Bass Bar-verticle or not

[Melvin Goldsmith]

I always measure the combined belly and bar heights with caliper as well as the East/West heights....

[~ Ben Conover]

To answer the original question, bass bar not vertical.

 

[curious1]

12mm measured from the inside of the bar. I remeasured just to be sure. Curtin's method is based on a triangle. I think Carl does a similar thing but with the high point in the middle. I'll write later with a better description.

Carl Becker that is.

[Davide Sora]

I always measure the combined belly and bar heights with caliper as well as the East/West heights....

 

Me too, skipping the East/West measurements, only the height of bassbar + top thichness taken with my thickness gauge.

 

Usually ranging from about 15.2mm to 15.7mm max height.

 

I take also the heights at the end of the central "flat" area and at the end of the bar.

 

 

Davide

[curious1]

Carl Becker that is.

Basically, you draw a straight line through the heights of the bass bar. For instance, if the bar is 15mm high (including the top) and the end is 5mm (including the top), the quarters should measure 10mm (including the top) and the eights should be 12.5mm and 7.5mm. You could measure the bar without the top and it works also. If the top is 3mm thick the heights would be 12, 9.5, 7, 4.5, 2.

Curtin left his bars very pointy in cross section and left them quite high. The bar gains strength exponentially the taller it is but only gains mass linearly.

I leave the cross section similar to Melvin's. I'm not to concerned about a violin bass bar's mass. A light bar weighs 3gms and a heavy bar 5gms. That difference is distributed through the entire bar in a top that weighs ~65gms. Not something to be terribly concerned about.

[JohnCockburn]

Basically, you draw a straight line through the heights of the bass bar. For instance, if the bar is 15mm high (including the top) and the end is 5mm (including the top), the quarters should measure 10mm (including the top) and the eights should be 12.5mm and 7.5mm. You could measure the bar without the top and it works also. If the top is 3mm thick the heights would be 12, 9.5, 7, 4.5, 2.

Curtin left his bars very pointy in cross section and left them quite high. The bar gains strength exponentially the taller it is but only gains mass linearly.

I leave the cross section similar to Melvin's. I'm not to concerned about a violin bass bar's mass. A light bar weighs 3gms and a heavy bar 5gms. That difference is distributed through the entire bar in a top that weighs ~65gms. Not something to be terribly concerned about.

Thanks for the info. This sounds similar to what Michael Darnton recommended when he used to post on here. I recall that he too acknowledged Carl Becker as the originator of the idea.

Do you always work to these numbers, or do you tweak things according to arch heights, tap tones, flex etc?

[curious1]

Thanks for the info. This sounds similar to what Michael Darnton recommended when he used to post on here. I recall that he too acknowledged Carl Becker as the originator of the idea.

Do you always work to these numbers, or do you tweak things according to arch heights, tap tones, flex etc?

My bars can range from 10mm-15mm (without top, measured on inside edge of bar) at highest to 1mm-3mm at lowest. :^)

[Carl Stross]

Basically, you draw a straight line through the heights of the bass bar. For instance, if the bar is 15mm high (including the top) and the end is 5mm (including the top), the quarters should measure 10mm (including the top) and the eights should be 12.5mm and 7.5mm. You could measure the bar without the top and it works also. If the top is 3mm thick the heights would be 12, 9.5, 7, 4.5, 2.

Curtin left his bars very pointy in cross section and left them quite high. The bar gains strength exponentially the taller it is but only gains mass linearly.

I leave the cross section similar to Melvin's. I'm not to concerned about a violin bass bar's mass. A light bar weighs 3gms and a heavy bar 5gms. That difference is distributed through the entire bar in a top that weighs ~65gms. Not something to be terribly concerned about.

 

Thank you ! Nice explanation.

[curious1]

Thank you ! Nice explanation.

Thanks Carl. :^)

As simple as this is I always get nervous with the engineering stuff (something I'm totally unqualified to lecture anyone about).

[Michael_Molnar]

I use a spreadsheet to calculate the bass bar shape. I will post this on the forum for my bench. The calculation is based on Becker. Here is a snapshot.

