Intonation help

[n7188u]

Dear Lutherie group,

I have a Behringer iaxe393 USB guitar (strat copy) that I have been working on to make a slightly better guitar (at least a good as I can). The guitarnuts QTB modification has done wonders to this thing, where at least the noise has been eliminated and sound improved.

OK, now to my question: I checked intonation, at the 12th fret, using the built in tuner in the USB guitar software. The tuner seems to work well although I don't have a professional tuner to compare against. All strings needed small adjustments except for the Low E string.

This string was quite sharpe and required moving back the the bridge saddle by a considerable amount, about a 1/8" more than the other saddles. This is so much that I had to remove the spring in the screw to accomplish this. The string is still a little sharper than perfect. I am being very careful not to apply too much pressure on the string against the fret. I am using DR tite fit 9s strings.

Is this normal? I would think that if this was a fret or bridge location problem it would show on all strings.

Chris

[sumgai]

n,

I'd suspect that the bridge is mis-located.

Do this:

1) Measure the distance from the front of the fret nut to the middle of the 12th fret, on the first string (high E).

2) Meaure the distance between the 12th fret and the bridge saddle, right at the breakover point.


They should be roughly the same. More to the point, all strings will exhibit a very small offset, the second measurement being a tiny bit longer than the first one. A standard first string will have an offset of perhaps 0.050", probably even less than that. As you move to the larger gauge strings, that offset will increase. At the 6th string, it can be as much as ¼" - don't worry, that would be normal.

The rule-of-thumb is, the 3rd and 4th string bridge saddles should be located approximately in the center of the possible travel lane. If they're so far back that the 6th string can't get to the point of correct intonation, then the bridge is too close to the neck, pure and simple.

How that is fixed is a horse of a different story.

HTH


sumgai

[ChrisK]

How that is fixed is a horse of a different story.

?A ball peen hammer and WD-40?

[ux4484]

Ah....the speed wrench method!

[UnklMickey]

I think before I did ANYTHING other than adjusting the saddle positions, I'd replace the strings.

Your low E might have a defect. How unfortunate, if you went to a bunch of trouble to compensate for a messed up string. If the problem isn't the string, you haven't wasted much money.

[sumgai]

ux,

-1 for stealing my line before I could post it! ;D

Unk's correct of course, the first step should be the easiest one. I just buttumed that Chris(3) had already changed the strings from the original equipment to something he liked and trusted to be of good quality. My mistake.


sumgai

p.s. Oh, and ChrisK, about that WD-40? That might harm the finish, so I'd recommend 3-in-1 oil, it's easier to clean up.

[n7188u]

Thanks for the replies guys,

Yes I changed the strings (twice actually, due to me doing the QTB mod) to DR tite-fit 9s.

I checked the string legths:

Low E: 25.75" overall, 12.8" 12th fret to nut, results in .075" offset; High E: 25.55" overall, 12.8" 12th fret to nut, results in -.025" offset.

I include a picture of the bridge showing what I had to do to bring it into what I think is proper intonation.

Last question, when checking intonation, do you actually fret the string in the 12th fret or do you do it by ringing (if that is the right term) the 2nd harmonic only.

Chris

BTW, in the picture it looks like the saddle screw is touching the 6th string but there is actually quite a bit of clearance.

[ChrisK]

when checking intonation, do you actually fret the string in the 12th fret or do you do it by ringing (if that is the right term) the 2nd harmonic only.

Yes, BOTH!

I check the intonation by comparing the 2nd harmonic (ringing) against the fretted note at the 12th fret. Intonation thus is.

"INTONATION (FINE TUNING)
......Check tuning. Check each string at the 12th fret, harmonic to fretted note (make sure you are depressing the string evenly to the fret, not the fingerboard). If sharp, lengthen the string by adjusting the saddle back. If flat, shorten the string by moving the saddle forward. Remember, guitars are tempered instruments! Re-tune, play and make further adjustments as needed."

www.fender.com/support/stratocaster.php


I also don't like how the other 5 string saddles are almost in a perfect horizontal row.

I assume that you detune the applicable string while moving a saddle. I also assume that you retune all strings after moving a saddle, especially if the vibrato is floating (not set against the body for detuning/pitch dropping only).

I further assume that you stretched out the (new) strings before intonation.

[n7188u]

Thanks ChrisK,

Great link. I had most of this information from bits an pieces collected in the net but this is better.

Now, I need to make sure I understand the statement "harmonic to fretted note".

As I understand it, I need to ring the 2nd harmonic (I'm doing this by picking the string while lightly brushing the tip of my finger on that string over the 12th fret to kill the fundamental frequency) and then compare it against the note created by lightly fretting the same string at the 12th fret. Is this correct?

If so, what I did before was wrong as I thought that the intonation adjustment was made by simply fretting the note at the 12th and checking and adjusting the note in the tuner to be an octave higher than the tuned open string.

