Bore roughness and tone

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Bore roughness and tone

Post by tradlad123 »

Questions for experienced players/makers…
To what extent does bore roughness (or smoothness) influence the tone/playability or other characteristics of the sound?
As an example Delrin is probably much smoother than wood in general, and within different woods I’m assuming it varies too (to what extent it could be smoothened out).
Or, it may sound odd, but is there any benefit at all in actually not going extremely smooth?
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Re: Bore roughness and tone

Post by Conical bore »

My $.02 as a player, is that I think it's a question of the threshold where it makes a difference, and the smoothness of a well-maintained wooden flute's bore is below the threshold where it's a problem.

Swab out the flute after playing, oil it every once in a while, and the bore of a wooden flute is smooth enough to have a great tone. The smoothness isn't perfect, but it's below the threshold that would cause any major tonal issues. Otherwise everyone would be playing Delrin or glass flutes. Or metal Boehm flutes. You're more likely to notice it with a badly made wooden flute like a cheap Pakistani example where the bore is rough enough to be over the threshold, and it just doesn't sound good.

On the last question -- is there any benefit in not going extremely smooth -- I doubt there is. The flute bore is a container for a vibrating air column. The air doesn't flow along the length of the barrel and out the end, so there is no benefit in any exotic "dolphin skin" drag reduction textures. It's why Delrin flutes can still sound great. If there was any benefit to roughness in the bore, I think we'd see experiments along those lines with metal Boehm flute. As far as I know, the ideal design is still a smooth metal bore.
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Re: Bore roughness and tone

Post by Geoffrey Ellis »

I've been able to make a lot of observations about bore smoothness, in part because unlike most (but certainly not all) of the makers on this forum I do a lot of world flutes from a lot of diverse materials, including softwoods, which are never used for conical bore flutes (for good reason). Consequently, I've gotten to test the response of a wide variety of different flutes whose bores are anything from totally rough, pockmarked and "hairy" to absolutely glass smooth.

I would say that roughness in the bore is not advantageous in any sense, unless you just like a flute that fights back. The smoother the bore, the easier the tone development, response, articulation of notes, etc.. I don't have anything to say to the physics of why this is the case, but it definitely is the way it works. Most of the woods used for conical bore flutes are naturally dense or oily (or both) and once polished and oiled, etc. they are all on the "very smooth" end of the spectrum, which is why most of the popular flute timbers sound and respond very well.

It's true that the air doesn't necessarily experience "drag" inside the bore, but the vibrations can certainly experience something like dampening. I think of it like that "popcorn" stuff they spray on ceilings to reduce the amount of reflected sound waves. The uneven, softer material on the inner surface of the flute bore absorbs some of the energy and dampens the tones.

I mentioned in a much older thread somewhere on C&F an experiment I did with making some flutes from curly redwood. This stuff is soft and is one of the worst machining woods I've ever encountered. Gun drilling the bore can leave it looking like the surface of the moon. Trying to develop a tone on such a flute, if the wooden bore is "raw" (no treatment) is seriously uphill work, and in some cases barely possible. So I made a few flutes from it, tried playing them in the raw state (impossible), then I added a single, thinned down coat of marine epoxy to the bore, sealing the wood a bit but not altering the "moonscape" surface (though I did polish it enough to knock down any micro-fibers that were standing on the surface--an important step). A slight improvement ensued. Then I added a thicker mix of the clear epoxy, gave it a polish and tried again. A bigger improvement. I did this a couple of more times, polishing in between. After about four treatments the flute was playing and responding very nicely. If you looked in the bore, it still looked uneven, pitted and full of micro-tears, but every surface and crevice was shiny with a hard finish. These irregularities didn't seem to matter too much once the actual surface of said irregularities was uniformly smooth and hard.

