Intonation nightmare on my 'little guitar'...

[aussieadam]

Firstly-
Hello everyone!
Just discovered this forum today, and it looks great! I can see myself coming back for sure!

Secondly...

I'm having some real trouble with the intonation on a miniature (1/2 size?) 'guitar' I acquired. I realise these things are banged together in china for about 20c a pop and don't expect much from it... but it is a great size for taking traveling, and i don't have to worry if it gets knocked around a little.

The thing that's got me stumped is that when i first got it the intonation was almost perfect... it was as good as any equally tempered instrument i'd heard, (the other 5 'identical' guitars in the shop were rubbish!) but it seemed they'd gotten one right. so i handed over my $18 and went home happy. Played it quite a lot, sounded great... (well... sounded in tune, rather. ) and everyone had a lot of fun singing along to the silly guitar.

THEN... I got a dumb idea. "It's not very loud... what if i but a pick-up in it?" ..."i have a few spares, and some jacks, and pots, i could amplify it and more people can sing!"

All of which went quite well... until it was time to re-string it. Since i just bolted a standard electric guitar pick-up to the soundhole, it seemed logical that i would need to put some steel strings on it, rather then the fishing line it came with (I quite like nylon strings... but i'm pretty sure those things weren't nylon...!)

chucked the strings on plugged it in... woohoo sound!
oooh needs a tune though... woohoo sound!
ooooh... guess the strings need a bit more of a stretch... woohoo!
oooooooooh... 3 of the strings must be slipping.... woohoo?
oooooooooooooh... ?? I must be goin tone deaf?
i'll try tuning the open strings to eachother?
try tuning them all to the low E....??

eventually i tried checking the open strings with the 12th fret and the fretted note is a semi-tone higher than it should be!!

got out the tape measure...
The nut to the bridge is 825mm <--(when measured correctly it's actually 480mm)

distance between nut and 12th fret 425mm <--(really 243mm)
and 12th fret to bridge obviously 400mm (...237mm)
string clearance at 12th fret is 3.5mm

I've always used my ears for setting up the intonation on my electrics so i'm not totally sure on how to do it with a measuring tape... but the distance to the crown of the 12th fret should be half the string length...? right...?

which would mean either the string needs to get 2.5mm longer on the bridge side... or 2.5mm shorter on the nut side?

i tried using a nail as a temporary nut to find where i might need to relocate the nut to... but the 12th fret didn't sound in tune until the nut was moved about 14mm!! half-way to the first fret!

I feel i'm obviously overlooking something...? the stretch of the strings...? This was just meant to be a fun little project... it certainly doesn't need to be perfect... but now it's unplayable.

If anyone has any advice on how to get it back to playing in tune, or anyother measurements they would like me to take i'd be happy to supply them...

edit* fixed up the whole millimeter/centimeter thing... thanks jeff.

Thanks for your time guys,
-Adam

[Allen]

Welcome to the forum Adam.

First off, is this instrument built as a nylon stung one? Are you trying to change it to a steel strung one? If so, there are going to be several issues that come up, but the most serious is that a nylon strung instrument is usually built much more lightly, and the tension of steel strings are going to cause all kinds of grief.

Is the bridge compensated? Is the saddle parallel to the nut, or does is get longer on towards the low E side?

More info needed, and I'm sure that some of the brighter members here will be able to help out.

I've set up the permissions for you to upload pictures, so if you can post a picture of the instrument, it may be of help.

[sebastiaan56]

Firstly, Welcome Adam,

It may be going backwards but what happens if you turn off the amp? From the measurements you have given us I expect there would be problems. Acoustic and electrics are the same in that respect.

[aussieadam]

Wow, thanks for the quick replies guys!

Yes, is a very cheap nylon string which I have put some very light steel strings on.

I had hoped that the fact that it is basically a toy, and such a short scale, that the body would hold up ok to the steel strings.

as for the bridge being re-enforced... I haven't done anything to it?
I the soundboard does flex a little if you bend a string, pulling the others temporarily out of tune, like a very primitive vibrato set-up.

