"Mounting holes" for the bridge on an old mandolin

[Raldanash]

I recently got an old German Mandolin, which I am cleaning up and restoring a little. It's a nice little instrument, but after taking all the strings off and removing the bridge, I came across something I haven't seen before. The bridge was sitting on what I thought to be two small washers, but once it came off, I noticed that these are basically bushes around two holes drilled through the (spruce) top of the instrument. (see photo)

This basically gives a set position for the bridge, but what flummoxed me further was that the bridge is quite a bit off where I would expect it (by judging the 12 fret as the centre of the scale length), 18.5 cm from bridge to 12th, 16.5 from 12th to nut.

Has anyone come across this type of setup before? Should I stick the bridge on these "posts" or position it on the wood instead? Intonation seemed a little off in the original bridge position before I took the rusty strings off, but hard to know whether this was due to the strings or the bridge position for a noob like me.

For those interested, it is a Arion mando (manufacturer), but I have been unable to get any details about them so far.



Thanks!

[MikeEdgerton]

I'm not sure if those are bridge positioning holes or the holes that seem to be drilled for no known reason in many German mandolins.Usually they have some sort of insert in them. Perhaps someone decided to put the bridge there.

http://www.mandolincafe.com/forum/sh...s-in-mandolins

[Raldanash]

Ah - interesting that other German instruments had these, too. Thanks for sharing your expertise.

I will have a play with it over the next few days and find the "good" bridge position.

[plinkey]

Those could be some sort of "sound vents" that some European mandolin makers commonly used. (For example Calace.)
Their positioning on the mandolin top varies from one maker to another. Some makers used to drilled those "vents" on their mandolin sides.
I doubt it those "sound vents" make any perceptible difference in mandolin tone, however, perhaps there is some valid reasoning/experimenting behind it.

On the other hand, bridge position markers need not be drilled thru the top, they typically consisted of tiny wood buttons glued onto the soundboard at each bridge tip, after the maker positioned the bridge "properly" (at the time).

[Tavy]

They're common, functionality unknown

Whatever the bridge should not actually be on them - between them maybe - but certainly you should place it at the correct point, not where someone happened to place it before by mistake.

[MikeEdgerton]

Those plastic inserts aren't original either.

[Ray(T)]

Ah! The return of the mystery holes! Never seen them there before. They're usually off centre or on the side of the instrument. One day someone will tell us what they are.

[EdHanrahan]

... 18.5 cm from bridge to 12th, 16.5 from 12th to nut. ... Intonation seemed a little off in the original bridge position ...

Twice the nut-to-12th-fret distance is defined as the formal "scale length" but, to compensate for stretching, thus sharping, the strings in the act of fretting, the 12th-fret-to-bridge distance is always a slight bit longer. (It's the varying reaction of differing strings that gives us the zig-zag "compensation offsets" of the typical bridge; older bridges are often straight).

So the distance from 12th fret to bridge should be just SLIGHTLY more than 16.5cm (but certainly not 18.5), leaving your sound holes in the clear.

Fret.com has info on setting the proper bridge position / intonation. See the bottom of this page, on restringing an archtop guitar (that also has a floating bridge):
http://www.frets.com/FretsPages/Musi...tstring02.html

[plinkey]

Perhaps the best known mandolin builder who made some of his mandolins with "sound vents" in the top, on the soundhole side of the bridge, is Raffaele Calace from Naples, Italy. His typical "sound vent" configuration is shown in the enclosed picture, early 20th century. Some older German mandolin builders used to position such vents only on one side of the mandolin top.
In any event, all of those "sound vents" which I've seen were probably originally provisioned with some sort of bushings for a more finished look as well as hole edge protection, although the bushings are often gone missing too .

[Raldanash]

Thanks for the info from everyone. Good link for the bridge positioning, too. I just tend to use the 2x 12th distance as a starting point for the bridge position. Has anyone ever heard of Arion as a guitar / mando maker?

[Jeff Mando]

Buick used those vents, also. Makes the car look "faster"....

[Bertram Henze]

Buick used those vents, also. Makes the car look "faster"....

I thought those were for dropping an anchor in case the brakes would fail...

[Jess L.]

I thought those were for dropping an anchor in case the brakes would fail...

We didn't drive them long enough to notice brake problems, as the automatic transmissions failed first. We had two Specials (3 port-holes) and a Roadmaster (4 port-holes), and several other Buicks for parts, they all had transmission issues. They eventually all got parked out in the back field where they sat for the next 40 years or so.

[theCOOP]

Looks to me like these holes might be meant to 'soften' the top, ahead of the hard stiff break in the top (and the bridge).

[Beanzy]

Nah, it's so you can hold them up and scare the audience in the spooky numbers

[Tavy]

Nah, it's so you can hold them up and scare the audience in the spooky numbers

[MikeEdgerton]

That looks familiar.