Now, compared to the same flute made from something like Delrin or cocobolo, there was a difference. The flutes that had more regular surface and were also smooth and shiny responded even better. At this point is was possible that some players might actually prefer the curly redwood because it had a slightly darker timbre. The smoother the bore, the brighter the tone, and even the polished bore of the curly redwood was irregular enough to reduce some of that brightness. So there might be some players who would willingly trade down on responsiveness for the interesting tonal difference, but I personally would choose the flute that had the smoothest, easiest response.
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Re: Bore roughness and tone

Post by Loren »

My experience as a maker and player mirrors Geoffrey’s. I had a boat load of opportunities to hear before and after direct comparisons between instruments that came in for service: Those that arrived with rough bores got test played, sanded, and then test played again. Always a noticeable difference - sometimes, a small difference on a smaller instrument made from a harder wood, other times a pretty “massive” difference on a larger instrument made from a softer wood.

Overall, the smoother and harder you can make the bore surface, the better the instrument will sound and play. The only practical reasons to have a less smooth bore would be if, as Geoffrey suggests, you like a particularly mellow sound, or if high frequencies actually bother you, or perhaps if you are looking for a quieter instrument. Still, in all of these scenarios you’ll sacrifice responsiveness with a rough bore.

Many things affect the tone and response of a wood flute, including: Density/hardness of the material used for the body, smoothness of the bore, hardness of the bore, as well as other details. Note that the hardness of the bore surface need not necessarily match the hardness of the wood itself since the bore can be treated/coated to produce a hardness that surpasses that of the underlying wood.

Ultimately some people will notice the differences that Geoffrey and I describe, while others will not, and there are reasons for this, but that’s another topic entirely…..
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Re: Bore roughness and tone

Post by Ben Shaffer »

I mainly play Clarinet
In general most Clarinets are made using the correct Reamers
That said there was a period were Leblanc imported their Professional Level Blackwood Clarinets from France.
The Manager in the US felt that in coming across the Atlantic there was significant " Shrinkage" in the Bores which he felt negatively effected the sound
So, he decided to rebore the Clarinets :(
The reaming was done by some People there who probably did not know what they were doing.
The Bores went from 14.6mm to 15m. ( would be Medium to Large)
The intonation and Sound took a hit on these great Horns
I'm not sure if it was the roughness or the enlargement of the Bore that created the Issue
You can often identify these Clarinets as they don't have a shiny smooth Bore but are pretty rough
I kind of cringe whenever I think of these wonderful Clarinets being mutilated
That said Don't get me wrong many wood Flutes that are reamed can have their Sound improved for the better in the right Hands :poke:
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Re: Bore roughness and tone

Post by Geoffrey Ellis »

Ben Shaffer wrote: Wed Jun 09, 2021 10:33 am I mainly play Clarinet
In general most Clarinets are made using the correct Reamers
That said there was a period were Leblanc imported their Professional Level Blackwood Clarinets from France.
The Manager in the US felt that in coming across the Atlantic there was significant " Shrinkage" in the Bores which he felt negatively effected the sound
So, he decided to rebore the Clarinets :(
The reaming was done by some People there who probably did not know what they were doing.
The Bores went from 14.6mm to 15m. ( would be Medium to Large)
The intonation and Sound took a hit on these great Horns
I'm not sure if it was the roughness or the enlargement of the Bore that created the Issue
You can often identify these Clarinets as they don't have a shiny smooth Bore but are pretty rough
I kind of cringe whenever I think of these wonderful Clarinets being mutilated
That said Don't get me wrong many wood Flutes that are reamed can have their Sound improved for the better in the right Hands :poke:
Upsizing the bore like that can certainly impact both the timbre and the intonation (though it might not be radical), but if they make the bore rough in the process, that's a whole other problem. But it's difficult to imagine that blackwood clarinets, made by a reputable maker (and therefore presumably made with properly seasoned timber that is worked and rested in stages throughout its construction) would shrink that much on a simple trip across the Atlantic! I have some 40 year-old surplus clarinet pieces (blackwood) that are about as stable and settled as you can get. I re-bored and re-shaped some of them into a kaval, put cork on the joints and sent it to a friend to test out. The re-working caused the wood to be mobile again, and caused the tenons to shrink just enough that the cork joints were no longer snug. But interestingly, the bore diameter was completely unchanged. It was drilled with a 17mm drill, and I just checked it again and it's still 17mm. The point being that even blackwood that was well seasoned but not allowed to settle after working still didn't shrink enough to make the bore smaller. To shrink so the bore diameter goes down by .4mm is quite a bit of shrinking.
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Re: Bore roughness and tone

Post by Conical bore »

Another variable to consider, is that some wooden flutes have a metal lined headjoint. If there was a significant tonal advantage in having that much of your wooden flute with a very smooth bore, it would be the universal standard, instead of an option some modern makers offer.

