3d-printed whistle head: strengthening lower octave

[Nazrax]

I've been working on making a 3d-printed tin whistle head to put on a (c)pvc pipe, and I've been making good progress. I'm happy with the tone, and I can get all the way to the top of the second octave without the sound getting breathy. However, my lower notes are too weak and want to flip into the upper octave too easily. I've already printed a couple of dozen test heads, and I'll probably print that many again before I'm done ... but there are just so many parameters to tweak ...

Windway length: 20mm. Windway height: 1.3mm. The windway (and blade) follow the curve of the pipe.

Window length is currently 4mm. I know lengthening the window can improve the first octave, but it also tends to make the sound breathier.

Window width is currently 3mm. I know that's considered extremely narrow, but I'm trying to make a really quiet whistle. Once I solve this I'm actually going to try to narrow it ever further ...

Windway radii (both roof and floor): .5mm. I only just started playing around with radii at the end of the windway, but I've read so much semi-conflicting information about them - they improve tone, they should only be used on lower whistles, they stabilize the notes, a roof radius stabilizes lower notes while a floor radius actually weakens them, ...

The height extension around the window is also a recent addition, as some sources indicate that a higher window can improve sound quality, but I've had trouble finding any real details about it.

The taper is also a new addition, based on results from WI Designer. It starts at 16mm and narrows to the cpvc bore of 12mm over a length of 10mm. Its addition made a real difference to the tone and especially the quality of the higher notes.



Any tips you can provide would be much appreciated!

[Tunborough]

In my limited experience, I'd say the 4 mm window length is too short; you aren't going to get decent performance on the lowest notes without a longer window. The narrow window width might be contributing to breathiness.

For a high D whistle, I think I'd start without a radius or bevel at the windway exit. It is easier to experiment with adding a bevel by hand after fabrication than it is to remove a bevel or radius that's already there.

A height extension around the window probably won't make much difference until you get into low whistles.

Interesting about the reverse taper in the whistle head. I would have expected that to make the tuning between the octaves worse, not better.

[RoberTunes]

If the card game "poker" could be renamed, then "Parameters" could be a good one. Every factor affects everything else (and the whistle market has some bluffers in it).
I noticed three things:
1) The taper where the tube area starts, is going to affect response/balance between high and low frequencies. Experiment.
2) You didn't mention sharpness of the blade edge. If you increase the diameter of the window to help increase lower frequency response, assuring the blade is sharp, may help if the diameter adjustment isn't much, and the current blade hasn't been sharp. In the photo/diagram, the blade edge looks to be typically narrow, but square edged. I'd sharpen that as much as it will go without getting brittle. Plastic may have it's limits.
3) Adding a three-sided wall above the window seems to greatly assist the projection of a fuller tone, and maybe even give the impression of slightly increased loudness as it might focus the release of sound. But I don't think it would be a correction for breathiness or a general poor response in the lower register. However, experiment. The three sides of the wall should be considerable; like with some high-end whistles I've seen (Copeland?), the wall around the three sides of the window is at least 4 or 5 mm high, and maybe it would help to go from there all the way up to 8mm or 1cm. Needs experimenting. On one of his YouTube whistle reviews, reviewer Nathaniel Dowell played a whistle where he added and then removed some wall material, a putty of some kind, with a height of roughly 5mm, and to my ears it made a vast improvement in the tone of the whistle, as if capturing lots of fundamentals and overtones that were otherwise mostly being unheard.

By the way, since you're in the process of designing whistles, I notice that every whistle design seems to have the windway perfectly parallel to the linear path of the tube. I've been wondering if a slight angling of air downward into the tube, like 5 degrees or so, would help strengthen the tone. I don't know if the blade would have to be altered. Has ANYONE ever experimented with that? I suppose if it would help, they'd already be doing it, but then again, they were making violins before Stradivarius started making them, and designers are not conservatives.

