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Variables in building acoustic guitars
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Author:  guitarjtb [ Sun Jun 19, 2022 1:14 pm ]
Post subject:  Variables in building acoustic guitars
This is not meant to be all inclusive, but is to demonstrate some of the variables that will affect a guitar's sound. When inspecting existing guitars, some things are visible and somewhat easy to measure and copy. These are marked with ********. Other things, that have as much or more effect on the sound and tone, are not so easy to measure. This list only deals with the body construction and does not address the neck or neck attachment.

What affects sound/tone in body construction of an X-braced acoustic guitar?
*****Body size, shape, and depth.
*****Scale length. Added, thanks to Colin.
*****Angle of the X-brace crossing. This usually varies from 90 degrees to 102 degrees.
*****Placement of the X-brace, relative to the bridge.
*****Placement and angle of the tone bars, relative to the X-brace.
*****Size and placement of the front transverse brace.
How much arch is induced into the front transverse brace? Is it glued with a flat backing board or an arched board that matches the arch of the brace?
******Size and thickness of popsicle brace.
******Number and shape of back braces. Usually either 4 or 5 back braces.
How much arch is induced into the back braces? Are they glued with a flat backing board or an arched board that matches the arch of the brace?
How much arch is induced into the top’s X-brace? Does the arch in the top’s X-brace flatten out at and behind the bridge? Is it glued with a flat backing board or an arched board that matches the arch of the brace?
Are the gluing surfaces of the tone bars flat or arched the same as the X-brace?
*****Is the profile of the sides, for the back, spherical or cylindrical?
*****Is the profile of the sides, for the top. flat or angled to match the arch of the top bracing?
Is the bridge plate glued with an arched backer board or a flat backer board?
Is the gluing surface of the bridge flat or arched to match the arch of the top?
*****Shape and scalloping of top braces.
*****Thickness of top, back, and sides.
Stiffness of un-braced top.
*****Tap tone of braced top relative to tap tone of braced back.
*****Wood species of top and body.

It's complicated.
Author:  meddlingfool [ Sun Jun 19, 2022 2:23 pm ]
Post subject:  Re: Variables in building acoustic guitars
Do yourself a favour and treat yourself to the Gore/Gilet books…its complicated but extraordinarily easy.
Author:  Freeman [ Sun Jun 19, 2022 8:56 pm ]
Post subject:  Re: Variables in building acoustic guitars
Gosh, how do you ever decide?
Author:  guitarjtb [ Sun Jun 19, 2022 10:43 pm ]
Post subject:  Re: Variables in building acoustic guitars
meddlingfool wrote:
Do yourself a favour and treat yourself to the Gore/Gilet books…its complicated but extraordinarily easy.


I have my answers to all these questions. I may not have it right, but I have it repeatable. I am just pointing out the things that must be considered when someone decides they want to build one. I probably would have some different answers, and would have had them sooner, if I had started with those books.
Author:  Colin North [ Mon Jun 20, 2022 6:32 am ]
Post subject:  Re: Variables in building acoustic guitars
One basic thing missing, scale length has quite a significant effect on the sound of a guitar.
Author:  guitarjtb [ Mon Jun 20, 2022 7:03 am ]
Post subject:  Re: Variables in building acoustic guitars
Colin North wrote:
One basic thing missing, scale length has quite a significant effect on the sound of a guitar.

Added to the list. Thanks
Author:  doncaparker [ Mon Jun 20, 2022 7:06 am ]
Post subject:  Re: Variables in building acoustic guitars
Another factor not yet mentioned: the fact that wood is a variable material. Two pieces of the same species of wood, cut and dimensioned in a manner that makes them as identical as possible, will have different acoustic properties. So, you might have to dimension them differently from each other in order to achieve similar acoustic properties.
Author:  Herr Dalbergia [ Mon Jun 20, 2022 8:59 am ]
Post subject:  Re: Variables in building acoustic guitars
yes
Author:  Barry Daniels [ Mon Jun 20, 2022 10:02 am ]
Post subject:  Re: Variables in building acoustic guitars
guitarjtb wrote:
I have my answers to all these questions. I may not have it right, but I have it repeatable. I am just pointing out the things that must be considered when someone decides they want to build one.


And the answers are?
Author:  WudWerkr [ Mon Jun 20, 2022 10:15 am ]
Post subject:  Re: Variables in building acoustic guitars
The Answers are "subjective" to a degree ... You can build two identical guitars and they will sound different . Each builder answers these questions for himself and his liking. I may leave my backs and sides slightly thicker and my tops slightly thinner. than another builder etc: This is where time and experience come to play. As we get better we adjust and move forward. Following someone else's ideas is not a bad practice , however the guitar gets better as we experiment and learn and share what we have done. The other Part of " Subjective" is that customers by and large hear with their eyes. If they love the look they will hear what they want to..... idunno

That part we as builders have very little control over .
Author:  Elman Concepcion [ Mon Jun 20, 2022 6:02 pm ]
Post subject:  Re: Variables in building acoustic guitars
guitarjtb wrote:
This is not meant to be all inclusive, but is to demonstrate some of the variables that will affect a guitars sound. When inspecting existing guitars, some things are visible and somewhat easy to measure and copy. These are marked with ********. Other things that have as much or more effect on the sound and tone are not so easy to measure. This list only deals with the body construction and does not address the neck or neck attachment.
It's complicated.


It is not as complicated as you are making it out to be.
My old friend Augie LoPrinzi used to tell me.
After making thousands and thousands of guitars.
They all sound like guitars.
Author:  Terence Kennedy [ Tue Jun 21, 2022 8:37 am ]
Post subject:  Re: Variables in building acoustic guitars
Whenever a thread like this surfaces I always remember the time I showed one of my early efforts to Jim Olson.
I asked him how he thought it sounded? The answer -

“Good, they all sound good - to someone “
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