Here I will be adding a soundport to a Leoff custom Dreadnaught.
Soundports have become popular for the way they enhance what the player actually hears, sort of like a stage monitor for an acoustic guitar. While on the surface it seems simple enough (just drill a hole in the side and that’s that), but as with most things involving guitars, it is not really that simple. First, the size of the port must be determined. This will also involve the size of the main soundhole. On a new build this is not an issue, as one can adjust the size of the soundholes before they are cut. But on an already existing guitar, sizing the port is critical to avoid spoiling tone. In this case, I was lucky that the main soundhole was a bit small for the body size.
The side of the upper bout where the port will be placed will need some reinforcement to keep it from warping or splitting as the guitar goes through its natural aging process. The body of the guitar is Walnut so that will be the main part of my reinforcement. I thin out a piece of walnut to the same thickness as the side and bend it to match the shape of the body on a hot pipe. The patch is then trimmed to size. I love to use this old saw that was my Great Grandfather’s for these types of tasks.
The side that will glue against the inside of the guitar is laminated with a .025” thick mahogany veneer oriented cross grain. The mahogany will add some stability and will serve to create a balanced veneer core panel like a piece of furniture grade plywood. Here, we see both sides of the panel and how it fits the shape of the guitar. Notice it is not bent to the same shape as the outside of the guitar, but rather the inside, where it will fit against.
The fit must be really good. Any voids in the glue up will ruin the structural integrity of the reinforcement.
There is a small side brace in the guitar that is in the way. It had to be removed very carefully to avoid tearing up the walnut side and creating a void when I glue in the panel.
The inside of the guitar is prepped for the installation of the panel by sanding the area with 220 and then a thorough cleaning. The panel is glued in and held tightly in place by some repair magnets at the corners and then firmly clamped with some wooden go-bars. This clamp arrangement is run through a few times dry until I am satisfied that the panel is tight, in the right position and can be accomplished in a reasonable time before the glue starts to set.
Once this is completed I am ready to cut the new port. The side is masked off and the port is laid out. The hole is cut using my dremel with a router base and a spiral cut mill.
A bit of sanding and some finish and it is all finished. Anyone would be hard-pressed to tell that this was an addition to this guitar.
Originally published in Brian Howard's Guitar Building & Repair Blog.