Intonation & Resonance Shifting Example

[Clancy]

G’day Trevor,

This section of the books (amongst others) intrigued me, probably because I am well and truly in the 70% who never notice any dissonance.

Never noticing anything, I’d never given any thought to intonation beyond the standard “12th fret check”.
(and I call myself an engineer , lucky I don't call myself a musician )

So the example of tuning errors for each fret on each string was an eye opener.
I’m yet to decide where I’ll go with nut intonation, but as a ‘diagnosis & correction’ of existing instruments this section is invaluable. Thankyou.

I do have a query though with regard to Table 4.7-1, page 4-100.

I can understand the 6th string errors on frets 2 & 3 as being caused by the T(1,1)1 of 92Hz as this is F#-10c.

Next you attribute the large errors on the 5th frets 7-12 to over-coupling with a T(1,1)2 of 160Hz.

However 160Hz is E-50c and is also less than an octave above T(1,1)1.
These are both desirable outcomes when designing/building/tuning according to Section 2.4 (and summarised as such on page 2-52)

What I can’t work out is how this ‘over-coupling’ has occurred. What am I missing

Cheers

[Trevor Gore]

Hi Craig,

What I can’t work out is how this ‘over-coupling’ has occurred. What am I missing

For one who's "not the sharpest tool in your shed" you don't miss much!

There's a bit of back story behind this guitar which might help make things clearer. This guitar was an "old favourite" of a customer of mine (either a late 1940's or early 50's instrument), one reason for it being so was that it was so loud. The reason it was so loud was that it had reached that glorious stage of advanced decrepitude where it was all but falling apart, but just hanging together, and just before it all starts going to mush. It was very lightly built, with a very high monopole mobility (average admittance). So the problem was that anywhere near a resonance you would likely have an over coupling problem. So I'm reasonably comfortable with that as a diagnosis on the 5th string. The next question is why don't you see much of a problem on the 4th string around the third fret? On most guitars you would. There's two reasons I can give: the first is that I'd already had one go at correcting the intonation (you should have seen it before!) so I'd made some progress and the 4th string consequently wasn't too bad. The second reason is what I just call "old guitar syndrome", because I never see anything of this sort on new guitars (usually mine, of course). And this, I think, is due to the advanced stage of decrepitude and things no longer necessarily behaving in a linear elastic way, with local soft spots and dead spots which just don't seem to exist on new guitars (well, not mine, anyway).

Here's another story about this guitar and why I was having another go at trying to fix the intonation. The guy who owns it is left handed. I'm right handed. I did the original error mapping, playing it right handed, but upside down. I fixed the intonation and did a pretty good job - until the guitar was played left handed by its owner. The intonation errors were clearly audible. Now Jack (lets call him that to protect the innocent!) being left handed, can also play right handed guitars reasonably well upside down and could play other guitars without pulling them out of tune. So we reckoned it was the guitar being turned over that was the problem. So I turned the guitar over and mapped the errors in left handed orientation and got a completely different result. So I fixed those intonation errors and that "worked". On the other hand (if you'll pardon the expression), my new guitars intonate the same both ways up and I expect most other guitars do to. So another example of "old guitar syndrome" where I can't even pretend that I understand what is going on!

I hope that helped!

[Clancy]

Sounds like it was a fun challenge
I hope you were re-imbursed well for all that .
Did you have any hair left at the end?
Maybe you should talk your friend into changing to an upright bass!

Actually your OGS explanation makes a lot of sense.
However, now that I'm armed with the knowledge in the books, I can't throw around the OGS solution too lightly.
Before your books my main weapon for demonstrated expertise in the field was ignorance!
No more!!
But it is good to know that OGS is still viable, if only after all other solutions have been exhausted.

And while my edge tools are certainly sharper than me, it's good to know I'm not yet dull.

Thanks Trev

[Dominic]

Actually your OGS explanation makes a lot of sense.
However, now that I'm armed with the knowledge in the books, I can't throw around the OGS solution too lightly.
Before your books my man weapon for demonstrated expertise in the field was ignorance!
No more!!

Your main weapon eh? Although I know what you mean how could I pass up this opportunity to point out to you that because of the new improved features of this site this comment will forever exist and bare your name.

But you are right, these books are ignorances worst enemy. And hopefully it will lead to a day where ""gurus"" will be required to more accurately explain what they are saying and not just rely on philisophical or the cred will go the way of ignorance. I think we have lots of homework to do but its like nuclear weapons, once we learn how to do it, we can't unlearn it.

Cheers
Dom

[Clancy]

edit, edit, where's the edit button....
.... and it just sounds worse to ask the mods to 'please put i in man'