Intonation myths

Construction and repair of Classical Guitar and related instruments
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chrispeppler
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Intonation myths

Post by chrispeppler » Tue Dec 01, 2015 10:38 am

I built my own guitar 8 months ago under instruction by a master craftsman. On the last day of construction we adjusted the intonation by filing off some of the leading edge of the saddle under the different strings. We took each string in turn and checked the intonation against an electronic tuning app before making adjustments. But guess what... when I got the guitar back home where the altitude is much higher than the coastal town where I made the guitar, the intonation changed. Also, as the strings settled in after dozens of tuning exercises the intonation changed again. I started making further changes to the saddle until now the bone edge looks ... well, wavy is the best word to describe it :) So I started doing some research (something I should have done right at the start), and this is what I ascertained:
1. Intonation issues will be different for different tensions, and even makes, of strings.
2. The intonation will change a little as the new wood of the guitar settles in and ages.
3. Humidity levels will effect intonation.
4. The pressure and angle of the finger when fretting at the 12th will effect intonation.
5. Even the best made guitars will have some intonation issues (probably because of 1 to 3 above)

Then the GREAT REVELATION .... the human ear can only detect differences of more than 3 cents and sometimes even 5 cents... SO WHAT"S THE POINT OF FUSSING OVER AN INTONATION DIFFERENCE OF LESS THAN 3 CENTS!

To allow for differences in actual tuning of the open strings I took whatever the actual Hz reading was on the open string and doubled it to find what it should be at the 12th fret... then I fingered the string at the 12th and compared the Hz reading against what it should be. The results for my guitar yielded the following intonation differences:
Top E -0.5 cents
B -0.2 cents
G +1.3 cents
D 0.0
A 0.0
Bottom E 0.0

The notorious G string has the biggest problem but still way below my hearing threshold... so why mess around with the saddle.

I am a novice so very happy to be corrected if I have got it wrong :)

Pat Dodson
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Re: Intonation myths

Post by Pat Dodson » Tue Dec 01, 2015 11:16 am

A couple of thoughts:

You have compensated your saddle (twice :) ) so your readings are perhaps a record of a job well done. If you hadn't compensated it perhaps the results would look worse?

The biggest problems with intonation are not usually at the twelfth fret so readings elsewhere might again have shown a different picture.

Although for several reasons a guitar can never be perfectly intonated on all strings at all frets (even with those wavy line frets) folk on this forum with high levels of knowledge and experience say that a well compensated nut and saddle do very usefully improve a guitar's intonation in ways that can clearly be perceived. I don't think they are fooling themselves but no doubt someone like Trevor Gore will be along to shed some light.

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rojarosguitar
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Re: Intonation myths

Post by rojarosguitar » Tue Dec 01, 2015 11:37 am

Apart from all physical issues that can be listed for why intonation is never perfect on even most well made guitar there comes a second big field of influences: the psycho-accoustical phenomena that influence our perception of pitch.

One of the most important factors here is the overtone spectrum comprising higher harmonics as well as near-harmonic and non-harmonic components in the sound spectrum of a given note. Another important factor is the transient form. Again another important factor is the sensitivity curve of the ear, which is pitch and volume dependent.

And last not least: the 'uncertainty relation' ((delta t)x(delta f)>~1 which is the wave-theoretical basis for Heisenberg relation, see: http://newt.phys.unsw.edu.au/jw/uncertainty.html) is also valid for sound waves: the shorter the duration of a sound the less precise is the pitch. From this would follow that guitars with longer sustain could exhibit more nagging intonation problems than guitars with little sustain, all other factors being equal.
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Philosopherguy
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Re: Intonation myths

Post by Philosopherguy » Tue Dec 01, 2015 6:01 pm

chrispeppler wrote: The notorious G string has the biggest problem but still way below my hearing threshold... so why mess around with the saddle.

I am a novice so very happy to be corrected if I have got it wrong :)
I am just a player, but I rarely ever compensate any of my guitars. If the G string needs it, I will do it. Otherwise, I leave well enough alone. It's a guitar and its just built like that. So, why fuss so much and introduce other problems to "fix" issues that rarely become big problems in themselves?

I don't think you need correcting at all! It's personal preference. Rarely do any of the traditional Spanish makers compensate anything.

