Intonation, how many cents sharp/flat at 12th fret is accepatable?

[expertune]

About intonation, how many cents sharp/flat at 12th fret is accepatable?

 

I bought a good sounding Simon & Patrick guitar, but all strings at 12th fret are about 5 cents sharp even the saddle is a compensate one.

 

I might be able to correct the intonation problem a little bit by file down the nut to reduce the tension(The action is a bit high) . To me, the guy who made the guitar put the bridge at wrong location.

 

Thanks

[nip]

You might have a look if neck relief is unnecessary large. Tighten tross rod a bit, would make it go closer to good.

 

I think ear can hear 2 cent or less. And that is for a single note to a correct note kind of. But one certain intervals it's probably much more sensitive since guitar is tempered and will start sounding ugly much sooner.

 

The error in intonation will produce a slight extra error the higher you go on the neck.

 

So make a test if your neck would suffer from a small extra straightened neck. 1/4 to 1/2 turn maybe on truss rod(loosen strings a bit before tightening).

 

If neck is all straight already, next step i probably to make a new bridge saddle.

[Freeman Keller]

You mean that if you fret at 12 it is 5 cents sharp, but in tune when open? What about the 12th harmonic, is it in tune? If the open string and harmonic are correct you probably won't change anything fiddling with the nut and be careful trying to file it down any more - you'll need the correct files and if you go too far it is hard to correct. Lowering the saddle might help a little as it will lessen the amount the strings are stretched when fretted, but probably not 5 cents.

 

JT has a neat trick for checking (and correcting) compensation at the saddle

 

http://acapella.harmony-central.com/forums/showthread.php?threadid=1327298

 

And yes, it is possible that the bridge is in the wrong location - it should be twice the distance to the 12th fret plus somewhere around 1/8 inch more at the centerline. Most modern guitars are built with pretty accurate jigs so I wouldn't expect that to be an issue, however (Martin's problems were that the jigs were built wrong, as I understand the story).

 

Lastly, if you only play in the first positions you probably won't notice the intonation at all - if you play up the neck a lot it might be more bothersome.

[expertune]

Thanks guys.

 

Yes, if open string and harmonic are correct, 12th fret 5 cents sharp.

 

The reason I do not want to touch the saddle is there's undersaddle BBand pickup in it.

 

I will try to check the neck relief after work.

[Freeman Keller]

 

Originally posted by expertune Thanks guys. Yes, if open string and harmonic are correct, 12th fret 5 cents sharp. The reason I do not want to touch the saddle is there's undersaddle BBand pickup in it. I will try to check the neck relief after work.

 

 

Don't screw up the playability by screwing with something that isn't mean to affect the intonation (the TR). And if the action is too high as per your first post you may have to "touch the saddle". Could the addition of the UST be the reason the action is too high (ie. the saddle should have been lowered the thickness of the UST)

[expertune]

It's weird. I went back to the guitar store and played couple Seagull and SimonPatrick guitars, they all have the same problem. Especially on 4th D string, some guitars are over 10 cents sharp.

 

[theGOOCH]

Ok, I am mostly self taught so I am ignorant in many areas.....so exactly what is a harmonic?

 

Don't let the lameness of my question fool you. I'm not trying to troll, I'm serious.

[markwayne]

 

so exactly what is a harmonic?

 

As my 6th grade teacher was fond of saying "there are no lame questions".

 

All vibrating bodies produce a fundamental frequency as well as a series of overtones. The relative strength of these overtones are what give an instrument it unique timbre. A harmonic is what we call one of those overtones when isolated. On a guitar the easiest way to isolate an overtone is to divide the vibrating string into some multiple of its length by lightly touching the string instead of fretting the string. In this case, touching the string at the 12th fret neatly divides the string into two vibrating halves which then doubles the frequency so that instead of hearing the fundamental we hear a note exactly one octave above.

 

I also believe that the 12th fret harmonic will always be a perfect octave as that octave is such a strong overtone that getting anywhere close to center on a string will work.

 

Wayne

[Freeman Keller]

 

Originally posted by theGOOCH Ok, I am mostly self taught so I am ignorant in many areas.....so exactly what is a harmonic? Don't let the lameness of my question fool you. I'm not trying to troll, I'm serious.

 

 

Ah, good question, Grasshopper...

