Mujitsu and Tairaku's Shakuhachi BBQ

ABRAXAS wrote:

I may be too optimistic expecting a concise ready-made answer to this question.

I've hit the search function and various free instructions online, but I've either missed it or didn't recognize the direct answer to this question:

At what point does bore width effect hole placement, how, and how is it calculated?

[I know you're gonna hate this..., but you DID ask.]

Have you done any poking around in navaching.com?

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

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

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

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

Note: Not all of this is directly germaine to the relationship between bore size and hole placement. Some interpolation may be required.

You are going to hate this answer, but a lot of it is developing intuition after making a few dozen of them...

Hole placement depends on hole size, but is almost independent of bore size. You can copy the hole sizes and placements of your favorite flute and they should be in the ballpark for any reasonable bore configuration.

Toby

Ok, so basically earball it?

Yes, I was curious, even in general terms, at or around what bore width does it start to become a factor.

I'll see how it goes and post more questions as they arise.

ABRAXAS wrote:

Ok, so basically earball it?

Yes, I was curious, even in general terms, at or around what bore width does it start to become a factor.

I'll see how it goes and post more questions as they arise.

Jim,

What I've experienced is that when I move to wider bore shakuhachi around 3.5 cm (interior diameter) or so at the top, changes need to be made to the hole locations. The first few holes (starting from the bottom) are pretty close to the hole locations found on conventional bore shakuhachi. The higher holes, especially hole four and five (thumb hole) need to be moved a little closer to the blowing end. Exactly at what width it becomes a factor is a matter of feel for me so I'm afraid I can't be helpful with a formula or a clearer road map.

These hole location differences are consistent with wide bore shakuhachi of Gudo Ishibashi.

Mujitsu wrote:

What I've experienced is that when I move to wider bore shakuhachi around 3.5 cm (interior diameter) or so at the top, changes need to be made to the hole locations.

A quick Google search puts it at 3.4415926535897932384626434...give or take.

Thanks to the flute makers for chiming in on this thread. These are the conversations that will inspire new makers and development! I wanted to comment on what struck me while reading the variety of responses.

One of the things I love about shakuhachi making is that there are so many ways to go about it. Every maker is unique in the way he/she approaches this marriage of art and science. It's enjoyable to see these unique differences developed from honest, personal endeavor. What a mystery. And, what a fascinating way to practice being ourselves!

Ken


And Ed ~ Google! Now I know why I've been a little "off" all these years!

It is also fun because most of my flutes were made by Perry, Ken and Jon!

I get the feeling here that there is a relationship between bore width and hole width, though we, or Jim initially, approached this as a relationship between bore width and hole distance, ore placement. As Perry notes, he needs to make the hole closer because the pitch is usually flat, but perhaps that is because the hole is still only 10mm rather that say 15mm, which may well be in pitch, but too large for a finger to cover. So, the regular calculation for hole placement would work until the finger hole gets too big, then the adjustment has to be applied.
if there is anything in this, then as a bore narrowed the finger hole should also narrow, or moved further away from the top end.

I have a couple of 'clients' who have particularly narrow fingers that almost can't cover an 8mm hole, and also have relatively shorter fingers, This looks all the more interesting.

Now, what did ken say about hole size and placement on the Taimu's ? 

Kel.

Ken, yes, I can do that sometimes also !

However, i think we are in the same ballpark, though I have not made many lon or wide bore flutes, because I am only just approaching the blowing strength to actually play them.
so it is interesting to me to read your notes on your wide bore  models.

I like a 10.5 fingerhole to start with as it seems to me this gives a good initial volume, then I work from that depending on the tuning adjustment and tone adjustment I think the flute needs to balance it. My flutes are mainly between 1.6 and 2.3 and 20-25mm bbore at the top end.

And as you say not a lot of shifting from the normal calculations.

But it appears here to me that we may be looking at a fundamental equation, that as the bore widens, so the 'vibratory' relationship to the hole diameter becomes more apparent. You, or we, then need to raise the hole location to keep the pitch tuned, i.e. if the hole was 20-25mm dia. it may still be in pitch but obviously too large.

Also, when you mention your 'one octave' flute, I assume this is due to the aspect ratio being so far off the ideal for octave balance that the upper octaves are disregarded in these flutes.

There is probably more to add regarding nlarge bore bottom end diameters also.

A comment on my particular perspective when approaching my flute making.
I am blind and work solely by feel, sound and a talking tape measure. so, I can't relate to information in pictures, or looking down the bore, I visualize in my mind. But I think this may help me 'feel' what the potential of a flute may be. Strangely, I use this as an advantage, though probably regarded as a disadvantage.
I am always sticking my fingers into the ends of the flute and 'feeling the bore volume, and as I work the bore with my 'garibu' etc. I develop an image of the bore as a whole.
So, my perspective is perhaps different and this relationship discussed here regarding bore diameter and hole characteristics is actually becoming more relevant as the information grows.
That may explain why I am sometimes misunderstood, or don't respond directly to images presented.
Are we still on track ?


Kel.

There is a property of wind instruments called end correction, in which the actual length of the air column extends a certain length beyond an open side hole and thus the wavelength (and pitch) of the note is lowered from what it would be if the tube were simply cut off at the position of the hole. If you are into math here is the answer:

"The acoustical length for a particular note includes a portion which extends past the tone hole which primarily controls that note.  This is called the "open hole end correction"; it depends on a number of factors, including the diameter of the tone hole, the diameter of the bore, the distance to the next open hole, the thickness of the body wall, and the height of the pad over the hole.

If we use the symbol c for the open hole end correction, it can be calculated from:

c = (z/2) x [sqr(1 + (4/z)(t + hd)(D/d)²) -1]

where

d = diameter of tone hole in question
D = bore diameter at tone hole in question
z = distance to next open tone hole
t = depth of tone hole
h = a numerical factor accounting for the height of the pad over the hole;
      it can be taken as approximately 0.75 for an open hole with no pad,
      or 1.0 for a pad at average opening height "

This is for keyed woodwinds. For the shakuhachi you can leave off "h" since it is keyless, so the formula becomes:

c = (z/2) x [sqrt(1 + (4/z)(t )(D/d)²) -1]

or, more compactly, if we use Q to denote the square root,

c = (z/2) x (Q -1)

Continuing:

"This formula (adapted from Benade, Fundamentals of Musical Acoustics, 2nd ed., p. 450) is accurate enough to be useful as long as we stay in the low registers of the instrument's range.

If we make a proportionally small change in any of the above dimensions, we can calculate the effect on the open hole end correction, and hence the effect on the pitch of the note in question.

If we change the hole diameter (d) by a small amount, then:

(change in c) = - (change in d) x (D/d)² x (2t/d) / Q"

Speaking generally, a smaller hole increases end correction and plays flatter, and end correction is increased if the ratio of the hole diameter to the bore diameter is decreased. So when you increase the bore, you need to increase the hole diameter proportionally to maintain tuning. For example, if your bore is 20mm and your hole is 10mm and the tuning is correct, increasing the bore to 21mm would require increasing the hole diameter to 10.5mm to maintain tuning.

A much trickier point has to do with cutoff frequency, in which smaller holes reduce higher harmonics and reduce maximum sound output at high blowing pressures. In addition hole diameters are critical in the upper kan and dai-kan for achieving higher notes through cross-fingerings.


Toby

Last edited by Toby (2009-09-29 22:31:02)