Topic: Sound post settings

[piersdad]

 
 The sound post is one of the more important parts of the violin family of instruments.
Normally it is set about 3 mm behind the position of the bridge but this varies according to the instrument.
A rule of thumb is that the higher the tap tone( and the thicker ) the top sounds then the further away from the bridge the sound post has to be.
The theory behind this is that a heavier top needs more leverage to get the top vibrating in a nice harmonic in sympathy with the back.
A thin top is weaker and will resonate at a lower frequency and is easier for the bridge to set up those lovely 3 and 4th harmonics.
You will find the opposite with a cheap hard varnished violin that students first try out
 The hard varnish stops the top from moving and the manufacturers always err on the side of caution and make the tops thicker than they need to (students are often a bit hard on handling violins) so if the top is hard varnished and it sounds very high note when tapped with a knuckle, then the sound post could be as much as 4 or 5 mm for a violin and 6 to 8 mm for a cello away from the base of the bridge above it.

The sound post should be just gently pushed into place and not jammed up hard against the top and back.
Putting the sound post in is a skill that requires patience and I use a special sound post-setting tool.
This can be made with a piece of coat hanger wire by flattening one end with a hammer till it looks more like a screw driver.
This is bent in such a way that when the post is impaled on it the post when inserted carefully in through the 'F' hole it can be placed in the right place.
If it falls over then you swear loudly and get a sharp long needle and impale the post and gently pull it out through the 'F' hole.
Moving the post while it is in place you need a curved and hooked piece of wire (the other end of the post setter) and hold the post in place with this, and using a steel ruler in the opposite 'F' hole, you can tap the post sideways gently at the bottom and the near 'F' hole for the top of the post.
Though even for the experts a sound post can go in and be exactly where it is needed first pop and just a few seconds to fit.--- of it can be  an hour of exasperating prop and fall and retrieving of the sound post .
A bright light and peering through the end pin hole is always a good way to see what you are doing