your own seminal work in The Book.
I felt it could be theft of the your hard work and not an original.

After learning a bit more about it I decided to buy it, and see how if stood up on it's own feet as it were, and discovered you are indeed acknowledged in his book.
I read it and decided to use the formulas and try the specific equipment he recommends.
One of the wood properties fascinated me, damping and it's measurement, particularly after seeing a YouTube video you were actually had no small input into - "ACOUSTICS for Spruce Tonewood: with Dr. David Olson // Pacific Rim Tonewoods" exploring Q's importance in making guitars.
Very interesting conclusions. And he does suggest ways to measure damping, so I'm exploring that too, especially by logarithmic decrement.

You said -
"My objective has been to try to bring understanding, rather than quick fixes, so writing your own spreadsheets encourages that and hopefully encourages people to do their own spreadsheets on other guitar related stuff that is of particular interest to them"
I do appreciate that, and it spurred me on to do my own spreadsheets, (with a small silly error corrected by an ANZLF member who checked it over for me), and I'm continuing to work on other guitar related stuff that really interests me.

Without any degrees or experience in Acoustics and at the age of 77, I don't think that's bad a bad result for the inspiration you gave me.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I'm pleased you still get inspiration from the books, Colin. I didn't take what you said as criticism, but I did want to explain why, historically, I have encouraged people to write their own spreadsheets. The 4-dof model (for example) is particularly difficult to execute in a spreadsheet and I've tended not to supply one because it is easy to over-rely on the results rather than to see the model as indicative of how things interact. Rick's model (on the Lutherie Academy site) is fun to play with though, but regard it as showing directions to move in rather than giving specific solutions.

Damping is another fascinating parameter. It is very difficult to get truly comparative results between specimens and is something we struggled a lot with. It is also pretty difficult to get definitive results from listening tests, where getting people to select which guitar is made of what damping wood in a statistically significant way is very complex. It needs double blind building, playing and listening to be valid. The playing is a difficult variable to control and recording performances to get a consistent listening experience results in the loss of important time-phase information from the sound. Damping is very much the last frontier, I think. Instrument building has to be at a very high level for it to come into play, and then I suspect the variation of damping with frequency is at least as important as the value of a single damping figure taken at a specific frequency. As for what is the "right" or "best" damping, it largely depends on the type of music you want to play and personal preference. If you haven't heard it already, see if you can pick which guitar was made with hi/med/lo damping top wood from these recordings.

The upcoming Timber to Tunes Modal Tuning Course will be fun, because we will have all the major protagonists there: the Pacific Rim Tonewoods team, David Olson, Miroslav Tadic, Yvette Holzwarth, Robbie O'Brien, Rick Malloy, Michael Gurian and lil ol' me!

Keep on having fun!

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Y seemed to be the lowest damped with the first being the most damped to me but hard to tell, I was too lost in the playing.

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Steve Smith
"Music is what feelings sound like"

Lowest damping I would say Y followed by R, then B as highest.
But then my hearing is not great anyway at my age, and I'm a bit tone deaf anyway, so......
As you say, lowest damping is not necessarily best for different types of guitar/playing, - flamenco/bluegrass/jazz/fingerpicking.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Thanks Colin and Steve for taking the challenge! And yes Steve, it is easy to get lost in Miro's playing.

Before I give the answers, could I prevail on you gentlemen to describe (as well as our admittedly poor acoustical vocabulary allows) what differences you were hearing?

Thanks in anticipation.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

I was trying to listen to the Harmonics.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Like Colin I was listening for more harmonics. No doubt the way my engineer brain understands damping colored my opinion, not sure if that is good or bad. I also wear hearing aids so my ears aren’t that good these days.

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Steve Smith
"Music is what feelings sound like"

My ears are the same, 'cept I don't got no hearings aids....
How'd we do?

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

They all sounded pretty similar to me, I could only guess at which is which, and any variances could also be attributed to other things as well. It’s not like any of them were wildly different than each other, which is what I like about modal tuning.

I don't consider my ears to be particularly good but I'm always happy for a chance to train them to be better so I did the listening. I thought Y had the least damping and R the most. I thought the overtones, while not necessarily more plentiful, rang out longer (sustained) in Y and B. But everybody else thought B had high damping so I'm probably just fooling myself, that I could tell the difference.

Proves how differently ears hear, and sometimes dramatically so! Thanks for the lesson Trevor.

From least dampening to most I hear B - Y - R.

Based on a combination of richness, depth, tone and sustain and everything that plays a part in those. Sustain and richness would be something that follows my order and my ear. To me they all had great tone and depth. I suppose what I call richness could be pleasant overtones w/sustain.

Thanks, Brian

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Brian R, Wood Mechanic
N8ZED

I could perceive differences, but for dampening, I don't have the ability to tell the differences. Ear training would help.
Only certain specific notes sound different to me from sample to sample; "shimmer" and "timbre" are descriptions that come to my mind.
Although I can perceive differences, I can't describe the differences, "tone" wise in amps or electric PUPS either.
I have listened to this trio of guitars on that URL before, in depth.

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Measure Twice,

Karl Borum

In Trevor Gore's response he mentioned that Rick Molloy and he would be participating in my Shop Talk Live stream talking about some modal tuning apps that they developed for the Lutherie Academy. The Live Stream will be this coming Friday, July 24th at 5PM Mountain Time. For those interested, here is the link. https://youtube.com/live/n-xIDzmcOmc It will be viewable on the O'Brien Guitars YouTube channel.

I'm confused, date on the link's page is Jul 25, 2026
Ooops - maybe that's my time in UK.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Will this be available to view after it's live?
Just it's one in the morning here.......

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Yes, it can be watched on the O'Brien Guitars YouTube channel after the live event. The link will be the same.

I tried to eliminate the other possible variables, as far as that can ever be done. The guitar backs, sides, necks etc. were built from sister panels from the same slabs; same density, same elastic constants etc. The main modal frequencies were all matched to better than 0.5 Hz. The tops were made of panels that had very similar density and elastic constants, the only difference being the damping, one being the average for the species, the other two being plus and minus one standard deviation either side of the mean.

I agree with the guys who said they heard the difference mainly in the harmonics present, and that makes good technical sense as damping kills the higher harmonics first.

Thanks to all those who ventured an opinion. The Blue had the highest damping, the Yellow the lowest and the Red was the one with average damping, so damping decreased through the playing order (B, R, Y).

Many of you got this right, even those declaring impaired hearing, which I think demonstrates that hearing these sorts of difference is a learnable skill.

A very different question is "Which do you prefer?" to which there is no right answer and little consistency!

Thanks again, all.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

I remember probably the "best" sounding guitar I have made I liked because the all the natural harmonics (at every position on the fretboard) were louder with longer sustain than I'd seen before.
Gave me a good first impression of Torrefied Sitka Spruce.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

That’s interesting Colin. The best sounding guitar (mine and others opinions) I’ve built has a torrefied red spruce top. The reason I like it so much is the rich harmonics. I kept that one.

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Steve Smith
"Music is what feelings sound like"

Unfortunately I had to sell mine, but got a good but discounted price for a guitar that wasn't so nicely finished as it was a "trial" guitar (thin top. triple X braced with compression bracing on the back)
He then sold it to another fan of my guitars for a profit!
But I did get another guitar commission (full price) on the basis of the first one, everyone who played it liked it.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.