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 Post subject: Adjusting the head cork
PostPosted: Fri Feb 23, 2018 5:41 pm 
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I have a flute that plays a bit flat on the lowest three notes and a bit sharp on the G-A-B in the upper register—not a whole lot in either direction, but just enough. Is that something that can be fixed by adjusting the head cork? And, if so, which way should I move it? Or is it more apt to be operator error whose embouchure or air stream should be adjusted?

Thanks and best wishes.

Steve

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PostPosted: Fri Feb 23, 2018 7:05 pm 
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When the cork needs to be adjusted, ussually all notes are flat or sharp. Does that happens in both octaves?


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PostPosted: Fri Feb 23, 2018 7:55 pm 
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My understanding (and I'm no expert) is that cork adjustments are only for making very fine-tuned adjustments for the upper octave relative to the lower one. And if you're a relative beginner like me, you should just follow the flute marker's advice for where to set the cork and not use it for upper/lower octave adjustment. Because this is something you're probably not doing correctly with embouchure.

That said, I do have my cork adjusted just a hair to the left (towards the end cap) more than the theoretically best position. Just a tiny bit. It works for me, in getting the upper octave in tune with the lower one, but everyone's flute is different.

One piece of advice I read here recently is to listen to the sound of the low G and high octave G. If they sound the same, your cork is in a good position. I like this, because it's a good reality check that keeps me from obsessing over the cork position. :)


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PostPosted: Sat Feb 24, 2018 12:01 am 
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Steve,
Time to haul this out again:

viewtopic.php?f=2&t=60057&p=787462&hilit=cork+position#p787462

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PostPosted: Sat Feb 24, 2018 8:01 am 
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Thanks all. And Kevin, that is what I was after—for some reason I didn't locate it with a search but I vaguely remembered reading that way back when...

Best wishes.

Steve

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~ Antoine Mahaut, 1759 in a tutor for playing the transverse flute ~


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PostPosted: Sat Feb 24, 2018 10:29 am 
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Here is my philosophy for adjusting the head cork or plug - and a peek into my tuning and voicing style:

I learned early on in my career from observation that the position of the head joint cork or plug on these conically bored flutes should be set to where the tone quality is best. On my flutes this ends up being a deeper setting (up to 25mm) than what is considered the standard setting on Modern flutes (19mm).

19th century authors on the flute such as Rockstro considered the ideal position (center of embouchure to face of the plug) equal to the bore diameter, which has remained the orthodoxy since. But even he mentioned better tone can be had in the 1st octave bottom notes by moving the cork farther out.

In general moving the cork out flattens the 2nd octave with respect to the first while making the first easier to play and richer in tone. Moving it in destroys the bottom and makes the 2nd octave and higher octaves easier to play. The Cuban Charanga players take this practice to an extreme and move the cork so that it is 3.7mm (on average) away from the edge of the embouchure, which they have commonly enlarged. This allows playing in the 3rd and 4th registers but the bottom registers are trashed. Its no problem as they never use these lower registers!

On a modern flute made in metal with its cylindrical bore and large tone holes there is no way to adjust except by the compromise position of the cork. On our tapered wooden flutes however, we have the wall thickness and generally smaller holes which allow us to work with some additional parameters. I never adopted the orthodoxy and have always used a farther out position for the plugs on my flutes to benefit tone quality. I suspect this was also the case for some of the 19th century makers such as Boosey, Prowse and Rudall.

If you set your plug at 19mm after cleaning or oiling the bore, you may have simply moved it away from its "factory" setting.

When tuning up a flute body, I first voice the embouchure or used an already voiced head joint, and size each of the holes to pitch in the 1st octave by first drilling these undersized and then reaming each individually to pitch. Increased diameter = sharper. The hole size seems to control the 1st octave pitch and as long as the diameter isn't increased by additional tasks (undercutting and finishing the surfaces) the 1st octave pitches remain stable. For the bottom D the pitch can be tuned by keeping a strict attention to sounding length (521 on my Standard flute). It can also be reamed from the end on a 6 hole flute to sharpen if necessary and on some bores this improves the tone. If all else fails, length can be removed from the bottom end of the foot joint. I frequently have to do this when prototyping. On a flute with an extended foot joint, increasing the size of the two vent holes will have a similar effect but not be as effective. In this case the scaling may be off. This flat bottom D phenomenon could be solved by simply moving the foot joint up. But this means shortening the middle joint (or lower middle joint on a 4 piece flute) and recutting the tenon. Sometimes the tenon will be a few mm shorter than the corresponding socket. If so, making the tenon use all of that socket length will make a difference.

