Re: Moving nut for perfect intonation?
Perhaps you can explain the theory behind why the 12th fret harmonic is up to a few cents off from the open note. The assumption that they are the same is what misled me.
I'll refer you to the second link in my post from yesterday. This explains why the forces contained in the body of the vibrating string act to accelerate the harmonics, although in fact the 12th fret harmonic is barely affected by this normally and I'd be more inclined to believe that your digital tuner is not accurate and can't cope with the inherent instability of the open string with its plethora of overtones. The first harmonic is generally more stable, while the frequency of the open string tends to "wander"; most notably, the initial attack transient causes the string to sound slightly sharp. As the attack transient passes the string settles into a slowly decaying stable resonance. Tuning to the attack transient will always introduce errors. I have never found that there is any significant difference between the pitch accuracy of the first harmonic and the open string's stable resonant phase.
I distrust digital tuners and I have a lot of unwelcome experience with them. When I first started playing the guitar about 42 years ago, there were no digital tuners. We learned to tune by ear, using a tuning fork. This is a skill that a whole generation of guitarists, raised to be reliant on digital technology, have lost.
In 1983 when I started working for Hohner I was handed a digital tuner; "Use this" I was told, "it'll make tuning the guitar a breeze..."
It didn't. My productivity went down. The Korg DT-1 found it's way into my bin and never came out; my productivity went back up again. Not only was I able to tune guitars more quickly if I didn't have to watch for the little flickering green light but they also sounded better afterwards, regardless of what the tuner said.
I've always tempered intonation the same way; using higher level harmonics to temper the fretted notes on the higher frets. I didn't really think about what I was doing but I noticed that my customers came back to me time and time again and said more or less the same thing; that their guitars had never sounded quite in tune before, and now they did. They are still saying it. It wasn't until about 15 years ago that I began to realise that I was on to something and began to think about the relationship between the arc relief, nut height, inharmonicity and the applied strain on the string.
I have on occasion, used a digital tuner in an emergency, but never relied upon one. I'd go as far as to say they are the worst device ever offered to musicians.
I always remember a conversation I had with one of my customers. I'd set the intonation on one of his spiky heavy metal guitars. He'd taken it away and gone back home then checked it with a tuner, 'cos he's a bit like that.
"you set my intonation wrong!" he came back to me with later, in full combat mode.
"how so?"
"all the notes above the 12th fret are sharp, according to my tuner"
"but how does it sound?"
There was a pause. "well, it
sounds OK; but the tuner says it's wrong!!"
"well" I said, when you brought it to me, you'd set it with the tuner, but it wasn't sounding right. Now it sounds right, but doesn't agree with the tuner. Which is more important to you; how it looks or how it sounds?"
I went on to explain to him about inharmonicity, how piano tuners pull up the pitch of the shorter and stiffer strings to counter this, and how guitars, although not subject to the same extent of inharmonicity, nevertheless required a similar approach to pitch management. He got it in the end
:beerchug:
