The exact function of the sound post.

[Wolfjk]

Hi All,

There are currently two threads dealing with the fitting of sound post. Could the experts on this forum give an opinion on what the exact function of the sound post is in an instrument?

Cheers Wolfjk

[Jacob]

There is some structural function (supporting the top). It also transmits vibrations to the back. It would also seem to me that the support it provides to the top and its interaction with the bridge influences the way the strings respond.

Obviously this is only scratching the surface of the topic, but it represents the sum total of what I can contribute.

[Michael Darnton]

Aside from the structural issue, which should be obvious, play a violin without a post (no, it won't hurt it, in the short term) and you'll see the tonal reason in a hurry. Therefore, I'd say there are two basic functions of the post: to hold up the top and to make the violin sound good.

I assume the original question isn't a search from some arcane acoustical theory with a 90% chance of being BS. I doubt very much that the original post-putter had any interest in that, which precludes theory as a "reason" for the soundpost.

Once you decide to have one, you have to find the place where it causes the least damage to the sound. I think of the post as interfering with the movement of the plates, and there's usually one place (this is in conjunction with movements of the bridge, which has a simlar effect, but from outside) where it permits them to work the best, where the sound has the least amount of dissonance. IF you want to add a bit of noise to a violin that's too clean-sounding at that point, you have that option, but in my experience very few people will ask for that if the post's in the cleanest place, initially, For outright tonal adjustments I usually go to places other than the post. I guess this is different from the usual concept of creating sound with the post, but the results are really working well for me.

[florea]

I think my soundpost may possibly be too tight. When it was shipped - it came in with the bridge down and the strings all over the place. The soundpost remained erect through it all then and through subsequent teardowns to play with the tailpiece. Getting harmonics out of the instrument is like pulling teeth. Could this be attributed to the soundpost or its adjustment?

[Woodland]

The general consensus is that the post transmits sound to the back, there's also a theory that the post keeps the top and back vibrating in unison.

[H_Axel]

The soundpost helps convert the lateral motion of the oscillating strings into a vertical motion of the top plate.

Basically, the bridge rocks on the soundpost. Since one side of the bridge is "fixed," the "free" foot moves the top plate up and down when it rocks.

There's a lot more going on than this of course. If you really want to get into it have a look at "Physics of the Violin" by Lothar Cremer, trans. by John S. Allen.

[Michael Darnton]

Florea--A post shouldn't fall while you're messing with the violin, so that's not a problem. As to why you have trouble with harmonics--it could be almost anything, including the position of the post. I might look at the bridge as well as the post, though, myself.

[maestramusica]

Exactly what side of the bridge is "fixed"? and by what means is it "fixed"?

[H_Axel]

By "fixed" I mean supported by the soundpost. Fixed is in quotes because the treble side of the bridge isn't exactly over the soundpost. Also, eveything is interacting with everything else anyway so nothing is really stationary.

[Michael Darnton]

I often find myself at odds with accoustics folks, and this is, I guess, another time. Grab your bridge at the top and rock it back and forth, and decide if one side is all that much more more "fixed" than the other. They just achieve their flexibility in different ways: the treble side is moderated by the stiffnes of the back, the bass by the bar.

[Wolfjk]

Hi Jacob,

Thanks for your post.

Do you think the fitting and placing (distance from bridge, in or out) is critical to the higher registers? Same as the bass bar is to the lower notes of the G and D?

Cheers Wolfjk

[Jacob]

As usual, Michael has cut through a veritable fog of urban legends about the sound post:

1. placing it "...where it causes the least damage to the sound..."

2. "For outright tonal adjustments I usually go to places other than the post".

To me this means that the best spot for a post on a particular violin will be good for ALL the strings, and this is what my personal experience would seem to bear out. For instance, the ideal spot for the post normally results in an even tone across the strings. If I get a noticable "break" in tone quality between the strings, I can in most cases overcome this by moving the post around. In such cases other things which I might not have particulartly noticed before would also have improved. For instance, a squeeky E is easy to notice. A weak upper G string could be ascribed to other factors as well. However, moving the post to fix the E will often improve the G (and the other strings) as well.

[Michael Darnton]

Yes, that's exactly what I meant. I know the one adjustment fits all players concept is anathema to players, but I think that's just because they haven't had it done well. I rarely have players asking for further adjustments after I've set something up, and they're often surprised their violin is working so well. I have one customer with a "problem" Pressenda who says it's never, ever, sounded better. It was the same story--after I set it up, in spite of it being a problem instrument and a particular player, he didn't want me to change a thing. And I get to hear him tell me about once a month what an amazing change it is.

