Brace yourself, Bridget.

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Who Knows best? (The fake news of Luthery)

There is a serious problem for new builders of stringed instruments when looking for good advice and direction. It seems to me that while there is a dirth of information on the “how” of guitar building, there is much less clarity in what is ‘correct’ concerning the “why”.
This is a problem, because if for example I want to know why Spruce or Cedar are the only two woods recommended regularly for use in making soundboards, the reasons generally given are because they have the best weight/strength/flexibility ratio. Yet, Tom Bills, in his book “The art of Lutherie” advises “quit thinking about the differences between German and Sitka spruce, because really, the string doesn’t care”.  imagesHe also points out that there are so many variations between any two pieces of wood from the same species that, “ideas about one wood species or another don’t line up much of the time anyway”.
Now, compare that to Mcleod and Welford in their book The CLASSICAL GUITAR (DESIGN AND CONSTRUCTION). In this text the authors state, ” Timber of less than 15 rings per inch should not be used for a fine guitar”. Yet Roger Siminoff in THE LUTHIERS HANDBOOK, states that grain no less than 10 rings per inch is the standard to aim at for soundboards….and in GUITAR MAKING, TRADITION AND TECHNOLOGY by Cumpiano and Natalson, it is suggested that “evenness and straightness of grain are generally matters of personal preference”.
So immediately, when the new builder goes looking for info on the ‘what’ and ‘why’, they are faced with a myriad of contradictory claims and assertions about what the best wood might be, what one might be looking for in the wood, and what categorically won’t work in terms of wood choice.
The nub of the problem might be that the ultimate goal all makers at least claim to be aiming for is good tone. The experience of a wood’s tone is completely subjective. Different makers and players prize different tones, and different ears in different circumstances and cultures experience tone …….well…..differently. So knowing what you are at least aiming for is one thing, finding out what might be the best materials and construction techniques to attain that sound is another matter altogether. What we are aiming for, surely, is a piece of wood that resonates in a coherent and distinct way for as long as possible, regardless of what that tone is.

Brace yourself, Bridget.

This little rant started to form in my mind when I began to think about the bracing of the guitar I am currently building, (pics above and below). I have repaired the sound boards of a few acoustic instruments and am familiar with various bracing patterns and some of the basic theories around why they were developed. I chose to make an ‘arch top’ acoustic guitar for my first full build, mainly out of bloody mindedness, but also as a challenge and experiment. I was keen to try as many important techniques of building as I could include in one instrument. This is because I am a strong believer in innovation above tradition. There are plenty of good Luthiers out there building the same ole nylon and steel string designs….I have no intention of adding to that. Fancy perflings and clever inlays on the finger board are not guitar design innovations, in my book.
Once I start thinking deeply about the ‘why’ of bracing and reading some of the reasons behind different patterns, I find I start to question the ‘engineering logic’ behind some of them. As an example, many books and online builders talk about the string energy from the bridge being ‘transferred’ evenly across the sound board by a fanned pattern of bracing. While that sounds like a reasonable idea at first glance, it starts to look dubious when you analyse it more deeply. Ask yourself the question, based on basic engineering and physics principles you probably learnt in school, “Why would strips of wood on the back of a flat surface transfer energy coming from a block of wood, (the bridge) stuck to the other side of that surface”. images-5I am not questioning that some of the energy of the moving strings is transferred through the fanned braces on the underside of the sound board, I just wonder that surely most of the energy goes directly across the top surface of the sound board from the bridge….because that’s what the bridge is glued to. Also, reflect on this in light of the knowledge that many builders use assymetrical bracing for the reason that they believe it is important for good ‘tone’ that the sound board doesn’t resonate evenly. Go figure.
Before you dismiss me, consider this statement from Cumpiano and Natelson.
” ...the study of guitar acoustics currently seems to be of little direct technical use to the practicing Luthier. For example, we can learn from acoustics that a guitar is not an “amplifier” of the string signal, that the soundboard is not the sole sound generator, that the guitar cannot be subdivided into bass and treble halves, that the neck is not acoustically innactive, that sound does not ‘radiate’ in waves from the bridge or travel down the braces….”
So why all the ideas about stiffer braces on the treble side when we know the soundboard is not divided into vibrations related directly to the treble or bass strings? When we know the sound board “vibrates”, or more correctly “flexes” assymetrically, why do we entertain ideas of the braces enhancing certain frequencies when placed in certain configurations? It all has the whiff of ” its always been done that way” about it, with some dubious constructional, engineering sounding babble used to explain the tradition.

If the braces placed on the underside of the sound board are there, in the first instance, to reinforce a very thin piece of wood that is going to have up to 80 pounds of pressure on it, (either pushing or pulling), at rest, do we need to consider any more than that? If many different brace patterns are used by many different makers, all claiming their method ‘enhances’ the sound best, had we not better take it all with a pinch of salt and go back to first principles?

Sound Board “Tuning”…or is it “voicing?”

