RTTA and Cork Position

Irish Flute
1

I wanted to characterize the impact that cork position has on flute tuning, so I used RTTA to look at the tuning of a couple of flutes with the cork at 0.5 bore diameter, 1.0 bore diameter and 1.5 bore diameter. As expected, there was some variability, but pushing the cork back consistently lowered (flattened) all the notes with a greater effect on higher notes than on lower notes.

D4 was flattened 5-10 cents for each 0.5 bore diameter. D5 was flattened more than D4. The octave gap shrank between 5 and 20% in my various trials.

G4 was flattened 5-20 cents for each 0.5 bore diameters. G5 was flattened more (and relatively more than D5), and the octave gap shrank between 8 and 25% on my trials.

If anyone else is willing to experiment with their flutes and characterize the impact of moving the cork, I’d be interested to see their results.

2

Moving the cork primarily changes the relative stregnth of the different overtones or partials as you are changing the distance of the blow hole vs. the effective end of the air column (where the cork is) - the change of tuning is a secondary effect and similar to moving the slide the same distance that you moved the cork. That’s why charanga players move the cork as they pretty much only care about the extreme high notes and don’t seem to care that the first octave becomes weak.

3

While moving the cork will affect overtones it also affects tuning of higher notes much more than lower ones, and so is used to get the 3 octaves in tune. So you really need to start looking at the 3rd ocatave as well not just the first two. If you use the chromatic version of Polygraph which plots all chromatic notes through 3 1/2 octaves (G3 to C7) you’ll see big changes in the flutes 3rd octave when you move the cork in or out. Usually about 1 bore diameter (about 19mm) back from the centre of the blow hole is the position to get it all in tune, but it does vary a little. It is common for Irish Flute players to push it out a bit (eg 22mm) strengthening the tone of the lowest notes, at the expense of flattening the top notes. Too far out and you’ll start driving the upper 2nd octave notes flat.

cheers
Graeme

4

Call me a slacker but since I never use the 3rd octave I’m not as interested in the effect there :slight_smile:. My interest is in quantifying the impact of moving the cork as a way of understanding what options are available for tuning a flute.

5

I did a study on this some time back, see:

http://www.mcgee-flutes.com/Stopper.html

and got this result:

Now it may vary from flute to flute, and RTTA is likely to be a better way to find it than me sitting in front of a tuner, so you’re not wasting your time. But hopefully the above will help you recognise it when you see it.

What RTTA (or a tuner) won’t tell you is the effect on tone quality on the lower octaves. We need RTFFTA for that. Graeme …

Terry

6

Simply set the cork in a position such that a smooth octave jump, up or down, can be made with the least amount of embouchure change. Yup, that’s all there is to it. That is, when the cork is in just the right place, octave transitions are at their easiest, just follow your ears.

Remember, of course, to first “warm up” the flute, to playing temperature, before making any head joint cork adjustment.

Please, get it set to the right place, but don’t worry about getting it perfect, as your embouchure will easily take care of any details, piece of cake.

Edit: I do, however, appreciate the efforts made to develop the RTTA program, especially as it potentially could lead to even better flutes.

In that regard, my thanks to Graeme, and to Terry McGee.

:slight_smile:

7

I agree with Corks position on this issue.

cheers
Graeme

8

Thank you, Graeme, and I am glad to see that we could have some common ground, my friend.

:slight_smile:

9

I think that many of us will sleep easier tonight with the thought that Cork knows cork positioning!

Dear Cork, this would have been a horrible thing for you to botch. :laughing:

10

Cork
While there are things we will disagree on, I’ll bet there’s lots of stuff we do agree on as well. I find that remote conversation via the internet like this forum to be a very poor method of communication. It’s very easy to misunderstand what someone else means etc etc.

To be truthful I was more making a joke about Cork’s position on the position of the cork than agreeing with you. But I do agree with you on the matter but think that sometimes with some flutes there’s a lot more to it than that.

Cheers
Graeme

11

shhh… There are many people on the board that have never moved their cork and think that it is part of some dark art that should only be practiced by a maker.

