#1
So, I was thinking...

As most of us know, with proper intonation the twelfth fret makes a sound one octave higher than the open string. As far as I understand, this is the same effect you get for halving the length of the string at the same tension. Of course, intonation is also set up to take into account the fact that you increase tension on a string as you fret it.

So, what I am getting at is that I noticed guitars are not adjusted to have all the strings precisely the same length.

Scientifically, how does string tension and thickness make a difference for intonation? I know it does, but how? Why is my intonation good even though the strings are at different lengths?

*EDIT* This probably should be in the Electric Guitar forum... hope that isn't too big of a deal!
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Last edited by JimDawson at Nov 23, 2011,
#2
Scientifically, because they are different pitches (tension).

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#3
Quote by jthm_guitarist
Scientifically, because they are different pitches (tension).


Wow, what a GREAT answer. Totally answers all my questions.

That was sarcasm.
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#5
What!? Seriously, I could give a better answer than he did and I'm the one asking the question! For that matter, his answer doesn't even make sense/requires more information.

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#6
well your question is written very poorly..
do you want to know how distinct guitars with different distances between the bridge saddles and nut can each have correct intonation with the same gauge strings even though the strings are of different length?
#7
An E does not have the same frequency as a D or a G note. Therefore, the first answer was correct: strings are located at different locations on your bridge because of different sting tensions (Generally the highest tensions in E std tuning are your A and D strings, lowest is your B string), pitches and sizes. A thicker, higher tension string will have to be placed at a different position than a thin, low tension string in order to achieve good intonation.

Also, I usually measure intonation at the 24th fret if you have one; it's more sensitive to minor adjustments but your intonation is spot on if you manage to pull it of.
#8
#7 got it, thanks guys!

I get that, but would you care to explain with math how the intonation on a given string would change according to it's thickness, pitch and tension? It just puzzles me how my intonation isn't supposed to be adjusted in a straight line like all the frets are.

Does the extra tension it takes to fret a string make all that difference?
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#9
Quote by jthm_guitarist
Scientifically, because they are different pitches (tension).

That doesn't really address the opening post.


The frequency of your strings does not depend on the length of string between the bridge and nut, but on the length of string that actually vibrates. The strings are rather rigid on both ends, so the two lengths are not the same. With intonation-adjustments, we compensate for the short stiff parts on the ends by adding a little bit of length.
How much tension is added by fretting, and how significant it is, I don't know, though I'd suspect it is important as well.


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#10
^ @ #9 That makes perfect sense. Thanks!
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#11
It also has to do with how uniform the density is along the length of the string. That's why intonation goes out as your strings wear out. You get little dents on the strings and it affects how uniform it is. Watching your intonation is a good way to know how worn your strings are becoming.
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#12
Quote by JimDawson
It just puzzles me how my intonation isn't supposed to be adjusted in a straight line like all the frets are.

well you see, the frets are all in straight lines and you move the saddles to adjust the string relative to those frets, which makes sense if you think of the fret position as being totally immutable (not really true but i suppose that would be the ideal scenario working with an adjustable bridge saddle)

to put it very basically moving the bridge saddles is the alternative to adjustable frets for getting the pitches correct/closer as you progress up the neck

i know this is a horrible answer if you wanted an equation but basically the saddles end up not being in a straight line because each string is different, i haven't studied any of the physics behind intonation so i can't give you figures sorry
#13
Well, I think TheQuailman explained it in a way that makes me asking for a mathematical explanation rather pointless anyway.

I don't consider myself a newb to this stuff, I just didn't anticipate that the rigidity of the strings would effect the intonation the way TheQuailman described it. That's why this didn't make sense to me.

Long story short, I was expecting a completely different kind of answer to explain this; I misunderstood the reason why thicker strings generally have the saddle adjusted further back than thinner ones. Really, it's hard to put what I was thinking into words and it's rather irrelevant now anyway.

Thanks for the input!
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#14
the truth TS, is that it is kinda complicated.

this gets into how harmonics are derived from... uh... things

http://www.physicsclassroom.com/class/sound/u11l5b.cfm

and this just gets into the physics of scale length.

http://en.wikipedia.org/wiki/Scale_%28string_instruments%29

Quote by wikipedia
In stringed instruments, the scale length (often simply called the "scale") is the maximum vibrating length of the strings to produce sound. In the classical community, it may be called simply "string length" or less often "mensure." On instruments in which strings are not "stopped" or divided in length (typically by frets, the player's fingers, or other mechanism) like for example the piano, it is the actual length of string between the nut and the bridge.

In many but not all instruments, the strings are at least roughly the same length, so the instrument's scale can be expressed as a single length measurement, as for example in the case of the violin or guitar. In other instruments, the strings are of different lengths according to their pitch, as for example in the case of the harp or piano.

On most modern fretted instruments, the actual string length is a bit longer than the scale length, to provide some compensation for the "sharp" effect caused by the string being slightly stretched, when it is pressed against the fingerboard. This causes the pitch of the note to go slightly "sharp" (higher in pitch). Another factor in modern instrument design, is that at the same tension, thicker strings are more sensitive to this effect, which is why saddles on acoustic (and often electric) guitars are set in a slight diagonal. This gives the thicker strings slightly more length.

All other things being equal, increasing the scale length of an instrument requires an increase in string tension for a given pitch.


and is that G G Allen as your avatar pic? if so, KICK ASS!
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Last edited by gumbilicious at Nov 23, 2011,
#15
^ I already know about the physics behind harmonics and different scale lengths, but thanks anyway! For all applied purposes I already knew what I really need to know about intonation before I started this topic; I was just curious about a little detail.

And yes, my avatar pic is GG Allin. You're actually the first person to point that out to me since his face became my avatar! Considering what the man did, I'm surprised that so few have ever heard of him.

I don't mean to seem ungrateful- I am grateful for the advice- but all this extra information really is unnecessary. I already got what i started this topic for...
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#16
Quote by Cathbard
It also has to do with how uniform the density is along the length of the string. That's why intonation goes out as your strings wear out. You get little dents on the strings and it affects how uniform it is. Watching your intonation is a good way to know how worn your strings are becoming.


This +1.

On a microscopic level, the entire length of any string is not uniform across its diameter even when new. All the thousands of little imperfections along its length determine the final tension to intonate. You can switch a string like for like and the intonation will be slightly off, even though you set the intonation with the first string to be spot on with the exact same action height and relief settings.

As the string ages, you introduce more imperfections and parts of the string begin to 'neck' as it is beginning to fail. Eventually you won't be able to intonate at all over time because its stretches out of range
#17
...I know...

Someone should really close this topic!

Honestly, I've never been helped more aggressively in my entire life than on this forum!
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Last edited by JimDawson at Nov 23, 2011,
#19
Quote by JimDawson
And yes, my avatar pic is GG Allin. You're actually the first person to point that out to me since his face became my avatar! Considering what the man did, I'm surprised that so few have ever heard of him.


GG really gets no consideration, even among contemporary punk enthusiasts. in his time, he was iconoclastic. mainstream punk seems to be neglecting it's roots, it's good to see someone trying to keep it alive.
punk isn't dead, it's always smelled that way.

"A perfection of means, and confusion of aims, seems to be our main problem."
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#20
^ @ #18

And yet, I didn't "attack" anyone who actually helped me. I really didn't mean for that to come off as rude as it may have been, but it can be hard to come off as lighthearted on the internet; sometimes you can't really perceive the mood of a poster.

Just like gumbilicious' sig says: "A perfection of means, and confusion of aims, seems to be our main problem."

If anyone wants to talk about GG Allin until a mod closes this thread, I'm down!
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