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Viola versus violin bridges.


nathan slobodkin
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Tried this on the bridge styles thread with no results so I'm starting a new discussion on the topic.

I've been thinking about the differences between viola and violin bridge geometry and whether or not they should be cut differently.  The string spacing is only 2 mm. wider on a viola but the feet are a minimum of 4 mm. wider and often as much as 8 or 10. This not only gives a different angle between the strings and the feet but leaves considerably more weight outside the strings in the upper portion of the bridge. This would seem to indicate that there should be considerable difference in how the bridge should be cut not to mention that there is a difference in the desired sound even if everything else was proportional. I usually cut viola bridges with slightly more open heart and kidneys than a violin bridge but wonder what the respective force diagrams actually look like and if other people make more radical accommodations in cutting.

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16 hours ago, nathan slobodkin said:

... wonder what the respective force diagrams actually look like and if other people make more radical accommodations in cutting.

I have never wondered what the force diagrams look like, since I don't think that would give anything useful.  

What matters is the sound and response, and what goes into that is so mind-boggling complex AND the better/worse evaluation is in the end only by the player, so trying to analyze the situation is not appropriate.  Experience and trial-and-error are called for, I'd say.  However, some overall engineering-ish concepts still apply, like bridge mass attenuating the higher frequencies more than the lows... so there's at least one fairly obvious balance knob to turn.  Rocking frequency and stiffness might be another, although I think that's a much smaller knob than the mass.

Opening the heart and kidneys would fall into the category of reducing mass... so I'd guess that improves the brightness and projection.  If that's what the player wants.

I I have only built 4 violas so far, so I can't say much more than general arm-waving.  For now, I have been making bridges high enough to not have the bow hit the body, and then WAGing the cut of the bridge to be a little thicker than what I do for violins.  Hey, it's just a viola.  That said, I'd be very interested to hear what more experienced viola makers (Manfio) have to say about how they cut their bridges.  I'll be at that stage on my current viola soon.

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As usual, Don gives a very good answer. As a hardangerfiddle maker I do pretty wild things. Of course, a hardangerfiddle is something rather different from a violin or a viola, but it might give the more narrowminded (sorry!) violin makers some perspective. It's more about resonance, with the complexity that Don writes about, than it is about levers or "force diagrams".

 

sfwbridge.jpg

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13 hours ago, Nik Kyklo said:

Very interesting topic. I would also like to know about feet length. How much is it related to the general viola dimensions? Does it follow the principles of soundpost and bass bar or it depends upon the kind of sound we are looking for? 

I don't really pay much attention to the length of the feet although the total bridge width from the outside of the feet is determined by the bass bar position. On a new instrument or a major restoration the size of the viola and the FF hole positions help me decide where to put the bass however. I would invite comments about that process as well while we are talking violas.

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I don't have any great insights, but I *think* I know that the narrower bridges have more focus, where the wider ones are more diffuse sounding. So if you have a viola that sounds like a big violin, sometimes a wide bridge will help that, for instance. Or if the sound is too fuzzy, try a 46mm bridge.

Otherwise, I treat them about the same as violin bridges. You're probably right about the extra wood in the bigger bridge having an effect, and normally I'd think that this would hurt the loudness, but I haven't noticed that.

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11 hours ago, Michael Darnton said:

I don't have any great insights, but I *think* I know that the narrower bridges have more focus, where the wider ones are more diffuse sounding. So if you have a viola that sounds like a big violin, sometimes a wide bridge will help that, for instance. Or if the sound is too fuzzy, try a 46mm bridge.

Otherwise, I treat them about the same as violin bridges. You're probably right about the extra wood in the bigger bridge having an effect, and normally I'd think that this would hurt the loudness, but I haven't noticed that.

Michael, how much importance do you place on the relationship between bass bar position and the bass foot of the bridge? Would you consider trying various bridge widths in tonal adjustments, even though it messed with the "optimum" (whatever that is) overlap with the bass bar?

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1 minute ago, Michael Darnton said:

As long as the bar is under the foot I don't believe the.precise.position is critical. I have done a lot of testing of bass bar effects and haven't been impressed, so I look at this as mainly a structural question I do not think that bar placement is analogous to post placement.

Thanks, Michael. When you say "bass bar effects" have you also concluded that varying the shaping is also a relatively minor effect? (within reasonable limits, I guess).

Sorry if this takes things too far off topic!

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