Lending Support
Alex Bishop peeks behind the curtain to unveil the mysterious world of acoustic guitar bracing, and what makes it so important
When I’m discussing a potential guitar commission with a client, there are so many different aspects to cover, but a handful of topics are perennial. Naturally, a lot of players are keen to talk over which timbers we might be using. The shape and outward design of the guitar is key, too. But how often do players think about what’s going on ‘under the hood’, so to speak? I have been working on a pair of guitar soundboards for clients, and (perhaps dauntingly) one of them has requested that I experiment a little bit, so this week I have been turning my attention to bracing patterns.
Soundboard bracing is the name given to the arrangement of struts on the underside of the top of the guitar. To understand the purpose of bracing, one must appreciate how delicate the top of a typical acoustic guitar is. Soundboards tend to be made of lightweight softwood measuring less than three millimetres thick, which is necessary for the top to vibrate freely. Given that the typical string tension on an acoustic guitar equates to a full-grown adult standing on top of it, without some supporting structure glued to it the soundboard would be crushed to bits before you could even finish tuning up. Too much bracing in the wrong place adds excessive mass, inhibiting the ability of the top to vibrate. Simply put, this could limit how good the guitar is going to sound.
At this point, the role of any pioneering guitar luthier is to consider exactly where these supporting struts should be placed, and how much of it there should be. The ‘perfect’ guitar is delicately balanced between the two extremes, keeping the bracing lightweight and in all the right places, without compromising tone but providing enough strength for longterm reliability. For my experimental soundboard I decided I should start by reconsidering some archetypal bracing patterns.
Luthiers of the past two centuries offered a plethora of solutions, including ladder bracing (struts arranged directly across the grain), fanned braces (radiating from the soundhole) and most famously X-bracing (primarily a pair of intersecting braces that span the whole top). Without doubt, each bracing pattern has a signature sound. I build steel-string guitars of both ladder- and X-braced flavours, and I daresay in a blindfold test
I could confidently tell you which was which every time.
For this model – a nylon-strung guitar – I was asked to incorporate a lattice-braced design. Australian luthier Greg Smallman is credited with pioneering this design: an ultra-thin soundboard coupled with a grid-like structure of thin intersecting braces. Smallman guitars make use of modern materials, such as carbon-fibre reinforcement, but as a devoted disciple of all things dendrological, I’ll be sticking with wood throughout. I decided to use this system on the area of the soundboard directly beneath the bridge only, in an effort to avoid unnecessarily stiffening parts of the top that might not need extra strength.
This week I’ve been putting these plans into reality by cutting up spruce from my timber store. I have an ideal selection of short, super-tight grained blocks that I decided to chop up into thin strips for the lattice-braced section. The tighter the grain, the thinner and lighter I can go with these braces without compromising strength. It’s at this point that I’ve become aware that I leave the ‘science’ behind and instead begin to engage the artistic, intuitive side of my brain.
If people ask me about what I enjoy about guitar making, in part it’s about the joy of operating at the boundary where art and science blend. There is an inherent unpredictability that comes from working with wood that means you just never know which guitars are going to be extra-special. While there isn’t a magic formula for this, I’m feeling confident that the end result will be a highly responsive guitar, and – most importantly – one that holds up to the rigours of many generations’ worth of music making.
“The ‘perfect’ guitar keeps bracing lightweight and in all the right places, but provides enough strength for longterm reliability”