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May 28, 2020 - 10:38:26 AM
38 posts since 8/20/2019

I am trying to understand correct soundpost length (height?). Assume a desired placement of the soundpost. Should the distance between the top and bottom plates for that desired placement be measured with normal string tension, no string tension, or somewhere in between?
I have measured using a slackened E and A, but when I install the post, I notice that the top plate elevates very slightly. I am concerned about this and want to make sure I am not creating a situation that could eventually lead to a top crack.

May 28, 2020 - 11:29:49 AM

1696 posts since 8/27/2008
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Sometimes they're put in with not string tension because you get a good view of perpendicular through the end pin hole. I prefer to fit a post with strings on with just enough tension to hold the bridge in place. That helps me locate the post with the treble side bridge foot.

Either way I recommend pushing in the post just enough that it stays in place by itself. That's little enough pressure that it will likely fall down if you squeeze the C bouts together.

May 28, 2020 - 5:36:30 PM

38 posts since 8/20/2019

That makes sense. I have the sense that too little pressure on the soundpost leads to a soundpost that falls over when the strings are relaxed. And too much pressure reduces the freedom of the plates to move and vibrate. Bit of an art.

May 28, 2020 - 5:59:31 PM
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151 posts since 3/1/2020

The sound post must be fitted without tension so that the fit can be checked from from the endbutton. Getting the amount of tension and the fit at both ends right is what separates good setup from bad setup. Never put the strings at tension without a soundpost in place—that’s extremely dangerous and could cause a crack!

There is an old myth that the post should fall over if the strings are loosened. The post shouldn’t be fitted with too much tension, but too little is just as much of a problem.

May 28, 2020 - 8:32:24 PM

1696 posts since 8/27/2008
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quote:
Originally posted by The Violin Beautiful

The sound post must be fitted without tension so that the fit can be checked from from the endbutton. Getting the amount of tension and the fit at both ends right is what separates good setup from bad setup. Never put the strings at tension without a soundpost in place—that’s extremely dangerous and could cause a crack!

There is an old myth that the post should fall over if the strings are loosened. The post shouldn’t be fitted with too much tension, but too little is just as much of a problem.


     That’s right. Although to be clear the strings don’t want to be all the way off unless you want that view through the end pin hole. You might do that to start. When I install a post I am more interested in getting its position optimal which requires viewing and measuring its proximity to the bridge through th F holes.  And when it’s there you want the freedom to quickly loosen the strings and move the post, tighten the strings and test the result. That’s because it is also strongly not recommended to move a post under string tension.

May 28, 2020 - 11:53:13 PM
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151 posts since 3/1/2020

The strings do need to be at tension to make soundpost adjustments. Keep in mind that adjustments should really be small movements of a fraction of a millimeter. The post should be fitted with the setup down in order to check the fit and position from the endbutton hole. Just viewing the post from the ff gives information for north/south position but it doesn’t allow for accurate monitoring of vertical placement. The bridge doesn’t need to be there to fit the post. Cutting the post comes first in setup because the fit of the bridge is often affected by the soundpost.

May 29, 2020 - 7:34:46 AM

38 posts since 8/20/2019

Very interesting and helpful. I had not considered that the bridge fit could/would be affected by the soundpost.
So what I am understanding is that the soundpost is best fitted and placed with the strings off so that the post can be viewed through the end pin hole. The fit includes both ends of the post and the length. The length of the post should allow a fit that is just snug enough to not fall over when there is zero string tension.
Once the post is so fitted, the bridge can be fitted. Then the strings can be replaced and actual finetuning of the soundpost placement can be done with the strings at a partial tension. Sound about right?

May 29, 2020 - 8:21:13 AM

DougD

USA

9609 posts since 12/2/2007

Reread Rich's post above. Final adjustments (which are very small) are made with the strings tuned up because you are listening for changes in the sound.
I used to be able to buy violins at an auction, usually unstrung, and they always needed work. Fortunately I knew a very good and very reasonable luthier who didn't mind working on these things. When I would go to pick them up we'd spend some time knocking the soundpost around very slightly to try and improve the sound. It always seemed the position just before the last one was the best, but it was interesting. I never touched any of them after that.

May 29, 2020 - 8:23:18 AM

1696 posts since 8/27/2008
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Okay. There are different ways. The other ways described work well too. Be careful moving a post under tension because over time that can damage the underside of the top, which is relatively soft.

Edited by - Brian Wood on 05/29/2020 08:26:06

May 29, 2020 - 10:53:27 AM

151 posts since 3/1/2020

quote:
Originally posted by papawhisky

Very interesting and helpful. I had not considered that the bridge fit could/would be affected by the soundpost.....Sound about right?


Yes, that's right. The top moves a little as the post goes into position, even before the strings are put on. This is less noticeable on a violin than on a cello.

Getting the fit of the post right on several axes is crucial, not only for the sound quality, but for the structural safety of the top. If a post isn't seated well it can cause a buildup of pressure in one spot on the end of the post and eventually cause a sound post crack. 
 

I agree that it's not good for the top to have the sound post moving around all over the place. However, adjustments should be very small, and the ends of the post should fit well enough that they shouldn't do damage to the top with adjustment.

May 30, 2020 - 1:49:29 PM

38 posts since 8/20/2019

I truly appreciate all the 'sound' advice. I learn so much in this forum. I'm probably stretching the topic a bit but I wonder why the grain of a soundpost should run perpendicular to the grain of the top plate?

May 30, 2020 - 3:20:38 PM

955 posts since 6/26/2007

Obviously, so the grain of the post won't interlock with the grain of the top.

Jun 5, 2020 - 12:14:07 PM

38 posts since 8/20/2019

Makes sense. Thanks!

Jul 5, 2020 - 11:50:19 AM

3 posts since 7/5/2020

here, this might help
youtube.com/watch?v=t0bnckj19F8

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