I am detuning the string while moving the saddle, tuning again and yes the strings have been stretched.

One last question, when you adjust the action, do you detune before moving the saddle setscrews up of down? I think the answer should be yes as I didn't and it gouged the bridge plate were the setscrews rotated. I just never heard of the need to do it. Oh well, a cool thing about this cheap guitar is that I'm learning a bundle so that when I get my cool expensive one I will now better Although I have to admit that this guitar is sounding better and better every day with small adjustments and modifications (of the inexpensive kind).

Thanks,
Chris

[sumgai]

Chris(3),

You do indeed de-tune before adjusting anything on the bridge, as you now know. Three or four semi-tones should be plenty.

You should set the string to the correct pitch, then adjust the string height such that it doesn't rattle against any other fret as you press the string to the fretboard at each position. Once you've got your action where you want it (high/low/whatever), then you can adjust the intonation. The string height affects the intonation much more than the other way around, but there is still some interaction between the two - always re-check everything before you put your tools away.

It appears to me in your photo that the screw for the low E is much longer than the screw for the high E - they could have been reversed at the factory.

Your latest description is pretty much correct for setting the intonation. Whether you kill the fundamental and use the 1st harmonic, or you just use the open string, your tuning meter should not be able to tell the difference. Setting the string length so that the 12th fret reads exactly the same is what its all about. And keep in mind that there are players out there who advocate that you use a capo on the first fret (and depress the string at the 13th fret). Their thinking is that it removes the fret nut from the equation. Me, I'm not so sure that's necessary. Seems to me that if I'm gonna play open strings at least once in awhile, I outta consider them when I'm setting up, and tuning, my guitar, no?

BTW, I am of the very close-minded school that you don't trust your ears, no matter who says they're golden. You use a chromatic tuner capable of resolving a single centime - anything less and you're peeing up a rope. And please, don't get me started on strobo-tuners, you won't like what I've got to say about them. (Oblique reference: Cables and Con Men)

HTH


sumgai

[UnklMickey]

n7188u said:

If so, what I did before was wrong as I thought that the intonation adjustment was made by simply fretting the note at the 12th and checking and adjusting the note in the tuner to be an octave higher than the tuned open string.

Chris,

There is nothing wrong with that method. As long as you are using a tuner, it will work fine. The only reason to need to do it as ChrisK described would be if you were doing it by ear. It's easier to hear if the two notes are in tune, if they are in the same octave.

The positions on that bridge are NOT typical.
Usually the 1st string is farthest from the tail,
the 2nd a little closer,
the 3rd closer yet.
the 4th is usually about the same distance as the 2nd,
the 5th closer to the tail similar to the 3rd
the 6th is the closest to the tail.

I have NEVER seen such a big jump between the distances as your has between the 5th and 6th strings. My guess is, this set is "bottom heavy".

I'd like to know what the gauges of each the strings are. I suspect the 6th is way thicker than "normal".

cheers,
Unk

[n7188u]

Thanks again for the information.

I will be checking intonation again today. The strings I am using are DR LT-9 with the following thicknesses: 9,11,16,24,32,42.

One thing ChrisK mentioned that made me think is to stretch the string before intonation. I did stretch them but due to my lack of experience it is possible I am not stretching them enough. Also, since I'm learning and don't play hard, the strings may never get a chance to fully stretch.

One last thought is that I am using Fenders spec for action for the Strat: 5/64" 1-4 and 3/32" 5-6 at the 17th. Maybe that spec is a little conservative and it causes the intonation to be a little sharp at the 12th fret.

I'll report after giving it a try today.
Chris

[ChrisK]

I thought that the intonation adjustment was made by simply fretting the note at the 12th and checking and adjusting the note in the tuner to be an octave higher than the tuned open string

"adjusting the note in the tuner"

[n7188u]

OK ChrisK, replace "in" with "with" and I guess it will be closer to reality

BTW, I rechecked intonation by: 1- Using a different tuner, 2- Removing all saddles, cleaning and smoothing the bridge plate (remember I slightly gouged it during previous work and learning), 3.- Slightly lubricating saddles at point of contact with strings (per Fender recommendations), 4.- Readjusting action, 5.- Stretching string some more.

One thing I also did was remove the action adjustment set screws from the saddles and, using a fine abrasive rubber wheel, I deburred the bottom of the screws tips flatter and smoother. The tips where originally cup tipped and very sharp, gouging the plate very easily even when detuned.

The result is that now the intonation adjustment is more sensitive and the saddles are in a reasonable (midway in their adjustment) position in the bridge. In fact it looks very similar to the description UnklMickey provided.

I don't know what really made the difference, possibly the new tuner.

Again, thanks to the group for the opportunity to learn all this and keep my guitar in top shape.

Chris

[ChrisK]

Glad that things worked out.

[sumgai]

Chris(3),

chrisk said:

Glad that things worked out.

Or to put it in Latin, "Learnum est funem!"


sumgai