You and Your Soundpost
by Peter Van Arsdale

In “How Does A Violin Work?” I talked about the relationship between the bridge, soundpost and bassbar.  Now I would like to go into a little more detail on the soundpost. I will cover checking the position, and how the position affects the tone and response of the instrument. Some of this you can do yourself, perhaps the more adventurous will attempt cutting a new soundpost.

This tiny piece of wood, l’anima or “soul” in Italian, can affect the tone of the violin more than any other piece of wood in the instrument. Movement of just a fraction of a millimeter can dramatically change the tone and power.

I had an interesting experience at VOM camp this summer (actually I had non-stop interesting experiences at camp, but this one in particular had to do with a soundpost). Martin Hayes came into the shop with his newly acquired fiddle. He said he loved the sound but the A string was a little muted and could I help him. The first thing I checked was the condition of the strings, they appeared relatively new and in good shape, so then I turned my attention to the soundpost and noticed that it seemed a little close to the bridge. I took some measurements and with my handy dandy soundpost setter I gently tapped the post back, probably no more than a tenth of a millimeter. I think I was more surprised than he was when he played it and the A string jumped out of bed and started stepdancing right there in the shop.

Let me explain more about this lovely little frustrating piece of wood. The wood should be straight grained spruce which can be purchased in lengths already turned or can be carved from a piece of scrap tonewood. When set in the violin the grain will run perpendicular to the grain of the top. Before attempting any adjustments first hold your violin horizontally with the right foot of the bridge closest to you. With good light look through the right f hole and notice the position of the soundpost. It should be vertical and approximately one diameter behind the foot of the bridge. It should be set in from the edge of the f hole 18mm or 23/32”. 

An easy way to determine this is to take a piece of heavy paper or cardboard such as a matchbook cover and first measure the distance of the inside edge of the LEFT f hole to the bassbar and then compare this with the distance of the inside edge of the RIGHT f hole to the soundpost. They should be the same and if the violin was made with standard specifications it will be 18mm.  If the soundpost is not in the correct position and the tone is not what you want now is the time you might want to go to your favorite luthier and have it adjusted. Or you can try it yourself.

To adjust the soundpost insert the soundpost setter through the left f hole and tap gently on the upper and lower ends of the soundpost. Move in small increments and test by measuring, looking and playing. This can be done with the instrument tuned to pitch. If the soundpost will not move, it is probably too long and will need to be trimmed or replaced. A soundpost that is too long can put undue pressure on the top plate and cause serious damage to the instrument, the much dreaded “soundpost crack”. This crack is not actually in the soundpost but runs along the top of the instrument under the right foot of the bridge. This greatly reduces the value of the instrument, affects the tone and is a very expensive repair. So the rule is don’t force the soundpost, use small movements and test frequently.

Generally, moving the soundpost too close to the bridge the sound becomes scratchy with slow response, too far away and the sound becomes weak and fuzzy. To enhance the lower strings, move the top of the soundpost toward the centerline. To enhance the top strings, move the soundpost away from the centerline.

Peter Van Arsdale is a local Berkeley violin maker who also does repair, restoration and bow rehair.
© Peter Van Arsdale, 12/2000

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