Bore perturbations and register breaks?

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Peter Duggan
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Bore perturbations and register breaks?

Post by Peter Duggan »

I've long felt non-tuneable whistles have some advantages, especially when thicker-walled. Now I'm convinced of it...

My favourite alloy whistles have always delighted me for their tone, tuning and response apart from one perennial wee frustration, which is a reluctance (at some pitch/bore combinations) to break cleanly to some upper-octave notes when slurring wide leaps from the lower register. It's really important to me to be able to do this effortlessly and predictably, not just in slow tunes but at speed in reels and jigs (note the 'STT' pattern etc.), but I've not hitherto found a guaranteed way past this Achilles heel of my otherwise beloved whistles.

Tonight I was thinking about some experiments I'd done a few years back with another whistle I no longer have and it came to me; thick-walled tubes with external tuning slides and room to tune sharp can have unwanted side effects of the kind I've described, with the solution being to eliminate the bore perturbation caused by tuning to the designed pitch. Now, the whistles I'm discussing here have room to tune really quite sharp (way sharper than I'll ever need), but either push them right in or roll up a small piece of plastic film to smooth the internal head/body join and the problem all but disappears. Having tested multiple pitches and bore sizes, I'm convinced of it. How to implement the best semi-permanent fix is less clear; my preference would be to fill the unneeded tuning slide voids with short lengths of the same tube (which could be reversibly dry-fitted), but that's hampered by some of the heads sharing more than one body at different pitches and slightly-varying slide lengths. The other obvious possibility (short of commissioning/making new bodies with longer tuning slides matched to head capacity) is just sticking with the rolled-up film, but that's not risk-free with slippage potential even if carefully monitored.

So... interested (beyond my immediate issue with these whistles) in comment from makers or others with the acoustic know-how about what I've found and the likely technical reasons for it. The alloy whistle with external tuning slide is a very popular configuration, I suppose largely because it's relatively easy/inexpensive to make, but it's clearly not the best way to do tuneable with thicker walls. As a player with the experience to know what my whistles can and can't do, I have complete confidence in my observations here, but don't fully understand the science behind them.
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Re: Bore perturbations and register breaks?

Post by whistlecollector »

Out of curiosity, wouldn't inserting a sleeve tube inside the whistle just create two seams where turbulence could occur, possibly adversely affecting the results you're aiming for?
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Re: Bore perturbations and register breaks?

Post by Matt NQ »

whistlecollector wrote:Out of curiosity, wouldn't inserting a sleeve tube inside the whistle just create two seams where turbulence could occur, possibly adversely affecting the results you're aiming for?
But perhaps the size of the perturbation is the most important here? A couple of tiny ripples from the seams creating less turbulence than one large cavity?
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Re: Bore perturbations and register breaks?

Post by Peter Duggan »

whistlecollector wrote:Out of curiosity, wouldn't inserting a sleeve tube inside the whistle just create two seams where turbulence could occur, possibly adversely affecting the results you're aiming for?
It's not really a sleeve at all. With an inserted ring of bore-diameter tube, you'd essentially be filling a gap and any seams would be minimal. With the plastic film trick, the thickness of the film is slight enough to have little effect.
Matt NQ wrote:But perhaps the size of the perturbation is the most important here? A couple of tiny ripples from the seams creating less turbulence than one large cavity?
Yes, exactly.
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Re: Bore perturbations and register breaks?

Post by Tunborough »

Peter Duggan wrote:As a player with the experience to know what my whistles can and can't do, I have complete confidence in my observations here, but don't fully understand the science behind them.
When you observe a register break that isn't clean, are you hearing multiphonics (warbling) at a broader range of mouth pressures than a "clean" break, or is there something else happening between the registers?

(I don't know enough about the physics of the register break to answer your question, but I'm certainly intrigued by your observation.)
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Re: Bore perturbations and register breaks?

Post by Peter Duggan »

Tunborough wrote:When you observe a register break that isn't clean, are you hearing multiphonics (warbling) at a broader range of mouth pressures than a "clean" break, or is there something else happening between the registers?
A moment of rasping sound a bit like flutter-tonguing (or a bluesy growl?) with, yes, hints of both octaves as it either breaks more slowly than needed to the clean upper octave or in some cases refuses to go at all without excessive pressure. While I might not claim 100% correspondence between elimination of the void and clean breaks at acceptable pressure changes, I'd put it subjectively at something like 90–95%. The sticking point's more prevalent on the wider bore-to-length ratios, but even there the clean-up rate from eliminating that void is very good.