 

BASS BAR SPREADSHEET.pdf

 

 

[Peter White]

Ben Conover says not vertical. Prier's book says not vertical. The 1980s Hill and sons diagram of the Messiah shows a very very small bass bar--but if you have seen the original Messiah you see that the bass side of the violin is warped or sunk down very considerably. So, if this poster is accurate Strad used very short bass bars.  My bar is 270 mm (depending upon length of violin) or 40 mm from each end, slanted from upper left to lower right, about 12 mm high and a fairly constant 6 MM wide. I taper the top slightly. The foot of the bridge hangs 1.5 mm over the bar. I almost always make my tops 15.5 mm high so I almost always make the bar around 12 mm high more or less. I measure from the center line side of the top. My bars tilt towards the center line. I find it easier to fit such bars. My instruments have good bass and clear high strings. Given all the variables in traditional (non-acoustical) violin making,  I think the responses here show that the bar is not such a big deal in the production of sound. Lots of different styles seem to be used and the makers seem happy with those styles.

I suppose a good fit is the best practice.  As you can see, even a relatively simple thing like the bass bar can cause a wide variety of responses--all of which I will show my students in New Mexico.  Let me think of another question.  Thanks, Peter White

[JohnCockburn]

My bars can range from 10mm-15mm (without top, measured on inside edge of bar) at highest to 1mm-3mm at lowest. :^)

Thanks. How do you decide on max bar height for a given top, if you don't mind me asking?

[Christopher Jacoby]

Curious, can I ask why you put the high point of your bar at the mensur, instead of the halfway point of the plate?

[curious1]

Curious, can I ask why you put the high point of your bar at the mensur, instead of the halfway point of the plate?

See post #28

[curious1]

Thanks. How do you decide on max bar height for a given top, if you don't mind me asking?

The old fashioned way. Trial and error. :^)

Mostly error.

I leave the bar high, close the box, try it out strung up, and reshape the bar as needed.

[Christopher Jacoby]

Craig, sorry! Been on a little getaway with my girls. I made a "piecrust" edge, inspired by a plaster cast set next6 to me on the bench at Oberlin last summer of a late del Gesu. The edgework peaked no more than .7 or .8 mm from the edge, a good 1.25-1.5 mm off the low point of the channel.

So I made a 30's del Gesu and a Peter of Venice with this fantastical miniature skateboarder's paradise around the whole edge, and was told by makers I admire: Cut it out.

[Michael_Molnar]

According to my very knowledgeable source, the peak lies between the plate center and mensur. Notice my spreadsheet printout above where I give the bar heights for the every eighth position, plate center, bar peak, and mensur (nicks). It's what I use because this guru said it is how Carl Becker laid out his bass bars. I adjust the peak to get a tone I like.

 

In any case, I get the feeling that there are several ways to lay out a bass bar. It all matters what religion you practice. 

[Peter K-G]

This is about typical for me.

image.jpg

 

 

Imagine  lines across the widest parts of the upper and lower bouts of the front. I try to have my bar at near 90 degrees to the belly where it passes in these places. I also put the highest part ahead of the bridge....pic below is all I could find in a copy of 23mm high Belly Goffriller viola. (The high arch makes it an example to be taken in context)

 

http://www.maestronet.com/forum/index.php?app=core&module=attach&section=attach&attach_rel_module=post&attach_id=29459

 

 

It very elegant yes, I use to make them like that, but now I do them like this:

 

BassBarShape.JPG

 

Vertical or not, this is a bigger difference. Have you thought about why you shape them like you do?

Not intended to be a debate, only a question. I have made 3 violins with BBs like that. With my ongoing project it will be the fourth top like I do them now. (Tuning is not an issue because it's possible to tune with both BB style)

[curious1]

I chose to shape it that way because, as I understand it, the point or area of the greatest longitudinal bending is not in the middle of the plate but lower. More in the area of the bridge. So I like to put more strength where there is more bending.

[Carl Stross]

I chose to shape it that way because, as I understand it, the point or area of the greatest longitudinal bending is not in the middle of the plate but lower. More in the area of the bridge. So I like to put more strength where there is more bending.

image.jpg

 

 

That makes a lot of sense to me.