[Nazrax]

A standard conical-bore tin whistle starts larger at the head and gets smaller towards the bell; and something I read (somewhere ...) claimed that the taper doesn't actually have to extend the whole length of the whistle, that just putting it in the head is almost as good; so it makes intuitive sense to me that the head taper should start large and get smaller. My numbers came from experimentation with WIDesigner, though I haven't actually tried to print a small-to-large taper to see what it would sound like. I keep seeing mentions of Fajardo wedges and Boehm tapers, but it's been frustrating trying to get any real details. The closest I could find for the wedge is the Tipple-Fajardo wedge, but that's for flutes. I never did find any details on what a Boehm taper actually is. Given that you called mine a "reverse taper" I'm guessing that one or the other (or both) of those starts small and gets larger?

I finally tamed much of the breathiness when I moved the blade edge from closer to the middle of the air stream down to near the bottom, so I'll try making the window longer and see what happens.

The thickness of the blade's edge is limited by the 3d printer itself. Right now, I'm using a standard 0.4mm nozzle, so I can't print anything narrower than 0.4mm. At some point I may try switching to a 0.2mm nozzle; but I haven't yet because switching nozzles is a pain and it would double the print time. In the render the blade looks blocky, but - because it's plastic squirted out of a round hole - I expect it actually ends up slightly rounded.

That's good to know about the higher window walls; I had no idea they should be so tall.

I've seen references to adding a slope to the floor, the roof, or both; but always in a > shape to "focus" the air stream. What would be the purpose of angling the air stream?

[Narzog]

I second making the window length longer. Is the easiest way to make a whistle harder or softer blowing.

Another thing is making the windway taller if you are trying to go narrow. Tiny hole = more back pressure. More back pressure = blowing less hard is still prob faster air than if there was no back pressure. Which seems to make it feel easier to overblow.

My example of this. I have a small bore reyburn G. Which has a very narrow but tall windway, and small bore. It play amazingly. I got a used brass reyburn G which I thought would overblow harder because it has a bigger bore. But it didn't. His brass whistles have a much shorter windway. So the air efficiency was significantly better. But it actually felt like it would overblow easier, even though it had a bigger bore. Both were good, just depends on what the player wants.

Also having a short windway but really narrow will give way better air efficiency than everything else. Which sounds nice. But it will make playing it feel different than other whistles. If your quiet whistle uses the same air as a wider windway loud whistle, switching between the two will feel more natural.

I've actually put a lot of time and effort into researching and trying to 3d print whistle heads myself a while back. What are you trying to 3d print them with? To my knowledge 3d printing and mouth contact aren't overly safe. Especially if you are using a resin printer, which are generally super toxic. FDM printers have plenty of safe filaments, the issue is just all the little gaps for bacteria to grow after using it. Which is annoying because 3d printing is so close to be amazing for making whistle heads.

I notice that every whistle design seems to have the windway perfectly parallel to the linear path of the tube. I've been wondering if a slight angling of air downward into the tube, like 5 degrees or so, would help strengthen the tone.

Kerry thunderbird and Busker actually have air air angled down very slightly I believe. When you look through the windway the lip totally blocks the view, and theres no gap under the lip that you can see like on most whistles. Which they do have a very strong low end, but the yare also really easy to squeak, which generally is a con with harder blowing whistles. These seem to be the most extreme at this. so could be related. I think its mostly that you cant see any light under the lip though.

[Nazrax]

My goal is to make a really quiet whistle for my ears only, so I'm trying to see just how small I can get anything related to volume - and my understanding is that windway height, window width, and hole size are the main contributing factors to volume.

I'm not so much concerned with how hard it is to overblow - I know these whistles will probably be prone to that (and I've considered adding extra windways which exit to the sides so I don't mess with the actual whistle sound). The problem is that the low notes end up feeling weaker than the higher notes in the lower octave - they just want to flip too easily. The air efficiency is amazing - I often have to stop to breathe out before I take another breath because I ran out of oxygen, not out of air!

On examination, I realized that my last attempt was extra-flawed - a redesign in the head introduced a bug and the window ended up even narrower than I'd intended for it to be. Since I'd changed a couple of other things at the same time, that bug ended up invalidating a couple of heads' worth of tests ...

