Bridge Placement

I searched on this thinking it must have come up before, but I may not be using the right work combo.
After changing strings I always put the bridge back "about" where it was, using the "footprints" on the top, and the nicks in the F-holes as reference. Then I tune the G strings and the E strings. I check to see if the harmonic is over the 12th fret, and make minor adjustments to make sure that the harmonic is strongest directly over the fret.
I finish tuning and that is that.
All of this is a bit inexact. I was wondering if anyone has a more exact way of doing this, that doesn't require special tools.

Thanks-
Papawhisky

You can get it exact with an electronic tuner.

The harmonic alone isn't exact, as you are really guessing its position approximately above the 12th fret.

Set it so the the 12th fret harmonic produces the right note AND the fretted 12th fret note is exact and the same.

Rod

If you change strings 1 or 2 at a time, you won't have to go through repositioning your bridge after every string change.

I would follow Rod's advice. My understanding is that there will always be some compromise. You can get it close, but not perfect for all the string pairs. I spend most of my time at the lower end of the fretboard, so for me, it is not as critical.

Why take the bridge off when you change strings. Do as Don describes.

You need to remove all your strings to clean the fretboard properly, it's easy to mark the bridge position with tape or a non permanent marker pen or measuring, or using 2x nut to 12th fret distance if you're not confident of getting it right by tuning up.

Dave H

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Originally Posted by Dave Hanson

You need to remove all your strings to clean the fretboard properly, it's easy to mark the bridge position with tape or a non permanent marker pen or measuring, or using 2x nut to 12th fret distance if you're not confident of getting it right by tuning up.

Dave H

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Dave, You clean the fretboard?? :disbelief:

Seriously though, one can keep a fretboard quite free of detritus using a dry toothbrush( or similar) and/or a microfiber cloth gently fitted under the string pairs. It may not be the 1-2-3 quick wipedown that is possible with no strings but for me, taking off ALL the strings leads me to think about what i might do with the bridge and THAT is a very dangerous thing!

I'm just a noob, but I have zero fear of taking my bridge off. I've done it on a couple of 'em, and there is a very clear "footprint" of the bridge in the top finish. If I really want to put it back exactly where it was, I'll put it where that shadow/ footprint is. Otherwise, I can measure from the 12th fret. Cinch up all eight strings to the point where the bridge can still be moved, and bump it forward or back until the note on the 12th fret on the E string is exactly E on my tuner. What's so scary about that? ~:>

The only thing scary about Me removing my bridge is that I have a tendency to *@#$ around with things in an attempt to "optimize". Last few bridges I have removed had no problems with intonation- Except for the attempt on my inlaidartist special - the intonation from the eighth fret up was perfect, as in the perfect sound of strings resting on frets from a bridge sanded wayyyy too low... DOH! :whistling:

Whether you're cleaning the fretboard, changing strings, or whatever; everyone that plays a mandolin with a movable bridge should know at least a little about proper bridge placement. Rod is absolutely correct, and the OP is obviously not worried about moving the bridge around, so here's my 2 cents on getting it accurate: Loosen tension on all strings except for 1 and 8. Get those two strings in tune on a reliable tuner and then play them at the twelfth fret. If the 12th fret note is high move the bridge towards the fingerboard, if it's low move it toward the tailpiece, making sure that the bridge stays flush to the top with no gaps whatsoever and that it is perpendicular to the top (i.e. saddle is not leaning). When both the E (1) and G (8) strings are perfectly in-tune open and on the 12th fret, your bridge is roughly in the right place. After you get it intonated, adjust the bridge height to when you want it and then re-check the intonation. Most want the action just high enough to where it will not buzz on the first couple of frets. After everything is in the proper and comfortable place, you are ready to bring all the strings to tension and check for intonation at the 12th fret on the A and D strings. If there are issues with these strings, your bridge compensation may need to be adjusted. Lot of other factors involved with complete intonation up the fretboard, see a luthier/repairman if this doesn't get you pretty close.

It seems like two techniques have emerged. The way I am doing it, using the midpoint node (12 fret harmonic), and/or fretting the string at the 12th fret and using a tuner. Actually I have done it both ways, but have started to prefer using the harmonic.

I started using the harmonic so I could avoid depressing the string at the 12 fret, which necessarily sharps the string. It is the nature of fretted instruments that the act of fretting increases the tension on the string, thereby raising the pitch of the string. Because this happens, I wasn't sure if when I adjusted for an exact octave difference, I was actually finding the exact scale length. (I've also measured for scale length).

Clearly I've spent too much time on this. And it probably gets into the practical application of the equal-tempered scale, which I do not claim to understand.

I was just changing strings and wondered "does anyone have a better way?"

Papawhisky

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Originally Posted by papawhisky

It seems like two techniques have emerged. The way I am doing it, using the midpoint node (12 fret harmonic), and/or fretting the string at the 12th fret and using a tuner. Actually I have done it both ways, but have started to prefer using the harmonic.

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Actually, you could position the bridge an inch out of place, tune the top string to an E and have the harmonic perfect! But it wouldnt play right fretted! See my point?

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I started using the harmonic so I could avoid depressing the string at the 12 fret, which necessarily sharps the string. It is the nature of fretted instruments that the act of fretting increases the tension on the string, thereby raising the pitch of the string.

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Indeed it does. But how often do you play a tune with all harmonics? The idea is to play with the strings fretted, and hence tune the E to the 12th fret.

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Because this happens, I wasn't sure if when I adjusted for an exact octave difference, I was actually finding the exact scale length. (I've also measured for scale length).