[Don Noon]

This is about typical for me.

image.jpg

I chose to shape it that way because, as I understand it, the point or area of the greatest longitudinal bending is not in the middle of the plate but lower. More in the area of the bridge. So I like to put more strength where there is more bending.

image.jpg

That makes a lot of sense to me.

 

While it might make sense at first glance, you really have to be careful which bending you're talking about, and there is also mass to consider when vibration is involved.

 

For static stresses, the bridge foot is where you'll get the highest bending stress.  So if that was the only concern, then it makes sense to have the tallest part of the bar there.

 

However, in the second post, it appears to be Stoppani's map of the B1+ mode displacement, and you need to take the second derivative of that to get a bending map. (much as I respect George's work, his attempts to show modal bending maps appear to me to have major flaws, last I saw). 

 

Even if you had a good bending map of the modes, it is not necessarily clear what changes would be better or worse.  Vibrational stresses are of no concern in the way static stresses are, i.e. there is no distortion or splitting that will occur.  So the only concerns are tone and playability, and I'd challenge anybody to look at modal (or bending) maps and correctly judge what's good or bad, much less decide where to make changes to improve things.

 

The bottom line is trial and error for the vibration part.  Personally, I put some stock in the apparently traditional idea that the highest point of the bar should be slightly ahead of the bridge foot, and I have no interest in undertaking a lot of tedious test with dubious results.  The tests I HAVE done show that it isn't all that sensitive, anyway.  Tilted, vertical, flat-topped, various locations of the high point... they all seem to be working.

[Craig Tucker]

 The tests I HAVE done show that it isn't all that sensitive, anyway.  Tilted, vertical, flat-topped, various locations of the high point... they all seem to be working.

 

Yes, well said.

I agree,

I believe that the bar is one of the very forgiving things that can be made on the violin.

Not only the design but the exact positioning. They're fairly well open to individual claims of either working or not working. The bar in conjunction with the rest of the violin - now that's one complex thing to get a workable figure on. (as in, perhaps, a workable mathematical formula for placement or design)

 

Intuition may work as well here  - as well as figuring out some formula, that is...

 

Or not.

 

Only playing the finished violin seems to be able tell us what worked well for that particular violin - and what did not - all of the various professional claims about what must be done, notwithstanding.

[Carl Stross]

 

For static stresses, the bridge foot is where you'll get the highest bending stress.  

 

Are you sure ?

 

Anyway, there is also the possibility that the bass bar as commonly fitted is over-designed by some factor. I'd like to hear from one of our restorer/maker experts what the tonal effect of too low a bar is. I've got two very similar violins - one has a short(ish) and low bar as far as I can see but tonally is fine. Nothing which would pinch the ear.  

[Michael_Molnar]

  Tilted, vertical, flat-topped, various locations of the high point... they all seem to be working.

That is exactly my point: Settle on one system. Then, make adjustments according to our experience and tastes. I used to chase every idea, and wasted a lot of time and wood.     As I have said before: Ask two makers to recommend a design and you get three opinions. 

[nathan slobodkin]

Are you sure ?

 

Anyway, there is also the possibility that the bass bar as commonly fitted is over-designed by some factor. I'd like to hear from one of our restorer/maker experts what the tonal effect of too low a bar is. I've got two very similar violins - one has a short(ish) and low bar as far as I can see but tonally is fine. Nothing which would pinch the ear.  

 I once decided to experiment a bit by making some reasonably large deviations from  "normal" practice and seeing the effects. I made a violin with an abnormally small bar about 2mm lower in height and 1mm narrower than my usual 6mm. My expectation was that the weaker bar would allow more freedom of movement to the plate and accentuate the bass. In fact the opposite resulted with a weaker,

tinnier sound. When the bar was replaced with a normal bar the sound was much better.

 

I generally use Carl Becker's system which several people have described.  This includes a slight inward tilt to the bar and a high point between the center of the bar lengthwise and the stop. Mr. Becker told me he could see the argument either way so he split the difference.

 

There is an interesting diagram which relates to the angling of the bar in relation to a circle drawn transversally  across the fiddle and passing through the G and E string notches on the bridge. I think it was published in a catalog of the Shapes of the Baroque exhibition put on by Bill Monical  some years ago.