 

A harmonic is that wonderful ringing bell like sound that you get at certain places on the fretboard by lightly touching the string with your fingertip right over the fretwire (12th, 5th, and 7th work really well). Do not push the string to the fret. What happens is that it vibrates on both sides of your fingertip - between the finger and saddle AND between the finger and nut - and you get this chime like sound. You can do individual strings with a finger tip or all strings by barring, but make sure it is directly over the fret wire and doesn't touch it.

 

Harmonics have lots of cool uses within a song, and can be used in tuning and for checking intonation (because you have not stretched the string a harmonic at the 12th fret should be half the length of the scale and should be in tune with the open string).

 

The opening of EL&P's From the Beginning, Blind Blake's Police Dog Blues and (who did?) Sleep Walk all use harmonics, as does Neil Kwak's cover of Vincent. Try 'em, you'll dig it.

[theGOOCH]

Thanks guys. I think I get the general idea, but how could the harmonic be in tune, but the 12th fret be sharp? Maybe I don't totally understand. How could the harmonic be out of tune? It seems like it is what it is.

[Freeman Keller]

The harmonic will be in tune because it is the half or quarter point of the string, and the string is straight between the nut and saddle. The fretted note at the 12th fret will be sharp because you are stretching the string when you pull it down to the fret. So you make the distance from the fret to the saddle a little longer. Because the diameter of the string wire affects the amount of sharpness you have to make that distance different for each string, so the saddle is at an angle. Because the wire inside the third string is smaller that the 2nd (but bigger than the 1st) its compensation has to be a little different (hence the little notch in a "compensated" saddle). Technically, any saddle that is setting at an angle is in fact compensated.

 

Clear as mud?

[theGOOCH]

My head is going to "asplode":D

[bardsley]

Harmonics are present in all notes you play on the guitar. If you think of the note you pluck as the fundamental frequency (say 440hz), the harmonics are all the other frequencies created by playing that string. It's more noticeable in other instruments, but if you listen hard, you should hear a note the same as what you played, only an octave up. You might also hear a perfect 5th above that (which is why the 5th works so well to strengthen a sound, but does nothing to add to the harmony of a tune - it's already there in the harmonics of the root note). In fact, every note in our chromatic scale is there, only inaudible. But it's the presence of these frequencies that are how we hear differences in tone (also, the difference in vowels in speech is purely the sound of different harmonics sounding).

When we touch the string lightly over particular frets, we create what's called a "node", which in effect cancels out all the other harmonics (pretty much) except for the one related to where we touch the string. If it's halfway, it's an octave, but experiment with other positions, and you'll hear other notes (often faintly, but you can get them).

Now here's the tricky part.

The harmonic series (the series of notes that sound as harmonics of the original pitch) is not the way we tune our notes, because they don't mix well with other keys. The A created as a harmonic of the D string is different (slightly) from the A created as a harmonic from the G. This is because, when the modern chromatic scale was invented, it was designed so that we could change keys, and that every note was equal, hence what we call "equal temperament". This means that, although the octaves of any note are the same as their harmonic, and the fifths are pretty close too, the other notes are slightly out. The interval of a major third in equal temperament is slightly sharper than the interval of a major third found in harmonic series. The minor third is flatter. The Minor 7th is way out.

This means a few things. One is that, in general, harmonic based music (essentially western music) is suited to equal temperament. Melodic based, single key music ("eastern", Indian classical music etc) is suited to harmonic tuning, as the intervals in the harmonic series is much more "pure" and beautiful (you haven't heard a major third until you've heard it on a non-fixed pitch instrument).

It also means that it sucks to be a guitarist. Why? Because, as a stringed instrument, it's very well suited to creating harmonics, and because each string counts for several notes, the harmonic series is a sensible way of intonating it. However, we are somewhat fixed in out pitch, due to frets. It's like having equal temperament (frets) overlaid on harmonic series (strings).

Tuning, therefore, is always an issue, and it demonstrates why tuning to harmonics can be problematic (though we normally use the harmonic of the 5th, which is pretty close). An E played as a harmonic on the 7th fret of the A string shouldn't be quite the same as the octave harmonic from the 5th fret of the E string.

The harmonic you get over the 12th fret will always be in tune (unless the string's crappy) because that's the node at halfway down the string. The trouble is that it has nothing to do with the intonation, which is determined by frets (equal temperament again).

 

How was that?

[expertune]

Great article.

 

But I think at least 12th fret harmonic is useful for intonation. The harmonic you get over the 12th fret and the note you play at 12th fret should be the same, they are all one octave over the open string.

