Tenor Guitar Intonation Issues

[Bernie Daniel]

I have a question about fixing intonation problems on a pin bridge tenor guitar.

Couple of years ago I bought a relatively inexpensive Soares "baby" tenor -- a pic is attached. It is a nice little instrument with a fixed pin bridge, zero fret, and an a 20.75" scale. -- see pic

As I've grown more proficient with the tenor guitars and started playing more at other than first position I've been noticing intonation issues.

I checked today and indeed all four strings are 20 - 25 cent sharp at the 12th fret.

Since the bridge is fixed what is the usual repair for this?

The neck seems straight enough.

[Jean Fugal]

Is that thing strung up left handed? How high is the action at the 12th?

[Bernie Daniel]

Thanks Jean!

No it is strung right-handed -- CGDA.

When I flipped the image vertically I should have also flipped it horizontally -- so you are seeing a mirror image in the photo --my fault.

The action at the 12th on the C is 0.080" and on the A is 0.065"

Thoughts?

[Jean Fugal]

put a capo on 2 and check 14th. still the same?

[acousticphd]

The intonation issues I have seen on many inexpensive short-scale guitars have led me to the opinion that some of the mfrs of these guitars have flat-out miscalculated and misplaced the bridge position. Add to that, I believe the shorter string length needs more individual string compensation at the saddle (which is connected to the first problem). The capoing suggestion is a good one, but I would suspect the bridge/saddle; if that is wrong, the error should get worse the higher up the fingerboard you go.

My guess is your saddle position needs to be set farther back somehow. One solution is to widen the saddle slot and replace the adjustable saddle with a wider piece of material and add more compensation, or have a new saddle slot cut rearwards of the current adjustable saddle.

[Bernie Daniel]

Guys thanks for the suggestions. I think you are right the bridge needs to be set back. I looked closely at it and I think when I will try to turn the piece of ebony that makes up the saddle around. There are no string grooves cut anyway that would make the scale length about 0.1" longer. Be worth a try I guess.

Capoing at 2 with and fretting at 14 produce some inconsistent results:

For example with the capo on 2 the D, A & E are already 20 cents sharp! Where as the B on the A-string is only 10 cents sharp -- at 14 the lower three strings are about 25 - 30 cents sharp (i.e., a bit worse) but the A-string is dead on or at most 5 cents sharp?

[Rob Gerety]

Ugh. I hate this issue. I had a new luthier built guitar with exactly this issue. Sharp. Need to move the saddle back probably - or maybe the whole bridge. Ugh.

[allenhopkins]

Since your Soares'y has a zero fret, nothing you can do with the nut. If you crank down the action as low as possible before you get buzzing, you'll minimize string stretching when you fret it, which should reduce the 12th-fret sharping somewhat. Apparently there's an adjustable bridge which makes changing string height a bit easier.

If the strings are as sharp as 20+ cents, probably relocating the bridge saddle is the only alternative. You can try reshaping or replacing the current saddle so that the string contact is as far away from the nut as possible. If you can gain a tenth of an inch that should moderate, though not eliminate, the mis-intonation.

The other possibility is to experiment with string gauges. Possibly a heavier gauge string might have a lower stretch-to-diameter ratio and thus "sharp" less. I've never tried this, so evaluate it as "pure speculation..."

[Bernie Daniel]

allenhopkins: If the strings are as sharp as 20+ cents, probably relocating the bridge saddle is the only alternative. You can try reshaping or replacing the current saddle so that the string contact is as far away from the nut as possible. If you can gain a tenth of an inch that should moderate, though not eliminate, the mis-intonation.

Thanks for the thoughts! Actually I have been thinking there is not reason that I cannot carve an L[shaped saddle (from a piece of ebony) that extends the string contact point farther back toward the pins -- with this arrangement I might be able to gain significantly more that 0.1" scale extension.

I also thought I might contact the Soares'y (is it Mike?) to if he has seen this before on these baby tenors and if so how they dealt with it.

Other than that its a cute little axe.