Is the saddle parallel to the nut, or does is get longer on towards the low E side?

The saddle is very slightly angled to be longer at the low E... but only by about 2mm?

But the problem isn't that it won't stay in tune... whatever i tune each string to it will stay at fairly consistantly, it's just that there is no way to tune it so that the guitar sounds "in-tune".

what happens if you turn off the amp?

Haven't got to plug it in yet... installed the pick-up without a hitch, and waiting to borrow a soldering iron to attach a jack. But i'll need to get the tuning sorted out first...

I've attached a picture of the bridge, and of where abouts my nail has to be to get the 12th fret playing an octave on the low E string.



[/quote]

[jeffhigh]

Ditch the pickup, ditch the steel strings, go back to nylon.
With the steels you are likely to pull the bridge right off and innotation will never be right unless you move the bridge back

I think you are getting your cm and mm confused with your scale length measurements, but if it is really shorter from nut to 12th than 12th to saddle, it is never going to play in tune (and adjusting the nut will not fix it)

[aussieadam]

Jeff,

Yes, that is most likely what i'll end up doing... but i'm still curious as to why the intonation has shifted SO FAR by changing the type of string?

are there different formulas for nylon and steel string scale lengths/ bridge positions?

Why did my tests suggest i need to shorten the string length by almost 14mm rather than 2.5mm?

Are there other factors then just overall string length to take into account?

How would I calculate where to shift the bridge too?

[kiwigeo]

Jeff,

Yes, that is most likely what i'll end up doing... but i'm still curious as to why the intonation has shifted SO FAR by changing the type of string?

Nylon.....steel. Very different materials.....they stretch differently for a start.

I recently eyeballed an old Ibanez classical that had been re-string with steel strings. The top looked like the surf break at the Banzai Pipeline in Hawaii, the top braces were protruding through the sides and the neck looked like Robin Hood's Bow.

[hilo_kawika]

Hi Jeff,

This jig might be useful for you to get a better handle on steel string vs. nylon string compensation values...:

http://www.ukuleles.com/Technology/compensate.html

aloha,

Dave Hurd
http://www.ukuleles.com

[jeffhigh]

I've got a pretty good grasp of innotation David,LOL
I would consider using your jug if I were doing an unusual instrument in terns of scale lenght, tuning etc.
The op is having some trouble with his measurements though
He originally posted nut to bridge at (from memory) 82.5mm
and has now ammended that to 825mm---on a small instrument
Obviously neither makes sense.

[Localele]

The nut to the bridge is 825mm
distance between nut and 12th fret 425mm
and 12th fret to bridge obviously 400mm

i tried using a nail as a temporary nut to find where i might need to relocate the nut to... but the 12th fret didn't sound in tune until the nut was moved about 14mm!! half-way to the first fret!

Hello Adam, With those measurements it wouldn't have had correct intonation to start with.The 12th fret should be at 412.5mm which looks about right with your nail test.Cheers.

[jeffhigh]

Maybe the factory had an off day and put a bass neck on it.
825mm scale length? Needs some lessons in using a measuring tape.

[DarwinStrings]

G'day Adam, My guess is it should be more like about 525mm for a 'half' scale and even though your measurements seem totally wrong it might be worth re-counting your frets carefully as you maybe getting to the 13th fret with your measurements rather than the 12th.

Jim

[Nick]

G'Day Adam and welcome to the forum. As pretty much has been said already the twelve fret should be exactly at the half way point between the nut and saddle, I've looked at your picture and that makes the twelth fret the one where the neck meets the body.
It has a classical bridge and came with nylon type strings I would put it back to nylon as being an $18 chinese quality guitar, steel strings will tear either the selotape holding the bridge down or rip the top layer of ply off the soundboard
BTW 825mm between nut and saddle is one hellava scale length there my friend, puts it in the same league as a bass guitar, might want to just check the divisions on your rule/tape measure.

[aussieadam]

Thanks for the replies guys!

