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Hello all --

Here's a link to an audio clip of me bangin on my latest top. It's a sitka GA shape that's going on cocobolo back and sides. The braces are at an intermediate stage of shaping, and I am hoping you might be so kind as to lend me your ears and tell me what you're hearing, ie, tone, resonance, voices from beyond, etc.

http://sculptorjones.com/artwork/631452.html

I don't think it's too far from being done, though audacity is indicating a bump around 222hz or A3. When I've done this previously, most suggested a goal of around G3, or 200hz. Anyway, I appreciate any feedback or thoughts you might be willing to share.

Ken

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Mountain Song Guitars www.mountainsongguitars.com

I might be a newbie here, but from all I've read about tap tuning (and instrument making in general), you want to use a tap hammer that has a light head and is made of felt for the striking surface. Also you want to tune the soundboard while it is held around the perimeter, either mounted to the instrument or to a frame that mimics how it will be held to the instrument.

I have tapped both ways and the sonic signature is quite different between mounted and unmounted.

Lastly the soundboard will respond in an asymmetric way depending on where it is tapped. Thus tone-bars will represent different tones from one another. The back however is tuned to a single tone.

That said, it's not surprising you are getting different tones at different locations of the soundboard. Also how is it being supported? A soundboard will be supported around the edge, thus causing it to vibrate in a particular way. When supported at top and bottom, for example, it will vibrate more with waves from top to bottom that left to right. I think to understand the final tonal effect of the braces, it needs to be pretty darn close to its final support setting, which means rigidly held edges.

Just my opinion, but it is based upon a lot of reading and mathematical study of the making of instruments these past few years.

Joe --

Thanks for your response. I use a small mallet salvaged from an old upright piano, actually not a piano hammer, but a tiny little mallet thingy, which I've covered with felt.

Regarding support, I've recorded tap tones several different ways, all of which are some variant on the down and dirty "hold-it-with-thumb-and-forefinger" approach, which seems to be a pretty popular, albeit empirical technique. That's really all I'm after here, is an autonomous reference point by which I can shave some braces, pick up the top, tap it, and ascertain something about whether or not I'm headed in the right direction.

In the past, I've done comparisons by holding the top at the bass side upper bout between the X-brace and transverse brace, and it does indeed affect the tone. From what I could tell, it muted much of the lower fundamental, but otherwise sounded the same tone. Therefore, I decided to start doing my comparisons by supporting the top in the most unobtrusive way I can easily achieve, so I can try to use the additional audio info in some productive way, hence holding it at the transverse brace truss rod hole.

In other words, I'm not really trying to understand the final tonal effect of the braces, but rather what a given top tone will contribute to the final tone of the guitar, based on data drawn from previous builds, at similar stages.

At this point, it's really just interesting comparing the audio data, but hopefully, after a dozen or so more builds, I'll actually be able to apply the gathered data in a meaningful way.

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Mountain Song Guitars www.mountainsongguitars.com

OK, but if you do get the top to intonate at frequencies that are in tune doesn't that suggest a better sounding instrument when all buttoned up?

I guess it is useful information to tap before putting together as then you'll be able to start aiming for a more accurate build before the top is attached, but ultimately isn't the goal to get the top ringing out a pure tone? Perhaps I'm putting to much value into the frequency of the vibration of the top.

Well, that's a good question, and one I'm not really qualified to answer, as I've heard both ends of the spectrum on this -- one end says that achieving the same tone all around the top is the goal, and others assert that the opposite is more desirable, that the guitar will have a more balanced response if the top is tuned differently in different areas. Being a relative novice builder, I wouldn't begin to claim that I know the answer to this, but I would love to hear some other folks' opinions.

I should mention that when I analyze individual taps with audacity, I get generally the same audio spectrum all over the top, and I don't think it's due to my "skill" in brace carving. Maybe it's just the limitations of the recording technique and/or software.

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Mountain Song Guitars www.mountainsongguitars.com

Well, I just checked again, holding the plate between the X-brace and transverse brace, and I divided the top into three sections -- upper bout, lower bout and bridge plate areas. The spectrum analysis was considerably different for each area..., so I retract my statement at the end of my last post.

So, it will be interesting to see if I can bring those areas more in line with one another by selectively shaving their respective braces. Will post results for anyone who may be interested.

K

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Mountain Song Guitars www.mountainsongguitars.com

I would be interested. I'm studying like crazy. I want to apply my years of woodworking to building instruments and doing so in a correct way. Thus I am studying and reading extensively.

I think everyone would agree that a lot is science, but mostly it comes down to the art of putting it all together and the skill of the crafts-person applying the techniques.

I've put a new recording up of the sitka top in it's final state before attaching the top. Not really sure what to make of it, but it does seem to have a nice deep ring to it. The plate seems fairly stiff, and I've left it at .110" so I can sand the perimeter some once the top is attached. As always, I welcome any thoughts or comments.

http://sculptorjones.com/artwork/634136.html

Ken

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Mountain Song Guitars www.mountainsongguitars.com

Have you used Audacity to see the spectrum??

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http://www.youtube.com/watch?v=oEa8PkjO6_I

Yes, I'm interested