Intonation issue...

[3think]

Hi all,
Nice to meet you. I am an happy owner of a 4 string Rogue. The neck and fretboard look perfect, it has just been set up. However, I have this issue.
The intonation on the G and E strings is perfect, up to the 24th fret. This is great.
However, the intonation on the D and A strings is perfect up to the 17th fret; then it starts to raise, and at the 24th fret is even 20 cents crescent, which I feel to be too much. I can't explain myself how this can be... Do you have any idea?
Thanks anyone who might spend his/her time answering this.

[edwardofhuncote]

Congratulations on your new bass and Welcome to the Alembic Club!

Forgive me if I haven't quite understood, but is there no room to adjust the intonation of the D and A strings? The bridge saddles are designed to be set independently of each other, so it sounds like you just need some setup there. There are a few posts in the FAQ section here to get you started. Here's one: http://club.alembic.com/index.php?topic=3160

Again, Welcome. 

[3think]

Hi edwardofhuncote,
Thnaks for your kind reply. I know how to adjust the intonation, and the intonation is correct on the 12th fret and above; it just starts to get messed up as you go up on the neck. If I play the harmonic on the 12th fret and the note on the same fret, they have the same pitch. If I play a note on the 17th fret, the pitch is correct. But if I play a note in the 24th fret, the pitch is crescent. And this happen only on the A and D strings. Hope this is more clear now.

[edwardofhuncote]

It is more clear, thank you, and I have learned something! The term "crescent" was a little bit confusing... I think this must mean the fretted note is sharp. I may have that backwards, and it means that the fretted note is flat. The only references I could find were to tuning horns. (about which I know nothing) Regardless of which, I get that it means the fretted notes are not true.

I'm going to guess yours is a case of splitting the difference between accuracy at points most used. Using a good strobe tuner, I would set the intonation at the 12th, then the 24th fret, then check at the 19th fret harmonic. Make sure when you do this, to dampen the other strings with something, as Alembics tend to be extremely resonant, and sympathetic resonance could be interfering with the string you're trying to intonate. Also, particularly if these are new strings, press them firmly in front of and behind the saddles to create a solid 'witness point'. It's also a good idea to do a setup with new strings. (you may have done this)

Let us know how it goes. 

[mario_farufyno]

To be honest, seems that intonation isn't correct, someone missed something while setting or decided it was enough to intonate just below the 17th fret... If there is enough clearance to move saddles you should try set intonation again.

[gtrguy]

Sometimes if the action on a string is high (at either end of the fretboard), you can throw the intonation off, because you have to bend it some to push it down to hit the fret. A neck bow could also do this.
Sometimes the string itself can be made wrong.

However, it sounds like you are knowledgeable about the bass, which would mean you probably have thought of this already.

[JimmyJ]

I agree with what everybody has said here.  The bridge saddle position becomes more critical the higher you move up the neck.  So the 12th fret may seem ok but 17th may start to show the inaccuracy.  And when you get up that high we're sometimes talking about a 1/4 turn of the saddle adjustment screw, or even pulling on the string to be sure it's not stuck on the pivot point.  It's not an issue with the construction of the fretboard, but as mentioned if you have a high action that does come into play.  AND - although rare, sometimes you can have a false string which just won't intonate correctly.  Strings can also get wonky with age.

If you really get into this with a strobe tuner, you will find that sliding up or down into a note, or how the bass is hanging from your strap will effect the pitch.  (Let's not go CRAZY here!)

Personally, I hardly ever play a sustained note on my low-b or e-string up above the 12th fret and expect it to be a solid reliable pitch.  I'll use that area of the fingerboard in passing but in most cases there is a better location worth reaching for to get that note.   

Jimmy J

[3think]

I would set the intonation at the 12th, then the 24th fret, then check at the 19th fret harmonic.

Thank you so much. Do you mean to set the intonation at 12th and 24th fret played, not harmonics? The point is that at 12th is perfect with the harmonic, at 24th is 20 cents sharp... I guess I have to mediate between the two, having the intonation a bit flat on the 12th and a bit sharp on the 24th.
I'll try other strings too.

[edwardofhuncote]

Yes, set the intonation from a fretted note. But make absolutely certain that the string you are setting intonation for is in tune, open first.The 19th or 24th frets will give you a higher degree of accuracy than the 12th. The 12th will get you close... think of it as a coarse adjustment, then dial-in your fine adjustment from the extreme interval. 

*I like to 'spot check' around the neck for accuracy too.

Remember too, we're really pushing the physical limits up there... even squeezing a string too hard will give you a couple cents sharp on a good tuner. Be patient, and there is no better than an Alembic for these tiny adjustments.

[lbpesq]

Also, intonation should be set with the instrument positioned as if it were hanging from the strap as you play, not laying on its back. 

Bill, tgo

[edwin]

Also, make sure your strings are new and in good shape. Strings can get wonky intonation over time and a bad string direct from the factory can be an issue, too.

Also, make sure your pickups aren't so close to the strings that the magnets start to pull on them when you are fretting the higher notes.

[dfung60]

The intonation adjustment is compensating for the stiffness of the string.  In an ideal world, the string vibrates purely and perfectly, but real strings aren't like that at all.  The E string is fatter and stiffer than the G string, so the bridge adjustment will be set to compensate for that stiffness by making the string longer.

When you are hitting harmonics or fretted notes at the high extremes of the neck, the string stiffness is conspiring to throw off the tuning.  The intonation check that you did at the 12th fret is an approximation for all the different lengths of notes on that string and the approximation isn't good anymore for that string in the high ranges. 

One way to test this is to try a different set of strings - something radically different (gauge, material, or manufacturer) will probably exhibit different intonation behavior, and you may luck into to finding something that works  better (of course, the E and A may NOT work as well).  Different brands may have the same final gauge, but have a different mix of the size of core and wrap wires which will affect the stiffness a lot, as you've noticed when resetting your intonation when you try out a new set of strings.  This isn't a matter of string wear or "badness", it's just the characteristic of how that particular string was made.

The intonation adjustment is an approximation across the entire neck.  If you play really high, you can set the intonation at a higher position on the neck to make the high notes line up better.  And you don't have to have a dead on match either - if you set your intonation at the 12th fret either +/- 10 cents (I'm not sure which way is "crescent", either) and the intonation is better by 10 cents at the 24th fret this may be a good compromise.  When you see alternate intonation setups like Buzz Feiten, they are intentionally setting a different relation between fretted note and harmonic to try to correct the approximation for the real chords that people play.

With regard to whether there's a neck issue - if the fretted notes are in tune, then the frets are in the right place and there's not an issue.  The height of your action will definitely affect the fretted note tuning, so you may want to reduce relief if that's still playable for you and you really hear the tuning issues.