12

Do you find it odd that you saw no impact in the lowest octave? Did you retune the flute to put the low D in tune after moving the stopper? Intuitively I’d expect to see a delta proportional to the frequency of the played note (as your graph roughly shows from D5+).

Care to repeat your experiment using RTTA and see if it reveals any shift in the lower notes?

13

Are you suggesting that the octave jumps are easiest when the octave spacing is correct? Thinking about harmonics that seems reasonable (although I’m no acoustic engineer). Of course, it is hard to be subjective about when the octave jump is easiest. What note do you tune your octave jump to?

Of course, I’m really more interested in how the selection of cork position plays into the whole mix of variables that affect a flute’s tuning, but if your conjecture about octave jumps is correct it seems like a good rule of thumb for adjusting the cork on an existing flute.

14

@ srt19170, and to whom it may concern,

Re: Head joint cork placement

It’s not a matter of tuning octave jumps to any particular tone, rather, it’s a matter of setting the cork such that the average jump is at its easiest. Unfortunately, and for reasons, there simply may have never been a flute made which could have “perfect” internal tuning, meaning that a player necessarily must make slight tuning compensations, at the embouchure. So, it’s necessary to set the cork for an average of all of the tones, and their octave jumps, without attempting to set it to a “perfect” position, relative to any one tone.

There is a theoretically correct position, but in practice a cork may need to be shifted slightly away from that position, one way or the other.

Go ahead. Move the cork around a bit. It won’t hurt the flute, and although it might take a while to find just where the overall best position of the cork could be, you’ll be that much better of a flute player for knowing just where the cork should be for your particular flute. Let me add, however, that it’s simply better to not adjust the cork unless you either know, or are at least convinced, that any tuning issues are, or could be, a fault of the flute and not of your own, for beyond setting a cork to its theoretically correct position (which, BTW, generally works quite well), cork adjustment simply is a more advanced skill, very much dependent on the abilities of the player.

BTW, flutes which remain in regular use generally have a cork which stays in place, but if not kept in regular use, a cork can dry out, sometimes causing the cork to shrink slightly, and thereby to become loose, and likely to shift in position. Therefore, regular practice is good for the player, and for the flute.

I wholeheartedly support the RTTA program, less for how it could serve a player today, and more for the potential it could have to improve the internal tuning of flutes, in the future.

:slight_smile:

15

I expect there would be some effect lower, but it would be too small to measure reliably, certainly with a tuner, and probably also with RTTA. I’m talking around 5 cents. The sharpening effect we get from the stopper chamber resonance is quite tightly tuned and lives up in the third register. You have to do something pretty dramatic to even get it down into the 2nd register. The maximum effect on tuning in the third octave is only about 25 cents, so I’d expect to see much less further down.

Care to repeat your experiment using RTTA and see if it reveals any shift in the lower notes?

I should. Just a bit busy at the moment!

A difficulty with this test is making sure you use the same embouchure as you did before moving the stopper. Even if you have a screw stopper and somebody else to adjust it while you keep playing, it would be hard to be sure! I guess repeating the test a number of times and see if you always get the same result would be a way forward.

Terry

16

Thank you, Cork.
It’s good to read didactical explanations like this, because some beginners like me probably didn’t even know what the heck is the cork for and may be shy to ask (is it the same as the stopper? Is it that “thing” in the headjoint, between the embouchure hole and the cap? :blush: ) . I’ve been playing for only around 2 years and I wouldn’t dare to tinker with it at the moment, since most of the problems should be resulting from my bad embouchure.

17

But a very good thing is to check from time to time that it’s in a plausible place, even if not the best place for you. You won’t be far wrong if it’s somewhere near 19mm (3/4") from the centre of the embouchure hole.

But if you find your topmost notes are flat, try moving it in.

And if you feel your bottom octave is thin, try moving it out.

Terry

18

Does one need any special tool to do it? :blush:

19

For an Irish type flute (not a Boehm type flute), try a wood dowel, one which is just slightly smaller in diameter than the cork. First, however, make a note of just where the face of the cork is, especially in the case of a “frozen” cork, which might move a lot more than expected when it breaks loose!

Avoid using anything of “small” diameter, such as a thin cleaning rod, for instance, as it could damage the cork.