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PostPosted: Sat Jan 01, 2011 5:10 pm 
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Walnut
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Joined: Sun Apr 27, 2008 2:00 pm
Posts: 13
First name: Allen
Last Name: Abrassart
City: Amisk
State: Alberta
Zip/Postal Code: T0B 0B0
Country: Canada
Focus: Build
Status: Amateur
Hi Todd!
I found your post fascinating and informative. I will have to read it several more times to try to absorb all the pertinent things.
Everyone is entitled to their opinion(s), but not everyone will agree with those opinions. Some people disagree with others, just for the sake of being disagreeable. I would, and I think others would, appreciate it if those who do not agree with anyone's info here, offer an alternative opinion, in a more amicable manner. Aggressiveness here
just muddys the water and causes nothing good. That is my take on it!

Todd, I appreciate yours and anyone else's posts that I can learn from.
Have the Happiest year in 2011 all!!!! bliss
Allen


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PostPosted: Sun Jan 02, 2011 10:02 am 
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Brazilian Rosewood
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Joined: Tue May 02, 2006 9:02 am
Posts: 2349
Location: Canada
First name: Bob
Last Name: Garrish
City: Toronto
State: Ontario
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There's a bunch of good information along the same lines to be mined from this thread:

http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=17955

You'll have to do some Googling and maybe search the MIMF archives to find some more basic stuff on the Chladni tuning parts, but there's a lot about pitches etc in that thread.

The one I built that I'm sure of the top pitch is a G# (208Hz), and it's a cannon, but it also had a very nice top mode and matched back so the pitch is only a part of the picture.

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Former Canonized Purveyor of Fine CNC Luthier Services


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PostPosted: Sun Jan 02, 2011 4:35 pm 
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Koa
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Bob, what kind of tuner did you use, or is there a cheapi out there, I have no ipod. Thanks

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Here is what a Parlor Guitar is for!
http://www.youtube.com/watch?v=oEa8PkjO6_I


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PostPosted: Mon Jan 03, 2011 12:53 am 
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Brazilian Rosewood
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First name: Bob
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Frei wrote:
Bob, what kind of tuner did you use, or is there a cheapi out there, I have no ipod. Thanks


It was actually the other way around in that case, as I was using a tone generator. 208 was where the ring mode occurred.

If you're going about it the other way (bonking it and analyzing the recording) then you'd want to look for a freeware fft spectrum analyzer.

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services


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PostPosted: Mon Nov 21, 2011 11:57 pm 
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Cocobolo
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Joined: Sat Aug 14, 2010 10:50 am
Posts: 324
First name: herry
Last Name: trismono
City: malang
State: east java
Zip/Postal Code: 65142
Country: Indonesia
Focus: Build
Status: Amateur
tlguitars wrote:
Got it done tonight and man it's now amazing, dead strings and all. I took pics before I started shaving and after. Now that I know how to voice properly before I get the back on I won't have to do this again but it's nice to know that I can fix a BAD sounding guitar.

Here's what it sounded like, sorry I forgot to play it with strings on.


Now my Back started at a Sharp G# to in tune G#. So and G#3 +.35 to .06c. There are 100 cents between every half step so I was right on the cusp of it being a sharp G. (Just 57 cents away.)
Image

Which is what the Top was, G3 +.41c to +.76c.
Image

So the top and back we're really just, on average, 40 cents away from each other. Which is waaaaay to close. And being that close the top and back basically got in each others way. The air pump couldn't function because both doors were opening and closing at the same time, creating a vacum... so to speak. Neither one could move at it's optimum.


Hai, may I know what tool (machine) is? that's like guitar tuner?...
[uncle] [uncle]


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PostPosted: Tue Nov 22, 2011 12:01 am 
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Koa
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Location: Bothell, WA USA
First name: Jim
Last Name: Hansen
Country: USA
Focus: Build
Status: Amateur
Henry,

That is an iPhone (or Ipod Touch ?) running an 'App' called "ProTune".

