Under the hood of a flat top guitar

Bob-Dubery

Here's an interesting set of photos (taken with some kind of special camera) of the insides of various flat top acoustic guitars. Interesting to see the different bracing patterns....

A Gallery of X-Bracing

All X-Bracing patterns really have evolved from the classic pattern that Martin devised after they moved from gut to steel string guitars. In general Martin have been hugely influential as regards the design of steel-string, flat-top acoustic guitars.

So here is an article with pictures of Martin's X-bracing and some of their own variations on that theme.

Wizard

I wonder what effect it would have to have a soundpost in an acoustic guitar, like in a violin?

singemonkey

And speaking of violins, are archtop acoustics supported the same way? That seemed to be the big rivalry between Gibson and Martin, right? Martin made a steel-string guitar designed like a gut-string - but with different support to handle the increased pressure of steel-strings. Orville Gibson, master mandolin maker, made his guitars like violins. I wonder how they handle that pressure?

Bob-Dubery

singemonkey wrote: And speaking of violins, are archtop acoustics supported the same way? That seemed to be the big rivalry between Gibson and Martin, right? Martin made a steel-string guitar designed like a gut-string - but with different support to handle the increased pressure of steel-strings. Orville Gibson, master mandolin maker, made his guitars like violins. I wonder how they handle that pressure?

I'd imagine that the construction of an archtop guitar takes quite a bit of stress off of the top. The usually have a trapeze tailpiece which moves a lot of the stresses. With a flat top there is no tailpiece. The bridge also anchors the strings and that stress then gets transferred to the top. Schemes like X-bracing and ladder bracing were devised to deal with those stresses.

My Smoothtalker has heavy sides and a trapeze tailpiece, so there is not a lot of stress on the top. But it still has bracing - for tone not for re-inforcement.

I would also think that with the arch-top guitar the arched top must be stronger than a flat top, and that the specific design of the arch must account for some tone.

Bob-Dubery

Some googling has revealed that arch tops are braced. Indeed there are different bracing schemes. Gibson, since Lloyd Loar's days at the company anyway, use parallel braces with the braces running parallel to the strings in the area between the f-holes. D'Angelico used x-bracing. The bracing is still necessary to counteract the tension of steel strings, but it is a lot lighter than it is with a flat top.

singemonkey

Right. I guess the essential "arch" principle must help. Then, as you say, anchoring the strings to the body instead of the top - so that the top is effectively held down by the bridge rather than being pulled up. Interesting the parallel bracing.

Bob, have you ever played an archtop acoustic? If so, do you like 'em? This crappy one of my girlfriend's sounds so good that I wonder why there seem to be so few being made now - apart from the electric ones like the Gibson ES175 where the top is deadened quite a bit by the pickups screwed in there as far as I've heard.

Bob-Dubery

singemonkey wrote: Right. I guess the essential "arch" principle must help. Then, as you say, anchoring the strings to the body instead of the top - so that the top is effectively held down by the bridge rather than being pulled up. Interesting the parallel bracing.

Though I do wonder how they cope with the strain of the strings pulling on the tailpiece. On the Smoothtalker it's easy because the rim is about 3/4 inch thick. I guess they must have some kind of block re-inforcing the tail.

The braced top I can understand. These guitars are built to take big ass steel strings - we're not talking 9s or 10s here. So some bracing is still necessary - but not as much as on a flat top. And you will note that the style of bracing does effect the sound. Also the layout of the guitars effects the bracing. Before Loar Gibson arch tops had a central sound hole and so X-bracing was forced upon them. Loar got them to produce arch tops with 2 f-holes. That allowed parallel bracing - which in turn gives more volume and more tops.

Bob, have you ever played an archtop acoustic?

No. And the Smoothtalker doesn't count. George Gruhn said that there are generally 4 categories of acoustic guitars: Flat tops, arch tops, resonators and classical, but the Smoothtalker goes into a 5th category - "none of the above".

If so, do you like 'em? This crappy one of my girlfriend's sounds so good that I wonder why there seem to be so few being made now - apart from the electric ones like the Gibson ES175 where the top is deadened quite a bit by the pickups screwed in there as far as I've heard.

I am lead to believe that in quite a few cases Gibson arch tops with factory fitted pickups are made with laminated tops which
a) are cheaper
b) are more feedback resistant than a solid top
c) don't sound good

Early Gibson arch-tops where there was an OPTION for a pickup apparently sound great unplugged and even if they have pickups fitted.

I wouldn't make generalisations about "arch tops". Clearly there are lots of variables - always a good thing because it means there's a greater variety of tone.

For me we're in a golden age of flat top guitars right now because there are so many variations in body style, bracing patterns etc that give different guitars different voices. Larrivee, for example, use a variation on the Martin X-bracing. The tone bars between the rear legs of the X are parallel to the bridge rather than sloping. This gives them a different character from Martins, Gibsons, Taylors... Even their dreadnoughts have a different character to Martin, Collings etc...

It's a great time to be a flat top guitarist.

Keira-WitherKay

singemonkey wrote: Right. I guess the essential "arch" principle must help. Then, as you say, anchoring the strings to the body instead of the top - so that the top is effectively held down by the bridge rather than being pulled up. Interesting the parallel bracing.

Bob, have you ever played an archtop acoustic? If so, do you like 'em? This crappy one of my girlfriend's sounds so good that I wonder why there seem to be so few being made now - apart from the electric ones like the Gibson ES175 where the top is deadened quite a bit by the pickups screwed in there as far as I've heard.

well if you look at the jazz world there are a lot of steel and even nylon archtops that are made for that market ussually have f holes and very little acoustic volume but they all meant to be played plugged in .so yeah personally i think a flat top is easier to construct and hence cheaper to manufacture.......and money is always the bottom line........and most people want their acoustic to sound loud acoustically heheheh ...i recently played a gibson archtop in marshall music going for a sweet 50 K and it was so soft you could hardly hear it but it looked and felt beautiful and this one DID NOT have a pick up installed....it was a remake of a vintage model... so i don't know how one would use it ....

so yeah google jazz archtops and you'll see what i am refering to...a beautiful range of archtop instruments from many luthiers and manufacturers...

here's martin taylor and him vanden archtop