825mm scale length? Needs some lessons in using a measuring tape

It would seem that I do! or at least some lessons in converting Inches to Millimeters!

Does 480mm scale length sound more likely?
and 243mm from nut to 12th fret.

Could be why I failed woodwork... twice.

I also managed to find some of the answers I was looking for about string stretching and whatnot...
has got me curious about the processes involved with saddle/nut compensations... I'm out to the shed now to do some tinkering!

[Nick]

Yep, 480 would sound about right for a small scale (about 19 inches in real money) but that 12th fret measurement still aint right, it should be half of the 480 which = 240mm

A way you can check the fret placement (which sounds as though it's been off from the time it left the factory to me,if your measuring is right now)
Is go to here and follow the instructions and it will calculate where the frets should be, then check those measurements against your fine piece of chinese craftsmanship.

[jeffhigh]

Don't go messing with your nut now, adjustments need to be made at the saddle. Forget nut compensation, that is an advanced technique for fine tuning.
If your nut to 1th fret is exactly 243 (from nut face to cetre of 12th fret)
then your theoretical scale length is 243X2= 486.
The saddle position is therefore 486 + compensation which for a nylon string instrument of this size would be about 1.5mm
So from nut to saddle break point would be 487.5 so you are about 7.5mm too close on the bridge.
With steel strings you would need more compensation.

[Lillian]

Helps if I look at the pictures first. Never mind.

[aussieadam]

check the fret spacing... it was pretty much spot on, except for distance from the nut to the first fret was 2.5mm further than the fret calculator said it should be. but 1st to 2nd, 2nd to 3rd, etc were all spot on.

I shifted the bridge back about 9mm which almost fixed the issue of the 12th fret sounding sharp.

but the open position still sounds way out of whack... Ah well, it was worth a shot. Certainly learned a few new things anyway!
it'll be going back to nylons.

thanks for the help guys.

[Localele]

Nothing wrong with slipping the nylons on occasionally, Adam . Plenty of the guys here have tried it and don't mind a bit.

[sebastiaan56]

Nothing wrong with slipping the nylons on occasionally, Adam . Plenty of the guys here have tried it and don't mind a bit.

might even get you banned.....

[kiwigeo]

Nothing wrong with slipping the nylons on occasionally, Adam . Plenty of the guys here have tried it and don't mind a bit.

ANZLF's first outting????

[Lillian]

Nothing wrong with slipping the nylons on occasionally, Adam . Plenty of the guys here have tried it and don't mind a bit.

ANZLF's first outting????

Sorry Martin, that would be me last year.

Localele, if you like them more power to you. I find they itch and are cold when you want to be warm and hot when you want to be cool. But hey, whatever floats your boat. But I have to ask, do you get comments about your shaved legs? Do you tell people you are a cyclist?

[John Steele]

A young man recently brought me a guitar to look at. It was a classical style guitar that had been strung with steel strings. It too, was " a bear to tune" Looking at it from the side I noticed the top had collapsed in front of the bridge and there was a HUGE bow behind the bridge. This bow tilted the bridge & saddle forward, shortening the string length over an 1/8" Hence, the tuning issues. The guitar was not worth repairing.

[aussieadam]

Wow, yeah it had never occured to me (prior to this little experiment) that the extra tension could might distort the soundboard... at least not to the point that it would make tuning impossible!

Guess that's what happens when you get so used to playing solidbodies!

...I just took one look at the neck and said "Yeah, it'll take the extra couple of pounds!"

I've alway advised people against switching the string types (from nylon to steel) but tuning was never one of the reasons I'd give... It will be now!
In fact it could very well be the only reason! ( Aside from being unable to make music with it, what other reason do you need...??)

and yes... mine certainly falls into the "not worth repairing" category.
Has been a good learning experience though... and just makes me respect the art of guitar building even more!

-Adam

[Allen]

OK Adam. now to really screw with you. How about trying to build an acoustic that meets the requirements that you were trying to get this cheap Chinese beater to do.

There will be heaps of help from the members along the way, and hey, you just might like it. By the way, it's more addictive than beer and fishing