Why are acoustic guitars shaped like they are?

[TJE"]

I am becoming interested in the construction of guitars.

My first question is why are nearly all acoustic guitars shaped in the same way with a body that is widest towards the end, becoming much thinner in the middle and then widening out again towards the neck.

I understand this shape may make them easier to hold, but is there another reason for this standard shape perhaps to do with sound effect?

[Jaden]

I don’t know the answer except to say the dimension of the lower bout, both in width and depth is a huge determinant of the voice of the instrument, given life by the top and bracing. Upper bout cutaway I think has been shown to not have much effect on sound at all; pinched waist in my opinion acts as an aid to note definition.

[gitarro]

Probably historical convention?

[byudzai]

I think Rob Taylor said there should be no flat sides on a guitar, only curves, because flat surfaces set up non-diffused reflections.

I always wonder if the Grand Auditorium shape had anything to do with sound or just looks more shapely than the thick-waisted dreadnought. Cole Clark pokes fun at this by calling their Dreadnought the "Fat Lady."

[robey]

They wouldn't fit in the cases.

[Mr. Jelly]

What instrument did a guitar evolve from? Just a thought.

[The Bard Rocks]

This is something I have pondered, but not enough to research and find out. The waist makes them easier to hold and gives an attractive shapely look to them. I am not convinced it is necessary tonally for I have played Appollonio's "Bell" guitars which have no waist at all and they sounded pretty good. There are other guitar-like instruments the same way.

And I have wondered why have a waist on the upper half, the half that doesn't balance on a leg? If it were straighter across, you could have a greater body capacity and perhaps get the same volume of sound out of a smaller body.

But it wouldn't look right to me and I probably wouldn't buy one - which, assuming others feel the same way, may have much to do with why guitars remain shaped as they are.

[Lillis]

Originally Posted by robey

They wouldn't fit in the cases.

Thanks for the Sunday morning laugh.

[RP]

The shape of the very earliest musical instruments came from the naturally occurring materials, such as animal shells, sections of bamboo and gourds, used to build them. The round bowl backs of lutes and mandolins for example echo the natural shapes of earlier stringed instruments. These rounded shapes do have some advantages, their curves give them strength, minimise standing wave resonances and help acoustic projection, but they are difficult to construct out of flat, processed woods. Today the common shape of the acoustic guitar is a compromise between cost, acoustic perfection, practicality and ergonomic comfort. Given our increasing understanding of the acoustics of musical instruments there is certainly room for improvement in the materials and shape of acoustic guitars, although conservative attachment to the ‘traditional’ acts as a brake on innovation.

In the 16th century when the early guitars were being built, western thought was perhaps even more influenced by Arabic and classical Greek ideas than it is today. Proportion and symmetry, dictated by geometry, were thought to be very important. The earliest known treatise on lute making written by Henri Arnaut de Zwolle in about 1440 describes lute design in terms of geometric proportion, rather than giving dimensions and this approach to instrument design was still used over 200 years later. Today we know that symmetry is not necessarily desirable in acoustic design and some modern makers have produced very beautiful and practical, asymmetric guitars.

Early guitars had small bodies, with only a slight waist and vaulted, or even fluted backs. These weren’t comfortable shapes to hold (although they exhibited desirable acoustic properties), particularly with the vaulted back and as the size of the guitar was increased for more volume, the back flattened and the waist tightened. The idea of a waisted body, with a square back and sides, may have been inspired by the design of the bowed instruments of the time, where symmetric waist cutaways were introduced to allow clearance for the bow. Some versions of the vihuela (an instrument that is related to the guitar) were played with a bow (see www.lutesandguitars.co.uk for more info on early guitars).

[Mooh]

There's a sort of female form to them I like.

[Murphy Slaw]

I thought it was because they're shaped like a girl.

So more men would buy them.

Now someone will complain...

[lowrider]

Yeah, but who decided on this;



??????????

[Mooh]

Originally Posted by lowrider

Yeah, but who decided on this;



??????????

Ian Hunter, hense the H.

[Mobile1]

What RP posted. Ergonomics, aesthetics and tone have shaped the evolution of the guitar.

Or, have evolved the shape of the guitar.

[ctgagnon]

So they're not confused with banjos.