Please help me solve this tuning issue

[Capitano]

Hi all,

I am, let's say, at the late beginner stage, so as you can judge how to frame your responses.

I have a mandolin, an octave mandola and an Irish bouzouki. No problem with the mando or the zouk. But the Octave has the following issue:

I tune the open strings using an electronic tuner. I do this three times to ensure every string is tuned correctly. But when I then play a scale going up the neck to fret 12, the pitch becomes progressively higher than it should be for the note played. This happens with all the strings, although more so with the bass strings. On the g string for example, the pitch at fret 12 is not far off being a semitone higher than it should be.

I have checked that the bridge is placed at exactly double the distance of the 12th fret from the nut. The instrument is not very old and it is in excellent condition. I see no warping and there is no reason why there should be. It is a fairly economical model made by Ashbury, but it is not the cheapest, and certainly not "cheap and nasty". The strings are not that old either, maybe 6 months, and it is not as if the instrument is used very intensely. The only thing I can think of is that they are ultra light strings: could that be the reason for this behaviour? If not, what?

Many thanks.

[Mandobart]

Bridge location should be based more on actual string intonation than simple geometry. Have you checked 12th fret intonation by comparing the fretted note and harmonic for each string?

This sounds like more of an intonation adjustment needed than anything else, but other potential causes include the action is set too high or the nut slots are too shallow or angled wrong.

[Chuck Leyda]

Hi all,
I have checked that the bridge is placed at exactly double the distance of the 12th fret from the nut....

Even if it's theoretically in the right spot, if the instrument goes sharp I would still try adjusting the bridge and see if that helps. Try moving it just slightly away from the neck and see if that helps. Actually, what I would do is have a tech look at but I'm not very DIY with instruments

[Tom Wright]

Because the string needs to be deflected downward to fret, it will play sharp to the simple arithmetical location. This is not wrong, it is true for all stringed instruments.

Find the location by tuning, not by a ruler. The differing reactions of wound vs plain strings accounts for the steps in a compensated bridge, and all fretted instruments need a slight angling, with the thicker low-pitch strings needing a farther back bridge location. See my avatar, or any guitar.

[Capitano]

Have you checked 12th fret intonation by comparing the fretted note and harmonic for each string?

Thank you, that link is very helpful. I will feed back here when I have found a little time to do this.

[tmsweeney]

I have experienced similar conditions with some octaves, my thinking is the scale is too short which means the bridge should be moved away from the neck.

One surprise a luthier showed me was "bridge sag" (smiling) the bridge should be a straight line horizontally (the part that the strings rest on)
he simply reinforces the bridge with veneer, I had one luthier actually replace the entire bridge

[Simon DS]

The bridge could be too high? What’s the action hight at the 12th fret? -mine used to be 1.75 mm but now feels a bit higher.
There are variations with different instruments.

-Imagine a bridge that’s 6 inches high. Then you would have to stretch (sharpen) the string a lot to play a note at 12th fret but none at all for the open string note. The 12th fret note would be too sharp, hence the issue with a bridge that’s too high.

[ProfChris]

Thick strings on a short scale need a lot of compensation. If you adjust the bridge according to intonation, so that the 12th fretted note is an octave above the open note, your bridge might end up 3mm (1/8 inch) or more towards the tail from its current location.

[mandocello8]

others said it. keep moving the bridge until intonation is right. most likely it will want to be in different places for different strings. "split the difference" if this happens. this is basic motorcycle^Wmandolin zen and maintenance.

[Capitano]

What’s the action hight at the 12th fret?

I measure it as 3mm.

[Capitano]

I have adjusted the bridge position as suggested by many of the responses, in particular by following the tutorial linked to by Mandobart. I had to move it about half a centimetre back from where it was before i.e. towards the tail, and I have angled it a little so at the 1st string it is slightly closer to the nut than at the 4th string. Now it is good on the 1st and 2nd pairs of strings, acceptable on the 3rd, but still sharp at the 12th fret on the fourth. I am thinking the action may be too high.

[tmsweeney]

"and I have angled it a little so at the 1st string it is slightly closer to the nut than at the 4th string"
if you think about the nut slot and the string slots in the bridge they are not cut for the sting to ride at an angle, I've never really had any luck with this technique (though I know some people do it and it works for them)
if the action can't be adjusted down you may have a neck bow problem or fret work needs to be done.
to me it seem the if the nut is a straight line - the bridge should be as parallel to it as possible

[peter.coombe]

For correct intonation the saddle will need to be tilted because the compensation needed on the bass string is more than the treble string. That means the saddle needs to be stepped for each string so the saddle is parallel to the nut. This makes the length of the pairs of strings from nut to saddle the same. Lots of OMs are made with a straight saddle. That won't give you good intonation on all strings. OM's are not like guitars. My OM saddles are cut on a CNC machine by Vern Brekke to my specifications. A high action does not help the situation, but I doubt it is your main problem.

[Tom Wright]

For correct intonation the saddle will need to be tilted because the compensation needed on the bass string is more than the treble string. That means the saddle needs to be stepped for each string so the saddle is parallel to the nut. This makes the length of the pairs of strings from nut to saddle.

Somehow I have no trouble, although one might expect it. Ditto my electric 10-string with a Gibson Tune-o-matic style bridge, whose separate pieces are angled with the bridge angle. The string length difference is tiny.

If the action is very high, a significant angle is needed. My Buchanan could use a smidge more angle, but then I rarely fret the C pair at the octave.

