Sound Post Adjustments

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This page contains all you need to know about sound post adjustments.

The long term effect of sound post adjustments is misunderstood by many musicians. The movement of a post can change the sound. Moving it closer to the treble f hole usually makes the sound brighter, sometimes harder.

The opposite direction makes the violin sound warmer, darker, and sometimes a little less powerful. It’s not really the position of the post itself, which makes the sound brighter, but the different pressure it exerts on top and back.

We made a lot of experiments at my current shop and throughout my career with making two posts with slightly different lengths from the same long dowel. Then, we inserted them aiming for the same pressure. That resulted in two different positions of the post.

However, the sound felt identical. Of course, when moving the longer post to the position the shorter post had held, the sound was quite different.

So far, this is probably not a surprise to most of you seasoned musicians. But! There is a catch. We all know that changing humidity has quite the influence on the sound of instruments. Generally, dry wood is stiffer than wood in high humidity. Stiffer wood makes the sound brighter.

The stiffer the wood, the quicker it tends to want to get back to resting position after being forced to vibrate. The quicker vibrations cannot force the played note to be higher, but the higher harmonics of that note get more enforced. That is what makes the sound brighter, or in some cases, tighter. (adsbygoogle = window.adsbygoogle || []).push({});

In addition to this phenomenon, wood shrinks when the air is less humid. Cracks develop in the upper and lower bout near the edges when it’s very dry. Dryness doesn’t create cracks in the top where it’s arched.

Since the top is glued to the ribs, it cannot shrink sideways but flattens out. The top and back arching are now flatter than when it was humid. The post does not shrink lengthwise. The result of the flatter arches is that the post now exerts much more pressure on the top and back. That, as mentioned before, will also make the instrument sound brighter.

Depending on the initial stiffness of the wood, some instruments that are naturally on the tighter side sound better when it’s humid. And other better when it’s very dry. If your instrument has a better sound when it’s humid, you can alleviate the dry weather issue by using a humidifier. The Dampit brand works as a simple solution.

Case humidifiers only might prevent the pegs from shrinking and slipping down. The little two-inch tubes filled with water were originally made for cigar boxes.

Once the case is closed, there is no air movement within the case. For everyday use, there is no way that enough humidified air will penetrate the f holes all the way to the inside of the violin body, where it is really needed to prevent the plates from shrinking.

If you play your instrument a couple times a week, all the humidity, which may have slowly accumulated in its case, disappears when you open it.

Say you go on vacation for two weeks. A good case humidifier may help a little, though a Dampit in each f hole is much more sufficient for the inside of the violin body.

There’s not much you can do if the instruments sounds better in a dry climate. Inserting small silicone bags for dryness into the f holes is obviously not an option.

Post movements away from and closer to the bridge are more permanent in their effect. The further you move the post away from the bridge, the more leverage you have for it to move to the top, and the instrument may respond easier. However, if you move the post too far from the bridge, you will lose power.

In our experience at the shop, the differences in thickness of the post has more effect on the sound. A slightly thicker post makes the sound darker. Too thick will make the sound muffled. A thinner post creates a brighter sound. And too thin will create a shrill tone. The most apropos thickness depends entirely on the individual instrument.

A very effective way to manipulate the sound is to experiment with different strings. Don’t go out and buy lots of strings. If you are familiar enough with a particular string or string instrument dealer, ask them if they have some used G strings to compare to other strings of your violin. It’s easier to make a comparison to the neighboring D string as you play, rather than going by memory and play one set against another.

Finally, I would like to address another misconception. If there is a particular note on the violin, which doesn’t sound right, e.g., is too weak, you will not be able to improve the strength of this note in relation to the others by moving the sound post.

If you get more power with an adjustment, the whole area gets louder, but the individual note is still weaker than the notes above and below.

Most of all, don’t underestimate the power of suggestion, which can make you feel that the problem was resolved, but a few days later it miraculously comes back. Sort of like the magic trick where a woman is sawed in half, but after was instantly pieced back together.

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