 

 

 

Originally posted by bardsley Harmonics are present in all notes you play on the guitar. If you think of the note you pluck as the fundamental frequency (say 440hz), the harmonics are all the other frequencies created by playing that string. It's more noticeable in other instruments, but if you listen hard, you should hear a note the same as what you played, only an octave up. You might also hear a perfect 5th above that (which is why the 5th works so well to strengthen a sound, but does nothing to add to the harmony of a tune - it's already there in the harmonics of the root note). In fact, every note in our chromatic scale is there, only inaudible. But it's the presence of these frequencies that are how we hear differences in tone (also, the difference in vowels in speech is purely the sound of different harmonics sounding). When we touch the string lightly over particular frets, we create what's called a "node", which in effect cancels out all the other harmonics (pretty much) except for the one related to where we touch the string. If it's halfway, it's an octave, but experiment with other positions, and you'll hear other notes (often faintly, but you can get them). Now here's the tricky part. The harmonic series (the series of notes that sound as harmonics of the original pitch) is not the way we tune our notes, because they don't mix well with other keys. The A created as a harmonic of the D string is different (slightly) from the A created as a harmonic from the G. This is because, when the modern chromatic scale was invented, it was designed so that we could change keys, and that every note was equal, hence what we call "equal temperament". This means that, although the octaves of any note are the same as their harmonic, and the fifths are pretty close too, the other notes are slightly out. The interval of a major third in equal temperament is slightly sharper than the interval of a major third found in harmonic series. The minor third is flatter. The Minor 7th is way out. This means a few things. One is that, in general, harmonic based music (essentially western music) is suited to equal temperament. Melodic based, single key music ("eastern", Indian classical music etc) is suited to harmonic tuning, as the intervals in the harmonic series is much more "pure" and beautiful (you haven't heard a major third until you've heard it on a non-fixed pitch instrument). It also means that it sucks to be a guitarist. Why? Because, as a stringed instrument, it's very well suited to creating harmonics, and because each string counts for several notes, the harmonic series is a sensible way of intonating it. However, we are somewhat fixed in out pitch, due to frets. It's like having equal temperament (frets) overlaid on harmonic series (strings). Tuning, therefore, is always an issue, and it demonstrates why tuning to harmonics can be problematic (though we normally use the harmonic of the 5th, which is pretty close). An E played as a harmonic on the 7th fret of the A string shouldn't be quite the same as the octave harmonic from the 5th fret of the E string. The harmonic you get over the 12th fret will always be in tune (unless the string's crappy) because that's the node at halfway down the string. The trouble is that it has nothing to do with the intonation, which is determined by frets (equal temperament again). How was that?

[bardsley]

Yes, that's the one note which should be exactly the same. The problem is it's never going to sound quite the same, as the fretted note has a lot of other harmonic content that the pure harmonic doesn't. That's one of the reasons why tuning can be hard: recognising what difference in tone is slight pitch variation (out of tune) and what is just upper harmonic difference.

[t60 fan]

Originally posted by theGOOCH My head is going to "asplode":D

 

I know what you mean. These guys are sharp around here, and I think they make a commission on aspirin.

[therepairgod]

adjusting the truss rod is a perfectly viable fix to intonating an acoustic. like someone said here, the string is stretched down to the fret. its the excess stretching of the string that can cause the over pitch situation. the lower the action the less the string must be pulled down to the frets, and thus the less sharp that note will be. all that being said only if there is sufficient room for improvement in action, should you approach the truss rod. the bridge secondary and the nut last. shaving the nut will in fact reduce the action and thus reduce the ammount of stretch as well.

[expertune]

Thanks guys.

 

I think I am overreacted. I went to a guitar store today, and played at least 10 guitars, price tag from $400 to $1500. They all have intonation problem, or should I say the intonation is not perfect on any of them according to my ears. My ears might be too sensitive.

 

Sigh, this is guitar, looks like I have to live with it.

[Freeman Keller]

 

Originally posted by expertune Thanks guys. I think I am overreacted. I went to a guitar store today, and played at least 10 guitars, price tag from $400 to $1500. They all have intonation problem, or should I say the intonation is not perfect on any of them according to my ears. My ears might be too sensitive. Sigh, this is guitar, looks like I have to live with it.

 

 

Retorical question - is this due to the fact that our little wooden boxes are "equal tempered" instruments

 

http://www.precisionstrobe.com/apps/pianotemp/temper.html

 

or the physics of stretched strings of different diameters

 

http://www.phys.unsw.edu.au/~jw/strings.html

 

And don't worry about your ears. When you reach my age they will fix themselves so your guitar will sound just fine. Eh?