Intonation problem?

[1976fenderhead]

My band is now playing tuned half-step down so I fitted new heavier strings and so all this required a new setup.

After I intonated the bass so that harmonic and fretted note are in tune on the 12th fret, I noticed that as I go up, from the 16th fret to the 22nd (last) pitch gets progressively sharper until it's roughly 7 cents above pitch. It's noticeable and I can hear that it's not right when I play some open strings along with those high notes (which is why I checked tuning on those frets).

It just is the case that now I play a lot on those very high frets on some songs so that is a problem. How can I solve this? Is this something that has a solution at all or just inherent to any bass?

I remember when I had a bass with 24 frets that I could never match the pitch on the 12th with the 24th, but I don't think it was such a big difference...?

[josh3184]

thats quite odd, if its intonated on the 12th fret then I'd have thought it would be fine up to the 24th unless there are some fret placement issues. Perhaps a bend in the neck due to the new string tension?


I have no idea btw, but those are my thought

[octavedoctor]

[quote name='josh3184' post='428267' date='Mar 7 2009, 10:06 PM']thats quite odd, if its intonated on the 12th fret then I'd have thought it would be fine up to the 24th unless there are some fret placement issues. Perhaps a bend in the neck due to the new string tension?


I have no idea btw, but those are my thought [/quote]

You shouldn't intonate using the 12th fret, or using a meter. The reason for not using a meter is explained here [url="http://www.edgeguitarservices.co.uk/int/index.htm"]why you shouldn't use a digital tuner to set intonation[/url]

Arc relief causes quite a few problems for intonation. If you start with a straight neck, you have to set the action quite high or the curvature of the string's arc would cause it to crash the frets in the first quarter of the fingerboard.

The displacement of the saddle introduced to compensate for the stretch induced in the string when it is fretted represents a percentage lengthening of the string, and it's this lengthening of the string's sounding length that offsets the pitch increase which is approximately proportional to the string's stretch. This percentage is not constant however, as the displacement is a fixed value for each string; as the string gets shorter the displacement represents an increasing percentage lengthening of the string. If the neck is straight then the increasing gap between the string and the fret and the increasing percentage lengthening of the string created by the saddle displacement are approximately equivalent.

The moment arc relief is introduced however, the picture changes. Arc relief allows the string to sit closer to the fretboard in the higher register. What this means in practice is that the aspect angle presented to the fingerboard levels out as you proceed up the fingerboard, being at its steepest at the first fret and shallowest above the 12th. In most well set up instruments the string is virtually parallel to the fingerboard above the 12th fret so from the 12th fret on there is very little difference in the amount of stretch, but the string is still receiving an increasing percentage lengthening leading to the inevitable conclusion that it is being overcompensated.

The problem you are experiencing however is that the strings are sounding sharp; this suggests to me that perhaps you are using a meter which can't take account of the presence of inharmonicity.

The trick to compensate for this is to temper the intonation by ear and use harmonic comparison between the higher harmonics and the higher frets. Tune the strings in pairs first by comparing the harmonic at the fifth fret with the harmonic at the seventh on the next string up. Then compare the harmonic at the fifth fret with the fretted note at the nineteenth fret on the next string up. They should sound the same. If the fretted note is sharp, draw the saddle back and repeat the process. When the two are the same retune the string pair by using the harmonic at the 12th as a reference tone for the fretted note at the 7th fret on the next string up. This is a more accurate method of tuning to equal temperament but in the initial stages when the accuracy of fretted notes can't be relied upon harmonic comparison is more useful. Continue the process until you are satisfied with the intonation. As a final check, check the harmonic at the 12th fret against the fretted note at the 17th fret on the next string down. They should be approximately the same. You can continue to refine it by comparing fretted notes on neighbouring strings, e.g the sixteenth on the A string against the 21st on the E.


It's actually a lot easier to do than to explain...

[Low Down Dave]

If everything intonates OK up to the 12th fret, then starts to go wrong chances are as josh3184 said it could be a fret placement issue, in which case there is little you can do… I have come across this on a few basses including a Warwick Rockbass which I was quite surprised about due to the way they are made (fretted), and the quality otherwise was very good.

But trust you ears rather than a digital tuner as they are not that accurate for intonation.

