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Sound post questions
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JiminTexas
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June 1, 2019 - 4:26 am
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I do not understand the function of the sound post, so let's start with that one. Just what is the function of the Sound post? Is it to transfer sound vibrations to the back? Why is it not glued into place? Why just leave it as a friction fit? What effect does the material that it is made of have on the sound/tone/volume of my violin? What will using a harder or softer wood do the Sound of my violin? What kind of wood is used for violin sound posts. Does the diameter of the sound post make a difference? Do all viols use a standard wood type and/or diameter sound post? If so, what is it for violins? Why don't plectrum instruments i.e. guitar, mandolin, madola, etc. have sound posts, and why don't viols have sound bars like mandolins do?

The search for great technique does not always lead to great music, but the search for great music does always lead to great technique.

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BillyG
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June 1, 2019 - 8:55 am
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@JiminTexas - here's a few bits of my own understanding - it won't answer all your questions though !

First and foremost, IMO it adds structural integrity to what is, in some respects, quite a fragile instrument.  Without it, the top plate could well be deformed, if not actually damaged (by the string tension)

Secondly, because of the required presence of the SP, its position will have an effect on the sound.   Very small changes in position can have a large impact on the tonal quality of the instrument.   Many folks would leave SP setting to a luthier, but, it's not difficult, just time-consuming if it's not something you do regularly.  [ I've messed with the SP on my old Skylark fiddle, and indeed cut new ones to size - *small* positional changes can be made with the existing SP - larger movements may well require a different length of SP to fit tightly between top plate and back ]

That's about as much as I know (or need to) - I'm sure others will jump in with info about the material and so on....  as a starter, hope that helps 🙂

EDIT : There is a lot of really technical information (like audio spectrum analyses for different SP positions) - but here's a real quick bit of info gleaned from wikipedia - take from it what you will !!!!

Effect of position on the instrument

Moving the sound post towards the fingerboard tends to increase brilliance and loudness. Moving the sound post towards the tail piece decreases the loudness and adds a richness or hollowness to the tonal quality of the instrument. Moving it towards the outside of the instrument increases brightness and moving in towards the middle of the instrument increases the lower frequencies. There is very little room to move the post from side to side without fitting a new post (or shortening the existing one) since tension (how firmly the post is wedged between top and back) plays an important role in tone adjustment. Perfect wood-to-wood fit at both ends of the post is critical to getting the desired sound.

Soulpost2.gifImage Enlarger

I seriously recommend not copying my mistakes. D'oh - guntohead.JPG

Please make your own, different mistakes, and help us all learn :-)

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GregW
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June 1, 2019 - 9:42 am
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Jim I'm in the dark about this as well.  Great reply Billy especially the picture.  Good stuff thanks for that.

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MoonShadows
Stroudsburg, PA
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Yes, thanks @BillyG I also appreciate you taking the time to explain that.

Jim

Fiddling for Older Folks - Learning to Play the Fiddle as an Adult

The Friends of the Sons of Liberty - Three Inspiring Young Men playing Early American Fiddle Music 

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steveduf
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June 1, 2019 - 12:13 pm
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@billyg  nice diagram... thanks

Integrity is huge,  

also one of the benefits of having Mack helping me work on these violins at 14 years old is that she has had the chance to see the cause and effect of moving the sp around.  

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GregW
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June 1, 2019 - 3:19 pm
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steveduf said
@billyg  nice diagram... thanks

Integrity is huge,  

also one of the benefits of having Mack helping me work on these violins at 14 years old is that she has had the chance to see the cause and effect of moving the sp around.  

  

Good stuff Steve.  Wish I would have gotten into music when kids were growing up.  Hoping grandkids can get the musical itch like me.

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BillyG
Brora, North-east Scotland
June 2, 2019 - 1:02 am
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And, to go back to the SP related stuff - I didn't mention this at the time - 

It should be recognised that both the top plate and back of these instruments (that have sound posts) are, unlike guitars, actually specially carved out with areas of "gouged out depressions" in both plates (on the inside).   During construction these plates are "tuned" ( research "tap test, violins/violas/cellos", also research "Chladni patterns" ).  There are usually 4 primary resonating areas on the top plate.  In other words, the plates are being tuned to have different resonating characteristics across the plate.

Here is an interesting video (in truth it's not particularly realistic - it was just an experiment for someone's project - using non standard materials and a top plate in isolation - but - it visually gives a good idea as to what is happening as different notes (frequencies) are played ).  Even with the limitations of the demo, you can observe the different plate resonance patterns at the two frequencies he used.  [Where the little grains converge are at points of vibrational "nulls", and where they get cleared from, are areas of highest plate flexing - peaks in vibration]

Shame we didn't get to see some lower frequencies, but then again, it's not a real spruce plate, nor has it been carved-out on the underside - but from this you can perhaps understand just how come even very minor SP positional adjustments can affect the tonal colour and resonance characteristics of these instruments.

