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Schift between otsu an kan

 
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Andre
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PostPosted: 2011-03-25, 14:23    Post subject: Schift between otsu an kan Reply with quote

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Hi Experts,
I have a 1.8, which was not in tune. With correction on the hole location and hole diameter I brought it in tune referring to the shaku8 tuner. Otsu is fine and kan is fine as well. BUT if I move from otsu to kan without changing head position, there is a shift of approx 50cent where all notes on kan are to sharp. Does anybody know this strange behaviour? How can I fix the problem?
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Itamar Foguel
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PostPosted: 2011-03-25, 21:14    Post subject: Schift between otsu an kan Reply with quote

is it a non root end shakuhachi?
Im familiar with it, i think it depends on the bore taper.
either way You can try fixing it using the spot tuning method.
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Andre
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PostPosted: 2011-03-27, 21:18    Post subject: Schift between otsu an kan Reply with quote

Hi,
its a root end. See picture.
How does it work with the spot tuning method?
http://img.xooimage.com/files60/8/7/c/dscn1054-2712fc8.jpg]
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Itamar Foguel
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PostPosted: 2011-03-28, 00:41    Post subject: Schift between otsu an kan Reply with quote

that looks like a nice flute with good nodal placement, well i can tell you to go look up on Ken's site http://shakuhachiforum.com/viewtopic.php?id=2452

but also i hope it was a good idea to move the holes, it might be something else that you could have changed to fix the tuning (spot tuning) before going drastic and moving holes.
I would say if you have the ability and cash send it to someone professional for an inspection. or try whats written in the pdf and also try searching the forum for more info if you need.

Good luck
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zakarius
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PostPosted: 2011-04-02, 04:35    Post subject: Schift between otsu an kan Reply with quote

I hope my response isn't out of place, but unless you're a relatively proficient player, there's a chance that your blowing technique can cause a lack of proper tuning on the various octaves. To rule this out, you might consider handing the flute to a pro and ask their opinion.
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Andre
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PostPosted: 2011-04-02, 14:07    Post subject: Schift between otsu an kan Reply with quote

Hi Zakarius, hi Itamar,
your reply is not too late. I already realized, that I can compensate the shift by playing mor meri in the kan register. But this is not so easy, since it also effects the sound. Nodal tuning is whith what I started with five years ago to bring the flute in tune. I discussed this topic in Mujitsus shakuhach BBQ. Finally we came to the conclusion, that the holes need to be moved, because the flute was too much out of tune. Now it is pretty nice in tune (each register on its own) but there this xxxxing shift. Maybe nodal tuning can help. Ill start a try.
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Toby
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PostPosted: 2011-04-29, 08:03    Post subject: Schift between otsu an kan Reply with quote

Mode shifts like this are almost always caused by an incorrect bore taper, and if the shift is more or less equal for all notes then it is in the upper part of the bore, which is too narrow at some point.

However it is not a simple thing to fix using trial and error. Acoustically, it could all be analyzed using W curves and Rayleigh perturbation theory, but you should basically have a cylinder from the utaguchi for ~8 cm, and then a relatively straight reverse taper to the choke point. If the taper flares like a horn it will widen the modes, making the upper modes increasingly sharp. I'll bet your dai-kan is even sharper.


Last edited by Toby on 2011-04-29, 17:08; edited 1 time in total
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Andre
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PostPosted: 2011-04-29, 08:14    Post subject: Schift between otsu an kan Reply with quote

Ohio gozeimas Toby,
thanks for your reply. I will check the bore taper, maybe I can find the narrow region. What do you mean by flares like a horn?
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Toby
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PostPosted: 2011-04-29, 16:38    Post subject: Schift between otsu an kan Reply with quote

Hi Andre,

Speaking very generally, the bore has a diameter of ~20mm at the top, and that continues down for about 7-8 cm, and then the reverse-cone starts, so that it hits around 17.5mm at the joint, and down to something like 16mm at the choke point, after which it widens back out. Have a look at this graph

http://www.navaching.com/shaku/bore.html

and you will see that the generic profile has a straight line--the cone angle does not change--it is a straight cone, not a flaring horn shape. The cone angle (if it is constant) partly determines the tuning based on hole placement and size, and has an effect on the pitch variability when blowing at different dynamics, but a straight cone theoretically preserves the harmonic relationship of the octaves. However if the cone angle increases (the diameter gets smaller faster than a straight cone), the upper modes will be flat compared to the lower, and if the cone angle decreases we get your problem--sharp kan and dai-kan.

You would do well to measure your bore and graph the result, and compare with one of the generic bore graphs which are known to at least produce ballpark tuning.

W curves consist of mapping the position of the nodes and antinodes for each higher register note along the bore, and adjusting the diameter at those positions depending on whether the notes are sharp or flat. The problem is that those adjustments will affect more than one note, depending on nodal positions, so it is a difficult and complex analysis.
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