Many wooden flute players seem to be happy with an unlined headjoint where the wood grain surface isn't quite as smooth as a brass liner. I play a flute with a lined headjoint (Aebi), but I'm not convinced it does much more than maybe slightly brighten the tone. And I'm not even 100% sure of that, because I don't have an exact copy of an unlined headjoint to compare it with.
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Re: Bore roughness and tone

Post by Ben Shaffer »

Geoffrey Ellis wrote: Thu Jun 10, 2021 8:15 pm
Ben Shaffer wrote: Wed Jun 09, 2021 10:33 am I mainly play Clarinet
In general most Clarinets are made using the correct Reamers
That said there was a period were Leblanc imported their Professional Level Blackwood Clarinets from France.
The Manager in the US felt that in coming across the Atlantic there was significant " Shrinkage" in the Bores which he felt negatively effected the sound
So, he decided to rebore the Clarinets :(
The reaming was done by some People there who probably did not know what they were doing.
The Bores went from 14.6mm to 15m. ( would be Medium to Large)
The intonation and Sound took a hit on these great Horns
I'm not sure if it was the roughness or the enlargement of the Bore that created the Issue
You can often identify these Clarinets as they don't have a shiny smooth Bore but are pretty rough
I kind of cringe whenever I think of these wonderful Clarinets being mutilated
That said Don't get me wrong many wood Flutes that are reamed can have their Sound improved for the better in the right Hands :poke:
Upsizing the bore like that can certainly impact both the timbre and the intonation (though it might not be radical), but if they make the bore rough in the process, that's a whole other problem. But it's difficult to imagine that blackwood clarinets, made by a reputable maker (and therefore presumably made with properly seasoned timber that is worked and rested in stages throughout its construction) would shrink that much on a simple trip across the Atlantic! I have some 40 year-old surplus clarinet pieces (blackwood) that are about as stable and settled as you can get. I re-bored and re-shaped some of them into a kaval, put cork on the joints and sent it to a friend to test out. The re-working caused the wood to be mobile again, and caused the tenons to shrink just enough that the cork joints were no longer snug. But interestingly, the bore diameter was completely unchanged. It was drilled with a 17mm drill, and I just checked it again and it's still 17mm. The point being that even blackwood that was well seasoned but not allowed to settle after working still didn't shrink enough to make the bore smaller. To shrink so the bore diameter goes down by .4mm is quite a bit of shrinking.
You are 100% right.
Those Clarinets likely had no "shrinkage" as the Manager for US Sales said
The decision to rebore these Horns was made by one person
If you asked most Clarinet Makers,
Players and Repair Persons about doing this reboring that would likely tell you it was a crazy and sad thing to do
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Re: Bore roughness and tone

Post by pancelticpiper »

Back in the 1980s I was visiting the workshop of a highly respected Baroque flute maker.

His spoke of the difference in philosophy between himself and modern flute makers. Modern makers respond to the wishes of modern players; the players determine the sort of sound they're after.

18th century players are no longer with us, they can't tell the modern Baroque flute maker what they want in a flute.

Rather, he said, we must find the best-preserved original instruments and thoroughly learn how to play them, and let these instruments tell us what 18th century ears wanted to hear. The thing to avoid most of all is imposing our tastes upon peoples from another time.

Likewise as a modern maker his job is to make the most painstakingly accurate copies of the very best surviving instruments.

He made an electronic probe that he could put down the bores of Baroque flutes in museums that, without touching the flutes, recorded the complexities of the bores in great detail, allowing him to perfectly reproduce them.

He said that no matter how accurately he reproduced every nuance of bore and tone-hole and blow-hole he could not get his flutes to play precisely like the originals.

Then one day it dawned on him that the originals had rough bores, and his copies were smooth. He found that only by replicated every aspect of the originals including bore texture could he make his copies play identically.
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Re: Bore roughness and tone

Post by Terry McGee »

Heh heh, good story, Richard.