But trust me, interesting as it is, being aware of these effects and just why they influence the sound production, does not make me a better player......  facepalmexactly

I seriously recommend not copying my mistakes. D'oh - guntohead.JPG

Please make your own, different mistakes, and help us all learn :-)

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JiminTexas
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June 2, 2019 - 5:05 am
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You will have to excuse me. I'm a recovering Engineer. Well, yes and no on the differences. Arched top guitars have carved tops as well, and mandolins, mandolas and mandocellos. All have carved tops and no sound posts. Tap tuning is not restricted to carved top instruments. Some high end flat top guitars are tap tuned as well. The similarities that I see between viols and plectrum instruments are that the tops are made of a more porous, softer wood so as to allow the sound out of the resonating cavity (the body), i.e. Spruce, and the backs and sides are made of a harder wood i.e. Maple, in the case of violins and Maple, Mahogony or Rosewood in the case of guitars, so as to reflect the sound forward and out of the instrument. As to the structural reinforcement idea, I can see that as being valid, but plectrum instruments don't reinforce the tops that way and if reinforcement were the purpose, wouldn't it be a transverse brace, across the grain of the wood rather that placing a stress point right in the middle of the top and back that would promote those nasty little Sound post cracks? But then again, a transverse brace would inhibit the ability of the top to vibrate freely, so maybe the soudpost is a compromise solution? And, it still does not answer the question of why viols or bowed instruments like the violin are built or rather braced so radically different from plectrum instruments like the mandolin when they are roughly the same size, are tuned the same and even have comparable scale lengths.

The search for great technique does not always lead to great music, but the search for great music does always lead to great technique.

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Jim Dunleavy
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June 2, 2019 - 9:51 am
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Is the down-pressure on the bridge much less for guitars? The string height certainly seems quite low on my steel string acoustic and there is a much longer string length for the force to act over.

I also read somewhere that the sound post works in conjunction with the bass bar - it kind of acts like a pivot for the part of the front plate below the G string to swing around. 

Disclaimer: all the above is half-remembered stuff from google and conjecture. 😉

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JiminTexas
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June 2, 2019 - 3:17 pm
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Jim, it really depends on whether you are referring to a flat top or an arch top guitar. A flat top would have the stress on the bridge in a forward direction, towards the neck because the strings are anchored to the saddle that sits immediately behind the bridge.  An arch top guitar, a mandolin or mandola would be very similar to the violin in that the strings are anchored at the bottom end of the body through a tailpiece and the stress would be downward on the bridge.

The search for great technique does not always lead to great music, but the search for great music does always lead to great technique.

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Fiddlerman
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June 3, 2019 - 11:37 am
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Jim,
Remember that the violin family was invented hundreds of years ago.
That being said, many people have tried different designs to not much avail.

Who knows what changes could be advantageous. Without trial, improvements can't be made. I'm actually going to build a violin at Fiddlershop soon. We have teamed up with "Peter White" a very experienced violin maker/teacher from New Mexico, now living and working in Ft Laud and at Fiddlershop, to work with our luthiers on making instruments. 3 of our guys have made violins from scratch but the other 3 have not. Perhaps, I will go crazy (have nothing to loose) and test some new design. I had thoughts on changing the f-holes for example. That being said, I shouldn't get a head of myself. LOL.

"The richest person is not the one who has the most,
but the one who needs the least."

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Fiddlerman
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June 3, 2019 - 11:46 am
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Just some samples that I found on a quick search that I felt cold be interesting.

Obviously I wouldn't necessarily want to copy someone else if I'm to experiment. 🙂
Also, I'm no where near qualified to be experimenting, but what are the chances that I would make a good violin. ROFL

The baroque one is interesting in the sense that it was a predecessor to the modern f-hole.

Madill5-1-322x560.jpgHSSWEF_Details_345x276_0002.jpg51Zm2qRlNAL._SY879_.jpgviola-damore-custom_f-holes.jpgImage Enlargerdbcv-electric-bubinga-wood-six-string-violin-dolphin-f-holes.jpg

"The richest person is not the one who has the most,
but the one who needs the least."

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Fiddlerman
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June 3, 2019 - 11:47 am
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Sorry Jim, I know you were talking about sound posts. 😎

"The richest person is not the one who has the most,
but the one who needs the least."

