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I have a piece of wood I will be building with. It is over 9" wide with perfectly vertical grain across the full width. I want to build a guitar to take advantage of its width - I am thinking of a Quintuple-0 size. I have a nice Martin 000-28 - why couldn't I just increase the 15" body past the 16" M and J size to a 17" version?

A couple of questions

1) Would a standard 25" or so scale length work ok?

2) How can I ensure good trebles?

3) Should I increase the size of the soundhole? - I believe the 17" Gibson J-200 has a smaller hole at 3-3/4"

4) Should the depth be proportionally thicker or can I leave it at about the 000 size depth?

Thanks for considering

Ed M

This is interesting to me since we have an order for an oversize classic guitar. I warned the customer that there would be additional costs due to our need to make new forms and patterns and order a custom made case (he doesn't care). Anyway, I've been wondering about some of the very things you're considering. I suspect the style of bracing can help with the trebles. Our customer also wants the guitar very deep. We still haven't decided whether to make the guitar or not since it's such an enormous hassle to design and build something so different.

[/quote]This is interesting to me since we have an order for an oversize classic guitar. I warned the customer that there would be additional costs due to our need to make new forms and patterns and order a custom made case (he doesn't care). Anyway, I've been wondering about some of the very things you're considering. I suspect the style of bracing can help with the trebles. Our customer also wants the guitar very deep. We still haven't decided whether to make the guitar or not since it's such an enormous hassle to design and build something so different.[/quote]
Just been through that with a hybrid, OLF SJ size.
At the finishing stage now.

_________________
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.

Sound hole size discussions are always interesting. In theory if you enlarge the sound hole you increase the main pitch of the guitar. But the larger sound hole gives the guitar more power which can be perceived as more bass. It's an odd relationship. You may consider making a stiffer back too and even a slightly thinner body.

Colin

Where can I find the OLF SJ plans? And can you give us a couple of pictures of your instrument?

Eds M

Look at some of those old Prairie State Larson Brothers made guitars. They made some big ones:


http://www.sprucetreemusic.com/product/prairie-state-super-jumbo-c-1938/

Ed,
The LMII 200 style plan drawn by Rick Micholetti has a 4" soundhole. Depth 4 3/4" to 3 7/8". That body has worked great for a couple of ABGs I've built.
Also, made a couple of Prairie States based on a 1990s Washburn style, wide but short with sloped shoulders. I like them. Named one "Mae West".

Dave - thanks for the reference but I have never liked the look of those. The Quintuple 0 idea intrigues me

Carl - a 200 does sound interesting. A friend has one of the 100 Montana built, he got it 1990, and it is quite spectacular sounding



Ed M

FWIW I have made several non-standard sized guitars. I have never found that the size of the guitar affected the treble or bass of the guitars. I have 12” parlor guitars with a deep bassy voice and a 17” that unfortunately came out a bit harsh and bright. IMO it depends primarily on how you tune the top.

That said, my smaller guitars are quieter. You don’t notice playing them until you sit down to play with other guitarists.


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Making a successful wide-bodied guitar depends to some extent on getting the right piece for the top: one that has a higher cross grain stiffness than average. It has been said that 'the sound is in the top', and although you can make up for some things in the bracing that's limited.

The pitch placement of the low 'signature' resonances goes a long way toward determining the 'character' of the sound; things like the treble/bass balance, and so on. The soundhole size and box volume determine the pitch of the 'Helmholtz' air resonance, which works like blowing across the mouth of a wine bottle. This is the lowest pitched resonance that can produce useful sound. The problem is that when Helmholtz looked at it he used small spherical glass bottles; the sides, and particularly the back and top, of the guitar are much more flexible, and their mass and compliance drops the pitch of the Helmholtz-like 'main air' resonance. So much depends on the details of how things are done that you can't easily predict where that's going to end up.

In general, a larger hole will give a higher pitched and stronger 'air' resonance, and a stronger 'attack', all else equal. The tone tends to be more 'open' or 'forward'.

The pressure changes less inside the box for a given amount of top motion when the box is deeper. Deepening the box doesn't alter the 'air' pitch as much as it 'should' because of the way the top and the air interact. One researcher made a 6" deep guitar, and cut it down progressively an inch at a time to 3" or less, replacing the back each time, and the 'air' resonance only went up by a bit more than a semitone. What you get from a deep box is less attack, and a 'rounder' and weaker air tone.

It seems lie a paradox, but it's actually easier to make a powerful small guitar than a powerful big one. That's because the output depends a lot on the ratio of top Area to mass. With a wider top you have to beef it up to make it stiff enough to keep from folding, and the mass goes up faster than the area.

