Do you build your tops to a certain pitch or body resonance?

[Jeff Highland]

Sorry Sen, I saw DennisK's picture with the same colour graphs and thought it was yours

Now that you have posted your pictures,It does look like you have taken the centre down too far though.

I use a rubber eraser on a 3mm dowel about 350 long as a tapping hammer, gets me a cleaner result than tapping with a finger or a Knuckle.

[senunkan]

Jeff,

Thanks for the clarification and the hammer tip.
Let me hammer in the frets and report back on the tuning part.
I probably paste in a patch on the center portion and see how the response graph change.

Sen

[Trevor Gore]

Now that you have posted your pictures,It does look like you have taken the centre down too far though.

Agreed!

The book gives directions for a steel string live back guitar, where the T(1,1)2 is targeted for 170Hz or 180Hz. For a 4 semitone separation, this implies a T(1,1)3 of 214Hz or 226Hz, more or less the vicinity you are in. However, for a classical guitar where a T(1,1)2 of ~190Hz is preferable, the back needs to be no lower than ~240Hz to be certain of avoiding the "split peak" effect.

Sen, first stop thinking about graphs too much and fret it, see how it sounds. That's all that matters in the end

Agreed, again.

I still would be stiffening the back, but it will be one of the best learning experiences you will have, hearing the before and after differences.

[Nick Payne]

Jeff, I/m still reading the gore/gilet book .What meter or tester do you use to measure the live or inactive back frequency with ??thanks.

I just set my Zoom H2 to record and tap the top a few times with a felt-headed stick from a xylophone. Then I load the sound file into Audacity, truncate it down to the time period covering the taps, and tell Audacity to plot the spectrum. As you move the mouse pointer over the resultant graph, Audacity automatically jumps the cursor to the nearest peak and tells you its frequency.

[senunkan]

Here is a side profile of the guitar.
You can see that it is tapered in the front and at the back.

Agreed with the learning experience part, I certainly will be doing so after I finishing with the fretting.
It would be a great learning experience.
Thanks to all for the comments and guidance.
I would be reporting back soon maybe with sound clips of before and after.

As for recording the frequency response, I simply use a USB microphone (MXL 007) and record using audacity itself
There I can straightaway plot the frequency response graph.

[senunkan]

I thought I just report back what I have done.
I glued a 3mm spruce patch onto the central section and measure the resonance again...
Well not much changes. Top was still G 190 and Back was A 224.
I strung it up and it sounded pretty nice.
So I thought I just stop at that.
One thing I did notice when I play the bass strings, the back is really active as I can feel the vibration on my thigh.
Here are some sound clips

http://dl.dropbox.com/u/17856218/sengoh_g%232_acon_20120423_2_afterpatch.mp3

http://dl.dropbox.com/u/178http://dl.dropbox.com/u/17856218/sengoh_g%232_lacatedral1_20120423_1.mp356218/sengoh_g%232_lacatedral1_20120423_1.mp3

http://dl.dropbox.com/u/17856218/sengoh_g%232_lacatedral2_20120423_1.mp3