Jump to content
Maestronet Forums

Bass Bar-verticle or not


Peter White
 Share

Recommended Posts

Hello Makers:   a long time ago a nice person lent me his book from P.P. Prier's school.  The book showed that Prier advised students to put the bass bar at a left leaning angle rather than straight up and down, parallel to the ribs. I have done both and I don't see any difference but it is my guess that most makers place the bar parallel to the ribs.  What do you advise?

Link to comment
Share on other sites

  • Replies 75
  • Created
  • Last Reply

Top Posters In This Topic

Peter taught us to use a tapered bar, 4.5 at the top of the blank, 5.5 at the bottom and 20 mm wide. He suggested, if I correctly recall, that leaning "2 or 3 degrees..." was fine. Although I would hardly call that "leaning", it's not straight up either!

 

My guess is that the tapered bar, with the taper on the inside, makes the bar look more vertical  even if it isn't.

 

My two cents: It probably doesn't matter except in extremes in arching.

Link to comment
Share on other sites

It hurts my brain to ponder whether there is more strength if the bar is parallel to the ribs or parallel to the arch. All other considerations aside, any thoughts on which alignment offers more strength?

 

Doesn't hurt me any.  I'm fairly sure vertical is the "best" alignment... at least to resist static pressure.  However, it doesn't matter much.  According to my rough estimates, if you tilted the bass bar by 5 degrees (which is a lot), you'd lose stiffness equivalent to ~0.1mm of bass bar height.  Tell me anyone can tell the difference between a bass bar 15.2mm tall and 15.3mm tall, and I'll say they're delusional.  (I know that sound and static strength are separate issues, but I'm basing this statement in part on some fairly radical bass bar experiments which resulted in not much tonal change)

Link to comment
Share on other sites

Thanks Don. Great info. Thanks to your brain doing the heavy lifting, my brain feels better already. It intuitively feels that having the bar a few degrees off of parallel would give the top more movement, a little softer and receptive to up and down motion. Then again, I usually don't get past the "pondering" phase of these questions.

Link to comment
Share on other sites

You may well be right Don. We learned to fit the bar square to the rib surface at school, but it never felt quite right to me.

 

Lots of the little things we do in violin making are based on intuition, right or wrong. If things feel and look beautiful, they very often seem to work beautifully.

 

I know this is massively simplified, so forgive my intuition, it's just that. To me there are two principal movements in a violin bridge. The bar acts as a stable fulcrum as the soundpost is driven. The back through the soundpost acts as a stable fulcrum as the bar is driven, and the bar carries this movement, so that the bass side of the front moves as one. So I angle the bar in slightly, feeling that it might move better with the rolling of the front. 

Link to comment
Share on other sites

FWIW: Little Red Book  (Chimney Violin Maker's Workshop) Vol. 1, pg. 6, Fig. 1: "This angle not critical; tuning takes care of this variable."  This agrees with Don (#11) and with what I have experienced.

 

On a different but relevant point: Anyone use the flat top (plateau) bass bar that is depicted in the above figure?

 

Mike

Link to comment
Share on other sites

I would guess that it is the top's range of motion that makes the bass bar's angle largely irrelevant (within the 5% Don described). If its range was in the mms as opposed to 1/10ths(?) of mms there might be a problem but as it is the line of force always passes through the full height of the bar.

Is that about right Don?

Rene Morel suggested placing a wide square ruler on the interior arching at the sound post/bass bar location and setting the bass bar to that line as a general rule. This seemed an easy and practical idea.

post-53756-0-24883600-1388066174_thumb.jpg

Link to comment
Share on other sites

I know this is massively simplified, so forgive my intuition, it's just that. To me there are two principal movements in a violin bridge. The bar acts as a stable fulcrum as the soundpost is driven. The back through the soundpost acts as a stable fulcrum as the bar is driven, and the bar carries this movement, so that the bass side of the front moves as one. So I angle the bar in slightly, feeling that it might move better with the rolling of the front. 

 

 

I would guess that it is the top's range of motion that makes the bass bar's angle largely irrelevant (within the 5% Don described). If its range was in the mms as opposed to 1/10ths(?) of mms there might be a problem but as it is the line of force always passes through the full height of the bar.

Is that about right Don?

