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Why sound post fit matters


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Assuming a correctly fitting post I am still interested in how the pressure from the treble bridge foot is distributed via the belly over the surface area of the top of the post( especially in celli). For instance I feel that the further back from the bridge the post is positioned the more weight of the bridge foot could be distributed on the front edge of the top of the post ( i.e the edge nearer the bridge). ....... if not at all times at certain times during performance

 

We've been through this a while ago : the belly "rotates" over the top of the post. 

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The better the fit, the better the forces are distributed at point of contact. Therefore a perfect fit would result in less pressure at point of contact between top plate and post. A post contacting the top in a limited area (such as an oblique set or poor fit would substantially increase the pressure, not unlike a post cut much too long. Obviously there is a optimal degree of pressure, otherwise posts would be fatter than they are. The difference between a perfect fit and one contacting just on the rim could be more than 10x.

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Aaron Rosand had the same Wurlitzer bridge on the Kochanski for at least 40 years. That may be an exception but I don't see why a bridge shouldn't last forever too except that players don't take care of them.

My first full sized violin has had the same bridge since 1981. Been played a lot over the years and still in perfect playing condition.

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I suppose this is a tangent-but since sound post and bridge life are being discussed-I seem to remember hearing that after a year or two, a new instrument should have the sound post and bridge checked, and probably replaced.  I don't remember where I heard that though.

 

 

Any truth?

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Assuming a correctly fitting post I am still interested in how the pressure from the treble bridge foot is distributed via the belly over the surface area of the top of the post( especially in celli). For instance I feel that the further back from the bridge the post is positioned the more weight of the bridge foot could be distributed on the front edge of the top of the post ( i.e the edge nearer the bridge). ....... if not at all times at certain times during performance

 

Wouldn't the post act as a fulcrum point and the greater the distance between the fulcrum and the bridge foot, the more leverage? The more leverage, the greater the vertical movement of the belly? The fit of the post then influences the behavior of the fulcrum? Bad fit>>less stable fulcrum?

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Hooray!

What do you advise players to do to "take care" of their bridges?

1Start with a high quality bridge, expertly fitted and shaped.

2 Don't allow rosin to build up between string and bridge (thereby gluing strings to the bridge and pulling it forward). The notches can be cleaned with a very small amount of alcohol on a cotton swab (do not allow alcohol to drip onto the varnish!)

3 Don't allow strings to dig into the bridge at the notches. Especially A strings with corse windings. Ie Evah Pirazzi. If the notches are too deep have the top recut, or glue a parchment onto the bridge, or have new piece of maple inserted at the notch.

4 Lubricate the string notches with the lead of a soft (6B) pencil from time to time. You can also lubricate the underside of the string.

5 Lift the string out of its notch occasionally to equalize the string tension on each side of the bridge especially when putting on new strings. Do not loosen the string to do this. (You can't do it with the e string)

6 Make sure the bridge is standing upright at all times. After straightening up a leaning bridge see #4 and #5.

I'm sure there are more but can't think of them now.

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Wouldn't the post act as a fulcrum point and the greater the distance between the fulcrum and the bridge foot, the more leverage? The more leverage, the greater the vertical movement of the belly? The fit of the post then influences the behavior of the fulcrum? Bad fit>>less stable fulcrum?

Diving boards have an adjustable fulcrum. I guess to adjust for the different weight of a diver, or his/her technique. It's a mystery to me that soundposts work at all. I can imagine that a small kick with the setter at the base of the post would change things dramatically.

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3 Don't allow strings to dig into the bridge at the notches. Especially A strings with corse windings. Ie Evah Pirazzi. If the notches are too deep have the top recut, or glue a parchment onto the bridge, or have new piece of maple inserted at the notch.

 

Evah Pirazzi A strings are hell on upper nut grooves too. They can wear the groove right down to the fingerboard, while the other grooves are still at the height I made them.

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I suppose this is a tangent-but since sound post and bridge life are being discussed-I seem to remember hearing that after a year or two, a new instrument should have the sound post and bridge checked, and probably replaced.  I don't remember where I heard that though.

 

 

Any truth?

 

JSully,

 

Great question. This is something to think about.

It wouldn't  hurt to check them both. In particular, on a new instrument.

The fact of droop can happen with the fingerboard and/or the neck. so the bridge may well be slightly higher (the action) than it was originally, and need to be trimmed a bit in order for the strings not to be uncomfortably high for playing, and/or the sound post may also be too tight or too loose.

Very occasionally, the bridge itself can droop for various reasons. (droop, as in bend forward)

 

These conditions are very common with new violins. Depending somewhat on who has set them up. (or, if a really cheap bridge was used)

 

 Bridge height problems (with a bridge that hasn't bent) on a new violin, can usually be determined by the string height over the fingerboard, with the violin tuned up to pitch.

 

Sound post problems of this sort are usually found out when the violin has been de-strung... If the post simply falls over, it may well be too short, though unstrung, the post may well fall over just from the violin being moved around too much,

and if the post is wedged in it's position very tightly, it's too long, and needs to be removed and shortened - usually a tiny bit.

 

If you are technically minded, or are the "violin repair type" - go ahead and adjust these things - if not, take it to someone who knows how to do such adjustments. Either adjustment, when correctly done, should result in an improvement in either playing quality or ease of fingering - or in tone.

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I don't have an answer yet. Maybe I'll look into whether some of the synthetic materials used for guitar nuts have better wear properties than ebony. Anybody know?

 

I don't know what guitarmakers might use, but I experimented with Delrin inserts for the bridge slots.  Great stuff; tough and very slippery... except that slippery property also makes it nearly impossible to get any glue to stick.  Several of these inserts have popped off, so I'm not doing that any more.  Nuts might be less of a problem, and you can also get Delrin in black.

post-25192-0-60710800-1388426779_thumb.jpg

 

We've migrated a ways from soundposts, haven't we?

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Don,

 

Maybe we need Delrin soundposts; easier to reposition in the violin.

 

Okay, just kidding. I have to replace a violin nut due to excessive wear and wonder if a Delrin nut might be worth a try. I saw one place that sells black Delrin rod in 1 foot lengths in different diameters. Any thoughts?

 

Barry 

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