Bridge Placement

**mandrian** · May-28-2020, 3:11pm

Hi,

Looking for confirmation that when a zero fret exists that the bridge should be placed based on twice the difference between the zero fret and the 12th fret. Just picked up a mandolin where the bridge is twice the difference between the nut and 12th fret, but I think that is wrong. There is the mark of the bridge having been previously where I think it should be now.

Looking for confirmation that I’ve not misunderstood things.

Regards

**sblock** · May-28-2020, 3:46pm

Yes, the bridge needs to be placed -- as a starting point for further adjustment! -- at the place where the 12th fret bisects the length of the open string. With a normal nut (which acts as a "zero" fret), that's at a point which is twice the length between the nut and twelfth fret. With a zero fret, that's twice the length between the zero fret and the twelfth fret. You have that right.

However, this ought to be the starting place for further adjustment, not the final bridge location! Once the action is set to the way you want it at the 12th fret (usually about 1/16 or less", but different people vary in their preferences -- make it right for YOU), you will need to compare (1) the harmonic sounded at this 12th fret position with (2) the sound of the fretted string. These should both sound the identical note, one octave over the open string. You can compare these by ear, assuming your ear is good, or using an electronic tuner. If the fretted note sounds a bit sharp relative to the harmonic, then nudge the bridge slightly rearwards, towards the tailpiece, to lengthen the string just a bit. If the fretted note sounds a bit flat relative to the harmonic, then nudge the bridge slightly forwards, towards the nut, to shorten the string. Keep nudging the bridge until these notes sound exactly the same.

Most folks do this by checking the open G and E strings, and let the D and A wind up wherever they will, set by the saddle compensation at the bridge. It's extremely hard to reposition the bridge with all 8 strings under full tension, however! Instead, you can choose to check both G and E string pairs at the same time, leaving the A and D string pairs nearly slack (under very loose tension). Or, you can adjust just the G string pair first (leaving A, D, and E slack) and then the E pair (leaving G, A, D slack). Or the other way around: E pair first, then G pair. Your choice! You might even have to slacken all 8 strings between adjustments, which is OK, too. Just make sure that however you choose to do it, whatever strings you're checking at the 12th fret are brought up to full pitch at the time of the check. This doesn't work for strings that are not properly tensioned.

This procedure might leave the mandolin bridge saddle very slightly "tilted" with respect to the strings, i.e., not perfectly perpendicular to them, when viewed face-on to the fretboard. If the octaves match on the G and E strings, as described above, then don't worry about this tilt: it is perfectly normal.

Do not, however, leave your bridge and saddle "leaning" much. Viewed from the side (looking along the top, a right angles to the strings, from playing position), the saddle should be perpendicular to the strings.

Good luck!