Should mando bridges split the break angle?

[Stephen Perry]

On bowed stringed instruments one generally attempts to get the downforce from the strings to follow down the middle of the bridge. To date I haven't seen this in mandolins. The bridges seem universally at right angles to the top rather than leaning towards the tailpiece. Wouldn't fitting the bridge to split the break angle be superior?

[John Flynn]

There has been at least one Cafe' discussion on this before. A couple of luthiers responded to say they lean thier bridges back toward the tailpiece, about 8 degress if I remember right. I have two flat top mandolins with bridges that the builders set leaning backwards: a Parsons Flat-top and a Medieros travel mandolin.

[sunburst]

Wouldn't fitting the bridge to split the break angle be superior?

Are you speculating that this would be superior in terms of the physics of keeping the bridge stable, or in terms of transfering string energy to the top, or both, or other things?

[PaulD]

On my ~'49 Gibson A the bridge seems to split the break angle of the strings. I never knew if that was desirable, but since it fits the top well I left it alone. When I fit the F9 bridge I tried to get it perpendicular, which in any case was an improvement since it shipped with a slight lean toward the fretboard. I am interested in seeing where this thread goes because I always thought that it should be perpendicular to the top.

Paul Doubek

[Stephen Perry]

I'm not speculating. Just applying violinmaker thinking, which concerns both structural and acoustic elements. Usually a more symmetric structure works better visually. Maybe it works better acoustically, too. More even pressure across the contact surface perhaps. Rather than pushing down one edge. I don't know how mandolin acoustics are impacted by the bridges very much.

If I get a chance I'll make some bridges and see what they do on mandolins. Seem to have too many projects as it stands, though.

[sunburst]

Please help me understand here...
You say you're not speculating, yet you say "Maybe it works better acoustically,".

I, for one, have spent some time speculating on what would be different with changes in mandolin bridge angles, and am curious about what ideas other people have.

Here's an example of the sort of thing I've thought about:
If you bisect the angle of the string break with the bridge, the center of force should be at the center of the bridge base.
OK, that's true for the static force from string tension, but what's going on with the dynamic forces from the vibrating strings? Does most or all of that come from the part of the string between the nut and the bridge? and if so, what difference does bridge angle make? Is there bridge movement more or less straight up and down combined with rocking back and forth in the direction of the string length, and side to side? Suppose you could figure out and establish the optimal angel for both static load and dynamic load. Would you hear a noticable improvement in sound?

[Stephen Perry]

I don't have a speculation. I can understand the structural aspects well, but I don't know mandolin bridge acoustic research. I figured you guys had this all figured out. The amount of motion is rather small back and forth but has a powerful effect on the top; that's where most of the energy is. In a violin bridge the resonant frequency of the bridge as a whole helps set the overtone peak. Mandolin bridges are rather different, with the metal and so on.

[sunburst]

I don't know of any mandolin bridge acoustic research, though there may be some, and if there is, I doubt if anyone has it all figured out.
I know the basics of how a violin bridge works (since there is literature about that), but, like you say, mandolin bridges are rather different, and I don't see how some of the violin knowledge translates to mandolin bridges.

My experience with mandolin bridges indicates that they sound about the same whether straight up and down or leaning slightly toward the tailpiece. A slight backward lean does seem to help with the bridge's natural tendency to lean forward from tuning. Other than that, I don't feel like I know anything about Mandolin bridges, and I don't know where to find out anything either.

[PaulD]

I have wondered whether the physics of vector forces applies to mandolin bridges; so, if the bridge is leaned would the bulk of the vector force be directed down into the top and some small vector of energy traveling roughly perpendicular to that? I'm weak on physics so if I'm way off base I hope somebody at least gets a good laugh out of it!

In pondering this, I've figured that the difference in sound would be very, very minimal, but I can't say which is better. If some of the energy is directed back into the string rather than into the top maybe it would increase sustain??? I had actually written it off to the fact that the motions are so complex that chaos theory may describe the behavior better than vector physics.

I say I've pondered this, but I won't claim there is any validity to what I came up with.

Paul Doubek

[Chris Baird]

I fit them slightly towards the tailpiece so that when strung up they are about 90 degrees or slightly toward the tailpiece. #I do this just to avoid the neck side edge from digging in. #I very seriously doubt that there would be a perceivable difference in tone from one angle to another. Musical instruments, like all things, can be infinetely complex. The harder you look the more you see. I say look at the things which your ear can detect changes in and disregard the rest. Unless, you are a physicsist.

[Michael Lewis]

Like Chris Baird, I fit my bridges to lean back toward the tailpiece, firstly to help avoid the leading edge of the foot from digging into the finish, but also to prevent the bridge from tipping forward as the strings are tightened. I really dislike the bridge to slam into the top.

[PaulD]

Chris... that was kind of the point I was making... that if there's any difference it is probably miniscule and that I think about silly things like that way too much!

I hope you had a good Thanksgiving and were able to make it to some of the "real" music shops in SLC while you were up here!

Paul Doubek

[Lee]

There are number of one-piece violin type bridges on mandolins, but I've never heard of a two-piece adjustable mandolin type bridge used on a violin.

[martin impey]

I have modified the bridge on my Kentucky, making it lighter. At the same time I have leaned it back slightly to split the string angle more evenly. It seems to me this will enhance transmission of vibration from the strings to the top. martin

[Mando Medic]

5 years ago I did some research on John Monteleone's one piece mandolin bridges that he built in the early and mid 70's. I found that like violins, he was striving for the bridge to be perpendicular with top at the inntonation point. Like a violin, it would seem while looking at it, that the bridge leaned towards the tailpiece. As I set bridges for customers, I take this same approach and I find that it loads the top well if the tailpiece angle is natural begining from the rear rim/tailblock area. Ken C

[Jim Hilburn]

I don't have a lot to offer here, but I was at a party last weekend where a lady was playing a cello, and I was sitting where I was looking at the side profile and it brought this thread to mind. My thought was just how different these two animals are. To achieve the 45 degree break, we would have to start tilting the necks much further and making some very tall bridges and some very long tailpieces.
Obviously while some violin traits were built into the archtop mandolin, compromises were made and as far as I'm concerned, Orville and Lloyd and whoever else got it pretty much right.

[prairiewind]

FWIW, I own a mando that I believe was originally set up to try to achieve what I think Steve is talking about. Its a 30 year old Japanese copy of a Martin with the canted top. The original one-piece rosewood bridge was built with the front face (toward the neck) sloped about 30 degrees off vertical back toward the tail piece. The back face was a few degrees past vertial toward the tail piece, and the top of the bridge was beveled with the front face almost flat (parallel to the top)and the back face quite a bit more sloped. The bevel was the back takeoff point for the "e" and "d" courses to the tail piece and the front contact point for the "a" and "g" courses. I think this design was meant to split the break at the bevel and put most of the tension through the plane running from the top bevel through the middle of the long direction of the bridge base.

With time, wear in the grooves in the rosewood bridge and settling of the top resulted in buzzing "g" strings, so I made my own nonsloping maple bridge. If anything, it works better than the original.