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What happens if bass bar and soundpost are reverse?


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if we reverse both it would only mean that we mirror the structural elements and the bridge still can vibrate in a pivoting movement and a jack hammer movement.

So the question is what happens when the treble side bridge foot having more downforce drives the vibration of the 'bass bar'. I would expect some over resonance for the low strings.

I suppose no one made the experiment?

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It sounds pretty similar. (I've done it)

We were asked to convert a violin for "wrong-hand" ;) playing, and thought we'd try it without moving the bass bar first.  The person we were doing the conversion for, who had played the violin both before and after, was happy enough with the sound that we left it that way.

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2 hours ago, David Burgess said:

It sounds pretty similar. (I've done it)

We were asked to convert a violin for "wrong-hand" ;) playing, and thought we'd try it without moving the bass bar first.  The person we were doing the conversion for, who had played the violin both before and after, was happy enough with the sound that we left it that way.

The best part of that experience though was watching the very talented player try it for the first time. He carefully played a few scales, gained some confidence and started playing a not so simple piece of music.  He played a note a bit flat and hit himself in the nose with the bow trying to compensate for his intonation error.   He promptly left with the violin and I never saw it again.

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11 hours ago, Andreas Preuss said:

So the question is what happens when the treble side bridge foot having more downforce drives the vibration of the 'bass bar'. I would expect some over resonance for the low strings.

I would expect the opposite.

Due to the bowing angles, the lower strings have a greater vibration component normal to the bass bar, and the E string would have its vibration more normal to the soundpost.  Reversing these i would expect to have a thinner sound to the low strings and a fatter, less brilliant sound to the E string... but to what extent is unclear.  It may be minimal.  Or there could be other frequency sensitivities that get switched.

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It's easy enough to do a quickie check by just reversing the strings (although one probably needs to increase some of the string-groove widths so the larger strings don't get pinched by the smaller string grooves). It can still be fingered with the left hand and bowed with the right, so the unfamiliarity of switching those duties doesn't mess up the production and perception of the sound.

I didn't expect that the violin would sound decent without also moving the bass bar and soundpost, so I was quite surprised when it did.

I haven't tried this on a cello.

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2 hours ago, David Burgess said:

It's easy enough to do a quickie check by just reversing the strings (although one probably needs to increase some of the string-groove widths so the larger strings don't get pinched by the smaller string grooves). It can still be fingered with the left hand and bowed with the right, so the unfamiliarity of switching those duties doesn't mess up the production and perception of the sound.

I didn't expect that the violin would sound decent without also moving the bass bar and soundpost, so I was quite surprised when it did.

I haven't tried this on a cello.

I still regret that we didn’t have Joe make a left handed case for that violin...

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It isn't "far-fetched" to think that it would cause water to squeeze in the opposite direction throughout the instrument like a wet towel, but I need my small-angle X-ray scattering with synchrotron radiation device to say for sure. 

 

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5 hours ago, Mark Norfleet said:

I still regret that we didn’t have Joe make a left handed case for that violin...

So this can go beyond a private joke between Mark and I, Joe H. was the person who came in to take over the on-site "American Case"-making operation, after Steve Bobelock exited. Steve ended up re-establishing  the Bobelock manufacturing facility in the Philippines.

Mark and I prototyped and developed the production process for the American Case Company "Hatchtop" cello cases.

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9 hours ago, baroquecello said:

t is like to be a total beginner. It sounds like a cello, just a bad one. The lower strings superficial, and the a string flabby, without projection and brilliance. It

I have a cello in my rental fleet that came stock with the post and bb swapped around. top end was okay but bottom end had nothing to it. Switched out the bottom two strings and it improved enough to call good.

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Which gives more structural support to the downward forces of the two bridge feet, the bass bar or the sound post? Is there more support needed under the "e" string or under the "g" string? Maybe there is a structural reason for the current setup.

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4 hours ago, gtd said:

I have a cello in my rental fleet that came stock with the post and bb swapped around. top end was okay but bottom end had nothing to it. Switched out the bottom two strings and it improved enough to call good.

Do you mean the bass bar and sound post are inverse compared to normal, but you nonetheless strung it the normal way, meaning a string over the bass bar? I would find it highly surprising if your cello sounds anywhere near good and especially feels anywhere near normal when playing it.

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22 hours ago, Mark Norfleet said:

I still regret that we didn’t have Joe make a left handed case for that violin...

It wasn't until I got a strange "home-made" violin in its crude plywood home-made case that I realised there was a right and a wrong (left?) way round for violin cases.

Unfortunately the violin is a bit wider than normal and I have yet to find a right-handed case it will fit into. Still confuses me every time I open the case...

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On 5/2/2021 at 12:37 PM, Don Noon said:

I would expect the opposite.

Due to the bowing angles, the lower strings have a greater vibration component normal to the bass bar, and the E string would have its vibration more normal to the soundpost.  Reversing these i would expect to have a thinner sound to the low strings and a fatter, less brilliant sound to the E string... but to what extent is unclear.  It may be minimal.  Or there could be other frequency sensitivities that get switched.

