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PostPosted: Wed Apr 03, 2013 1:27 pm 
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Walnut
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Here are the taps:
https://docs.google.com/file/d/0BzCR9Aa ... sp=sharing
https://docs.google.com/file/d/0BzCR9Aa ... sp=sharing

The first file "Main Air" has just that, 2 taps on the bridge and the mic above the soundhole, nice and clean sinewave
The second file "Main Top + Back" has first 3 taps on the bridge with the mic about 3 inches back from the bridge and then 3 taps on the back with the mic about 3 inches off the back. Hope these are good for better analysis than just counting waves.


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PostPosted: Wed Apr 03, 2013 5:24 pm 
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Location: Windsor Ontario Canada
First name: Fred
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I looked at your files and I think that you need to try doing this. Hold the guitar with the mic at least a foot from it and tap on the bridge recording at least 6 or 8 taps. It will show what the guitar is doing as for as coupled resonances. I let the guitar rest on its butt with the soundboard facing the mic and tap with the strings damped. On what I could see from what you recorded the main air is fine and depending on which waveform I look at the top is 196 hz which is exactly G3 and the back is around 235 which is real close to A#3 ( 2 hz away). I will look at what you have when you do the taps I suggested above.

It looks like the top is the problem from what you provided so far which goes with the comments several people stated from just looking at the braces in the picture. A few hz lower would probably ease your problem.

Fred

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PostPosted: Thu Apr 04, 2013 12:35 am 
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Walnut
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Allrighty, I'll tap some more tonight even though my wife is looking at me in a strange way when I do that, she probably thinks I'm trying to communicate with the guitar?


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PostPosted: Thu Apr 04, 2013 11:01 am 
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First name: Tim
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Tell her it's trying to communicate with you.

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PostPosted: Thu Apr 04, 2013 12:29 pm 
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Walnut
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Here's some more tapping:

https://docs.google.com/file/d/0BzCR9Aa ... sp=sharing

I still get 44ms per wave so about 227hz for the main top?

Edit: I downloaded the new Audacity and it has the analyze button so this is what I got. 229hz peak and 109hz main air?


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PostPosted: Thu Apr 04, 2013 6:01 pm 
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The 109 hz main air is only 1 hz away from A2 at 110 hz, your top is also between A2 and A#2 so you do have 2 A's. Making the sound hole smaller should lower the main air, Reducing the top frequency will also affect the main air a bit, try adding weight to the top on the bridge plate and see where it goes, also try adding weight to the back and see what that changes. Now that you can see the wave form you can easily track your progress. I use rare earth magnets to add weight as they are easy to add and remove.

Good luck
Fred

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PostPosted: Fri Apr 05, 2013 1:13 am 
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Walnut
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I'm hoping that the main air could come down a bit as the guitar gets played?

What would you suggest for the frequencies I should be targeting to? I've made some angled sanding blocks so I'm pretty well equipped to start modifying the braces but I would like to get some opinions for the target frequencies. My mind says something like 105-107hz for the main air, 205-210hz for main top and 225-230hz for main back?


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PostPosted: Fri Apr 05, 2013 1:09 pm 
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Try the adding weights thing and see what results you get on your wolf tone problem. This will give you an idea of what amount of frequency changes are needed. I would try top weights 1st then back weights then try some combos of both. Each change will affect the other frequencies also.

Keep on banging the box
Fred

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PostPosted: Fri Apr 05, 2013 1:11 pm 
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Brazilian Rosewood
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The main top mode will usually drop a bit on my guitars as they get played; often by about 1/2 semitone.

Aside from making the hole smaller, the best way I've found to lower the 'main air' mode pitch is to reduce the stiffness of the back, if the 'main back' tap tone is not already too close to the 'main top' mode.


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PostPosted: Sun Apr 07, 2013 2:01 am 
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Walnut
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I've made some progress: my wrist looks like I've been arrested by the KGB..

The main air is now down to to 107hz and the main top is at 219hz and the main back 233hz. Even though there is still some wolfing on the region of the A-note I'm really glad I started, the guitar sounds so much better than originally that it's hard to believe it's the same guitar. It's warmer, more balanced, bassier and louder. I tried adding weights and I noticed that adding weight to bridge made the sound much fuller so now I've got the 2 middle bridge pins swapped from ebony to brass. That's probably a 7-8 grams but it makes a huge difference. Anyway now it's pretty close to what I originally wanted so now I'll just play.

Thank you all for your help!


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PostPosted: Sun Apr 07, 2013 8:01 am 
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Glad to hear you have improved the guitar, if the heavier bridge pins are helping that tells me you need to do more brace carving on the top. Using the pins are a good idea until your arm bruises heal, have you tried a 3rd brass pin.

Fred

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PostPosted: Mon Apr 08, 2013 11:04 am 
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Brazilian Rosewood
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Seems like the main air is almost an exact octave below the main top. Could this be the source of the wolfy A?


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PostPosted: Mon Apr 08, 2013 11:56 am 
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Quote:
Seems like the main air is almost an exact octave below the main top


The 219 is almost exactly on A3 which is 220hz I would like to see it drop to closer to 1/2 way between the A3 and G#3 which is 207.65hz. My last 12 fret 000 was around 99hz main air 175hz coupled top and 224hz coupled back and it is a canon with great tone. I had another with 96/176/230 also a great sounding and projecting guitar.
Here is a video from my mini concert at the Montreal guitar show of the 2nd mentioned guitar, recorde with my Sony cybershot camera so the audio could have been better.
https://www.youtube.com/watch?v=Iol1QjKhT8w

Fred

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PostPosted: Mon Apr 08, 2013 1:54 pm 
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Walnut
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It ain't perfect yet but it's way better than it used to be. I like it where it's at now so I'll play it for a while and see if I feel like doing some more carving. The heavier bridgepins do take the resonance freuency down but they also cut volume and brightness so I don't want to go too heavy.

Fred, I don't want to ask you to to expose all your secrets but would you happen to have a few photos of your top bracing? Just so I'll get some feel on how light I can go?


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PostPosted: Mon Apr 08, 2013 3:02 pm 
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Joined: Fri Mar 24, 2006 12:42 pm
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Location: Windsor Ontario Canada
First name: Fred
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City: Windsor
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Zip/Postal Code: N8T2C6
Country: Canada
Focus: Build
Status: Amateur
Check some of the build photos on my web site, from where you were at the start you can go a long ways.
http://www.fetellierguitars.com/index.php?p=1_16

The build photos for the 000 12 fret in the video. There are no secrets at my shop, I gave you the numbers and have a file of the entire build from audacity. I have been accumulating data since my 4th build and adding to the things I record as I progress and learn more about how the guitars work, I will be stringing up # 18 and 19 this month, the 000 was #13.

Fred

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