[Capitano]

For correct intonation the saddle will need to be tilted because the compensation needed on the bass string is more than the treble string. That means the saddle needs to be stepped for each string so the saddle is parallel to the nut. This makes the length of the pairs of strings from nut to saddle the same.

Mine is stepped but not in the way I might expect from your description. The saddle at the first and third string pairs is closer to the nut than at the second and fourth. The first and third are equal to each other, as are the second and fourth. I wish I could attach a photo but I cannot see a way to do so.

[RobH]

That's how my bridge is. I just completed an Octave mandolin and used Graham McDonalds recommendation for bridge compensation
I find that my D string is not compensated perfectly and if I made a new saddle I think each string would have an equal setback to start (not a slant but a stair step.

[NDO]

Sorry to hijack but I have a somewhat similar issue. I’m brand new to the OM (after two years with mandolin) but just got a Pono with 23” scale and love it. It has an angled bone saddle in a fixed location so I don’t see an easy way to adjust the intonation. I’ve noticed that the intonation tends to be sharp up the frets particularly on the A strings. Any thoughts on mitigating this? I’m sure some of it is my technique since I tend to fret harder than I need to. I’ve been compensating by compromising a little flat on open tuning on the A strings and focusing on a lighter touch on the frets.
It came from the seller with a new set of strings installed (not sure exactly what set) and the A strings are bare, would switching to a set with wound A strings be likely to make it better or worse?
Is there typically a way to adjust position (both height and scale length) on this style of bridge?

[EdHanrahan]

... intonation tends to be sharp up the frets ...

I suspect that most read that as "toward the body", normally said as "UP the neck". But your further description could mean that frets 1 thru 5 or so have the problem. THAT is often caused by too-high nut slots, causing string deflection & stretching (higher pitch) when fretting. When you fret at 2, there should be minimal clearance between the string and fret 1.

Or I'm way off!

[John Kelly]

NDO asks about his Pono with fixed bridge and bone saddle: "Is there typically a way to adjust position (both height and scale length) on this style of bridge"? On a fixed bridge the height can be adjusted by placing shims under the bone saddle to raise it. As far as the intonation correction, you would be best to have a new saddle cut. You can use the compensation on your existing saddle as a starting point for getting the new saddle cut accurately - if the fretted notes are sharp then you need more length in the string, so the saddle needs to be cut further back, and if the notes are flat then the saddle needs less of an indent.

[NDO]

Thanks for the quick replies. I should clarify that the problem exists all the way up the neck but is also present on frets 1-5 so I was thinking I might need to lower the nut slots. It does seem like I’m getting some string stretching.
The current saddle doesn’t have any individual string compensation, it’s a thin bone saddle that is angled to be shorter at the E string and longer towards G.

Does someone have recommended string height specs at frets 2 and 12 for an octave?

[mandocello8]

23in scale length, check. unknown strings, check. uncertain intonation at nut, check. uncertain intonation at bridge, check. fixed bridge, check.

as reference, my bruce weber sage-1 octave is 23.5in scale length, I use flat wound thomastic strings 12-gb20-gb28-gb41, individual strings from juststrings.com, $$$.

to check intonation at the nut, put a capo on 2nd fret, tune, check intonation. (this takes the nut out of the equation). if it looks sane (intonation gets progressively sharp or flat, consistent with out-of position bridge), remove the capo, tune, check intonation again. if you see different result with capo and without, something is wrong at the nut. read on.

to check intonation at the bridge you do as above (observe progressive sharp/flat), but you cannot move a fixed bridge to fix it. read on.

it is important to accept that it is unlikely the instrument was build with incorrectly placed bridge.

most likely cause of trouble: you have wrong strings.

a) wrong diameter strings would not sit happily in slots in the nut, there will be intonation trouble.
b) if bridge intonation was set for wound A string, but you have a plain A string (or vice-versa) there will be trouble, different type/material strings need different compensation at the bridge.

if I had this instrument, I would do this. I would contact the maker, find out what strings they recommend, buy and install those. (note: most common sets use wound A strings). I would observe that new strings sit well at the nut (better than old strings, this is easy to see while swapping old strings to new strings one-by-one).

as likely as not, problem at nut will go away and problem at bridge will get better, but not prefect.

this is because with a straight bridge saddle (no compensation), wound G, wound D, would A, plain E will always have unhappy intonation (angled at any angle).

to improve, a compensated saddle must be made. this is a job for a luthier. at the same time, they will adjust action at the nut, they will adjust the truss rod and anything else as they see fit.

to repeat, first step is to get rid of unknown strings, best is to start with strings recommended by the maker.

[mandocello8]

i misread 2nd OPs message. it does say plain A strings. if instrument was build for wound A strings, definitely trouble at the nut (different string stiffness and diameter) and trouble at the bridge (compensation for wound-G, would-D, plain-A, plain-E is quite large). replacing the plain A strings with wound A strings will likely fix the trouble, but without knowing the guage of other strings it is hard to recommend guage of replacement A strings. start over using a set of known strings, preferably one recommended by the maker is the way to go, I think.

[DougC]

Guitar body octave mandolins seem to be quite sensitive about string size. I had a short scale Pono MD30 and was surprised at how a change in string material and gauge made a huge difference.

So before you make any changes to the instrument, try other strings.

I sold the instrument a few months ago and I can't remember what strings ended up with. (They were flatwound lights however. Emando strings probably has the 'set' selected. A good place to start...)


There are many comments about this issue on other threads. Here is one.
https://www.mandolincafe.com/forum/t...ctave-Mandolin