The Sound Post
The sound post has both a structural and acoustic function in the instrument. A bowed instrument is a system of harmonic relationships, a system of resonances that all work together to produce overtone structures that are pleasing to the ear. An instrument then is "tuned," not in the sense that strings are tuned to a pitch, but in the sense that the various parts of the instrument that vibrate are all in harmony with each other. This includes all of the wooden parts as well as the air cavity itself. The sound post is part of that harmonic design.
The secret of Stradivari (really Amati, but that is another subject) is in this harmonic system, and it is a complete system. This is much like tuning an engine and exhaust system in a car, if you are familiar with that concept.
As a structural component, the sound post is giving support to the treble side of the instrument. Without it, the top would slowly cave in. The corresponding structural component on the bass side of the instrument is the bass bar (which functions something like a leaf spring in a car.) The bass bar is fitted and glued into the top before being put together with the body, and it is also "tuned" at this stage. The sound post is fitted through the f-hole after the instrument is put together.
The sound post is a dowel, but not a hardware store dowel. It is made of spruce, the same material as the top, and just like the top, the quality of the spruce is important. These spruce dowels that are suitable for sound posts are purchased from specialty supply companies. For better instruments the violin maker will often make the dowel starting with a block of fine spruce.
It is critical that the sound post fits perfectly. This is accomplished by first approximating the length of the post, then inserting it into the instrument through the f-hole with a special tool. The repair person then uses a dental mirror and a tiny flashlight in order to assess the fit. The post is removed and reinserted as many times as it takes to continuously remove material from the high spots until it fits.
The proper placement of the post that supports the harmonic design of the instrument, is just behind the treble side bridge foot. There is also a measurement that relates to the edge of the f-hole, the foot of the bridge, and the bass bar. Along with a fitting that puts the sound post in the proper placement, it must also fit perfectly all the way around on the ends. All of this is done with a very sharp violin maker's knife, removing very small amounts of material at a time, to accomplish the critical perfect one-to-one fit with the top and back.
Once the sound post fits perfectly in the correct position, and the instrument is strung up, then there are very subtle, micro-movement adjustments to the post that are done by ear, the final "tuning" of the post with the instrument.
A properly fitted and well adjusted sound post makes a world of difference, and skill levels vary tremendously in this regard. You may have seen people take a "hit or miss" approach to sound post adjustment, but that is only done when someone has not been schooled in the harmonic design principles, and application of those principles, that the old Italians like Amati, Stradivari, and Guarneri understood so well.
Many bowed instruments are sold with the sound post either not fitting correctly, not adjusted correctly, or both. This is something that I pay close attention to, and it is something that I know how to get right. If you purchased your instrument from me, the post was adjusted perfectly for you. If your instrument was purchased elsewhere, and you think it might have potential for better sound, give me a call and I will assess that for you.
The secret of Stradivari (really Amati, but that is another subject) is in this harmonic system, and it is a complete system. This is much like tuning an engine and exhaust system in a car, if you are familiar with that concept.
As a structural component, the sound post is giving support to the treble side of the instrument. Without it, the top would slowly cave in. The corresponding structural component on the bass side of the instrument is the bass bar (which functions something like a leaf spring in a car.) The bass bar is fitted and glued into the top before being put together with the body, and it is also "tuned" at this stage. The sound post is fitted through the f-hole after the instrument is put together.
The sound post is a dowel, but not a hardware store dowel. It is made of spruce, the same material as the top, and just like the top, the quality of the spruce is important. These spruce dowels that are suitable for sound posts are purchased from specialty supply companies. For better instruments the violin maker will often make the dowel starting with a block of fine spruce.
It is critical that the sound post fits perfectly. This is accomplished by first approximating the length of the post, then inserting it into the instrument through the f-hole with a special tool. The repair person then uses a dental mirror and a tiny flashlight in order to assess the fit. The post is removed and reinserted as many times as it takes to continuously remove material from the high spots until it fits.
The proper placement of the post that supports the harmonic design of the instrument, is just behind the treble side bridge foot. There is also a measurement that relates to the edge of the f-hole, the foot of the bridge, and the bass bar. Along with a fitting that puts the sound post in the proper placement, it must also fit perfectly all the way around on the ends. All of this is done with a very sharp violin maker's knife, removing very small amounts of material at a time, to accomplish the critical perfect one-to-one fit with the top and back.
Once the sound post fits perfectly in the correct position, and the instrument is strung up, then there are very subtle, micro-movement adjustments to the post that are done by ear, the final "tuning" of the post with the instrument.
A properly fitted and well adjusted sound post makes a world of difference, and skill levels vary tremendously in this regard. You may have seen people take a "hit or miss" approach to sound post adjustment, but that is only done when someone has not been schooled in the harmonic design principles, and application of those principles, that the old Italians like Amati, Stradivari, and Guarneri understood so well.
Many bowed instruments are sold with the sound post either not fitting correctly, not adjusted correctly, or both. This is something that I pay close attention to, and it is something that I know how to get right. If you purchased your instrument from me, the post was adjusted perfectly for you. If your instrument was purchased elsewhere, and you think it might have potential for better sound, give me a call and I will assess that for you.