A great online source for practical tips on guitar building, from an experienced builder, is O’Brien Guitars’ YouTube channel and their “Tips du Jour” videos. While these are obviously mainly adverts for tools sold by the online provider LMI (Luthiers Mercantile International), that O’Brien guitars seems associated with, they are a great resource of straightforward explanations of tried and tested methods for being successful at certain aspects of guitar building. I was intrigued to see on their video regarding ‘voicing the sound board’ that the Luthier, Robert O’Brien stated something to the effect “I’m not going to voice the sound board, it is what it is. I am going to try and make it more responsive”. Put up against all the ‘babble and gobbledigook’ I have been reading recently about “voicing” or “tuning” the sound board, it came like a breath of honest, straightforward, fresh air. I have watched videos online with very renowned builders stating you have to get a variety of tones across the sound board when tap tuning it, so as not to have a ‘dominant’ frequency. I have also heard equally renowned builders state the idea that you can tune the sound board, preferably to one of the less important tones of the 440 Hz concert ‘A’. On reflection, it strikes me that what you surely want is a good resonance across the soundboard, but more importantly, what has to be born in mind is the fact you are ‘tap tuning/voicing” the sound board before you have glued it to the rest of the body, or put tensioned strings on it, or stuck another big block of wood on its top, called the bridge. It seems to me that anyone who has convinced themselves that shaving small slithers of wood off a brace is going to ‘tune’ a sound board, before they have glued it to the rest of the body and before they have stuck on the bridge, is delusional. That is why when I hear a builder talking in practical terms, focusing on what the desired, realistic goals for the wood are, i.e. “we want to make it resonate the best we can”, then I listen to them. I am not dismissing the idea that ‘voicing’ a sound board is a very skilled art, it obviously takes years of experience to get good at it.

I am however saying that learning techniques and gaining experience that allows me to thin braces down to a point where they are still strong enough to do their job and thin enough to let the sound board resonate to it’s best potential, is something I would like to do. That is going to take time and many builds, I’m sure. Sifting through the babble and baseless assertions about guitar building and the acoustic nature of woods and construction designs, so I can find useful, practical advice, is going to be even more of a challenge!

Final thoughts on Braces and Sound Boards.

Apparently, Jazz style arch top guitars often have their sound boards thinned even finer close to the edge and then go thicker again where they attach to the sides. My understanding is that the reasoning behind this is due to the nature of floating bridges. These types of bridges found on arch top instruments, generally push the string energy down into the sound board, with most of the sound boards movement being a pumping back and forth. The thinner wood around the edge facilitates more back and forth movement. Trouble is, the commonest bracing pattern on arch tops is apparently a big cross brace. By that principle most of the braces in that configuration are across the thicker part of the sound board, (the central part), which is moving less than the thinner outer section, that has almost no bracing across it. So where is the engineering logic in that? If the braces are there to strengthen then they are on the stronger part and if the thinner part has almost no bracing but theoretically is moving more……why have bracing at all? On top of that I see some luthiers putting just two, independent longitudinal braces on arch tops……none of it really makes much sense. If you like the tone of the final instrument, then I suppose any bracing pattern that doesn’t hinder the acoustic nature of the guitar can be argued to be a good one.
It is from this stand point that I chose to use an assymetrical fanned bracing configuration for my arch top acoustic.

IMG_8972
lining up the braces for gluing and shaping. Need to cut sound hole first, though.

The choice is justified by the fact that the sound board is not a traditional arch top design, or a traditional wood for that matter. In general looks the body is based on the arch top guitars by Stephan Sobel. These are evenly arched across the whole guitar width. I don’t know what brace pattern he uses, but I do know that I am putting on a fixed bridge to this guitar, not a floating bridge with a tailpiece. The reason is that the whole thing is an experiment in unusual woods, unusual designs and the breaking of convention and I can find nothing to say you cant do things this way. In profile the bracing is 5mm by 5mm and the supporting cross braces are 10mm by 7mm at their thickest. I have ‘voiced’ the sound board, to the best of my ability. It is a bit dead sounding in places but has a pleasant/coherent ring across the lower bout and around the sound hole. The top was thinned as much as I dared and the bracing was meticulously executed in its fitting to the soundboard. It is the best and finest woodwork I have ever attempted…….weather it all ends up sounding any good…..well, we will have to see.

Here is the build so far

Bibliography:

THE ART OF LUTHERIE  T. Bills 2014 Mel Bay.

THE CLASSICAL GUITAR Mcleod & Welford 1971 Dryad

THE LUTHIERS HAND BOOK. R Siminoff 1980

GUITAR MAKING, TRADITION AND TECHNOLOGY Cumpiano and Natalson,

 
Online resources I find useful:

O’Brien Guitars on you Tube

PabloRequena

Stephen Raphael Marchione

Crimson Custom Guitars

 

note:  Brace yourself, Bridget?  In Ireland there is the joke that Irish foreplay consists of the husband shouting out to his wife, “Brace yourself, Bridget, I’m on my way up the stairs”.

One thought on “Brace yourself, Bridget.

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