zig zag bridges and placement

[Squeegeeman]

When I was first placing the bridge on my mandolin I was told to keep the length of string the same on either side of the 12th fret. It didn't really make sense to me because the bridge had a zigzag shape where the E and D notches were further up than the A and G. I just measured to the center of the zigzag and left it at that. Then recently I saw a video that said another way to do it is to play the string on either side of the 12th fret to see if the tones matched so I tried it and just like you'd expect, the A and G matched while the E and D were a little sharp on the bridge side. My question is, what is the purpose of the zigzag and how are you supposed to compensate while placing such a bridge?

[Folkmusician.com]

Hello,

An ideal string length for intonation will be based the scale length, string height and gauge of strings. A normal compensated mandolin bridge is meant to be a good all around compromise. It will never be perfect. So what most do is to intonate the E and G strings and the check the A and D strings and attempt to place the bridge for the best all around intonation. It is common for the bridge to end up twisted one way or the other. This is fine as long as you end up with the mandolin intonated.

A measurement will get you close, but this really needs to be done with a high-grade tuner and use the 12th fret harmonic and fretted 12th fret and compare them. It is impossible to get all four courses perfect, so just get as close as practical with your current bridge. To go beyond that, you will need to finalize on the set of strings you like and the action. Then make a custom saddle and cut the compensation to the specific strings/setup.


To complicate matters, the intonation changes up and down the fingerboard. Each fret will vary. If you rarely play up the neck, you can set the bridge for the best intonation at the bottom of the fretboard.

[Mandoplumb]

In the past there was straight adjustable bridges available , I assume there still is. To really have a problem with intonation you could use one. Tempered tuning itself is a compromise, the compensated bridge is just trying to make the compromise as close as possible.