Edit: Looks like the name was changed to "TuneUp"

http://itunes.apple.com/us/app/protune/id359063365?mt=8

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PostPosted: Sat Dec 10, 2011 10:43 pm 
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Mahogany
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Joined: Fri Oct 01, 2010 11:30 pm
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Country: usa
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Status: Amateur
hay man thanx for posting this up. I have only built one acoustic, and at the time, I was just focused on getting it done (You know -avoiding the rabbit hole). I did tap the top and back throughout the process, just to hear how they were changing, as braces were added and then shaved. I was honestly left with the feeling that it was grasping at straws, to tune your plates individually and then expect them to stay tuned once glued up. Seeing this has me excited about the prospect again, (though "going back in" doesn't sound fun, I can see it's worth it). In the case of my guitar there is quite a bit of difference between the two plates (possibly to much) so I doubt I will mess with it... well maybe the back. ; )


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PostPosted: Sat Dec 10, 2011 11:06 pm 
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Contributing Member
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Joined: Mon Jul 11, 2011 12:43 am
Posts: 1326
Location: chicagoland, illinois
City: chicagoland
State: illinois
Country: usa
Focus: Build
Status: Amateur
so regarding the relationship between top and bottom tap tones, and how they "need" to be quite different...i was just thinking last night, with a violin(and maybe even a cello, i don't know), the top and bottom are actually coupled with a spruce "sound post", which resembles an upright dowel very near the bridge footprint... when this post is absent, the violin is reputed to sound thin/quiet/and generally much worse.
but this seems to go against what is being said in here, with "airpumps" and all. anyone know the difference in theory? and if soundposts are so great in violins, how come they arent used in guitars?
cheers


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PostPosted: Sun Dec 11, 2011 3:13 am 
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Contributing Member
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Joined: Thu Nov 17, 2011 1:01 pm
Posts: 184
First name: Joe
Last Name: Hill
City: Wesley Chapel
State: Fl.
Zip/Postal Code: 33543
Country: United States
Focus: Repair
Status: Amateur
Well, to be perfectly frank, I never even knew, or had a clue about tuning a top. I just started with no apprenticeship or formal education. Books, Video and common sense have taken me this far. When this was brought up I had no clue about tuning a top to G# or F# or between an A and a G#. Now I have something new to research and explore. The whole reason I started to build a guitar was that I was bored with furniture. I am learning a whole new wood craft for me, and I like talking and learning about methods and Ideas. Now I know that if this guitar I built sounds like crap I know of nother reason why. My braces were built from pictures in a book and tearing apart a trashed Washburn . I will glean every bit of knowledge from any pedigoug willing to share. What I have learned from this thread make me feel like I am in the beginers book learning the first scale and jumped right into bar chords in one lesson.

Thanks Todd and every othe member who has educated me.

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Joe

My wife asks me "How many Guitars do you need?"
I reply "When I die count them; thats how many I needed".


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PostPosted: Sun Dec 11, 2011 11:51 am 
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Mahogany
Mahogany

Joined: Fri Oct 01, 2010 11:30 pm
Posts: 55
Country: usa
Focus: Build
Status: Amateur
out of curiosity I tapped on an old violin I have -stainer type- the top and back definitely tap a different tone, -even with the post set properly. I don't have a tuner on hand that will register such a brief note, so I can't give details other than to say that its approximately a half step, to my ear -which is not trained to this.


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PostPosted: Tue Mar 13, 2012 9:23 pm 
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Cocobolo
Cocobolo

Joined: Mon Jan 28, 2008 3:29 pm
Posts: 213
Location: Meredosia, IL 62665
Hey Todd,

Thanks for your posts. I read them all thoroughly and a bit of understanding did come through for me. I also read the article in the FJ regarding your instructors and have to admit to feeling somewhat like Bob and the others. Your enthusiasm after the FJ article gives the "concept" a little more credence. Please share more when you feel it appropriate.

I would suggest that you don't make your next post "Ovations, a Better Guitar Through Science". I'm just sayin' ....


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