Official Luthiers Forum!

I have a bit of a rant here.. It's about intonation. I've spoken about this issue to many guitar techs.. I usually get a blank stare, followed by "Have you ever heard about Buzz Feiten?". The issue of Equal Temperament.


Question to luthiers: How do you achieve true equal temperament? (I know about major thirds. And no, I don't think that ET sounds out of tune)

Seriously, I've played and owned a couple of $2k and up acoustics and not one of them was even close to true ET!


I mean HOW can you have frets # 3,4,5,6 that are within 2 cents of Equal Temperament,

then fret 7 off by +10 cents,
and then the next fret off by -10 cents
and the rest of frets back to being within 2 cents?


Aren't these things supposed to be precision cut? I mean, how can you be 10 cents off on fret to fret distance? Isn't 10 cents like 0.10"? Help me out here please..


Walter

Are you determining that your intonation is off with a tuner or with calipers?

Intonation isn't just about the distance between the frets. Getting that to be accurate is the easy part. Neck tension vs string height & compensation is where you will run into problems. There is a video somewhere here that shows you how to do a proper setup. Unfortunately most of the employees at Guitar Center or "techs", have no clue how to do a proper setup job. A common mistake many people make is using the truss rod to adjust the action. Doing that will majorly throw your intonation out of whack. Adjust string height by lowering (sanding down) the bridge. The neck should be perfectly flat. Once you have that done, you finish off by compensating the bridge by checking intonation at the 12th fret harmonic with the open string. They should match.

If that doesn't work, then your frets are probably out of whack.

Hope that helps.

Perfect equal temperament guarantees you will be slightly out of tune .. true musical scales are just intonated .. guitars are not. the 12 root of 2 metthod of placing frets is a compromise to make all scales play equally close to being in tune. 3rds and 6ths will be the worst ...

_________________
Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

Having a guitar in "perfect" equal temperament doesn't result in an instrument that plays "in tune", unfortunately. Before J.S. Bach's campaign to promote equal temperament in the 1600's, instruments were tuned to play in tune in a specific key. Guitar players knowingly or unknowlingly do the same thing. If you strobe a guitar so that all strings are perfectly in tune (on an equal temperament scale) and play and E chord in 1st position, I guarantee that the G string note (G#) will be out of tune. Two things are happening in this example. First, equal temperament by definition is a little out of tune. Second, notes fretted close to the nut tend to be sharper due to increased string tension (this is the reason I prefer to compensate at the nut as well as at the saddle). The players I've known that have especially good ears usually tweak their tuning as they play to adjust these small differences.

Also, I'm working on a theory that strong resonances in an instrument affect tuning as well. No proof, just a hunch. It's about the only way to explain the need to do this to the A string! And yes, I checked it with several strings to make sure it wasn't the string itself. This guitar would not play in tune on the A string until I added this saddle "extension".

Interesting Pat, thanks for sharing.

Tony,

I'm not looking to be "in tune". Being in tune is subjective, and has nothing to do with equal temperament. I'm talking about fret to fret inconsistencies within equal temperament (where there should be none). Why can't you build a guitar that's within 2-3% of ET specs?

You should have 100 cents between frets- not 108, not 112, not 94. I've never seen a guitar that's within 2-3% of specs. Sorry for the rant. I'm about to refret a brand new handbuilt 4k guitar.

What do you mean by 100 cents between frets?

_________________
Peter M.
Cornerstone Guitars
http://www.cornerstoneukes.com

'cents' is a unit of measure, with an octave being 1200 cents, and a
half-step, or semitone, or fret, being 100 cents in size in equal temperament.

after that it get complicated pretty fast.

Equal temperament is a system in which all the semitones are the same size,
which is not the case in most historically used tunings. ET allows the player
to modulate to any key with equal amount of out-of-tuneness.
Why out of tune? Because the musical intervals, especially thirds, do not fit
into the octaves, as they 'should'. *See Pythagorean comma*

BTW, Bach didn't use or advocate Equal Temperament; but rather Well Temperament, which in fact had semitones of varying sizes.