I'm using an FDM printer with PLA. It's not something I'd eat off of, but given the minimal contact I haven't been too concerned about other aspects (I don't know, maybe I should be ...). I actually got a heat gun a while back to smooth out my prints, though I never got around to trying it out. I could probably tape over most of the head then give the mouthpiece a couple of passes to smooth out the FDM ridges.

[hans]

For a 12mm bore 4mm window length would be about right. On my 12mm bore high D (narrow bore design) I got a window 7mm wide and 3.5mm long. But looking at your image, I see that the top of the windway exit is aligned with the bottom (the block). I always let the block intrude a little into the window, about 0.5mm for the high D, and have it slightly chamfered. But I never chamfer the top exit of the windway, just the bottom. Another thing nobody mentioned: I find it very important that the windway (bottom, sides, roof) is really really smooth, the smoother the better. I think this helps with condensation problems, but, more importantly, it helps generating really quiet tones. I find smoothness on all parts of the window, and the tone holes, quite important. Raising the window walls by a millimeter on your design may also aid the strength of bottom end notes.

I don't know what to make of the extreme opposite taper in the head bore in your design. Making the bore at the head narrower makes some sense, but not the opposite. The Overton design achieves that by having the tube pressed square at the head. I myself use a small piece of insert tubing to restrict the bore just below the window. This in order to bring the second octave top end notes in line with the first octave.

[Tunborough]

A standard conical-bore tin whistle starts larger at the head and gets smaller towards the bell; and something I read (somewhere ...) claimed that the taper doesn't actually have to extend the whole length of the whistle, that just putting it in the head is almost as good; so it makes intuitive sense to me that the head taper should start large and get smaller. My numbers came from experimentation with WIDesigner, though I haven't actually tried to print a small-to-large taper to see what it would sound like. I keep seeing mentions of Fajardo wedges and Boehm tapers, but it's been frustrating trying to get any real details. The closest I could find for the wedge is the Tipple-Fajardo wedge, but that's for flutes. I never did find any details on what a Boehm taper actually is. Given that you called mine a "reverse taper" I'm guessing that one or the other (or both) of those starts small and gets larger?

In Section 22.6 of Fundamentals of Musical Acoustics, Arthur Benade discusses the options for bore profile to line up the resonance modes. If the headjoint is cylindrical, the body needs to get narrower toward the bottom end. If the body is cylindrical, the headjoint needs to get narrower toward the top end. You can find more on the Boehm headjoint at http://www.mcgee-flutes.com/Carte-on-Bo ... patent.htm. Although Boehm called it "parabolic" it's actually pretty close to conical, getting narrower as you move up the headjoint toward the cork.

I finally tamed much of the breathiness when I moved the blade edge from closer to the middle of the air stream down to near the bottom

Definitely. The image you posted suggested the bottom of the blade was lined up at or close to the bottom of the windway. I'd suggest the blade should line up a bit above the bottom of the windway, but not as high as the middle of the air stream.

The thickness of the blade's edge is limited by the 3d printer itself. Right now, I'm using a standard 0.4mm nozzle, so I can't print anything narrower than 0.4mm. At some point I may try switching to a 0.2mm nozzle; but I haven't yet because switching nozzles is a pain and it would double the print time. In the render the blade looks blocky, but - because it's plastic squirted out of a round hole - I expect it actually ends up slightly rounded.

Personally, I'm not convinced a knife edge on the blade is necessary. A rounded edge might soften the tone some, but that could suit your goal of a quiet whistle. In the organ world, the rounded edge is called Flauto Dolce.

[Nazrax]

I've made a couple of new heads so far. The first one increased the roof radius to .75mm and dropped the floor radius to .25mm, and that helped some. The second one increased the window length to 5mm. That helped more, but it also introduced some "reediness" to the tone.

There's a .1mm gap between the windway floor and the bottom of the blade.

I'd never heard of extending the block past the start of the window (there are just so many things to fiddle with!), but I'll give it a shot.

I'm definitely going to have to find a copy of Fundamentals of Musical Acoustics. Based on what I've learned so far I just can't wrap my head around where the "tipping point" is that flips the taper's direction - hopefully Fundamentals will help ...

[Nazrax]

Wow, ok, that was way over my head.

