Thread: How certain features affect an acoustic guitar

Originally Posted by mimstrel

SDoes the width of the neck have any bearing on the tone or structural integrity of the instrument? It doesn't seem like it should affect tone... but it might have some effect because the point where the neck attaches to the body would be reduced in size.

Necks can bend. This is why builders will often add reinforcing such as carbon fibre into a neck. The join between the neck and the body can be made reasonable large, google "spanish heel" and you will see how it can be done. You can also make your sides more rigid to compensate for the forces put onto the body by the neck. The top braces on the soundboard need to be strong as well. But as with everything with lutherie you will end up with a sound dictated by your design.

Secondly, I'm curious about the modern variations in tone holes. I've seen a few guitars with tone holes in the sides instead of the top, and all manner of variation in location and size and shape besides. Many of these, I find to be really lovely to look at - but how do they affect tone and volume? I would assume that shape would have little effect, all else being equal, unless one shape is extremely intricate.

Not quite, the bracing on the inside of the guitar is a large determinant of the sound. The placement of the soundhole to an extent determines how the bracing is shaped and placed.

What is the effect of replacing the main hole with multiple smaller holes? What is the effect of moving the main hole or any smaller holes?

This is a very big question that absorbs a lot of builders, myself included. The best I can offer is a starting place. Guitar acoustics

Has anyone been creative with this?

Lots of people.

Originally Posted by mimstrel

So I have some questions about how different design choices affect the sound and structural integrity of a guitar.

First off, I have short little fingers and a full-width neck puts certain chords just out of reach. This is the main reason that I would build a guitar for myself - a full-sized body and full-length fretboard, but the neck reduced in width by a cm or less. Does the width of the neck have any bearing on the tone or structural integrity of the instrument? It doesn't seem like it should affect tone... but it might have some effect because the point where the neck attaches to the body would be reduced in size.

Secondly, I'm curious about the modern variations in tone holes. I've seen a few guitars with tone holes in the sides instead of the top, and all manner of variation in location and size and shape besides. Many of these, I find to be really lovely to look at - but how do they affect tone and volume? I would assume that shape would have little effect, all else being equal, unless one shape is extremely intricate.
What is the effect of replacing the main hole with multiple smaller holes? What is the effect of moving the main hole or any smaller holes?

Has anyone been creative with this?

Hi Mimstrel,

Comments/answers to your queries:

1. you can play with the width of the neck but like Seb says if you get to a point where structural integrity of the neck is at risk then consider a couple of CF rods glued into the neck. I use them on all my steel strings regardless of neck dimensions.

2. Soundhole size will have more of an affect on sound of an acoustic instrument then shape. The size of the hole will directly influence the instruments Helmholtz frequency..... similar to a ported speaker system. For more reading on this see here: http://www.phys.unsw.edu.au/jw/Helmholtz.html

3. Soundports....a controversial subject. Last year I recall reading in the GAL Journal of a blind test where listeners were asked to evaluate the sound of a test instrument with a number of soundports in different locations and able to be plugged in different combinations. The end result of the test was that with the soundports open people generally didnt think the instrument sounded better. I would comment that a soundport on top of the instrument would make it more audible to the player but not to the audience.