Intonation, truss rod and action.

[TimR]

Put new strings on my bass and noticed that around the 5th-8th fret the intonation was sharp.

 

The action at the 12th fret and intonation were spot on and the saddles as low as they'll go.

 

So I've given the truss rod a quarter turn and that's bought everything back into tune. Great. 

 

I'm wondering though if having the saddles as low as they'll go indicates the neck could do with some shims. 

 

Ibanez SR400.

[Waddo Soqable]

8 minutes ago, TimR said:

Put new strings on my bass and noticed that around the 5th-8th fret the intonation was sharp.

 

The action at the 12th fret and intonation were spot on and the saddles as low as they'll go.

 

So I've given the truss rod a quarter turn and that's bought everything back into tune. Great. 

 

I'm wondering though if having the saddles as low as they'll go indicates the neck could do with some shims. 

 

Ibanez SR400.

Well it can't hurt to shim the neck, seeing as you can.. If the saddles are right on the floor as it stands you've no future wiggle room to lower them obviously. 

[snorkie635]

53 minutes ago, Waddo Soqable said:

Well it can't hurt to shim the neck, seeing as you can.. If the saddles are right on the floor as it stands you've no future wiggle room to lower them obviously. 

If it works now, I'd leave it. You might never have to lower them further. 

[warwickhunt]

I've never encountered intonation issues on a neck that actually go away as you go up the neck.  If it was out at the 5-8th I'd expected it to get progressively worse as you went further up the neck! 

 

[TimR]

14 minutes ago, warwickhunt said:

I've never encountered intonation issues on a neck that actually go away as you go up the neck.  If it was out at the 5-8th I'd expected it to get progressively worse as you went further up the neck! 

 

 

Yes. It threw me for a bit. But if you think about it, I put a rule on the frets and there was a slight bow, so was bending the string slightly more. It was only a couple of cents but noticeable. 

[TimR]

38 minutes ago, snorkie635 said:

If it works now, I'd leave it. You might never have to lower them further. 

 

Yes. They're ok where they are. Guess I can shim it in the future if I feel I ever need to. 

[Waddo Soqable]

Certainly easy enough to shim it whenever or if ever it becomes an issue. 

Are you "squeezing" the out of tune notes out of tune ?. I've had this on a guitar with extra skinny strings.. 

[TimR]

No. I did think so initailly, but just resting my finger and pulling it to the fret was doing it. There was visible relief on the neck when I put a straight edge on it which has eased right off. 

 

I had an old 80s Japanese bass that was like a boomerang and I had to straighten that every time I got it out of the case. 

 

I shimmed that but it was never right. 

[warwickhunt]

1 hour ago, TimR said:

 

Yes. It threw me for a bit. But if you think about it, I put a rule on the frets and there was a slight bow, so was bending the string slightly more. It was only a couple of cents but noticeable. 

 

Most basses/bassists need a degree of relief (bow) in the neck to allow the string to vibrate without buzzing, playing with a light touch you can get away with less relief.  Fretting the bass around the 5-8th fret if you have too much relief shouldn't put it out of tune any more than fretting from 8-12.  If you've got it working now that's the main thing.

[BigRedX]

The tuning of the harmonics at any position other than the 12th fret will always be slightly "out" as the fret positions are compromises to allow fretted instruments to be tolerably in tune in all keys, and are only as accurate as the fret slot cutting and fret dressing allow, while the harmonics the mathematically correct pitches arrived from the pitch of the unfitted string.

 

So using the 5th and 7th fret harmonics are fine for getting the strings in relative tune with each other, but don't ever expect the 7th fret harmonic to be in tune with the fretted note.

[TimR]

47 minutes ago, BigRedX said:

The tuning of the harmonics at any position other than the 12th fret will always be slightly "out" as the fret positions are compromises to allow fretted instruments to be tolerably in tune in all keys, and are only as accurate as the fret slot cutting and fret dressing allow, while the harmonics the mathematically correct pitches arrived from the pitch of the unfitted string.

 

So using the 5th and 7th fret harmonics are fine for getting the strings in relative tune with each other, but don't ever expect the 7th fret harmonic to be in tune with the fretted note.

 

I'm fairly sure Bass guitar frets are equal temperament. I'd expect the note fretted at the 5th fret to be exactly the same as the next string open note. 

 

Harmonics are a different matter. I wouldn't tune using harmonics. I know people do, but I don't understand why. 

[Andyjr1515]

I'm actually broadly with @BigRedX on this.  The fretting on a guitar and bass are both approximations.  Folks have tried to compensate with compensating nuts and z shaped frets but, most of the time it is close enough to all but the most discerning ear

 

On your original subject, that makes sense:

-  The intonation adjustment is because the string is actually bending, albeit vertically, when you press it down to the fret. 

- And the higher the action, the more it is bending and the sharper it sounds when you fret it

- And a loose truss rod will bow most in the middle.

- So a loose truss rod will lead the strings to sharpen more for the middle frets and less at the 12th...which is exactly what you found

- And straightening the neck with the truss rod reduces that bow which lowers the action most for the middle frets, but not a lot at the 12th.  And so the excessive sharpening of the middle-fretted strings will reduce and at the 12th will remain largely unaffected...which is also exactly what you found 

Edited June 3, 2023 by Andyjr1515

[Downunderwonder]

So you changed string gauges to get all this extra tension?

 

Why tune using the harmonics?

 

Because you can.

Because it's relatively quiet.

Because the high pitches are easy to make out.

But mostly because you forgot your tuner so you snag the guitarist's G and carry on.

[TimR]

8 hours ago, Downunderwonder said:

So you changed string gauges to get all this extra tension?

 

No standard gauge strings and same make as I always use. I don't think the intonation has been right for a while. 

[Waddo Soqable]

Oh well, shove a bit of chorus and a wee bit of delay on it, no one will notice.. 😁

[tauzero]

Tuning using harmonics is actually very slightly inaccurate, as the equal temperament fifth isn't 1.5 times the frequency of the fundamental (it's 1.49831 times). It's only a slight inaccuracy but carried across all five strings then it builds up. If you only play a 4-string then it doesn't matter, of course.