So, that section seemed to discuss the need to make the area right around the window narrower, but I don't think it touched on making the bore conical; indeed, figure 22.11 shows examples of a contracted "blowing end" with a straight bore, a conical bore getting narrower, and a conical bore getting wider.

Given that I'm dealing with a straight bore for most of the length of the instrument (please excuse the quick 'n dirty renders):



I'm currently using using option A (edit: I originally mistakenly said "B"). Should I be using B or C (or something else entirely)? WIDesigner doesn't like B at all, and it does actually say that C is the best option - though it rates the difference between A and C as less than half a cent's improvement. Or is WIDesigner giving me wrong answers (or am I using it wrong)?

[Tunborough]

Arthur Benade, Fundamentals of Musical Acoustics, https://www.amazon.com/Fundamentals-Mus ... ref=sr_1_1.

.... A classic, easy to read and still contains a lot of useful information.

Neville Fletcher and Thomas Rossing, The Physics of Musical Instruments, https://www.amazon.com/Physics-Musical- ... ref=sr_1_1.

.... Somewhat more recent, with more in-depth information and mathematics. Quite a bit pricier, but it is on sale now.

Antoine Chaigne and Jean Kergomard, Acoustics of Musical Instruments, https://www.amazon.com/Acoustics-Musica ... ref=sr_1_9.

.... I haven't read this one, it is priced out of my league, but I expect it represents close to the state of the art.

[Tunborough]

I'm currently using using option B. Should I be using A or C (or something else entirely)? WIDesigner doesn't like A at all, and it does actually say that C is the best option - though it rates the difference between B and C as less than half a cent's improvement. Or is WIDesigner giving me wrong answers (or am I using it wrong)?

That's exactly what I would expect. I got similar results, with a profile like C offering barely perceptible improvements over a profile like B. You may find the difference in diameters in B doesn't need to be much at all.

[Nazrax]

Gah, sorry, I made a typo - I meant to say I'm using A, not B (I haven't fundamentally redesigned anything since I made my original post - that head is still current).

With the "Just D5" profile, with 4 bore points, the best error factor I can manage is 237, net error .01, deviation 3.74:

Code: Select all

  0.00: 9.79
  5.91: 13.96
 20.65: 12.00
252.74: 12.00

With 3 bore points, the best I can manage is 361, net error .53, deviation 4.61:

Code: Select all

  0.00: 15.81
  9.53: 12.00
253.22: 12.00

If I try to shrink that first bore point, I get something like 7405, net error 5.99, deviation 20.87

Code: Select all

  0.00: 10
  9.53: 12.00
253.22: 12.00

I feel like I must be doing something wrong or otherwise missing something -- everyone is telling me I'm using a reverse taper, and even the sample data file with WIDesigner with "a Fajardo-style wedge under the window to improve octave balance" has the first bore point smaller -- but I can't see it ...

[Nazrax]

I decided to throw caution to the wind and make a head with a longer window (5mm), a higher wall (5mm), a larger roof radius (1mm), and some extra block length (.5mm) - and I ended up with a head with a lower octave so solid it says down there right up to the point it jumps to the third harmonic (there's a very tiny range that actually hits the second octave, but it's incredibly difficult to hit)! I guess I need to back off some of those changes ...

[Narzog]

You could do what makers do normally to adjust the space in the windway. Burkes, Reyburns, MK, Etc, all take up space by having the block on the inside continuing on the sides, and go forward as much as you need to, to adjust the tuning how you want. Taking up more space by having it longer makes the upper second octave more sharp. Having a little cave in the block or mouthpiece like in gens, feadogs, etc, will have an extra flat upper second octave. No spacer or cave will be in the middle.

Now obviously you don't have a 'block'. But you could still just make an extrusion that goes along the edges to take up space, for whatever length you want.

Not sure if theres any pros or cons to this method vs just making the whole circle inside smaller, if that makes any sense. Where the common method has no effect on the floor or roof, only the sides.

I would just start with a normal cylindrical windway and once you get the whistle playing more how you want, tweak the space inside to sharpen or flatten the second octave closer to how you want it. Then tweak it in increments to try and find the ideal breath curve for playing in tune.