Chris Lilley Violin Maker
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Useful information on stringed instrument setupChrislilleyviolins.com |
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The sound post -The heart of the violin The sound post is one of the most critical components in the acoustic setup of a bowed instrument, but what is it? If you look through the F-hole on the E string side of your violin you will see a little round piece of wood running between the top and the bottom of the instrument. It is about 5 to 6mm in diameter - that's the sound post. It serves 2 very important functions: The first is fairly obvious, it helps support the belly (top) of the instrument by transferring the load to the back. Without the sound post the belly would begin to sag and possibly even crack under the pressure placed on it by the bridge. The second function is its effect on the sound of the instrument. The exact placing of the post is essential in making the strings balanced relative to each other. Even moving the post by a millimeter forwards, backwards, left or right can significantly effect the evenness of volume and tone across the strings.
The post is fitted before the strings are put on the instrument. The end pin is removed to allow sighting of its vertical position relative to the belly and back. It is usual to use a small inspection lamp and dentist style mirror to check its exact fit. As the post is held in place solely by the friction between itself and the plates of the Violin, no glue is used at all, the ends of the post must perfectly match the internal curve of the instrument. Sound post related instrument problems There are a number of problems that can occur when a sound post is incorrectly fitted or when other external circumstances have effected your instrument. If the post is too loose it may not take enough load from the belly which can cause a lack of power in the A and E strings. This is possibly the least of your worries, as there is a chance that the belly will start to sag slightly. The belly of a violin is only 3mm thick at the most and the pressure on it is very high. Also, should you be in a situation where the pegs de tune and the bridge falls down the post may drop and need to be refitted. Under no circumstances should you put the bridge back up and try to use the instrument until the post has been put back in place properly. If the post is fitted too tightly, it pushes the plates of the instrument apart. It will start sounding hard, the E string will become very brash. A much bigger problem if the post is far too tight is the possibility of a "sound post crack" where the post, instead of supporting the belly can actually make it split open (this can also happen to the back). Sound post cracks are very difficult to repair as they actually involve taking the instrument apart and putting in a patch. They cannot be fixed by the usual method of using reinforcing studs. If your instrument has a hard sound it is possible the post is too close to the bridge. If the E string is overly loud compared to the A string, the post may be too far out (in relation to the bridge foot). If the E string is too weak, the post may be too far in and if the sound post is too far back you will have an underpowered indefinite sound.
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