The guitar is much smaller than the wave length of the lowest notes it makes, so those sounds go out as from a 'point source', with similar power in all directions. As you go up in pitch the sound gets more directional, and at the highest frequencies it mostly comes out of the hole and off the top toward the audience. The player hears the low end sound as well as anybody in the room, but for the high end the player tends to rely on reflections back from the room. In a large, dead, or noisy space you may not get them. That's what side 'ports' are for; they put out some of the highs that get trapped in the box so that the player can hear them, if they can see into the port.

A big guitar that makes lots of low pitched sound can seem loud close up and to the player, but may not 'carry' very well due to a lack of power. I've seen an extreme case where the player could barely hear the guitar, and person standing a couple of feet off to the right side couldn't hear it at all, but people at the back of the room thought it was a 'cannon'. This tends to be more common with 'better' guitars.

IMO about 80% of treble response is in the top, and particularly as regards 'quality'. A very light, thin top with lots of bracing tends to have a 'sharp' or 'cutting' timbre, while a heavier top will be more muted and 'sweeter'. 'Clear' and 'ringing' trebles seem to be produced by a top that has the 'right' weight and, and bracing that's in balance with it. Again, you can produce different tonal 'characters' by using different brace layouts and profiles ('forward shifted' layout or 'scalloped' profile, for example), but whether the tone is mediocre or great of it's kind will depend on well you get everything in the top working together.

The guitar is deliberately complex, despite (and, in a sense, because of) how simple it looks, and it's impossible to do more than scratch the surface in a short post. 'Any road is fine if you don't know where you are going', but if you have a particular goal in mind you should start out by figuring out the best direction to get there.

In our case (if we decide to build it) the guitar will be a nomex double top/double body so it's a whole different can of worms. We built a very large (although normal width) double top/double body for this customer a couple of years ago and he loves it. He claims it's his favorite out of his 120 or so guitars which perhaps explains his desire for this peculiar guitar.

Nothing wrong with a J- 200...



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While I'm not as experienced as others on here. My first 2 builds were 17.5 wide jumbos. I did copious amounts of research before I built and the few things I found dictated the sound in my case at least were as follows.

Body depth. The typical almost 5" deep jumbo depth was something I didn't go with. My reasoning was that the thinner bodied guitars were much more responsive and didn't have the "air" that alot of J200s and likewise guitars had. On my 2 I went with a 4" depth at the lower bout. This seemed to be successful as neither jumbo was unbalanced or overly woofy.

Another thing was a tighter top radius. On both they had a 25'. I also deliberately made the bridges the typical Gibson style 1x6 and coupled that with a thin bridge plate (about 80 thou) and the responsiveness was right were I wanted it.

Bracing wise I actually went a little thicker than I would've liked but it seemed to have worked. Top thickness for both was a hair under 122 thou. The overall length I also shortened to 19" from the usual 21". Whether this made a difference sound wise I dont know but it definitely had a huge impact on the comfort factor when playing.

In all honesty though I feel like for wide bodied guitars the depth dictates alot of the overall responsiveness/feel. The top bracing and such can be varied to taste.

I’ve had trouble routing binding ledges with nomex. I even started a thread recently looking for alternatives. Have you had that issue? If not, do you mind sharing your layup?


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Brad - that is one gorgeous guitar. I have built 3 early L-1's, a J-185, and a 3/4 size in that shape and it is tempting to complete the set with that size. Where did you get the plans?

We hold the nomex back from the edge of the top so it's all wood where the bindings go. I tried to upload a photo but for some reason it failed.

The unique design of the Hiscox cases allows each size to handle multiple 12, 13. and 14 fret guitars...the Dreadnaught size alone handles small jumbo, 0000/J/M, Martin D, Gibson J-35/45/50, Taylor D/Grand Aud sizes, 16" archtops, as well as the growth hormone treated one-off Martin/Gruhn 0000 12 fretters. Hiscox makes an F/Jumbo model case which will take a 17" jumbo (J-200/17 inch archtops), so I would assume that would handle your 17 inch model.

https://www.elderly.com/collections/all ... uitar-case

_________________
For the times they are a changin'

- Bob Dylan

Ed
Here's the link to the LMII plan, https://www.lmii.com/plans/3543-plan-j- ... uitar.html.

Not seen a source for some time.
There is this, looks similar, may be an unofficial copy https://cadguitarplans.com/product/pdf-small-jumbo-acoustic-guitar-plan
My SS one - this post http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=40344&p=529933&hilit=+monster#p529933
Hybrid in finishing so not many pics -
Bracing 5 x 1/4" square fan struts with spruce bridge plate based on Taylor nylon string -

_________________
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, LMI plans

Three wide ones; J 200 style, the "Mae West" Prairie State and a 1954 Kay Jumbo. All 17" lower bout.
.
You guys sure take nice pictures .