How tight should a sound post be

[orenchi]

Hello MN, I am not an instrument maker so forgive my ignorance. How tight or loose should the sound post be? When adjusting the bridge on students' instruments I will loosen the strings and the sound post will fall. Other times, I will take off strings, bridge, tailpiece, etc, and the sound post will stay in place, unless the violin is jostled a bit, then the sound post will fall.

I read that the sound post should gently "slide" into place, but cannot remember if this said to do so with the strings tightened or loosened. 

I am also curious as to the sound difference if the sound post is more tight or loose.

Any help would be appreciated. Thanks!

[The Violin Beautiful]

That seems like it ought to be an easy question to answer, but there are different opinions on that subject. I think the majority of us fit posts so that they move into place with little resistance, with just enough tension that they won’t fall over unless the instrument is jostled. Some argue that the post should fall when the strings come off. Again, some shops set posts under a great deal of tension.

The “right” tension is somewhat dependent on the luthier and can only be understood through practice. The danger of fitting a post that’s at either extreme is that it will cause a soundpost crack or arching deformation.

A tight post tends to make the instrument edgy and bright, sometimes to the point that the sound will choke. A loose post tends to make the sound muddy and unfocused. 

[JacksonMaberry]

30 minutes ago, The Violin Beautiful said:

Fit posts so that they move into place with little resistance, with just enough tension that they won’t fall over unless the instrument is jostled

This is how I was taught, for what it's worth.

[PASEWICZ]

The soundpost should never fall over with or without string tension.  Tension is dependent on placement and relative humidity and sound characteristic is dependent on all three as related and independently.  

[JacksonMaberry]

3 minutes ago, Jerry Pasewicz said:

The soundpost should never fall over with or without string tension.

What he said.

[PASEWICZ]

It would be nice if we had some sort of screw mechanism or gauge this....

[Jim Bress]

2 hours ago, Jerry Pasewicz said:

It would be nice if we had some sort of screw mechanism or gauge this....

Trouble maker. 

[PASEWICZ]

Just now, Jim Bress said:

Trouble maker. 

[Pylorius]

7 hours ago, orenchi said:

Hello MN, I am not an instrument maker so forgive my ignorance. How tight or loose should the sound post be? When adjusting the bridge on students' instruments I will loosen the strings and the sound post will fall. Other times, I will take off strings, bridge, tailpiece, etc, and the sound post will stay in place, unless the violin is jostled a bit, then the sound post will fall.

I read that the sound post should gently "slide" into place, but cannot remember if this said to do so with the strings tightened or loosened. 

I am also curious as to the sound difference if the sound post is more tight or loose.

Any help would be appreciated. Thanks!

I have  come up with a good method based on comments made here about Rene Morel. Basically, squeeze the center bout on the back edges only, and  the sound post should not fall, then squeeze the center bout ribs only, and it should fall. This gives a good bracketing from which to start. Then, given that many things are "correct", when this fit is made, leave the sound post, but move the bridge only to find sonic relationships between the bridge and soundpost. I find this method precise and effective on a variety of different types of violins. This might not be what Rene Morel did, but that knowledge seems to have been lost, leaving one to glean from the scraps...

[jacobsaunders]

One should always realise that a violin, unromantically observed, is a wooden box that is placed under string tension. The string tension (albeit minimally) stretches the back along it's length resp. compresses the belly along its length. The effect of this is to elevate the arching of the belly slightly once the string tension is applied (comparative to when one fits the post without tension). Thus a sound post will be less “tight” with the strings on, than it was when one fitted it. Should one fit the post very loose, such that it is in peril to gravity without string tension, then it will be objectively too short with string tension and the bridge will be pushing the belly down onto the sound post, which I doubt is beneficial to the longer term health of the instrument. It is also, in my experience detrimental to the response.

[Nicolas Temino]

Does all of this apply the same way to the other string family instruments?

[David Burgess]

2 hours ago, jacobsaunders said:

The effect of this is to elevate the arching of the belly slightly once the string tension is applied (comparative to when one fits the post without tension). Thus a sound post will be less “tight” with the strings on, than it was when one fitted it.

How often do you find that a post will stand without string tension, and then fall over when you apply the string tension?

[Emilg]

2 minutes ago, David Burgess said:

How often do you find that a post will stand without string tension, and then fall over when you apply the string tension?

Not very often. I usually place the sp with low string tension, then tighten the strings halfway to tap the sp into place. Finally i bring the strings up to full tension, the sp is then pretty tight.

[GeorgeH]

3 hours ago, jacobsaunders said:

The string tension (albeit minimally) stretches the back along it's length resp. compresses the belly along its length. The effect of this is to elevate the arching of the belly slightly once the string tension is applied (comparative to when one fits the post without tension). Thus a sound post will be less “tight” with the strings on, than it was when one fitted it

There was an actual scientific study performed that shows that this does not happen. The bass bar prevents lateral flexing, and the top in the area of the sound post and bridge does, in fact, move down under string tension.

If what you describe were the norm, then loose-fitting sound posts would commonly tend to drop as string tension was applied, and I have never heard of this happening, only the opposite. If it did happen, I would assume the bass bar was dislodged from the top or otherwise defective.