Might add that my list of non-negotiable whistle features is pretty demanding, being something like this:
  1. The full two octaves clean with no trick fingerings to get to the top.
  2. Second octave that requires neither blowing your guts out nor backing right off to play in tune.
  3. Good note-to-note tuning throughout, preferably with usable OXXOOO + OXOXXX C and not-too-flat OOOOOO C# (yes, I want the moon on a stick!).
  4. Decent tone, (mid-)volume and steadiness without too much resistance (aka 'back pressure').
  5. Crisp ornaments, articulations etc.
  6. Properly 'whistle' sound and feel (hard to define, but see 4 and 5 above).
  7. Fast, accurate register breaks on upward slurs over leaps of any size.
So it's basically got to do all of that to get my full approval, with any whistle failing on two or more points simply unacceptable to me. To give some high D examples of what I do play, my Bracker narrow-bore D meets every requirement, my Dixon DX203Ds come close and my Killarney only fails on the sharper C nat. My Bracker standard-bore D, which is in many ways my favourite of the lot, needs the tuning slide void filling to pass the slurred break test on some tunes, and the Susato one-piece (Dublin?) I normally keep in my briefcase for work is maybe not quite so well tuned throughout. So I'm fussy, yes, but I like my instruments to do exactly what I tell them without making it more awkward for me.
(I don't know enough about the physics of the register break to answer your question, but I'm certainly intrigued by your observation.)
Thought you would be when you're one of the people I hoped might actually be able to tell me what's going on there!
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Re: Bore perturbations and register breaks?

Post by Tommy »

I had a Goldie Overton with a perturbation around the F# hole. It appeared that two tubes were welded togeather than the OD was machined leaving the weld inside. I think it gave strength to the lower end?
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Re: Bore perturbations and register breaks?

Post by Peter Duggan »

One thing I've been wondering about (and would like to throw into the mix) is the significance of where your void/perturbation's situated. Because there's no real reason except our possibly erroneous expectations for a whistle to have a traditionally-sited tuning slide with flute/recorder-like head length. You don't get that on cheap, plastic-headed models or Sindts/Killarneys, and I'd be interested to know whether you'd gain anything from a very short or max-length head. And there's also got to be a reason (apart from just looks) why Colin Goldie and others are machining their alloy tube into thinner tuning slides. (Less disturbance goes without saying here?)
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Re: Bore perturbations and register breaks?

Post by Tunborough »

Peter Duggan wrote:
  1. The full two octaves clean with no trick fingerings to get to the top.
For high C-nat, would OXOXXX be your standard fingering, or do you insist on OXXOOO there? Would you accept OXXOOO for high D, or does it have to be OXXXXX?

Have you asked Hans your original question about the register breaks? I'd be interested in what he has to say about clean register breaks.
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Re: Bore perturbations and register breaks?

Post by Peter Duggan »

Tunborough wrote:For high C-nat, would OXOXXX be your standard fingering,
For top C nat, yes, though I've also had whistles that like OXOOXX.
or do you insist on OXXOOO there?
For lower (middle) C nat, I like OXXOOO on whistles and OXOXXX on flutes, where OXXOOO tends to sound stuffy. It's a bonus if OXOXXX works on whistles because it tends to be even sharper than OXXOOO, but having both fingerings working does ease playing the same tunes on whistles and flutes. I prefer not to have to go to OXXXOO or OXXXOX.
Would you accept OXXOOO for high D, or does it have to be OXXXXX?
I regard OXXOOO as standard, but will use OXXXXX or even XXXOOO/XXXXXX (with T1 leaking) if necessary to bring it into tune. OXXOOO works on most whistles I've tried.
Have you asked Hans your original question about the register breaks? I'd be interested in what he has to say about clean register breaks.
No, I haven't (partly because I've only just discovered the reason and partly because I'm not sure how to bring it up). He did spend some time working on other aspects of my standard-bore D one time I visited him, resulting in some slight improvement, but we didn't consider the tuning slide void. But I must stress this isn't just about Brackers; it's an observation that's possibly universally applicable though I'd imagine that susceptibility will also be influenced by other things like voicing etc. I've had other whistles with worse manifestations of the same thing, but haven't kept them whereas I still love my Brackers and now know how to effectively eliminate this one frustration. To which I might add that, if ordering more whistles with external tuning slides from anyone, I'd be asking for the shortest position to be only just above 440 because I just don't need the ability to tune way sharp (or flat). I rarely move my tuning slides at home, and only very slightly if out playing/recording, so wasn't joking when I said 'I've long felt non-tuneable whistles have some advantages'. Because (some?) tuning slides come at a price. Having said that, I could have used one on the Overton G I used to have because it was flat enough to steer us into slight pitch-shifting for recording. I never missed a slide on my Overton A and low D.
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Re: Bore perturbations and register breaks?

