The diameter of the finished soundpost is about 6 mm. The length depends on the arching, but may be a little above 50 mm in most cases.

To measure the required length of the soundpost, insert a pencil (or the soundpost blank) in the right upper f-hole eye at the right angle to the plane of the violin, until its tip touches the back plate. The point on the pencil level with the top of the arch at the center of the violin denotes the approximate length needed.

Choosing the wood

You need good quality spruce. It should be straight, and to ensure it has no runoff, it should be split. It should also be dense enough - ideally have around 5-6 annual rings in its final diameter (6 mm). The wood for the top plate is usually good for soundposts, but it varies in density, so split off a piece that has the required number of rings and is approximately 8 x 8 mm wide. The length of about 70 mm should be enough.

Now you need to round the stick, either by turning on a small lathe, or using your hand drill clamped in a vice, the stick fastened in stead of your regular drill bit. Use coarse {80} sandpaper and wrap it around the turning stick to remove material. Keep moving the sandpaper up and down the stick to achieve consistent thickness. When you have reached 6 mm everywhere, you are finished.

Or you can, of course, buy the soundpost blanks pre-made.

Cutting the soundpost

Use a razor sharp knife. Avoid files even though they may seem easier to work with in the beginning. The knife gives you the precision and flexibility needed. You know how much wood and where you have removed.

To cut the soundpost to its length, roll it on the table while making a cut around its circumference. When the cut is deep enough, you can break the soundpost off.

Now, to start fitting the post, you can try to insert it starting somewhere on point A. It will still be too long, so you will not be able to insert it farther to the side, to its final place, see Fig 1.

Using a knife, the soundpost resting on your workbench, cut a sliver of wood from both ends and reinsert again. Try to get a feeling for this, do as many cuts as possible, trying to get thin slivers, to get the hang of it. You should be able to remove just part or the diameter or a whole consistently thick wafer if needed.

Fitting the soundpost

The default position for the soundpost is about 2.5 mm behind the treble foot of the bridge, see Fig 1. You should aim to reach this position before adjusting the soundpost to change the sound.

The soundpost is held in position with the help of the soundpost setter, as in Fig 2 While the soundpost is inserted, you may keep the setter attached to the soundpost for easier manipulation.

This requires patience. Keep cutting and reinserting, inspecting the fit, also using the inspection mirror for parts where you cannot look. Perceive how both the top and the bottom plates are angled as you proceed more to the right side. The goal is to get the soundpost approximately in the position in Fig 1 standing at right angle to the plane of the plates, in full contact with the plates. Again, make sure the soundpost is perfectly perpendicular to the violin plane, both when you see it through the f-holes and the end-pin hole.

You can measure the position of the soundpost relative to the bridge foot using a simple strip of thicker paper, cut in the middle, as in Fig 3.

Finalizing the position

Once you have reached the default position. Check everything sits perfectly, both through the f-hole and the end-pin hole, using the mirror. It is important that the soundpost be put in its default position with just light force.

You can now put on a set of strings together with the bridge and try the sound of the violin.

The soundpost serves as a kind of fulcrum for the top plate so its position influences the action of the plates, the bridge and the strings. With this in mind, you can change to a certain degree the timbre of the violin (and playability). With the soundposts position you not only change the spatial relationship between it and the moving parts but also the tension. The more east you go, the more tension you get.

Category: Setup
Comment by
2014-12-08 01:46:10
A good tip is to squeeze the side of the violin gently at the C bouts to release the sound post if it is wrong positioned, since this reduces the tension between the belly and back at the soundpost position and lets it fall.

It is essential to use a well padded soundpost setter so that its edges do not damage the F holes, and to make sure the end of the soundpost setter is really sharp, to be able to spear the soundpost effectively when putting it in or retrieving it.
Comment by
2016-03-09 02:37:30
The top and bottom of the sound post should be shaped to the top and bottom of the violin plates for perfect fit.
Comment by
2016-07-13 23:24:57
You can look through the button hole to make sure the sound post is standing dead vertical.