I still haven't seen one professional guitarist playing with a compensated nut. Saddle yes, nut no. A well built guitar shouldn't need all that much in the way of compensation. And, like you have noticed, you change strings or environmental factors and it all becomes a waste of time anyways. Stick with the easy solutions. Fix what "really" bothers you and just let slide the minor issues.

That's my opinion anyways.. Why waste time and money on something that you can't fix 100% and ends up being a moving target? Perhaps you might need an arsenal of 100 different saddles and 20 different nuts to account for every type of string you might put on or climate change.

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Imbler
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Re: Intonation myths

Post by Imbler » Tue Dec 01, 2015 6:45 pm

It would be the rare Spanish maker that does not compensate the saddle, it just isn't obvious. Typically the saddle is compensated approximately 2 mm longer than actual scale length. It isn't obvious because there isn't individual string compensation nor the slanted compensation more typical of steel string guitars, but it is there,
Mike

Alan Carruth
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Re: Intonation myths

Post by Alan Carruth » Tue Dec 01, 2015 8:24 pm

Intonation on Classical guitars is far less of a problem than it is on steel strings because nylon stretches more than steel and thus doesn't show as much pitch rise. The G string is the big exception. AS Imbler says, it's usual to shift the saddle back a couple of millimeters from the theoretically 'correct' position on a Classical guitar, which generally gets them 'pretty close'.

You could say that intonation issues are simply part of the sound of the guitar, accept them, and let it go at that. Players can, of course, compensate to some extent for these problems, and probably do so more or less unconsciously, particularly the better payers. OTOH, I can say that everybody I know who has tried one that is better compensated at the nut and saddle has appreciated it. It's one more area where they can frget about technique and simply play music. As far as I'm concerned, the more 'transparent' the instrument is in that way, the better.

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Steve Ganz
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Re: Intonation myths

Post by Steve Ganz » Tue Dec 01, 2015 9:52 pm

Because an open string / octave is cents off does not mean that it plays in tune up and down all the frets. The problem is more complex than that, as you probably learned through your further reading.
The human ear is also not standard.
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Imbler
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Re: Intonation myths

Post by Imbler » Tue Dec 01, 2015 10:45 pm

I also think the human ear becomes "attuned" to the tuning :). The more I play, the more sensitive to intonation I become, and conversely, I've noticed that my wife who has played only a few years is much less sensitive. Although I still use a tuner to get absolute pitch, I've noticed my ears are more accurate than the tuner sometimes as by the time it stabilizes the pitch is different from when first plucked, and the human ear appears to pick the harmonics and time to determine if a note "sounds" in tune. I used to use the tuner purely on the last of the sustained note as I got the steadiest reading then. However, it didn't sound good when playing, and I learned I had to capture the tuning earlier in the sustain of the note even though it had not totally settled on its eventual freq.
Mike

Steven D'Antonio

Re: Intonation myths

Post by Steven D'Antonio » Wed Dec 02, 2015 1:11 am

3 cents, you have exceptional hearing my friend. I'm told most people my age (old) it's more like 20cents (which is about where it came in when I tested mine last, although this could also be the limitation of the headphones I had on at the time).

Marcus Dominelli
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Re: Intonation myths

Post by Marcus Dominelli » Wed Dec 02, 2015 1:35 am

I agree with most of what has been said.
I did a fully compensated saddle on a steel string guitar using a strobe tuner, long ago. My boss said to get the intonation perfect for this client, because he had a super ear. Well I got them all perfect, except for one string, which was 1 cent sharp.
The guy came to pick up his guitar. After playing it a few minutes, he noticed the one cent sharp string, without using a tuner. He wanted it re-done!!!

Even though guys like this are really rare, there are a lot of musicians who have incredibly good ears, know how to tune properly, and play well enough to appreciate a guitar with really good intonation. They simply will not be happy with a Spanish classical, for example, that has zero compensation. BTW, there are lots of them out there. The Japanese did not copy this aspect of the Spanish guitar. They clearly are good at improving things...but that's another story.

I think it's worth doing the intonation to a fine degree if:

1) the guitar in question is not a temperamental one
2) the action is where the player wants it
3) the string type and tension are settled on.

