Intonation

[naccoachbob]

I just sat with my 1st build and decided to see if the intonation was right or not.
I've never done anything with it. But decided I need to explore.
Here's what I found:
Treble E is good, right on.
B string is good - surprising as I didn't file on the saddle at all.
G string is flat about 2Hz. Freq is lower by 2Hz
D is good.
A is sharp about 4Hz. Higher pitch.
E is sharp 1Hz. Higher pitch.
What adjustments are needed to correct this?
If it's sharper, I can just scrape some of the bridge material off and make the string longer, right?
What about the flat one?
Is aging of strings a consideration? Should I do this when I have new strings on and they've settled?
I hear the term "cent" used. Can cents be described in frequency? What's the frequency change from E to A, A to D, etc?
Were there posts that are archived that discuss this?
Lots of questions, but I appreciate any and all comments on this.

[tippie53]

A fretted instrument is not ever going to be perfectly intonated. There are so many variables . You sound like you are close. When we are talking cents we are talking a percent . Most people will not hear a 5% difference. As for bridge location you have to look at the controllable variables. Action height , and compensation length ,and compensation angle.
I like a 3 degree comp angle on the bridge and I use .100" comp length to the center of the saddle following the line of the string using a 3 1/2 2 1/2 action height. I like a .100 saddle to allow me to compensate to the string. What this means is 3 1/2 64ths and 2 1/2 64ths.
When you are building to a prescribed action line , if the action goes higher it will get sharper and this is not that much but in the big picture , if you placed the saddle to long or short or the wrong angle , the intonation can suffer. Allowing a bit more saddle allows for the compensation adjustment .
If you are flat you can lengthen the working length by filing the saddle. If you are sharp , you can try dropping action or see if you intonate at the nut. Sometimes it can be the strings .
I don't see a big problem that a little compensation on the saddle won't help. Double check your setup . 1st relief action height and here is one thing to consider , a steel string will not bend at a sharp angle , so you may need to arch the bottom of the nut slot so the string an ride the slot and not deflect. This can cause all kinds of intonation issues that are so hard to control.
If you can get to 2 - 3 % through the scales all up and down you did good.

[kencierp]

I assume you are checking the fretted note against the harmonic at the 12th fret? The 12th fret harmonic will always be perfect, one octive higher than the open string. Then when you press down at the 12th fret you can determine if the string length is long or short "Flat or Sharp" and move the take off point accordingly.

When doing a set up, especially correcting intonation proplems have the guitar strung with a fresh set of the Brand and gauge string you will be using. If a note is sharp file the saddle take off point more toward the tail block side --if the note is flat move the take off point closer to the sound hole -- here's the general look of a compensated saddle.

http://www.kennethmichaelguitars.com/saddle.html

[Freeman]

First, as I understand the definition of "cent" it is 1/100 of the distance between two semi-tones. In other words, if you divide the frequency between D and D# into one hundred parts, each of those would be a cent. It also my understanding that you probably can't hear one or two cents, but sure can hear 5, and that is considered pretty good intonation. My strobe tuner will indicate frequencies in cents.

Here is the method that I learned to make a saddle. After doing all of the other setup (relief and nut) as closely as I can, I make a saddle blank but leave it flat on top. Bring it down close to the final action to minimize the string stretching when fretting. I put a little piece of wire (a B string works nicely) on top of the saddle, tune it up and check the fretted 12 and harmonic (which my strobe tuner). Push the wire back and forth until they are as close as possible, then mark both sides of the wire with a pencil. That becomes the rounded part of the saddle break - when you do that you will lower the action slightly (because you take the wire out) which means the string stretches less and the intonation will be better.

I've done this on several 12 string saddles, it takes a while to do it but the guitars come out intonated about as well as I've ever heard.

Some other things to remember - if you don't play way up the neck or if you play slide, intonation is not as important. Also, don't forget all those old Martins where the saddle was located in the wrong place - lots of old bluegrass players didn't seem to notice the difference. Or the cherished old guitar with no slant to the saddle. Sometimes I think we get over anal about these things cause we've got digital tuners and the Intranet to talk about them....

[kencierp]

I've posted this before -- even though I have the expensive Strobosoft PC based tuner I now use this FREE software -- works better!

http://www.aptuner.com/cgi-bin/aptuner/apmain.html

[Tony_in_NYC]

Bob,
the notes that are flat are no problem. People tend to hear the sharp notes more so than the flat ones. Two or three cents flat is just about perfect and I wouldn't mess with it.
The sharp note could be an issue, but again, if you dont play up the neck, nobody will ever hear it anyway!

[naccoachbob]

Thanks for all the input. It's very helpful.
Now to make it weirder even, I found this page when trying to find out how to measure a "cent" in frequency.
Here's the link, then my thoughts: http://www.vaughns-1-pagers.com/music/m ... encies.htm
My tuner shows 440hz as the top reading, with plus to the right, minus to the left.
Green light and string name when in tune.
However, bass E is at 82.4 Hz if I read right, (seems very low cause I'm thinking of 60 cycle hum). F would be 87.31. The freqs get much higher as you go up. The difference from E to F (a semi-tone) is about 5hz. But at treble E, it's about 19hz. So a 1 hz change in tone would be about 20 cents at bass E, where it would be 5 cents per hz at treble E.
When I was showing the sharpness/flatness of strings yesterday, I guess I was asking whether 1-2 hz was significant or not.
Now I found a site that converts cents to freqs and back: http://www.sengpielaudio.com/calculator-centsratio.htm
If I punch in the freqs above for bass E and F, it comes to 100 cents. Hmm. Works all down the strings that way.
So a cent is relative!! It can be .05hz or it can be .2 hz depending on starting and stopping freqs.
Honestly I don't think it's worth pursuing further than do the best intonation I can and live with it.
I'm thinking to myself, and don't worry about it.
Tony, can I have your 2cents worth?
Fun exercise tho.

[deadedith]

Hey Ken - that APTuner works great.
DaveVB

[Tony_in_NYC]

Honestly I don't think it's worth pursuing further than do the best intonation I can and live with it.
I'm thinking to myself, and don't worry about it.
Tony, can I have your 2cents worth?
Fun exercise tho.

Wouldnt my two cents mess up your intonation? Heh heh heh.