As for the OP's question, frets can be correctly placed mathematically
and still not be in equal temperament in practice: strings, *fretting
pressure*, top/body resonances and more can all create "error".
Also, being "in tune" is in fact not subjective- it consists of
intervals playing in tune, acoustically "pure", without beats, whereas
in ET *only unisons and octaves are truly in tune*.

This is all really just the tip of the iceberg- if you're interested, search
'Just Intonation' as a start.

Have you measured and checked fret placement and the compensation? It may be that the frets are fine. There is a lot you can do by leveling the top of the frets and moving the apex one way or the other. May not look pretty but it's a method of fine tuning. Then again you could change strings and everything alters yet again. . .

Some thoughts ....

How do you plan to tell as you are refretting if all your semitones are now closer to being 100 cents apart than they were before you started ? Unless you plan to move fret slots, how is putting new frets in going to accomplish anything ? Are you going to crown each fret either slighly forward or backwards from where they are today?

one other thing to check .. does each fret on a per string basis, show the same amount of error .. ie .. if you fret the 4th and 5th fret, on two different strings, are the errors exactly the same ? if they are not, then there is more than just the fret position causing the error .... as others have mentioned, its not just the fret spacing the affects the frequency of the note, its a complex beast.

Something interesting ... I have a copy of a fairly complex fretting program off the web, that delves into more math than I used to do in engineering school ... its output says that the errors (in cents) will not be the same from string to string, across the frets ... (in reference to my question above).

_________________
Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

I check and correct any intonation issues at the saddle using a strobe tuner. Playing style, finger position and force seem to have a significant effect when you're looking at the final 2 cents.

I have, as well as most players noticed that a little tweaking is required when playing certain fret and chord progressions which seems to be easily corrected on the fly. In speaking to most players, they take a lot more time in recording sessions to adjust their intonation than they do during stage performances.

The most important advice I ever received about intonation was to avoid those folks with hearing acuity that exceeds the sensitivity of the available tuners. So far I've been successful.

_________________
JJ
Napa, CA
http://www.DonohueGuitars.com

If I'm reading acoustic12's post correctly, he is complaining about the accuracy of the the frets on all the guitars that he has tested. The +- error he quotes seems to be just a single example. That error may well be that the frets are misplaced. Measuring the fret to fret distance should be used to check that rather than a tuner. Although the tuner is the ultimate judge as to whether the fret board plays at equal temperment.

Earvana has a system similar in spirit to Buzz Feitin. They publish an interesting chart on the typical errors on a guitar fret board. http://www.earvana.com/technology.htm Ignore the one where they show what their system will do. It is not important for this discussion. The typical case is what is interesting. The guitars measured were not misfretted. The frets were probably within 1/100th of an inch from the mathematically correct location. What is going on is quite different and relates to string stretch and tensions issues. The easiest symptom of this phenomenon to see is to tune a guitar until it plays a sweet G chord and then play a D chord. It usually sounds awful. The B string has to be adjusted so that neither chord sounds as good as it should.

The Buzz Feitin and Earvana systems attempt to address this problem by compensating the net as well as the saddle. I've played guitars that used both systems and the results are quite striking. Earvana has the advantage in that you don't need to tune the guitar to a weird pitch. I was quite bummed when I played these instruments because my natural instinct was to write them off as pure bunk. But, there seems to be something to them.

On the earvana chart for a typical guitar .. notice how the errors on the third fret are not the same for every string ...

_________________
Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

Most of Earvana's market is for electrics and the chart probably reflects an electric guitar which uses an unwound G string. I think that the chart would be quite different for an acoustic which has both a wound G string and higher tension. An acoustic will have similar errors but they will be different amounts on different strings.

i read up on the earvana and buzz f. sytems, and from what i gather is that they only affect the first 5 frets.
also, one of the complaints is if you change string guage, you have to re-tune the nut.
i think it's for the player with an unrealistic sense of hearing,
but, i do know when something bothers you about your guitar, (tone or playability) it will drive you nuts.
a really good player can adjust his technique, if he/she knows their git.
just look at a classical git.
you think a ss has probs.