Post by Tunborough »

Well, I have found that a short expansion zone in the right spot can help balance out the octaves, much like a tapered bore or a Fajardo wedge. For example, a 1 cm section that's 2 mm larger in diameter, about 7 cm down from the window on a high D whistle, will nicely flatten the lower octave without changing the upper octave much. A constriction, on the other hand, makes it harder to balance the octaves.

This effect may have nothing to do with your observations of the register break, but they could be related. If the pitches of the two registers around the break are close to a harmonic relationship, I could see it being easier to sustain elements of both registers at the same time over a wider range of blowing pressures ... a less clean register break.

The only tapered-bore fipple flutes I have to hand are a Clark and a couple of cheap recorders. On all three, it's pretty easy to sustain the warble or burble in the middle of the register break. Not sure if this is much support for my hypothesis. What do you observe with tapered bores?

Thanks for the confirmation of the high C-nat and D fingerings.
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Re: Bore perturbations and register breaks?

Post by Peter Duggan »

Tunborough wrote:Well, I have found that a short expansion zone in the right spot can help balance out the octaves, much like a tapered bore or a Fajardo wedge. For example, a 1 cm section that's 2 mm larger in diameter, about 7 cm down from the window on a high D whistle, will nicely flatten the lower octave without changing the upper octave much. A constriction, on the other hand, makes it harder to balance the octaves.
Interesting (because that 7cm's not far below the voids left by my high D tuning slides). But I also remember Hans was able to improve the low D head by constricting the bore further up, where I think the original problem was a flat and/or reluctant top end.
The only tapered-bore fipple flutes I have to hand are a Clark and a couple of cheap recorders. On all three, it's pretty easy to sustain the warble or burble in the middle of the register break. Not sure if this is much support for my hypothesis. What do you observe with tapered bores?
Since I sold my Shaws, the only tapered-bore whistle I still have is an old Clarke C I never play. I can make it growl between octaves by expressly trying for that, but it doesn't happen in normal playing. But the same can probably be said for any whistle, where I can find the sticking point even on my Killarney if I really want to. So it's not so much about whether you can find the growl as whether it happens in normal playing at what I'd consider normal pressure changes, in which case the answer for the Killarney, Dixon DX203Ds and Bracker narrow-bore has to be never because they break (if you'll pardon the expression!) clean as a whistle.

I don't think it's ever an issue with recorders, where you've got the pinched thumb hole acting as a register speaker.
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Re: Bore perturbations and register breaks?

Post by waltsweet »

If you want science, the explanation is found in Rayleigh's Rules, applied by Stephen Fox:
http://www.sfoxclarinets.com/baclac_art.htm
Yes, the exact location is important. I call these "critical stations." When the tenon is pulled out of the mortise at the joint, a cavity is formed. I've seen flutes where the joint and its cavity, because of the position, will stretch the octave on F# and G. And from what you've written, this misalignment will make some notes difficult (misalignment always does). The tuning spaces are a good idea. They don't have to fit snugly: what counts is taking up the extra volume; having multiple spacers is OK, too. With that in mind, maybe you can find o-rings to fit inside the mortise, and just vary the number of them used. A metal tuning slide is of course the way to go, because typical wall thickness is 0.015" , and this results in a much smaller cavity. I've been working with a 16mm bore (0.630") and a change of 0.005" in the diameter is noticeable regarding playability.
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Re: Bore perturbations and register breaks?

Post by Peter Duggan »

Thanks, Walt... that's useful!

One thing I might still have to get my head round here is what difference in behaviour to expect from clarinets overblowing to the twelfth and whistles to the octave, but full understanding there's probably not critical when I already have my own empirical view of the problem and how to cure it.

Think the short rings of bore-diameter tube would still be my ideal fillers if I can cut them neat enough. In which case it shouldn't even matter that the void is shorter in, for example, my Db body than my D, because the tenons are very thinly corked so uncorked rings of different lengths should drop in and out easily enough.

Just to clarify one small point about what I've said (which I'm sure you get already), these notes are not 'difficult' as such (in which case I wouldn't give house room to the whistles let alone describe them as 'favourites')... just in certain, wide-ranging, upward slurs.
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Re: Bore perturbations and register breaks?

Post by Tunborough »

Not having a tunable whistle here, I tried a mock-up: whistle head, extension tube, and an outside sleeve between them. I didn't notice a change in the quality of the register break when there was a gap between the tubes. Walt's observation suggests it matters where the void sits in the tube.

Have you noticed the tuning slide affecting the register break of some notes more than others?
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