I was thinking that the bridge is a sort of clamped on the sound post side. With the e strung we have a strong clamping. If we put the clamping on the g string side it is less and should allow the bridge an easier pivoting movement 

For the high registers I am (after reading David burgess explanation) not so sure any more that it needs to stand on the post. I have the suspicion that there needs a blocking mechanism under the bridge so that the neck forces can work efficiently and this is also the reason why neck angle and projection can change so much on the sound of an instrument.

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On 5/3/2021 at 5:56 AM, Greg Sigworth said:

Which gives more structural support to the downward forces of the two bridge feet, the bass bar or the sound post? Is there more support needed under the "e" string or under the "g" string? Maybe there is a structural reason for the current setup.

We often assume things without further testing. The answer I got from David burgess confirms my theory that the bass bar and the sound post are important sound factors but reversing them doesn’t change awfully lot, at least on a violin. But maybe this minimum change can be used in a advantageous way for what I call sound calibration process.
 

With the new concept violin I am trying to find out how to calibrate single structural elements to each other to balance the sound in all aspects. I am working on the assumption that if the string forces can act most efficiently on the body I can gain a maximum sound output. This is certainly not the end of the story because sound response and overtone range also play a role. 

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On 5/3/2021 at 2:00 AM, gtd said:

I have a cello in my rental fleet that came stock with the post and bb swapped around. top end was okay but bottom end had nothing to it. Switched out the bottom two strings and it improved enough to call good.

I didn’t go too much into cello acoustics so far. There is a chance that for low sounding instruments the bass bar must be under the bass side bridge foot. 

Thanks for the response.

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2 hours ago, Andreas Preuss said:

I was thinking that the bridge is a sort of clamped on the sound post side. With the e strung we have a strong clamping. If we put the clamping on the g string side it is less and should allow the bridge an easier pivoting movement 

It might surprise you how much the soundpost (and back) move, even at some lower frequencies.  

If the bowing and string vibration are perfectly horizontal, then it should not matter AT ALL which side the post and bar are on.  Only when there is an angle, then it matters.  Bowing the G string gets more vertical vibration into the bass bar, and vice versa for the E.  

It looks to me like the A0 amplitude would be significantly affected by switching, since it is played on the G string and the mode is mostly moving on the bassbar side.  B1- is surprisingly symmetric as far as bridge foot movement, so it shouldn't matter much.  B1+ plate movement is biased toward the bass foot... but it's mostly played on the A string, or D in upper positions... so it shouldn't matter much.  If you play very high on the G to get to the B1+ frequency, it would matter... and explains why a B1+ wolf is worst on the high G string.  Reversed post and bar should make the wolf less of an issue on the high G string.

At higher frequencies, where things really matter a lot, it's too complex and varies all over the place depending on frequency and mode shape.

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3 hours ago, Don Noon said:

1. f the bowing and string vibration are perfectly horizontal, then it should not matter AT ALL which side the post and bar are onOnly when there is an angle, then it matters

2. Bowing the G string gets more vertical vibration into the bass bar, and vice versa for the E.  

1. I am really not at all sure that is the case***. I found a very noticeable effect on tone when swapping strings around. Also, replacing say a "Gold E" with a Thomastik one influences the other strings and it is perfectly noticeable.

2. For a while, yes.

*** in theory the string vibs can not be perfectly horizontal. It would be interesting if one found there are situations when they are very close to horizontal.

 

 

 

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4 hours ago, Carl Stross said:

in theory the string vibs can not be perfectly horizontal. It would be interesting if one found there are situations when they are very close to horizontal.

In theory, the Helmholtz motion of the string is in the plane of the bow hair and the bow movement.  The way bridges are normally cut, you could only get everything perfectly horizontal (parallel to the plane of the bridge feet) on the D string, close to hitting the A.

This is all simplified geometry, and assumes that bridge foot motion is all "vertical".  To the extent that mode shapes have horizontal and diagonal movement at the bridge feet (yes, I know it exists), these arguments don't apply as well.

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8 hours ago, Don Noon said:

It might surprise you how much the soundpost (and back) move, even at some lower frequencies.  

Yes, this can be seen on those holographic pictures. 

 

8 hours ago, Don Noon said:

Reversed post and bar should make the wolf less of an issue on the high G string.

If this would work, it would be a quite new and elegant approach in killing the wolf. This is something which extremely matters to players.

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18 minutes ago, Don Noon said:

In theory, the Helmholtz motion of the string is in the plane of the bow hair and the bow movement.  The way bridges are normally cut, you could only get everything perfectly horizontal (parallel to the plane of the bridge feet) on the D string, close to hitting the A.

This is all simplified geometry, and assumes that bridge foot motion is all "vertical".  To the extent that mode shapes have horizontal and diagonal movement at the bridge feet (yes, I know it exists), these arguments don't apply as well.

I'll have to think some more about this but for the moment I fail to understand why that would be the case. Even in a situation where the bridge foot is constrained to vertical motion. 

 

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