The question of the ‘sweet spot’ 12th fret join

As I have begun a sporadically timed blogging journey into aspects and components of the acoustic guitar, I thought this might be a good topic to delve into next.

How the 12 fret join came to be and why extreme alternatives generally won’t work

Technically a guitar’s neck can join the body at any fret the luthier chooses, as long as the scale length of the strings remain as planned.

Historically the acoustic guitar joined the body at the 12th fret. This makes for a sensible decision as the designated halfway point of the strings’ scale length. Considered in general terms, this also means that the bridge is safely away from your sound hole and well enough into the lower bout of the soundboard to get it well activated and moving effectively.

As boring as it sounds – it probably came to be because it was the most practical choice, and subsequently became defined as the expected norm from luthiers and customers alike.

If we then consider other fret join options in extreme low and high numbers – the flaws quickly begin to present themselves to us.

As an example, let’s consider the wider implications of an 8th fret joined guitar (within the scope of popular acoustic guitar designs). One could argue this would be perfect for an open chord strummer who rarely likes to dabble up the more ‘ostentatious’ end. Unfortunately, this set up would push the placement of the bridge so far down the lower bout of the body that from an aesthetic point of view, you would be physically laughed out of the pub for presenting an instrument of visual ridiculousness. Even more disappointing is that the instrument really wouldn’t sound very good either, with a bridge located so close the end block that it chokes the movement around the bridge and doesn’t activate the soundboard sufficiently.

On the opposite end of the spectrum, if you’re such a fingerstyle aficionado that you desperately need those extra frets before the dreaded ‘join’ resulting in a 15th or 16th fret join, you’ll soon find your nimble efforts are thwarted by your bridge very nearly falling into pit of your sound hole, taking all structural integrity with at the same time. Cue guitar implosion of great and wonderous magnitude. You also better hope you have super long arms to be able to reach all the way down a longer neck to the first fret position.

So, it was quickly identified by sound minds that there are certain parameters that need to be worked within, but there is however some scope for manoeuvre….

Martin Guitars, being the driving force of many innovations in steel string acoustic market, was the first company to present the idea of anything other than a 12 fret join, releasing their 14th fret join Orchestral Model in 1929 – and the punters loved it!

The 14th fret join became increasingly popular and ever-more associated with modern, larger steel string acoustics.

At this point in the blog, I could take the opportunity to digress into the prospect of the 11th or 13th fret join, as one could reasonably argue that this still falls within the parameters of guitar architecture, but there’s only so much time in the day to confuse oneself.

Tonal differences and the application to smaller bodied guitars

Since I started building guitars about 10 years ago, it seemed to me at the time that only smaller bodied and ‘Parlour’ style guitars were accepted as 12 fret models, and for tonal reasons this certainly makes sense.

The general understanding goes that the further the bridge moves down in to the more central ‘sweet spot’ of the lower bout, the more power and sustain an instrument will have. For small bodied guitars this an is important option to consider taking advantage of, as they can sometimes sound a bit ‘boxy’ because of lack of soundboard surface area and air volume in the body.

A 14 fret join guitar moves the bridge closer to the waist of the guitar which is generally a much stiffer area of the soundboard. Larger model guitars don’t tend to suffer so much from the boxy syndrome, so many players are fine to sacrifice the ‘sweet spot’ bridge placement for increased access and a feeling of familiarity.

But it’s still interesting to think of the tonal difference that can be achieved by bridge placement, even on a larger model. If a bridge is able to vibrate more freely in a more central spot away from the waist, the general physics of it all suggests an instrument that can produce more power and perhaps a tonal character that is a bit more open.

I hope this begins to demonstrate there is no theoretical basis of reason why bigger models can’t be 12 fret joins. Once again, it is often governed by tradition, what sells and what people are used to. I have begun to notice in the last 5 years or so more luthiers and guitar companies are beginning to adapt their larger models into 12 fret options too.

Physical adaptions from 14 to 12 fret model

Both my TM and TG models were originally designed as 14 fret models, but I have since adapted them both to be 12th fret join options too. I have also adapted my TG model for a multi-scale system. To be able to do this there are a number of other factors in the build to consider before taking the plunge.

I thought it might be interesting for players to understand the adaption process a little more to get a wider understanding of some other things that will be affected by these structural decisions.

Neck to body joins are embedded in a jumble of knock-on effects the luthier must mentally wrestle with. This includes sound hole placement, fretboard length, guitar waist position, bracing pattern and lower bout shape. No one decision can be made on any of these aspects without considering the effect it will have on the others in play.

When adapting a pre-existing 14 fret model into a 12 fret model, the fretboard for example will need to be re-thought out to ensure you get the right number of frets needed before it topples over the edge of the sound hole. The bracing pattern inside also needs to be quite markedly adjusted to lower the bridge plate toward the lower bout. All the connected brace placements will need to be adapted accordingly.

Unless the sound hole is moved from the originally designed position, then you will probably find that you won’t get as many frets on a 12 fret join guitar. To get the standard 21 frets, your sound hole will probably have to be way too far down the body to be structurally reasonable, in which case an increased fretboard ‘overhang’ is certainly an option here.

The X- brace (if that is the luthiers design choice) will generally be wider splayed on a 12 fret model to accommodate the lower placed bridge plate. Tonally this could have as much of an effect on the finished result as the bridge placement difference.  

For me these design adaptions have been interesting and insightful exercises to carry out, because it makes you consider and evaluate all of your prior decisions when adapting something that already existed rather than creating something completely from scratch. For a player I think it is interesting to have a general overview of how the guitars structure is changing when considering what option is best for you.

So, what does a 12 fret guitar have going for it over a 14 fret?

• Tonality – if you want the loudest, open and most powerful sound from an instrument you might want to consider a 12 fret join model.
• Playability – lack of accessibility through a shorter neck and less frets before the join can be compensated through cutaways or scoops into the body of the guitar.
• Comfort – having only 12 frets on a neck brings everything a little closer to your body. Your arm will not be stretched out so much when lower down the fretboard, which can feel more comfortable and perhaps less pressure on the wrist and hand in certain circumstances.

All sounds too good to be true – what’s the catch?

• Less frets – you don’t want a nasty surprise when you go to hit that final high note and find it’s not there anymore.
• Loss of familiarity – with the playing arm in a slightly different position, that can throw you off from what you’re used to.
• Character of sound – there is a certain sound of a 14 fret model that people have come to greatly appreciate and become lovingly familiar with – if you like the way your 14 fret model sounds that’s absolutely smashing – keep with it!