 

These simplified concepts are probably good enough.  As curious1 suggests, the scale of motion is very small, so things really don't "roll" around a piviot point, much like when you walk down a level street you don't think much about rolling around the center of the Earth.  It's all pretty linear.

 

The fulcrum concepts are somewhat close, but then there are differences which I think are significant.  The soundpost does move at some low frequencies.  The back is involved in some vibrations, and the soundpost is not on a nodal line.  Likewise, the bass bar does not become totally inert at higher frequencies, and goes into some higher order mode shapes occasionally.  It does not act as a rigid beam all the time.  But, in the most over-simplified view, the bass bar side moves most on the lows, and the soundpost side moves most on the highs.  Sortof.  With exceptions.  And not exactly.

 

But, like I said previously, a few degrees or tenths of a mm on the bar ain't gonna make a big difference in any of this anyway.  Save your brain and just glue the thing in the way that feels right to you.

Link to comment
Share on other sites

Doesn't hurt me any.  I'm fairly sure vertical is the "best" alignment... at least to resist static pressure.  However, it doesn't matter much.  According to my rough estimates, if you tilted the bass bar by 5 degrees (which is a lot), you'd lose stiffness equivalent to ~0.1mm of bass bar height.  Tell me anyone can tell the difference between a bass bar 15.2mm tall and 15.3mm tall, and I'll say they're delusional.  (I know that sound and static strength are separate issues, but I'm basing this statement in part on some fairly radical bass bar experiments which resulted in not much tonal change)

 

Nicely put, Don !

Link to comment
Share on other sites

My last visit with Carl Becker had him saying that one can make too much of bassbars.  Then he said,  "We keep things simple around here.  We make a 2-degree slant from vertial.  Seems like a reasonable compromise.  Myself,  I put it in vertical and just plane one side of the edge taper more than the other side.

Link to comment
Share on other sites

Hello Makers:  Thanks for all the commentary on this issue.  I think that the experience of most makers here is that the bar can function well either way.  I learned to put it in vertical to the ribs but then I found it was easier to do it the way I have it in Prier's book--leaning toward the center line. I am satisfied with my way but I wondered if I might be missing something, like having a stronger bass sound in my violins.  In my opinion, more important is keeping the placement of the bar correct in terms of the foot of the bridge, so that the rocking effect of the bridge foot exerts pressure properly on the bass bar.  For me, this means that the foot of the bridge hangs over the bar by about 1.5 mm. Any advice here?  I ask these questions because I teach and I like to hear what other makers think on various "simple" subjects.  Thanks for the help.

Peter White, New Mexico Musical Heritage project.

Link to comment
Share on other sites

  For me, this means that the foot of the bridge hangs over the bar by about 1.5 mm. Any advice here?  I ask these questions because I teach and I like to hear what other makers think on various "simple" subjects.  Thanks for the help.

 

Peter White, New Mexico Musical Heritage project.

 

Peter, I'm glad you asked.

 

My bass bars, go on a slant thru the area where the bass foot of the bridge will stand when the violin is strung up. Almost to the outer edge of where the bridge foot will be - pretty much just like you are saying. Since it's on a slant through that area, it's difficult (for me at ;least) to give a real concrete number. In my brain the exact measurement will vary slightly, as will the degree of slant and the bar height and width...

 

Much like the pictures in the Sacconi book show.

Not only is the information probably as close to what the makers of old did, it is what I also consider appropriate.

 

Good questions.

Link to comment
Share on other sites

FWIW: Little Red Book  (Chimney Violin Maker's Workshop) Vol. 1, pg. 6, Fig. 1: "This angle not critical; tuning takes care of this variable."  This agrees with Don (#11) and with what I have experienced.

 

On a different but relevant point: Anyone use the flat top (plateau) bass bar that is depicted in the above figure?

 

Mike

Can you share the figure? If it is what I think it is, yes, it is the style I was taught.

Link to comment
Share on other sites

For me, this means that the foot of the bridge hangs over the bar by about 1.5 mm. Any advice here?

That's what I do. I simply stand the bridge centered on the inside of the top (verified by measurement) and put a mark at that position. That becomes my only fixed point for positioning the bar. It seems to work well enough for my standards.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
 Share

  • Recently Browsing   0 members

    No registered users viewing this page.




×
×
  • Create New...