[Blank face]

Maybe it's a bit more complicated than this. In general (or theoretical) it should happen as Jacob descrbed, and of course posts in new made violins or freshly repaired have a tendency to become "too short" after being under string tension a while. Practically there are often other regions of the belly warping upside, for instance under the fingerboard in front of the block, or south of the bridge, while the center is hold in place or pressed downward caused by the bridge pressure. There's nothing simple straight forward and easily predictable.

[PASEWICZ]

I have only known a soundpost to get looser with tension on one occasion.   It was a Stephane Scarampella viola.  I do not know if it is a good thing or a bad thing, at the time I took it as an artifact from the relatively newly grafted neck performed by an eminently qualified restorer.

[Brad Dorsey]

On 4/29/2018 at 3:52 AM, jacobsaunders said:

...The string tension (albeit minimally) stretches the back along it's length resp. compresses the belly along its length. The effect of this is to elevate the arching of the belly slightly once the string tension is applied (comparative to when one fits the post without tension). Thus a sound post will be less “tight” with the strings on, than it was when one fitted it...

You are correct that compression of the top elevates the arching, but you have neglected the downward force, conveyed through the bridge and the top, that the strings exert on the soundpost.  A soundpost is tighter under string tension.  If you don't believe this, you should try moving a post without string tension then with string tension and see which way is easier.

[jacobsaunders]

3 hours ago, GeorgeH said:

There was an actual scientific study performed that shows that this does not happen. The bass bar prevents lateral flexing, and the top in the area of the sound post and bridge does, in fact, move down under string tension.

If what you describe were the norm, then loose-fitting sound posts would commonly tend to drop as string tension was applied, and I have never heard of this happening, only the opposite. If it did happen, I would assume the bass bar was dislodged from the top or otherwise defective.

I am not aware of the “scientific study” you cite, neither am I sure what you mean with “lateral flexing”. I was talking of longitudinal compression (of the belly) which surely happens. As anecdotal evidence, you may notice that old violins invariably have bellies that are 1 or 2mm shorter than backs after 200 or so years. In fact, if you were too come across an antique violin where the belly length measured longer than the back length, that would be an alarm bell to check that the belly was original to the instrument. You can also do a “scientific” experiment yourself, by cramping a violin belly into your bench, with one dog at the saddle position, and the other at the neck let in cut out (careful please!)

[jacobsaunders]

6 minutes ago, Brad Dorsey said:

You are correct that compression of the top elevates the arching, but you have neglected the downward force, conveyed through the bridge and the top, that the strings exert on the soundpost.  A soundpost is tighter under string tension.  I you don't believe this, you should try moving a post without string tension then with string tension and see which way is easier.

Yes we do not disagree, in fact I wrote “the bridge will be pushing the belly down onto the sound post” so I think this is the treachery of our “common” language once again.

[Brad Dorsey]

I missed that.  But if "the bridge will be pushing the belly down onto the sound post" as you said, then how can "a sound post...be less “tight” with the strings on, than it was when one fitted it" as you also said?

[Blank face]

18 minutes ago, Brad Dorsey said:

how can "a sound post...be less “tight” with the strings on

Maybe one could say better, that the post doesn't give the necessary substitute to hold the belly at the right level?

[David Burgess]

1 hour ago, jacobsaunders said:

I was talking of longitudinal compression (of the belly) which surely happens. As anecdotal evidence, you may notice that old violins invariably have bellies that are 1 or 2mm shorter than backs after 200 or so years. In fact, if you were too come across an antique violin where the belly length measured longer than the back length, that would be an alarm bell to check that the belly was original to the instrument.

Yes, but since the bridge is also pushing down at the center, this longitudinal compression generally will not result in an increase in arching height at the center, or an increase in the distance between the top and back at the soundpost position. The bulging occurs in other parts of the top, more under the fingerboard and tailpiece.

[jacobsaunders]

23 minutes ago, David Burgess said:

Yes, but since the bridge is also pushing down at the center, this longitudinal compression generally will not result in an increase in arching height at the center, or an increase in the distance between the top and back at the soundpost position. The bulging occurs in other parts of the top, more under the fingerboard and tailpiece.

Yes, the bridge will push the belly down onto the sound post. I said that already

[Brad H]

This is a topic which has been on my mind lately.  I will often get ahead of myself and set a post early on in the setup process.     Although I avoid bumping the violin, I never worry about the post falling while moving the violin around in different positions for subsequent setup tasks...and sometimes wonder whether I set them with too much tension.  I tug them into place with a firm pull but try to be vigilant about never raising the top.   When adjusting a post with no string tension, I want there to be enough tension that taps with the setter produce small post movements.   I also do the c-bout squeeze thing that I think Brad D. mentioned in a past thread - the post should fall over when the violin is turned sideways and a slight squeeze is given to the c-bouts.

Any comments?

 

[PASEWICZ]

9 minutes ago, Brad H said:

This is a topic which has been on my mind lately.  I will often get ahead of myself and set a post early on in the setup process.     Although I avoid bumping the violin, I never worry about the post falling while moving the violin around in different positions for subsequent setup tasks...and sometimes wonder whether I set them with too much tension.  I tug them into place with a firm pull but try to be vigilant about never raising the top.   When adjusting a post with no string tension, I want there to be enough tension that taps with the setter produce small post movements.   I also do the c-bout squeeze thing that I think Brad D. mentioned in a past thread - the post should fall over when the violin is turned sideways and a slight squeeze is given to the c-bouts.

Any comments?

 

It is exceedingly rare to ever install a shorter post.