Soundboards

This week I'd like to share some construction photos. I'm currently working on three new builds a the moment - a gypsy jazz guitar, a 000 folk guitar and a new model based on a Martin 'OM' size.

'000':

'OM':

The soundboard of the guitar is generally regarded as the 'heart' of the sound of an instrument, whereas the back and sides will add or take away overtones. So it's important that a soundboard is allowed to vibrate freely whilst also being made stable enough that the tension of the strings doesn't warp or break it. The bracing patterns I use are broadly based on the original Martin guitars, however this time I've decided to try some subtle new ideas.

Mainly I'm using ebony bridge plates, which is one of the densest and most sonorous of woods. The idea of the bridge plate is partly to protect the ball ends of the strings from damaging the softwood of the soundboard, however it also plays a tonal role as it's placed directly beneath the bridge - the area from which the string vibrations are transferred to the rest of the guitar.

I'm also experimenting with differently sized 'treble' braces. With most other variables kept the same, it will be interesting to hear the results. Of course this is no scientific experiment, but it's nice to try these things out, or you'd never know!

I also like the carve the join between the two 'X' brace bars:

Many people stick cloth over it like with some of the old Martin guitars. However it's only an extra 20 minutes to do, and adds a little artistic touch.

And this is my new jig for cutting out soundboard braces of any shape:

It's perspex, which is a nice material for jigs because you can see what you're working on. You can make out the brace clamped in place beneath the surface. That edge is curved to a radius that matches one of my workboards for my go-bar deck. Once routed out, they get glued up:

This system works great because no matter where I put the braces it fits against the dished surface like a glove. That way, I can make adjustments to the bracing pattern if I decide to in future. It also means I can used the same methods for every guitar I make. I have a corresponding set of jigs for the backs of the guitars too, which have a different curvature.

Also this week, I've been knocking out some linings with another new jig I made recently. I don't like buying linings pre made because they are often very big and inelegant. This way I can get things just how I like them:

I think the next step I want to take is to try some 'suspended braces', where the footprint of each brace is much smaller but it's structural significance is the same. The idea behind that would be to try and maximise top vibrations whilst maintaining the same structural rigidity. Who knows what new overtones that might uncover?? But that's for the next guitar...

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