Intonation Question

[KGreene]

So, I've been using D'Addario EJ74s basically forever. A friend gave me a set of D'Addario EXP75's (coated) to try, stating that they made a huge difference on his Sam Bush.

It was time for a fret board cleaning and fret dressing anyway so I dismantled the mandolin. During the reassemble I had to move my bridge back approximately 5/16 of an inch on the bass side and 1/4 inch on the treble side to achieve proper intonation. The intonation was previously correct with the EJ74's as well (I have a habit of checking it regularly).

My question ... is it common that simply going from 11/40's to 11.5/41's makes that much difference in the intonation?


Thanks,

[Ivan Kelsall]

IMHO - No !. I've tried out many different string brands & a couple of different string gauges,all without needing to move my bridge at all - unless it was already out of position. Resting my hand on it,even as lightly as i do,can sometimes move it over time.

The intonation is set by the bridge position,& bridges are usually compensated for the different string gauges,so that they intonate correctly. The small difference in string gauge of .001" shouldn't make much difference to the intonation if everything else remained the same. Needing to move it by 5/16" seems a heck of a lot. On the single occassion where i did need to re-set the bridge, when i first received my Weber,it was only by a 1/16" or so.

When i do a strip down & clean,i have to remove my bridge,but i always mark the position using 2 tiny pieces of low-tack masking tape. If i do ever need to re-set the bridge,or check it out,i position it so that i get as perfect an octave at the 12th fret on the "A" strings as i can. The "A" strings are usually the 'most used' strings,so i set those 'spot on',& usually the other strings as as close as makes no matter. On my Weber & Lebeda mandolins,after tuning up to my tuner,i check the strings,one to another, across the fingerboard & i always need to tune up the 'E' strings,to sound the same as the 'A' strings fretted at the 7th fret - a tiny amount. On my Ellis,they're already spot on - Tom Ellis makes his own bridges & compensates them for each mandolin.

That works 'for me' on 2 of my mandolins,but i know others on here 'do it differently' - as they should if need be,
Ivan

[John Kelly]

I would concur with Ivan on the amount you had to move your bridge to reset intonation; this seems like a big move you had to make - but also I note that you say you did a fret dress. How much did you dress your frets - a heavy or a light adjustment? This could affect your intonation, though you may well have readjusted the bridge height anyway after dressing the frets. Mandolin adjustments are much more sensitive than guitar adjustments because of the much shorter scale length, string height, etc.

[Mandoplumb]

I never mark my bridge when removing for cleaning. As stated they seem to move over time as played, if slight we don't notice in every day use, so I reset for intonation each time I have to remove bridge.

[EdHanrahan]

IF the new, wider strings are not seating in the bottom of the nut slots, then you would need to push down further at all frets, raising pitch, throwing off intonation, & implying a bridge move away from the fretboard. BUT, I suspect that the raised action, particularly near the nut, OR tightness and/or grinding in the nut slots while tuning, would present themselves as the bigger and more obvious problems.

[pops1]

I have found that if I take all the tension off the top I have to move the bridge back for a couple of days. Once the top has resettled to the string tension the bridge will go back to where it was. Just had it happen on my mandolin last week. It wasn't as far as yours, but I used the same strings and not heavier ones. Check it in a couple of days.

[Folkmusician.com]

If you had to move the bridge as much as 1/4", something else is happening. Going up one gauge on the strings would not sharpen the intonation to that degree.

[Ray(T)]

Are you sure you've put the saddle back on the right way round?

[KGreene]

Thanks for the replies ... I use the tape as well to mark position as a reference. The saddle wasn't switched on the bridge (I also use painters tape to keep them in position while its off the top). Tuning up/down is smooth and I don't feel or hear any dragging, resistance or jumping while tuning so I'm assuming there's no issue at the nut (although I did use a bit of graphite for lube). Fret dressing was very light (not even enough to call it an "actual" dressing IMHO), bridge height remained basically the same with an extremely small amount of adjustment to obtain .047 at the 12th fret (my usual setting). I've done this many times in the past using the EJ74's without this anomoly. I suppose it could have moved at some point over the weekend (with a total of 12 hours of playing pretty hard Friday and Saturday) ... I'm probably more anal than I should be regarding intonation (just one of my peeves), and keep a pretty close eye on it, ritualistically checking it daily after tuning ... Checked it this afternoon and the intonation is still good .... There's really no "issue" (per se) I suppose, given that it plays and sounds great. I'm going to give it 'til the end of the week and put a new set of EJ74's for sound comparison to the coated EXP75's. If I have to move it back, maybe it's just that it's a very temperamental instrument??? I'll post about it if that is in fact the case.

Thanks again.

[Roger Moss]

This is beginning to sound like a "perfect storm" of piddling little issues that just crept up on you so slowly you didn't notice until you removed the bridge and had to reintonate all at once. If it intonates well and plays well right now sounds like you're in good shape.

[KGreene]

So, after a week or so of some fairly hard playing:

1. I really like the EXP-75's, there is some tone and volume improvement, and they don't seem to be "tarnishing" as quickly where I brush my hand behind the bridge.

2. I put another set of EJ-74's on (until I go Pick up a few sets of the 75's)…. I had to move the bridge back to basically the original position (toward the head 1/4 inch on the bass side and 3/16ths on the treble side).


It's hard for me to believe that, that small of a difference in string thickness could make that much difference... I'll be picking up more 75's tomorrow and probably change them again after the weekend...I would suspect that I'll need to adjust again.

Very puzzling!!

[pops1]

It may also be a different core and that would make the difference more noticeable than just the gauge.