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Inless you can accurately measure to 1/64" and add the allowance for compensation, then that isn't going to work.

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Clearly I've spent too much time on this. And it probably gets into the practical application of the equal-tempered scale, which I do not claim to understand.

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Don't even go there. ;)
It isn't practical on a fretted instrument.

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I was just changing strings and wondered "does anyone have a better way?"
Papawhisky

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Change two strings at a time and don't move the bridge once you have it right. :grin:

Rod

I always remove all strings when I change so I can give the body and fretboard a good cleaning. The way I get the bridge placed correctly is to string up the two outer strings (one G, one E) first, and compare the 12th fret harmonic to the fretted note. I usually tune them two or three semitones low so the bridge is easier to move around. Once I get the harmonic in tune with the fretted note on both strings, I bring them up to pitch, then string up the rest normally.

I searched for this thread because I needed some advice on adjusting intonation. Very helpful.

If I understand correctly, there will always be a slight difference between the fretted note and either the open or harmonic note, due to the slight stretching of the string when depressed. If so, what would be considered the best compromise? In other words, what should the open note be tuned to and how much sharp or flat of that would be acceptable at fret 12? Should the open note be right on pitch, or is it better to "split the difference between" between the open note and the note on fret 12?

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Originally Posted by papawhisky

I was wondering if anyone has a more exact way of doing this, that doesn't require special tools.

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The simplest and most accurate way for me is this:
Put on only the two G strings and two E strings (or slack the D and A strings if they are already on), then tune the G and E strings exactly to pitch. Fret only one G at the 12th fret. I do that with a thumbnail, just enough pressure for a clean note, and pick the two G strings. One will be a G an octave above the other, and if the octave is correct there will be no beats. It is similar to tuning out the beats in the unison pairs of strings except in this case we're tuning the beats out of the octave by moving the bridge. When both the open G pair and the octave G pair have no beats, move on to the E strings and do the same thing. When the open G strings and open E strings have no beats and the octave G and E strings have no beats, the intonation is as close as the bridge will allow (almost, but no need to go into any further detail).
Put the rest of the strings on, or tune them up from their slack state, and tune the mandolin being sure the top of bridge does not move toward the neck in the process.

This method requires no equipment other than the mandolin and your ears and it is as accurate as any method.

Perfect. I was looking for this information today as well since a friend asked me to see if i could intonate his mandolin after he let someone play it and they messed around with the bridge and made it unplayable. many thanks!

A few other comments:
Octaves are octaves; they are not affected by equal temperament and octave harmonics can be used when tuning. 4th and 5th harmonics should not be used when tuning because those intervals are tempered when equal temperament is used. The 12th fret harmonic is an octave harmonic and should be the same note as the fretted 12th fret note. Yes, the string stretches when it is fretted, but that stretching is compensated for at the bridge, that's why it's called a compensated bridge. That's also why the 12th fret harmonic does not 'chime' exactly over the 12th fret.
Mandolin bridges move. That's just a fact of life, so whether we take the bridge off to change strings or not we still have to be sure it is correctly positioned for intonation, so we should learn how to do it.
Portable, clip-on electronic tuners usually have a window of about 3 cents +or- and are not the best reference for optimizing intonation.
Measuring for intonation would require careful use of very precise measuring tools, and even then, it does not take action height and string gauge into account, so the ear is more accurate.
There's more to intonation than simply positioning the bridge correctly for 12th fret intonation, but for most people that is enough.
Even if the intonation is set up more completely by a luthier or other good set-up tec, a mandolin still has frets, and our tuning system is still equal temperament, so "perfect" intonation is not possible.

As for the bridge 'footprint' left when you remove the bridge totally,i don't trust that either. You have to take account of the fact that it 'might not' have been in the correct place to begin with.That along with the way the instrument has 'settled' over maybe a long period might mean that it's not correct now.
I position the bridge so that the strings when fretted at the 12th,give a true octave above the open strings, using an electronic tuner that i've checked out with a tuning fork for accuracy. I tune all the strings using the tuner,then go back & make tiny adjustments to tune the strings to one another across the fingerboard. I've found that on both my Mandolins, all but the "E" strings are fine. To tune the "E" strings to the "A" strings,i have to tune them a few (usually around 3) 'cents' sharp.
Quote from John H. - " ...so the ear is more accurate" - i'll go with that John !.
Ivan :confused:

PS - Have a read & all will be revealed (if you're a mathematician that is !)
en.wikipedia.org/wiki/Pythagorean_comma

While John Hamlett´s tip on bridge placement is a sound description of what has to go on, none of the posts here really consider that sometimes more inexpensive instruments have intonation issues that sometimes even cannot be straightened out with a new bridge etc. So I change one string at a time and when it comes to the moment when even that kind of string change gets the harmonics off, it´s time for a setup person to straighten things out. (My Strad-O-Lin, as wonderful as it is, does have intonation problems. So the simple harmonics thingy does not really work there. You´ll have to hit the good average)

"Loosen tension on all strings except for 1 and 8. Get those two strings in tune on a reliable tuner and then play them at the twelfth fret. If the 12th fret note is high move the bridge towards the fingerboard, if it's low move it toward the tailpiece, making sure that the bridge stays flush to the top with no gaps whatsoever and that it is perpendicular to the top (i.e. saddle is not leaning). When both the E (1) and G (8) strings are perfectly in-tune open and on the 12th fret, your bridge is roughly in the right place."

Spot on advice. Used this to finally fix my chronic buzzing on my G strings. Thanks! :grin: