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intonation question: 5th sharp, 17th flat

H

hgregs

Sep 25, 2008
226
13
ct/ny border
#1
so before i ruin a nice instrument, please help me understand what the cause of this might be. i can get the fretted 12th string dead-on, but the 5th fret is sharp, and the 17th fret is flat (increasing/decreasing away from the 12th fret). it seems to be mostly the G string.

i have the front nut adjusted as low as it can go (alembics have adjustable nuts). i have tried to increase the back-bow (to get the string closer to the fretboard near the 5th fret, but it's not really helping... at least not based on the amount i've adjusted it so far.

reading on the gear page, they conclude a problem like this could be string related. so i'll admit, i keep my strings a long time - can a stretched out string cause this? seems to me i need even more back-bow, but wanted to ask before damaging my axe.
 
#5
This is actually pretty typical, but I don't know how bad it is on your bass. It shouldn't much more off either note much more than 10 cents either way.

I can't recall the link now, but there's a video on youtube where the bass tech for some band (I think it may be Rancid), teaches how to intonate a fretted bass, and mentions that this is true in most fretted basses and guitars. He recommends to first intonate it on the 12th, and then determine how far off it is at 5th and 17th and match them so they're both off by about the same amount - requires an electric tuner to do accurately.

A lot of people may not notice this, it depends how meticulous they are. There are factors involved that determine how far off it is at 5th and 17th, but I never pinpointed what they were. I had an American Fender when I saw this video and the first time I went about this, the best I could get it was about 8 cents off, but some time later I was only 1 or 2 wither way. Actually, now that I think about it, the strings weren't changed in between so the degree of how far it's off may have to do with something else. The only things I would have changed could have been relief or action, but that isn't to say that the strings are not the issue. I would swap them out and do a complete setup, then see if it got any better.
 
#6
New but fairly broken in strings will help. Action that is too high will cause this exact scenario. The higher you go up the neck, the sharper it gets when the Bridge is raised up pretty high. As stated above, it's hard to get it perfect but I believe that's the whole point of Plecking.
 
#7
How is the tuning at the 1st fret?

If it is as bad there, or worse than it is at the 5th, then the problem could be that the nut is spaced
too far back on the fretboard (too far from the frets). Or the take off point of the string from the nut
might be at the back of the nut (headstock side), instead of the fretboard side. The bottom of the
nut slot could angled wrong or the string might need to be seated, as many call "setting the witness
point".

As already mentioned, make sure the problem is not bad strings first.
Also just how far off is it? And how does it sound?

...
 
#8
megafiddle said:
How is the tuning at the 1st fret?

If it is as bad there, or worse than it is at the 5th, then the problem could be that the nut is spaced
too far back on the fretboard (too far from the frets). Or the take off point of the string from the nut
might be at the back of the nut (headstock side), instead of the fretboard side. The bottom of the
nut slot could angled wrong or the string might need to be seated, as many call "setting the witness
point".

As already mentioned, make sure the problem is not bad strings first.
Also just how far off is it? And how does it sound?

...
Click to expand...
+1!
 
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#9
i finally got around to changing my strings, and everything is pretty much dead-on except the high G string, below the 12th fret... mostly sharp. the first fret is surprisingly ok. 5th is sharp. i need to check with another tuner to say exactly how much (i use a strobe tuner that shows a rotation when out of tune). all the other strings and frets are ok. maybe it's the fret itself? maybe i'm being too particular?
 
#11
What tuner are you using? A true strobe like Turbo tuner, or a virtual strobe like the Peterson
can provide the tuning error by increasing or decreasing the cent adjustment until the display
becomes stationary. The cent adjustment is then the error amount.

That's one problem with strobe tuners; they don't read out errors directly. Indirectly though,
as above, they can determine the error and are very accurate. Often too accurate.

A few cents ( 2 or 3) are quite normal for fretted instuments, and normally inaudible if the
instrument is tuned properly. Also, all strings use the same frets, so a fret problem is not
likely.

-
 
#12
hgregs said:
i finally got around to changing my strings, and everything is pretty much dead-on except the high G string, below the 12th fret... mostly sharp. the first fret is surprisingly ok. 5th is sharp. i need to check with another tuner to say exactly how much (i use a strobe tuner that shows a rotation when out of tune). all the other strings and frets are ok. maybe it's the fret itself? maybe i'm being too particular?
Click to expand...

What's your set-up procedure? What's your relief? What's the G string > 1st fret gap while fretted at the 3rd? How does the 12th fret fretted vs 12th fret harmonic stack up? Set your witness points?

Riis
 
#13
it's only 1c off (1c = 1hz?) at the 5th fret. so i'm guessing: i don't need to be so exact. and yes, even the octave hearing test seems to be fine.

(my bandmate said he could hear that my intonation was off - so i set out to get it perfect. also, that turbo tuner made it look more severe than it really was).

Zooberwerx said:
What's your set-up procedure? What's your relief? What's the G string > 1st fret gap while fretted at the 3rd? How does the 12th fret fretted vs 12th fret harmonic stack up? Set your witness points?

Riis
Click to expand...

went back and checked my relief on the G string (holding the 1st and 12th fret down, and the string holds a business card at the 5th fret) - i'm guessing the relief is ok.

the 12th frets were all intonated against the open strings - i set my action and adjusted the string length until intonated. not a complete setup.
 
#16
hgregs said:
it's only 1c off (1c = 1hz?) at the 5th fret. so i'm guessing: i don't need to be so exact. and yes, even the octave hearing test seems to be fine.

(my bandmate said he could hear that my intonation was off - so i set out to get it perfect. also, that turbo tuner made it look more severe than it really was).



went back and checked my relief on the G string (holding the 1st and 12th fret down, and the string holds a business card at the 5th fret) - i'm guessing the relief is ok.

the 12th frets were all intonated against the open strings - i set my action and adjusted the string length until intonated. not a complete setup.
Click to expand...

Intonate against the fretted 12th. That being said, other parameters (nut slots, lack of witness points, etc) will throw off intonation until identified and corrected.

Riis
 
#17
hgregs said:
it's only 1c off (1c = 1hz?) at the 5th fret. so i'm guessing: i don't need to be so exact. and yes, even the octave hearing test seems to be fine.
Click to expand...

1 cent error is what you call in tune, at least at bass frequencies, and if your reference is perfect
equally tempered intervals. I cent is 1/100 of a semitone. The 5th fret on the G string is about 130 Hz.
A 1 cent error is a frequency difference of about 0.08 Hz.

hgregs said:
(my bandmate said he could hear that my intonation was off - so i set out to get it perfect. also, that turbo tuner made it look more severe than it really was).
Click to expand...

Possibly it did sound wrong to him, even if others would call it "in tune".
Many, including professional piano tuners, hear perfect octave intervals as sounding just a little to "small".
If allowed to adjust the octave, they will set the lower note a tiny bit flat. It's the nature of our hearing mechanism.

*
 
#18
megafiddle said:
1 cent error is what you call in tune, at least at bass frequencies, and if your reference is perfect
equally tempered intervals. I cent is 1/100 of a semitone. The 5th fret on the G string is about 130 Hz.
A 1 cent error is a frequency difference of about 0.08 Hz.
*
Click to expand...

so if it reads in tune when i set my tuner to 441hz... what percent off does that imply? seems like more than 1%?
 
#19
441 is 4 cents high. But that's not the same as percentage.

441 hz is about 0.23 percent high, as a percentage.

A tuning cent is a little more complicated than percentage.

It's easier to understand with octaves. To raise a frequency by 1 octave,
you multipy it by 2. To raise it by another octave you multiply it by 2 again.

So starting with a low A, you get:

55
110
220
440
880
1760
etc

The difference in Hz gets greater and greater, but the ratio, 2:1 remains
the same for each octave interval.

To raise a frequency by 1 cent, you multiply it by 1.000578 (approximately).
To raise it by another cent, you multiply it by 1.000578 again. It is now 2 cent
high. Multiply it again by 1.000578 and it is now 3 cent high.

So starting with 440:

440
440.25
440.51
440.76
etc

If you multiply 440 (A) by 1.000578 one hundred times, you get 466.16, which
is Bb. So the cent interval divides the semitone into 100 parts. just as a semitone
interval divides an octave into 12 parts.

*
 
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