Taptuning and tonewoods

[reb0964]

I've been told by some that tap tuning tops and such isnt really what its cracked up to be....and i dont know how you could really do this and expect it to stay the same when you did tune it to a certain key.....maybe im wrong,,,and i'm not arguing this,,,i was just thinking about this way of looking at it,,,,maybe some of you agree,

First off,,,if you use tonewood for the top,,,say the piece is glued up and the size is estimated 12 x 16, you hold this up to your ear and tap different places to find the right nodes...once this is located,,,you have to then cut the top shape from this which loses a percentage of the glued up tonewood,,,which has already changed the sound of the board by decreasing the size,,,then,,,,carving and shaping it is eliminating more wood changing the tone again ..once this is done,,,adding tone bars which are glued to the top changing even still the sound,,,then supposing you shape the tone bars to get the desired key..your then gluing the top to the sides, the neck on,,the fingerboard extension,,,then the back,,,which has now some what stiffened the plate to a degree and would think this once piece of tonewood you held up taping to find nodes and shaping to this key,,,has now been changed by the assembly process,,,so wouldnt this all change the way of looking at the tap tuning theory being now the mandolin is complete,,,and even the finishing process and stringing it up would cause the tuning process of the top and backs together to become a different tone because of the pressure of the bridge , strings against the top.....Just wondering if anyone else has thought about this in such a way.....,,,tonewood for tops,,,,is it really that much difference in the tightness of the grain compared to those with wider grain pattern that you could actully hear the difference by ear?http://www.mandolincafe.net/iB_html/non-cgi/emoticons/rock.gif?

[markishandsome]

I don't know much about tap tuning, but tap punctuation (....... ,,,,,,,) is probably unnecessary.

[Dave Cohen]

From the uncarved, joined plate to the carved plate with soundholes cut out, there is some similarity of the mode shapes and nodal patterns. Even gluing the braces on doesn't change the basic mode shapes and nodal patterns. The frequencies change every time you remove wood or add something to the plate, but you are looking at modes that are at least similar. Once you glue the parts together to make a mandolin soundbox, the mode shapes and nodal patterns are completely different.

I followed the peak frequencies through the carving and assembly process in my last batch of mandolins with the fft program. I can show you the results, if you like. There are also some good pictures of rectangular free-plate modes in the Fletcher & Rossing text. You are welcome to look at and discuss those if you like. Those modes will be at least similar until you start gluing things together.

http://www.erols.com/judcohen

[grandmainger]

If I remember correctly, there was a thread a little while back (by HoGo?) where the poster gave links to "recordings" of his mandolin plates as he was shaping them, kind of like a tap-tuning diary... Anyone has it bookmarked?

[HoGo]

Reb 0964, OK, after all the talk you can realize that you don't know what the pitch of the parts of the finished instrument should be. I have asked myself a question for many years if there is a certain tuning of the parts that will make it sound best? I used to think the answer was definately yes, but after I re-topped two mandolins (one of them was my #1 the other was made of plates that I carved) I found out that even parts that are tuned completely differently from original can produce equally good sounding(though different) instrument.

That my old thread is probably still in the archives, search for it. The MP3's are still uploaded in my account.
Actually it was complete white mandolin, not just plates. The tuning topic if far more complicated then most people realize. Mostly because the Siminoff writings, which I consider waste of paper in his books. He made people think they just carve until their tuner will hear what he told and the instrument will sound great. That's completely wrong.
There are more variables than just the tap tones. I have background in Math and IT and this is like finding minimum of a function of sveral variables. If you move just in one variable you will most likely miss the minimum area. You need to control as many variables as possible to gain control over tone. This is certainly not fully possible, as there are pitches(there are more tap tones than just two), weigths, stiffnesses, material combinations etc. that would need to be observed. And those variables are interdependent (i.g. change in thickness will change some pitches)
I bet that even strongest computer loaded with physic an math models cannot do this work.
The good news is that our brain IS better at this than any computer and it will derive the knowledge from our attempts (of course some folks will be faster at this) if we observe carefully what we do and evaluate the result.
There are some things that we can do intentionally (like my outside tuning), but they cannot compensate for large error in any of the variables. It's just fine tuning.
And one more good news is that there is not such consensus among mandolin players about what makes perfect sounding instrument as is among violin players, so the target is much wider especially for beginning maker.
Just my $0.02