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Mat Roop

sound post effect on tone

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Lots of info on the effects of moving a sound post... but all that is assuming the post is vertical.

What happens if just the top or just the bottom of the post is moved... either N, S, E or W?.. assuming of course that the fit is ajusted accordingly

Thoughts? Any experimental results/ general consensus??

Cheers, Mat

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Technically, moving only one end of the sound post while leaving the opposite end in place cocks the sound post

and ruins its fit to the top and back plates. However if the post was not correctly fit in the first place

any change could be an improvement. I believe the fit of the north edge sound post to the top is most

important as this defines the lever arm distance between the bridge foot and the post as fulcrum.

Moving the top end of the post back away from the bridge insures that the edge of the post closest to

the back of the bridge foot is making good firm contact and this alone an often cause an improvement

in playing and tonal qualities.

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38 minutes ago, donbarzino said:

...

... I believe the fit of the north edge sound post to the top is most

important as this defines the lever arm distance between the bridge foot and the post as fulcrum.

Moving the top end of the post back away from the bridge insures that the edge of the post closest to

the back of the bridge foot is making good firm contact and this alone an often cause an improvement

in playing and tonal qualities.

Interesting point!  I'll try it sometimes.

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I think that there is a consensus on the soundpost looking vertical when viewed from the side, apart from this, moving the base of the soundpost slightly nearer to the ribs, or towards the back's centerline, can be a way to adjust the soundpost tension when needed. I do that on basses especially (They rarely need "seasonal" soundposts and bridges here in Sicily). When I make a new soundpost, I always try to make it vertical also when looking from the button/endpin hole. I think that Donbarzino's answer is in perfect agreement with another fact, that is, quality of contact of the soundpost with top plate is very important (2nd string especially).

Chungviolins' advice is something that we recommend to musicians in our workshop, but sometimes they say that they are a bit afraid to do that.

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19 hours ago, donbarzino said:

Technically, moving only one end of the sound post while leaving the opposite end in place cocks the sound post and ruins its fit to the top and back plates. ...

Of course... I agree,  meaning that each angled fit needs to be a new post fitted to that angle. ..  a lot of work, so if someone has done some testing, then that would be helpful. Trying not to reinvent the wheel.

 Cheers, Mat

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1 hour ago, Giovanni Corazzol said:

....moving the base of the soundpost slightly nearer to the ribs, or towards the back's centerline, can be a way to adjust the soundpost tension when needed. ....

And that will change the fit of the top and bottom of the post ... but with basses, the top of the post is slightly rounded, so that allows some tilt.

Would that principle not apply to violins... just on a smaller scale?  Does anyone fit a violin post with a minimally rounded top?

Cheers... Mat

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20 hours ago, chungviolins said:

Try moving bridge a little bit rather than sound post if the sound post is set correctly.

You can adjust many things without adjusting post.

that means there's not a single correct position for the bridge?

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2 hours ago, Bill Merkel said:

that means there's not a single correct position for the bridge?

"Correct" according to whom? The customary position has been arrived at empirically as the one which most players and luthiers think gives the "best" result, but not all violins are constructed the same and not everybody agrees as to what balance of sound is "best". I suppose somebody must have published measurements to locate that position, which I'd be interested to know. However, that still leaves considerable room for disagreement and experimentation

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i know little about the hardware compared to you guys, but my thinking before reading that was correct bridge position comes from the center line and the stop length.  wondering if i should unlearn that

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I've played with moving my soundpost and bridge around a bit, trying to get the best sound out of my instrument. Generally speaking, I found that position of both in relation to one another (foot of the bridge and top of the soundpost) matters a great deal. And for my german trade del gesu copy, it actually sounded best having the bottom end of the sound post a few millimeters to the left of where it should stand. Your ear should be the judge for your instrument, methinks. 

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9 hours ago, Giovanni Corazzol said:

I think that there is a consensus on the soundpost looking vertical when viewed from ththe ribs, e side....

I don’t believe there is a consensus.  Moving the top of the post does different stuff than moving the back of the post.  Limiting your options based on arbitrary parameters and reasoning is a bit like trying to get a full house while only using 4 of the cards you were dealt,

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19 hours ago, Jerry Pasewicz said:

I don’t believe there is a consensus.  Moving the top of the post does different stuff than moving the back of the post.  Limiting your options based on arbitrary parameters and reasoning is a bit like trying to get a full house while only using 4 of the cards you were dealt,

Jerry, I am happy to hear this really, I am aware that I can rely too much on "conventional" rules and I should rather say "I hope that there is a consensus on this"! I usually don't want to change things that are working good, and in case an instrument with a slanted post (if the fit is OK) needs servicing, I will pay attention and try to understand why it's been made this way. But, please can you explain further: Mat was talking about "moving a sound post", and whenever I make small movements of the top of the post, I try to adjust its back too, (and restore "vertical") if I'm moving it North <-> South, but if I move the top on the East <-> West axis, and I find any improvement, I don't always move the back. My idea was that this doesn't ruin the fit (if the movement is very small) most of the times, while in bringing the top nearer or farther from the bridge without moving the back end, it's easier to create a gap. If I make a bigger movement, and bring the soundpost out of vertical, it will need trimming and I can't put it back where it was before... I am sure that my scheme is too rigid and that I need to look at the acoustical function of the instrument's back with more attention.

I am looking forward to reading your answer, thanks to you and to David for posting (or recalling) all this useful information.

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Most sound post adjustments involve dragging the poor thing around and scuffing the surface of the belly from one poor position to another to find the least worst. On instruments I have made or worked on all warranty is invalidated if the post is tinkered with without my approval

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11 minutes ago, Melvin Goldsmith said:

Most sound post adjustments involve dragging the poor thing around and scuffing the surface of the belly from one poor position to another to find the least worst. On instruments I have made or worked on all warranty is invalidated if the post is tinkered with without my approval

Interesting policy, which I had not considered. Might be valuable.

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21 minutes ago, David Burgess said:

Interesting policy, which I had not considered. Might be valuable.

I don't insist on doing the work myself but If I can't do the post adjustment I want it done by a colleague I can trust and work with. ie not the latest Svengali adjuster to be harassing the orchestra or No3 Viola who is compulsively handy with a soundpost adjuster and has nearly made his first viola. SO much damage can be done. 

 

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On 9/6/2019 at 1:22 AM, Mat Roop said:

 Does anyone fit a violin post with a minimally rounded top?

Cheers... Mat

There was some discussion in this thread, page three onwards.

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1 hour ago, Melvin Goldsmith said:

I don't insist on doing the work myself but If I can't do the post adjustment I want it done by a colleague I can trust and work with. ie not the latest Svengali adjuster to be harassing the orchestra or No3 Viola who is compulsively handy with a soundpost adjuster and has nearly made his first viola. SO much damage can be done. 

 

Aw shucks! There go my retirement plans!  :(And just when I got all excited about my emerging instrument adjusting skills - I even bought a dedicated crochet hook to add to my bassoon fixit kit...and I know how to use it!

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On 9/4/2019 at 7:38 PM, Mat Roop said:

Lots of info on the effects of moving a sound post... but all that is assuming the post is vertical.

What happens if just the top or just the bottom of the post is moved... either N, S, E or W?.. assuming of course that the fit is ajusted accordingly

Thoughts? Any experimental results/ general consensus??

Cheers, Mat

Hi Rue. How do we understand the function of the sound post? Well, the sound post is the support of a bending condition that arise when the strings pull the end blocks upward. A moment of force arises. P * L. P and L are different on the two end blocks. By moving the sound post along the center line, we change the L and P get more result on one side and less on the other side. That is what we do by finding an optimal behavior of stress result when the end blocks move upward stressing the bulging bout shapes that become stress. Stress on bout shapes are very important producing the result of a played frequency. As the tension = stress on the string is important producing a specific frequency also the stress condition on the bout shapes responding spontaneous on the frequency signal is important. The other direction of displacement thus moving inward or outward affect also the stress condition of the bout structures. Moving in the F-hole direction press the plates outward and when this happens the bout shape that was bulging now is directed to compensate and become less. This affect the stress condition which is so very important controlling. Moving the sound post in the direction of the center line reduces the stress of the plates and larger bulging may arise produced by the action of the strings on the end blocks. This explained behavior allow is moving the sound post in any direction affecting the stress conditions on the bout shape. Hope this explanation can help you. All the best.

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2 hours ago, reguz said:

As the tension = stress on the string is important producing a specific frequency also the stress condition on the bout shapes responding spontaneous on the frequency signal is important.

Please provide proof of this statement, either theoretical or experimental.

As I have repeated many times, static stress on a curved structural element has no significant effect on its bending frequency, and my experimental evidence supports this.  You repeating this arm-waving string analogy does not help anyone...  prove it or stop.

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3 hours ago, reguz said:

Hi Rue. How do we understand the function of the sound post? Well, the sound post is the support of a bending condition that arise when the strings pull the end blocks upward. A moment of force arises. P * L. P and L are different on the two end blocks. By moving the sound post along the center line, we change the L and P get more result on one side and less on the other side. That is what we do by finding an optimal behavior of stress result when the end blocks move upward stressing the bulging bout shapes that become stress. Stress on bout shapes are very important producing the result of a played frequency. As the tension = stress on the string is important producing a specific frequency also the stress condition on the bout shapes responding spontaneous on the frequency signal is important. The other direction of displacement thus moving inward or outward affect also the stress condition of the bout structures. Moving in the F-hole direction press the plates outward and when this happens the bout shape that was bulging now is directed to compensate and become less. This affect the stress condition which is so very important controlling. Moving the sound post in the direction of the center line reduces the stress of the plates and larger bulging may arise produced by the action of the strings on the end blocks. This explained behavior allow is moving the sound post in any direction affecting the stress conditions on the bout shape. Hope this explanation can help you. All the best.

Tongue-in-cheek maybe? I reckon its original function was to prevent the table collapsing

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1 hour ago, Don Noon said:

Please provide proof of this statement, either theoretical or experimental.

As I have repeated many times, static stress on a curved structural element has no significant effect on its bending frequency, and my experimental evidence supports this.  You repeating this arm-waving string analogy does not help anyone...  prove it or stop.

Dear Don, It's hard to belive that you have now understanding at all that a structure under stress has another behavior a structure without any stress condition. This is no no arm-waving this is simple technical understanding. Contact any structural engineer and you will get an explanation.

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