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chrispeppler
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Re: Intonation myths

Post by chrispeppler » Wed Dec 02, 2015 2:38 am

Thanks everyone... very interesting... my CG education continues :) By the way, at 68 years of age, I am loving learning about all aspects of the CG and enjoy my daily practices. Performing for others... well that is a different story, but I am sure I will come to love that too. I have to add that I appreciate the generous advice and tolerant responses I get when I post on this forum :)

Astroid
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Re: Intonation myths

Post by Astroid » Mon Oct 29, 2018 12:54 pm

Very true. A lot of fleecing for money going on. Let guitars retain some kind of human element. We don't want to sound like computers. We shouldn't expect our guitars to either. Notwithstanding any serious disability, or obvious disability, and if a guitar hasn't been properly made, why mess about with it ? It should be chucked in the bin, or money back or something . Substandard computers have made us come to accept substandard production. I think it is quite right , - a musical instrument should not have to be tampered with, at least not frustratingly or expensively.
I think the problem is possibly that most people can't afford to buy what can be thought of as a decent guitar and there are probably a lot of substandard instruments especially guitars on the market, which aren't cheap enough and thus the discontent. But even with the cheaper instruments and I mean starting at a couple or a few hundred pounds, just getting to know your instrument and practicing tuning by ear will help to produce a better performance.

Alan Carruth
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Re: Intonation myths

Post by Alan Carruth » Tue Oct 30, 2018 6:14 pm

Astroid wrote:
"Let guitars retain some kind of human element. We don't want to sound like computers."

There's no danger of that! With enough effort and understanding it's possible to get an acoustic guitar to play 'arbitrarily close' to 'perfect' intonation, but you'll never get one 'perfect'. Even if you managed that for a given set of strings on a certain day, the humidity would change, the strings would age (or the player would decide to try 'carbon' ones or whatever), and the player would press down a little harder or more softly, and the intonation would be different.

Also, intonation has to be understood in light of the temperament you've chosen. It's mathematically impossible to construct a 'perfect' scale, where all of the intervals sound 'true' and done' beat. You can't even get beatless fifths all the way down the line. It is, in a sense, a 'wicked' problem; one that cannot be solved, but only managed. Of all the different temperaments only one has all of the semitones the same size in a musical sense, and that's 12 Tone Equal Temperament. We use that by default on guitars because it allows for the use of straight frets, and also free modulation from one key to any other. The latter is possible because all of the intervals are 'out' in the same way in every key: they all sound bad in the same way. Once you learn to hear that it never goes away.

Guitar players often 'sweeten' their tuning in ways that make the usual keys sound a little nicer, at the expense of the ones that don't get used as often. It helps, but it's still not perfect.

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bacsidoan
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Re: Intonation myths

Post by bacsidoan » Tue Oct 30, 2018 7:51 pm

Let's just assume that most people will accept a 5 cent variation in a guitar. However, things are not always that simple. For instance:
- A major third in just intonation is 5/4 or 386.31 cents. This evokes the most pleasant sound to most listeners
- A perfect major third in equal temperament is 400 cents. There is already a built-in 14 cent deviation from the ideal sound.
- A guitar with a tolerance of 5 cent intonation deviation can generate a major third of 410 cents. I can guarantee that mot people will appreciate a 24 cent bad intonation for a major third.

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Re: Intonation myths

Post by lux » Tue Oct 30, 2018 10:11 pm

chrispeppler wrote:
Tue Dec 01, 2015 10:38 am
Then the GREAT REVELATION .... the human ear can only detect differences of more than 3 cents and sometimes even 5 cents... SO WHAT"S THE POINT OF FUSSING OVER AN INTONATION DIFFERENCE OF LESS THAN 3 CENTS!
That's part of it, sure. But when it comes to partitioning the octave, even perfection is imperfect. If we could make a guitar in which every fret produced a tone EXACTLY one twelfth of an octave higher than the one below it, you'd end up with a perfectly tempered guitar (you'd have to have a certain set of reference strings in mind, here, because if you used a different brand or tension then you'd be off again). And what is equal temperament? It's the ultimate compromise of intonation: one in which we sacrifice the purity of chordal tonality for freedom of modulation. That requires that we play notes and chords that are all a little bit off, but each one not much more than the next. We can play these somewhat imperfect pitches in any key -- a classic case of "splitting the difference" as a means of accommodating a discrepancy. The fact that no guitar's temperament is perfect probably accounts for the guitarist's sensation that on any particular instrument, some songs sound better in some keys than in others. Sometimes I'll play with a capo that isn't necessary for any reason other than the fact that I prefer the harmonic mojo the instrument produces in that key. Perfect intonation is an aspirational goal that is unachievable in practice...for the most part...don't get me started on microtonal fretboards. :shock:

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