At this point the 2nd octave will play flat, especially in the upper notes of the scale which are more sensitive. The 2nd octave is tuned by undercutting each hole to the degree needed. The more undercutting the sharper the 2nd octave pitch. Smaller holes (E and A) will be more sensitive to these changes than the larger holes. The amount of wall thickness will also have a bearing on this. Thinner walls seem to tune in with less undercutting sometimes. Undercutting also improves the overall tone quality, evenness and response of the flute.

Note that you should rely on your hearing to some degree instead of an electronic tuner to determine pitches. The tuners hear a flute in a way that is different than humans. What will look in pitch in the 2nd octave will actually sound flat to my ears. The 2nd octave should generally look 20-30 cents sharp. Also, the upper notes of the scale (B, C# especially) should also look sharp. People sometimes contact me saying their flutes are out of tune based on their tuners. I ask them if they have a modern flute and many do - and have them play that into the tuner. They discover a similar degree of deviations from pitch on the tuner and are surprised.

We should be playing for our ears, not some arbitrary electronic device!

So if on a flute that is otherwise working well but some notes seem sharp in the 2nd octave, there are some strategies that can be used. Pushing the plug out can bring down these higher notes and commonly increase the resonance of the instrument. But if these notes remain sharp in the 2nd octave, they can be adjusted down by careful application of resin to fill in some of the undercutting. Hot Stuff Superglue works well for this. I pour some onto a piece of plastic, and then use a bamboo skewer to pick some of it up and paint the inside wall of the finger hole and build it up in layers, testing as I go (and being careful not to glue my fingers to the finger holes!).

Just some practicalities for other makers: for undercutting tone holes some sandpaper (Garnet A120) wrapped around a narrow round file works. In my workshop I do the final shaping of the undercutting this way. But to rough these to shape I use a reverse tapered bit (approx 1/4" diam) at the end of a #45 Foredom handpiece for the larger holes and a 1/8" cylindrical bit for the smaller holes. Some holes respond better with a straight-sided undercut versus one that flares towards the bore. There is no general rule as one works with different bore shapes. Its best learned by iterative practice - tuning and voicing literally hundreds of flutes!

Casey

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PostPosted: Wed Feb 28, 2018 11:45 am 
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Casey Burns wrote:
Here is my philosophy for adjusting the head cork or plug - and a peek into my tuning and voicing style:
[...]


Thanks for the info, Casey!


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PostPosted: Wed Feb 28, 2018 4:19 pm 
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I have a Hudson Siccama made in the early 1850s. The screw that’s adjusts the position of RH stopper is scribed at regular intervals as an aid to positioning. Interestingly the maximum distance possible before one runs out of polished and scribed surface is just over 20mm. So at least this makerwas already hewing to the orthodoxy that was described about 30 years later, namely roughly equal the bore diameter.

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PostPosted: Wed Feb 28, 2018 6:44 pm 
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flutefry wrote:
I have a Hudson Siccama made in the early 1850s. The screw that’s adjusts the position of RH stopper is scribed at regular intervals as an aid to positioning. Interestingly the maximum distance possible before one runs out of polished and scribed surface is just over 20mm. So at least this makerwas already hewing to the orthodoxy that was described about 30 years later, namely roughly equal the bore diameter.

I may be misinterpreting your post here, and apologies if I am, but it seems likely that since the 1850s the cork part of the stopper will have been replaced numerous times. Replacing a cork like this typically involves shaping and cutting down a larger and longer cork, before attaching it to the screw adjuster part that threads into the crown. The length of the cork section (which is determined by where you choose to cut) will ultimately determine the position of the scribed marks for a given stopper-face to embouchure measurement. So, I would agree that whoever last replaced your cork probably subscribed to the orthodoxy, but I don't think you can really conclude much more than that unless you know the length of the flute's original cork.

This is an issue I run into frequently when restoring antique flutes -- trying to decide what length to cut the cork section before attaching it to the screw-adjustable holder/crown. I try to target a length that optimizes the performance of the flute across the lower two octaves (because my preferences are more towards ITM than classical use of these flutes) at the same time as trying to align with a scribed mark somewhere in the middle of the range. Basically, I try to optimize both the sound of the flute and the visual aesthetics of the externally visible crown/adjuster, while allowing room for adjustment in either direction. My experience in doing this a few dozen times has mirrored Casey's very closely. I find that the optimal cork-face to embouchure distance -- for my ear and my embouchure -- seems to be significantly more than the bore diameter, for most flutes. This seems to be true for the antiques I have worked on and for the flutes I make myself, and especially for those with a larger length to bore diameter ratio (for example, I've recently been working on a low Bb model, which is a very long, thick-walled, and relatively narrow bored flute).

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PostPosted: Thu Mar 01, 2018 7:57 am 
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Fair enough Paddler-I don't know if the stopper length has been altered since the Siccama was made, so I retract my observation.

Hugh

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