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JiminTexas
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June 3, 2019 - 12:12 pm
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Fiddlerman said
Sorry Jim, I know you were talking about sound posts. 😎

  

No problem, I really enjoyed the conversation, but getting back to the matter at hand, I have no questions about what the sound post does or about how well it works. I'm trying to figure out how it does it. It must effect something, and it appears to me that would be the top. The back being primarily a reflective surface and is wholly or nearly wholly passive in the tone production area. Then again, I'm just guessing.

The search for great technique does not always lead to great music, but the search for great music does always lead to great technique.

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bocaholly
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JiminTexas said
...  the sound post ... It must effect something, and it appears to me that would be the top. The back being primarily a reflective surface and is wholly or nearly wholly passive in the tone production area. Then again, I'm just guessing.

  

Hey Jim, I've been following your conversation and was struck by your guess that the back of a violin is "nearly wholly passive."

I thought of all of the online discussions I've read through about playing with or without a shoulder rest. They, notoriously, clamp on to the edge where the ribs meet the bottom plate. The "anti-crowd" insists that shoulder rests inhibit (muffle) the violin's sound. If that is so, then the back plate is actually actively involved in the sound production. 

For giggles, I just removed my shoulder rest and gave my violin a few firm strokes. I can definitely feel the bottom plate vibrating on my left shoulder (under my chin too, of course.) The vib is the strongest when bowing the G-string.

That was my experiment for the day 🙂 Have a good one!

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Shane "Chicken" Wang
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From woodwiz, (a violin builder)

Two main reasons for spruce: It sounds good, and it's soft enough that it doesn't damage the top excessively.

Harder heavier woods don't sound as good, and they can tear up the top so that nothing will fit properly without taking the top off and repairing it.

Stick with spruce. Learn to make your instruments conventionally until you are really good at it. It takes most makers, even with 3 or 4 years of full time school, about 20 instruments before they really begin to understand a little about making instruments, and a lot more before their style matures. It took Anton about 10 years to settle on his own model, and another 15 years of refinement until he reached his design goals, and I'd say he was pretty typical. Strad made his best instruments in his 60's, IIRC.

Michael R

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Shane "Chicken" Wang
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The violin is a genius design and so far ahead of it's time, the idea that it was created so long ago is mind boggling. When you play, you feel the vibrations every where. In the neck, , in the back and top, and in the bow, so you stay relaxed in order to keep from strangling your sound. When you pull your bow across the strings, the vibrations travell out in every direction, into the bow, why the bow material is so important,  down the bridge and into the top plate. Without the soundpost, the top plate will stop the vibration. The sound post allows the vibrations to reach the back plate, incorporating that area of the top and back to vibrate the air inside and project sound. Spruce is used because of its strength and vibrationional qualities. Notice this is the largest part of the cavity. But it doesn't stop there. 

The vibrations you feel in your hand from the neck is transferred against the vibrations from the corpus back into the violin body. Like throwing rocks in a pond, when the vibrations collide, they increase and the projection from the neck end of the violin. This is the importance of a dense wood in the neck and fingerboard. 

The tailpiece, gut strap and end pin. Allow the vibrations to enter the rear of the violin back into the main chamber from behind the bridge. Yes they highly affect The sound and projection of the instrument. You can customize the sound of your violin with these 3 pieces.

Imagine a room with water flowing in from all sides at great speed. When the water meets in the middle it explodes upward and outward. This is the same theory of how the sound erupts from your violino. With the soundpost connecting the top and back, you have 4 entry points for sound vibration into a an echo chamber. Combine that with a high quality aged and dried wood, preferably with a tight grain spruce top that allows the sound to more easily resonate and project outward and a hard maple back for its vibrational and reflective quality, and you have a work  of art on a visual and scientific level.

The violino is an evolution of pure genius.

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JiminTexas
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Shane, "Chicken", Wang, well.....I don't know about all of that. Let's see here...... just because you can feel vibrations in the back or any other part of the instrument, that does not signify that this particular part of section has any real influence on the sound, tone, volume or any other attribute of the sound coming out of the violin. I can feel vibrations in the bumper of my truck, but that does not mean that the bumper has anything to do with making that engine run.

Now the back and sides together with the top forms a nearly completely closed air chamber that vibrates in sympathy  with the strings. The top being relatively flexible allows the air mass inside the chamber to vibrate and escape through the top and. The "f" holes and be effectively amplified by taking the relatively small vibrations of the strings and causing them to move the much larger air mass in the body of the violin. This is usage of a pure mechanical advantage, not dissimilar to the mechanical use of levers. I'm just trying to figure out how the sound post works.

The search for great technique does not always lead to great music, but the search for great music does always lead to great technique.

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