I had a very interesting experience a couple of weeks ago: I set up (new post, bridge, etc.) the violin of a CSO player. When she came to pick it up she didn't even take off her coat--she plucked all four strings, smiled, said "that's much better" and packed it up. That was interesting to me because that's how I do adjustments--plucking, not bowing. I can hear a lot more of the violin itself without the constant interference of the bow forcing the string to play whether it wants to or not. Just an easy example: hold your violin facing you in your lap, rest it's head on a table in front of you, and pluck your A string near the middle. The open A string is the least subtle indicator of all of them that something's wrong. It takes concentrated hearing, but do you hear any instability whatsoever in the sound, something sort of like the start of a false string? If you do, and you probably will if your ears are good, something's wrong with the adjustment and you're not getting all you could out of your violin because something's fighting inside of it.

Most players will agree that the lack of dissonance (non-musical harmonics and sounds) is good, but there's an added benefit that dissonance saps a lot of resonance. Dissonance is pulling the sound of the violin in several different competing directions, and that requires energy that's just lost to bad sound. When the dissonance is gone, a violin becomes much more responsive, since every part is moving right instantly, rather than various parts having to be forced to come along with the majority, which takes energy and time. (Think herding cats.)

[Wolfjk]

Hi Everyone,

Thank you for the information.

(from Jacob): ------For instance, a squeeky E is easy to notice. A weak upper G string could be ascribed to other factors as well. However, moving the post to fix the E will often improve the G (and the other strings) as well.-----

Would you call this balancing the sound of the instrument?

Cheers Wolfjk

[Jacob]

No, I would call it "making the entire instrument function optimally". What you gain on the swings you lose on the roundabouts - at least if you try to do it by means of the soundpost. Tonally the positioning of the soundpost is pretty much an all-or-nothing affair. It's like trying to tweak the induction system of your motorcar to consume less gasoline - you can do it, but at some point you will start to lose performance. There is a setting where the fuel consumption and performance will both be optimal and balanced - trying to enhance the one over-and-above what the engine is capable of will lead to a greater loss in the other.

[Oded Kishony]

Very Interesting Michael,

I'm not sure I buy the whole explanation but I like the description.

Have you ever tried to run an FFT (soundlandscape) of the plucked string before and after adjustment?

Oded

[Michael Darnton]

No, I haven't.

This doesn't involve just the post, by the way--there are a number of ways to manipulate this stuff, and some things I still don't know how to deal with when I hear them. If you train your ears you learn to hear it. It can be a problem sometimes--I went to a memorial service a couple of weeks ago, and the church organ had some horrible dissonances that I probably never would have noticed before. I bought a pretty nice English concertina a decade ago, and now I can't bear to play it--that's going to be something I'm going to tackle one day. :-) All I can say is that I can hear it, and many of my more professional customers do as well. Realizing this completely revamped the way I did adjustments, and it's much less haphazard.

[Andres Sender]

Michael, has this impacted how far from 'normal' you will set the post to get the right sound?

Is this essentially an "on/off" issue or does the nature of the 'bad' sound vary? If the latter, do you experiment in different directions according to the way the sound is off?

[Michael Darnton]

It's an on/off thing. That's why I don't consider it an adjustment, per se. I'm pretty sure what I'm hearing is beating frequencies in most cases, generated by competing parts of the instrument, and I try to bring them together in pitch so they don't clash.

I wonder if anyone reading this thread actually did the thing to hear what their A strin is doing. . .

[Andres Sender]

Just give me a minute...

Okay, this is a gut-strung baroque setup instrument. I get a faint bright buzzy metallic noise at the instant of pluck which dies off immediately leaving a pure tone. Gives me the feeling something's not fitting right somewhere.

[Steve R.]

I just tried it. I think it sounds clean, but I think I would need to hear a bad one to be sure. No dissonant beat frequencies that I noticed anyway.

[Oded Kishony]

Did you know that there are two ways to hear and a test that's been developed by the American Acoustical Society (on a CD) that determines which of the two types you fit into?

I was in a room with all violinmakers and one engineer (he's also a fine violinist) we played this CD at the end of which you were supposed to decide if the last tone went up or down. The analytical listeners would hear it go up and the global listeners would hear it go down. ALL the violinmakers were analytical listeners, the engineer/violinist was global. We played the CD again, this time knowing what the outcome was going to be, I tried to make the last note go in the other direction but I just could not hear it. To me this meant that if you were an analytical listener you could not will yourself to be a global one.

Oded

[Regis]

The A string,,,Yes....4 violins. 3 seem the same and are somewhat rougher than the 4th. Not sure what I'm hearing though (as far as reason).

[Richf]

Sorry to come in so late with this question, but I've been wanting to ask it for some time and this seems to be the right place. I recall reading in Poidras or some old book about an experiment with soundpost placement, where the soundpost was affixed to the top of violin, secured by a wire or string around the body. Can you envision that, standing on the outside of the top? The conclusion from that experiment was that you got the same effect from the soundpost whether it was inside or outside of the violin body. And the ideal position still was just behind the treble side of the bridge. Do I recall that correctly? Could that be right? (There was no mention of any impact on squealing E strings. )

[Michael Darnton]

That's a strange concept!