size of sound hole

[Tygrys]

For start i did ordered the book
Contemporary Acoustic Guitar Design and Build by Gore and Gilet.

But it will take time before book will arrive, and I'm starting to drawing my future guitar.
Therefore I have question how I sould calculate size of sound hole it will be offset and "free form" I know that I can easy coppy proportion of size of soundhole in to sound boars from other's successful guitars but maybe there is another way just to start and later when the book will arrive i will read it and correct rough plans.

[Ned Milburn]

Tygrs,

You ask many questions to which there are no exact answers. In English, we say this is "putting the cart before the horse".

Sound hole size will affect tone, yes. But there is no "calculation" for it. Depending upon the bracing design and thicknesses of all areas of your soundboard (including brace thickness & scalloping & tapering), changing soundhole size can affect YOUR guitar different than it can affect MY guitar or HIS guitar or HER guitar.

Build a guitar within STANDARD dimensions first. Then build 2 more but alter ONLY one aspect of the guitar design. Then you will learn.

Your questions are like, "how do I calculate and design to build a perfect guitar?" But the only answer to this is to spend a lifetime at it, improving as you go along. Many people will spend a lifetime at it and due to their own limitations they will only build medium quality guitars, but other people will spend a lifetime and build instruments that surpass most other guitars. You won't find out what type of guitars YOU can build until YOU build them, make mistakes, learn from mistakes, and improve bit by bit.

The BEST starting point is standard tried and true designs and measurements. That is where you need to start.

[runamuck]

I'd suggest you wait for the book.

[charles Tauber]

To add to what Ned said...

A fine musical instruments is a very complex object. There are many variables related to each instrument. These variables, taken together, produce the sound quality that an instrument makes. In guitars, these variables include things like the type of woods used for top, back and sides, the thicknesses of these woods - uniform thickness, variable thickness, thinner around the edges, thicker on one side ... - the bracing arrangement used, the width and height of the braces, the profile of the braces, the type of material used - spruce, cedar, composite, balsa - a single top or a "double" top, the size and position of the sound hole, the position of the braces relative to sound hole, the height of the strings off of the top (neck angle), the type and thickness of finish used... And so many more variables.

Each maker uses his or her own set of values for these variables. Some make the top thicker, others thinner. Some use taller braces, some wider braces. Some brace this way, others a different way. The sound, playability and longevity of their guitars are the sum of those variables. Thus, asking, for example, "What size sound hole do you use?" has relatively little relevance, since it is but one of many variables, working together, that produce their finished guitar. Just changing the sound of your sound hole to match theirs, while using different values for the rest of the variables, may or may not produce a similar result on your guitar.

I had a fluid mechanics professor who used to say, "An art is a science with too many variables." Musical instrument making is an art for that very reason - too many variables to quantify each of them and form a definitive "solution". In short, there is no single set of values for all of the variables, no equation into which one can put the variables and produce "the answer".

Instrument making has always been an empirically based art. One has a starting point, often based upon what has come before, what others before you have done. From that starting point, one changes one or two variables at a time and observes what effect that has on the finished instrument. Did it improve the tone, or make it worse? Did it improve the structure of the instrument, or weaken it?

In relatively recent times, scientists and instrument makers have tried to better understand these variables and what effect each has on the finished instrument. Scientists and instrument makers have learned a lot about these variables, but are still very far from being able to plug values into an equation and guarantee the characteristics of an instrument's sound. Guitar making continues to be largely empirical.

Since about the 1960's, scientists and guitar makers have attempted to apply "hard" science to guitar design - determine cause and effect. While there are many who have contributed to advancing the scientific understanding of guitars Alan Carruth and Trevor Gore are particularly noteworthy. Recently, Mr. Gore has published a two-volume set of books. They are, so far, the most comprehensive discussion of the science of guitar making and for many guitar makers are an introduction to a scientific method that can be applied to guitar making. In short, much of what is contained in his books is not common knowledge amongst guitar makers.

As others have suggested, you have two options. The first is to base your starting point on what others have already successfully done in making composite guitars. Based on those designs, you can change variables in search of "improvement". The other option is to design your own composite materials guitar from the ground up, a considerable undertaking.

[Tygrys]

Well thank you you confirm me with what I was thinking.

So now the plan is easy.

I will make first one guitar with very small soundhole and play it then I increase size of it and play it again and so on... Till i decide that bigger sound hole is sounding worse then previous one in that pint i will do another one top and cut soundhole size which I decided as best one.

But as I did mantioned before first I will gain theoretical knowledge.

One more time thank you.

[John Arnold]

Basically, the larger the soundhole, the brighter the tone.