David

[1976fenderhead]

Thanks for the input, especially octavedoctor for the thorough explanation. I don't know if I trust my ears that much to do what you suggest though My feeling is that even if I achieved something that would be better than what I have now, that would be because the fretted 12th would be slightly flat, the fretted 22nd would be slightly sharp but none of them would be 100% in tune (which I'm guessing is probably impossible). It would sound better because none of them would be as far as 7 cents, but I would have lengthened the scale so that those 7 cents would be distributed more equally (3% flat on the 12th and 4% sharp on the 22nd, for example). Does this make sense?

I don't think it's a fret placement issue because the harmonics are 100% in tune on the 5th, 7th, 12th and 19th frets. It's only when I press the string down ("stretching" it down to touch the fingerboard) that it gets sharp, and it gets more pronounced from the 16th or 17th fret which is where the neck is bolted to the body. So I'm guessing the neck curvature and the action are all factors here. By the way, I have adjusted the trussrod to Fender's specs (0.3mm distance between 7th fret and strings when depressed on 1st and last fret) and action is slightly higher than recommended.

Further to this, even with the 12th fret in tune, if I press the strings in lower frets, I get random variations (like 9th will be fine, 10th will be sharp, 11th will be less sharp, but 10th on another string will have some different variation and so on).

What do you guys make of all this?

Bass is a US Fender Jazz Deluxe btw, with new DR Lo-Rider strings...

[mrcrow]

if you fitted new strings did you set a witness point on the bridge
ie...bend down on the strings near the saddles to 'settle' them and form a discrete point where they will vibrate from....dont press too hard
i have had a set of elixirs which didnt intonate well...they replaced them and all was ok

in theory any pitch which the string is set at should intonate for the octave fretted to the harmonic on the open string....that is what intonation is all about..just moving the saddle to compensate for a thick bend in the strings not giving a dead node directly on the saddle...usually slightly forward of the saddle...on normal gauges
going up a gauge should intonate...the string doesnt know whether the tuning is dropped

that doesnt solve anything though does it....

i use an electronic tuner with no problems..on my 5 with normal tunings
i check the cross string intonations on 5 and 7th positions
and finally intonation on the C on the G string to the fretted G on the D string fret 17 and so on
all sound well tempered and although not measured with a meter are pleasant and tuneful
as for 24th fretting...i never found that fret to be too accurate
if you are a player in the lower octave of the neck
all should be well with setting intonation with a tuner....i hope!!

i would say trying another set of strings could be the answer...

Edited March 9, 2009 by mrcrow

[Low Down Dave]

It is possible to get a string with a fractured core they sound fine but will not intonate, although it’s usually only the odd one in pack that is affected. And you can cause a similar problem by yanking on the strings rather than gently pulling to stretch them.

With regard digital tuners generally they do a good enough job, but if you intonate with a digital tuner then check it with a Peterson or other good strobe tuner you will see the intonation is not as accurate as you might have thought, and 5 cents either way in not uncommon.

But no matter how accurately the intonation if you use any more pressure than it takes to maintain contact between the string and the fret you will be sharp, this is why it is best to trust you ears, if you sound in tune you probably are.

[Count Bassy]

Not a lot of help in this case, but I had this problem on a bass and ended up fitting a compensated nut which solved the problem (actually what I ended up doing was fitting a zero fret directly in front of the nut, touching the nut at the G string, but a good 4mm clear at the E string - but the same affect).

I'm guessing that this worked because when ever you fret a string, even at the first fret, you're increasing the tension, and thus it will be sharp, realtive to the open string. The compensated nut means that this base level of increase is taken out by the nut, leaving the bridge end to adjust for the difference in the change as you go up the neck.

What you're effectively doing is accepting that all fretted notes will be sharp, and use the compensated nut to make the open string sharp by the same amount, then tune the open string down to the right note again.

Not at all sure on the theory, but it certainly worked for me.

[1976fenderhead]

It seems it has something to do with the new setup needing to settle. I left the bass alone for over a day and now picked it up... The G string needed the saddle adjusted again (checking the 12th fret only) as it was sharp. Did it and checked all strings: maximum 'sharpness' is now around 3 or 4 cents on the 22nd fret. Tuning also seems to be much more consistent and stable across strings... So hopefully it should settle at some point and anyway, a 1 to 4 cent error on the upper 5 frets is something I can live with!

[mrcrow]

did you set those witness points on the saddles...this action you are experiencing could be the results of the bending stress over the saddles slowly settling down
easier to do right a way and not too much pressure.
glad its improving