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I've been doing some research on the effects of the bridge location of a 12 fret vs 14 fret guitar. I keep hearing some iteration of the phrase "the location of the bridge further back on the 12th fret guitar "sweetens" the tone".
Can someone please elaborate on this for me?

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Mike

The only thing nescessary for evil to thrive is for good men to do nothing.

Closer to center of lower bout = bassier tone.

Here are a few things to consider...

It's dangerous to over-generalise given the neck/body/sound hole geometry options that are available. However, the mass of the bridge tends to make it self-centre in the middle of the lower bout vibrating zone, but you need to know where the vibrating zone actually is.

In the pic below, there's a 12 fret medium bodied guitar on the left and a 14 fret dread on the right. The Chladni patterns show the node lines of the T(1,1)2 (fully coupled main top) mode and how the bridge tends to self-centre in each case. The node lines (where the tea leaves have collected) show where there is no translation of the top, but the top does "rock" about the node line in the T(1,1)2 mode; i.e. if the top is moving "up" inside the node line, it is moving "down" outside the node line. In essence, a concentric dipole exists. That means that the sound radiating from the top motion inside of the node line is 180 degrees out of phase with the sound radiation from the top outside the node line and some cancellation of sound is likely to occur. In simplistic terms, the net radiating area is the difference between the positively radiating area (usually nominated as the central zone) and the negatively radiating area. The negative zone is a lot larger for the 14 fret dread, so the net radiating area is reduced more and so the 12 fret body has a larger net positively radiating surface and consequently is both louder and projects better.

Managing the position of the node line of the T(1,1)2 mode is critical to the nature of the sound of the guitar. The further outboard you can get it, the more positive sound radiating area you get and the less negatively radiating area you get subtracting from it, for a double-whammy win. Very rare in this business.

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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

this is something that people often overthink and lets face it ( I read it on the internet ) Translates to ( BS )

The bridge is set to a guitar by the dictated scale length . The above examples show that. The open statement is too vague for a true answer. If you just lower the bridge without thinking of the scale length you loose intonation .

If you use take a standard body shape and set a 12 fret on it yes you will change the tonal quality . Will it be better ? It depends on the person. This is a question that is asking for a subjective answer.

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

My thinking has been that with the "Martin" designs the shift from 12 fret to 14 fret usually entails a shortening of the body (soundboard length) and that this accounts for some of the difference in sound.

That's where my belief is based too. Among the Martin-defined shapes, a 00 12 fret body is nearly as long as a 14-fret dread.

Pat

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formerly known around here as burbank
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http://www.patfosterguitars.com

+1 Clay and Pat. I used info from Martin to make templates for 14 fret OOO (OM) and a 12 fret OOO. the body length is a bout 3/4" longer on the the 12 fret.
Maybe air volume ?
Brent

There can be a big difference with the Gibson L-00 shape. Not only does the bridge move, but the neck is shorter, the sound hole moves down, the X splays out because of the sound hole. Any of these can effect tone, all together they definitely affect tone. Whether you like it is another matter. I like the changes.
L.

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Cut to size.....Beat to fit.....Paint to match.

Firstly, thanks for all the responses. They're giving me a lot to think about.



This is the purpose of this thread to start with.
I'm doing as much research as I can. I'm prepping for an acoustic build (I'm sure everyone is tired of hearing that) and I'm considering design changes to enhance or effect tone, so I'm looking at everything I've read or heard about building to help determine what I want to finally do.
I keep looking at the question of the bridge location and body join(12 vs 14 fret) and I keep running into this phrase. I have even read discussions between luthiers where one claims it increases bass, while the other counters with,"no, not increased bass, but a "sweeter" sound".
But this is never described or explained, just stated as a fact and everyone should know what this means. And everyone acts like they do. Maybe I'm the dumb one? And I can't really ask because the threads I'm searching are sometimes years old.
It's not enough to take a bunch of opinions on a variety of builders forums and make changes willy-nilly. I don't want to guess at something, I want to know, at least in some definable way, why, before I put a design down on paper.
So I posted here, where the builders I most interact with and trust come, trying to get a handle on the truth.
Thanks.

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Mike

The only thing nescessary for evil to thrive is for good men to do nothing.

Good questions Mike. I like that you're digging deeper to find out what some of guitar making lingo / bs / hubbly-bubbly is actually about. I agree that words like "sweeter" often get tossed around without enough explanation.

My hunch is that for most people, it would be things like bass, overall volume, and quickness of response that would lead them to use a word like "sweet." But that is a guess, and it's lumping a lot of things together . . . and I'm not certain that a lot of 12 fretters actually accomplish these things.

My own totally uneducated opinion on this is that the shape of the lower bout especially (the shape of the 'speaker' is how I think about it) and where that speaker is driven from (saddle location) are very significant factors in what a guitar sounds like. Todd's illustration helps us to see that Martin's version of a 12 and 14 fret guitar in fact make very small changes to the shape of the speaker and where that speaker is powered. Keeping the scale length the same would likely lead to very similar volume. Increasing the volume of the guitar without increasing the speaker size threatens to muddy up the bass - which can sound like more bass at first blush. But most of us are interested in clarity rather than mud.

Something else you might consider that involves a lot less retooling / mold-making is shifting your x brace north a little. Your speaker would still be driven from the same location. But the shift changes that locations proximity to the strongest part of the top.

No matter what you're going to have to make a well thought through decision, then plunge into the work without any guarantees. This way of going about it might make it feel as though you're still experimenting without all that retooling.

Humbly submitted.

Phil

I took a tracing of a 14 fret 1937 Gibson Nick Lucas and modified it for a 13 fret. It moved the bridge down the distance equal to the distance between the 13th & 14th frets. Locate your bridge/bridge plate position, adjust your X bracing, (slightly wider to catch the ears of the bridge) and its making sawdust after that

Another question to ask:

When classical guitarists are always searching for volume, projection and playability, how come they never moved from the 12 fret format?

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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

It's a common error, Phil, but you don't actually know "the shape of the speaker" until you do the Chladni patterns. What Todd's picture shows is that the external geometry of the lower bout is similar. The difference between the two concepts is important.

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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

After building a ton of 14fret OM's I just completed my first 12F 000. Pretty much a Martin copy.
It sounds - well - "different". Quite pleasing and well received. As has been said, just dive in and build one and see if you and others like it. If so build more. I plan to.

One consideration, look for a case early, they may be back ordered for this rather uncommon size. TKL/Cedar Creek were when I finished mine.

Good luck!

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It's not what you don't know that hurts you, it's what you do know that's wrong.

I guess I will be one of those experimenting... I am building a Parlor based on the LMI kit which is based on a Lyon & Healy Columbus 12 fret. But I am putting a 14 fret neck on it. The bridge seems a lot farther forward than the 12 fret so we will see how it sounds when I am done. I did move the X bracing up to match the bridge position so it will be a mystery until I get strings on it.

Bob

Yeah, pretty much it's going to come down to "build it and see", regardless of how much info I get. And I'm fully prepared for that part. But I need to get a handle on exactly what I decide to build, and this question, along with many more I'll be asking, are the first steps to figuring out the direction I want to head in.
I wish you luck on your build, and hope to follow you soon.

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Mike

The only thing nescessary for evil to thrive is for good men to do nothing.