Bracing on an acoustic

[VikingBlues]

Video by Dana Bourgeois. Great insight into just how much skill can go into the bracing inside an acoustic guitar and just how much of a major difference can be made to the responsiveness of the wood. Realisation has been dawning on me with what I've seen and read over the last couple of months that bracing and geometry of the guitar design are probably at least as important to an acoustic guitars sound as the type of woods used.

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The variation in the tapping resonance between 1:00 and after even a relatively minor amount of work on the bracing at 5:40 is pretty big.

Also interesting to see the amount of work needed to get the right stiffness for best results.

All goes to illustrate how standard specifications does not get the best results.

Just how much further the design of bracing, while keeping the basic principles, can go can be seen in the like of this video from David Anthony Reid

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[12bar]

I think the question is how much influence does it have on the final guitar sound. There are so many things that matter, the wood, the construction, the strings etc., so it would be interesting if it is possible to hear this (without knowing what guitar)...

[VikingBlues]

Yes - I know what you mean - it would be great if there could be proper comparative testing.

But the sort of testing needed to compare guitars with bracing not fine tuned would of course mean building finished guitars that were substandard to varying degrees so I guess no-ones going to spend their time and money doing that. What a lot of these builders have in common is an experience when they started making guitars of ending up with ones that sounded good, bad and ugly and they've been a lifetime in fine tuning their methods to get rid of making the bad and ugly ones.

Unfortunately it's impossible to build two guitars the same of course. Even two bits of wood from the same batch will be different and that's before there's any work done on them! I understand that two identically thicknessed pieces of wood for a guitar top can vary by 100% in density, 200% on longitudinal stiffness and 300% in lateral stiffness.

Similar variability will be found in wood used for bracing. That variability of course explains exactly why we are advised to try as many of a particular factory built acoustic guitar as we can to find the best one - they're generally guitars built to a standard specification so the best one will be the one where standard specification is coincidentally closest to the best and most harmonious responsiveness. Ideally the handmade builder has enough skill to maximise to a high degree each individual guitar according to the particular bits of wood used. I do feel it's a shame the bigger manufacturers have been moving further and further away from building techniques that have involved the skill and judgement needed from real builders in the workforce.

What I have noticed is that in the majority of cases where I have tried comparisons of acoustic guitars both by tapping and by playing the better the resonance and note of the tapping the better the sound and sustain of the guitar. I am given to believe that the tops that resonate to tapping best are those that end up on a guitar that also responds best to tapping. Not 100% guaranteed to happen because the back will also have an influence and if done wrong can even have a negative effect on a good top.

I believe from what I have seen said from certain builders the bracing and geometry of a guitars design can make a combination of types of woods for the top and back and sides to be very different from the standard expectations. I have to a limited extent heard this with my own ears. For example a spruce and rosewood combination to sound more mellow than cedar and mahogany!

All very complicated - at least it is to me. This fine tuning of a guitar is not particularly relevant to quite a few styles of playing but for the styles where there are long sustaining notes, melodic lines and more subtle harmonies I feel there's a great benefit from a guitar that's been built to maximise the potential of the wood in all its parts.

It does strike me as interesting how much attention is given to the tonewoods used in acoustic guitars and so little attention is paid to the bracing and internal design / geometry. I guess it's partly down to lack of visibility, and greater difficulty in labelling a type of bracing or design with a particular sound.

[Blindboy]

I have seen my father (a luthier) disassemble a top name factory guitar ( I will mention no names, but it started with an M), shave and reposition the braces, then reassemble it. The result was a marked improvement in tone and sustain. The bracing on an acoustic guitar is, indeed, very important. I have also seen him selecting wood for the top and back. He would take a plank, at least 3/4 of an inch thick, and tap it. After discarding several (I could not hear much difference), he would select one and cut and bookmatch it for a top or back. It's magic... even more so for archtops.

[VikingBlues]

I have seen my father (a luthier) disassemble a top name factory guitar ( I will mention no names, but it started with an M), shave and reposition the braces, then reassemble it. The result was a marked improvement in tone and sustain. The bracing on an acoustic guitar is, indeed, very important. I have also seen him selecting wood for the top and back. He would take a plank, at least 3/4 of an inch thick, and tap it. After discarding several (I could not hear much difference), he would select one and cut and bookmatch it for a top or back. It's magic... even more so for archtops.

I'd love to see something like that first hand.

It must be wonderful to be able to work that sort of magic with your own hands on creating a special instrument or to make an overbuilt guitar into something more special.