Guitar Body Shapes - Flattop vs Archtop

[Woody Sound]

I've always wondered why archtops have a pretty much perfectly rounded lower bout, but flattops have a more flattened area at the bottom.

[cmajor9]

I think you can find exceptions in both directions. Gibson has many flattops with round lower bouts; think of the jumbos and the L-00 guitars. Then there are the ‘original’ flattops - classical guitars. The flatter ‘bottom’ came at least in part with the move to 14 frets clear of the body, I believe.

[whiskey02]

I believe you're thinking specifically of the overly boxy dreadnought. OM, 000, double and single ought and jumbo guitars have a much more defined, and comfortable, waist. How dreads became the defacto acoustic guitar is beyond me. 000 and OM's have a much more balanced and articulate sound along with being much more comfortable.

[deacon Mark]

Give me an OM over the dreadnaught guitar any day. They sound better to especially if body depth is shallower.

[mr. beaumont]

I'm guessing maximizing surface area on that lower bout increases bass, an attribute looked for in flat tops but not coveted in the arch top world?

At any rate, the 000/OM thing is very much my jam.

[AllanAllen]

. How dreads became the defacto acoustic guitar is beyond me.

It’s volume, people want a loud guitar.

[John A.]

Dreads are louder, especially useful in bluegrass, where they were called banjo-killers. I had a Gibson dread for many years. The sound was always cool (more balanced than a Martin dread, and not quite as loud), but the shape never really worked for me (despite hanging onto it for decades).

My new favorite is the “grand concert” (15" body, rounder bouts than a 000). The Sel-Mac shape is also a lot more comfortable than a dread. Louder too, but a different sound altogether.

[Archie]

Archtops have a domed structure so the rounded shape comes from that.

There are degrees of this between arch tops.

A lot of vintage Epiphones and Guilds (essentially the same thing) can have a more squashed shape to the back portion compared to say Gibson's.
I think Borys has the same early Epiphone style too.