Tuning Components Off Note or On?

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OiAcoustics
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Tuning Components Off Note or On?

Post by OiAcoustics » Mon Oct 25, 2021 3:11 am

Hi All

I'm digesting The Book in pretty good detail and beginning the process of creating FRCs for some unhappy guitars in preparation to zip off the backs and rebrace to falcate with live backs (I use a removable tilt neck which has a huge advantage for radical re-dos), in order to learn what I can (before/after tests) before building all new from scratch.

Trevor is very clear on his reasoning that all the components and air chamber should be tuned in between note frequencies so as to avoid wolf notes. As this section is about The Book, I presume we all are pretty much in agreement on that.

However, the preeminent authority on tap tuning (at least until The Book), Roger Siminoff, claims otherwise - that everything should be tuned onto a note to avoid beats between the played note and instrument response. That is the path I've been (attempting to) follow for a decade or so, but quite truthfully am finding Trevor's approach much more user friendly as:

1. It's very hard to tune to a very specific note - it addition to the preciseness required for jigging, measuring and adjusting, when you change one thing, everything else changes...it's chasing a moving target and the results haven't seemed to prove out.

2. It seems to me that beating on a grand piano with very long sustain (and in fact are sometimes intentionally are "off tuned" a hair between the same strings to create color), or on a bowed instrument (which I don't know much about other than the forces generated by a bow are entirely different from a pluck), is one thing, but on a relatively short duration sustain like a guitar, it seems to be hardly a factor in real life.

3. And it's just so much easier to tune off a note and avoid the dreaded wolf note, which even if on a rarely played note have diminished otherwise very nice instruments.

I'm just ruminating here, but found it interesting to find such a disagreement between the two authorities on the subject. If anyone has a thought, do tell. If not, I'm sticking with The Book (other than all my own quirks) :cl

OiAcoustics
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Re: Tuning Components Off Note or On?

Post by OiAcoustics » Mon Oct 25, 2021 7:30 am

So I'm going to answer my own question, based on today's very interesting experiment, so nobody else has to spend the time to educate me. Since I've got VA all set, and before taking the backs off, I thought I could learn something by creating FRCs off my two unhappy guitars.

Both air chambers T1,1,1 came in at very close to 116hz, which is A#2. The open A string wasn't horrible but muddled, A# lousy. No wonder.

Both tops T1,1,2 were extremely close to 196hz, which is G of course, and totally answered why my open G string was dead.

Then I did a FRC for each open string, plucked just once and allowed to die off over the 16 seconds. Again, this completely confirmed all of the above, especially with the G wolf note - a big spike in amplitiude (far more than I would have thought) followed by a rapid decay (which I could easily hear from the start). On the other hand, the other strings which ring true showed harmonics continuing right up to 5k hz with a nice soft decay after the initial 4 harmonics. Isn't science wonderful?

IMO this confirms Trevor's approach and refutes Siminoff's...off note it is.

Well done Trevor! Off come the backs and on to live backs/falcate tops.

johnparchem
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Re: Tuning Components Off Note or On?

Post by johnparchem » Mon Oct 25, 2021 8:51 am

I agree, I read Rodger Siminoff book at it made little sense to me. He advocated individually tuning each brace to specific notes. I could not understand how those tones meant anything once the brace is glued down. I got a DVD in my book and he contradicted half of what he said in the book. I am sure that a lot of the tuning and measuring that he did gave him some consistency. I just never felt that he understood why he had success. Also Simioff was really a mandolin builder, the mandolin are not guitars. I do not hear them playing slow Legato lines against a sustained chord as often.

OiAcoustics
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Re: Tuning Components Off Note or On?

Post by OiAcoustics » Mon Oct 25, 2021 9:42 am

Somewhat in defense of Roger, he did advocate tuning the top braces in a jig in order to replicate being glued to the sides... but this isn't horseshoes...

A mandolin is much closer to a plucked violin than a guitar top, and focuses on a completely different sound spectrum, so different factors are at play. I did build a tenor guitar CGDA along the lines of my not great standard tuning guitars, and a ton of ukes, none of which had the same problem. Even my Weissenborns tuned to Nashville C6 worked as they are tuned high. So different instruments, with different frequency requirements, do require different solutions.

I don't mean to dump on Roger, I just found the discrepancy in theory hard to reconcile, and feel that a limited experiment on my part answered it to my satisfaction.

So I shared that "finding". None of us want those dreaded wolf notes :evil:

seeaxe
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Re: Tuning Components Off Note or On?

Post by seeaxe » Mon Oct 25, 2021 3:12 pm

Well done Kevin. Its great when you can demonstrate the theory in practice. I think this demonstrates the real benefits of Trevors objective approach. There are things we can physically measure rather than trying to guess whats going based on what we think we hear.

The other point about Trevors approach is that he is very consistent in his building method so few things change from one instrument to another. As I understand it, that makes the effects of things you do change more trackable.

Will be interesting to see what you are able to achieve. Im not far away from pulling the top off my last (and only so far) falcate so watching with interest.

Cheers
Richard

jeffhigh
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Re: Tuning Components Off Note or On?

Post by jeffhigh » Sat Jan 29, 2022 7:15 pm

Besides the tuning to the note or off the note issue, Trevors method does NOT tune components separately unlike Siminoff. The Gore method involves testing the properties of the materials then modelling to determine desirable thicknesses and then testing the completed and strung up instrument and adjusting the various resonances.

I found Siminoff to be totally misleading rather than helpful.

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