But here's a complication. How could he (or anyone) tell what aspect of the roughened bore was original, and what was wear accumulated over the centuries?

I would imagine that, even back in the baroque day, makers would have polished and sharpened their reamers to yield a pretty slick bore. Those small-holed chromatic cross-fingered instruments were at a considerable disadvantage compared to most of the other orchestral instruments.

And perhaps they would have even used the sandpaper of the day - rushes - to polish the bore further if they felt the need. We know from our own experience that moisture from our breaths raises the grain of the bore, roughening it. Especially in softer timbers like the fruitwoods and boxwood. We know that a roughened bore brings down performance, and that repolishing a roughened bore restores the lost performance. If I were making baroque flutes, I wouldn't be so much interested in making them play like old baroque flutes play today. I'd want to be focusing on how they played when new.

I think another indicator that bore smoothness is important is our relentless drive to exploit harder, finer, smoother woods. We start off back in the renaissance with the readily available and easily worked fruitwoods. Move up to boxwood (Europe's hardest timber?) in the baroque. Move on to cocuswood when the West Indies are colonised, Ebony when we have the Indians under control, and then on to Blackwood when the people of that part of Africa are subdued. And here in Australia, the hard inland acacias, like Gidgee. Again, only after the indigenous people have been moved off the land. (No, it's not a pretty story, and we probably should consider it more deeply than we do.) These harder, finer timbers are capable of achieving and maintaining smoother bores.

Finally, we take a step into the synthetic world, to polymers like acetyl (eg Delrin). Finer and denser again and capable of even smoother bores, not affected by moisture. Have we finally arrived? Or perhaps taken a step too far? I make flutes in Delrin when asked, and can appreciate its many strengths. But I don't enjoy them as much. Is that just me, an acknowledged hopeless romantical tragic, missing the allure of the natural product? Or am I missing a nuance of acoustic texture, which depends on the less-than-perfect-but-still-more-than-adequate bore smoothness of real wood? Woah.....

(Younger makers and researchers will be pleased that we've left some of the bigger, more important questions for their generation to answer.....)
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Re: Bore roughness and tone

Post by Sedi »

Terry McGee wrote: Tue Jun 15, 2021 5:07 am But here's a complication. How could he (or anyone) tell what aspect of the roughened bore was original, and what was wear accumulated over the centuries?
My thoughts exactly. I wonder how the copies with the smooth bore played. Probably better, I imagine
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Re: Bore roughness and tone

Post by david_h »

Terry McGee wrote: Tue Jun 15, 2021 5:07 am And perhaps they would have even used the sandpaper of the day - rushes - to polish the bore further if they felt the need.
How did they use rushes Terry? (it's a search that sends Google off in several more obvious wrong directions).

Edit: Ah, OK, Equisitum, I hadn't thought of that as a rush
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Re: Bore roughness and tone

Post by Terry McGee »

Certainly Equisitum (Horsetail). But I imagine there are a number of rushes that could be used to polish timber, especially the softer timbers of renaissance and baroque times.

Wikipedia gives us a quick history lesson in abrasives, including horsetail:

The first recorded instance of sandpaper was in 13th-century China when crushed shells, seeds, and sand were bonded to parchment using natural gum.[1] In the Bible, King Solomon is mentioned to have used a mysterious abrasive called shamir allowing the king to build his temple (e.g. cut huge blocks of stone) without using iron tools, since the temple was meant to be a place of peace and iron was used in war. Shamir was also held in Hebrew lore as being a magical worm capable of cracking glass when resting on it.[2][3]

Shark skin (placoid scales) has also been used as an abrasive and the rough scales of the living fossil, Coelacanth are used for the same purpose by the natives of Comoros.[4] Boiled and dried, the rough horsetail plant is used in Japan as a traditional polishing material, finer than sandpaper.

Glass paper was manufactured in London in 1833 by John Oakey, whose company had developed new adhesive techniques and processes, enabling mass production. Glass frit has sharp-edged particles and cuts well whereas sand grains are smoothed down and do not work well as an abrasive. Cheap sandpaper was often passed off as glass paper; Stalker and Parker cautioned against it in A Treatise of Japaning and Varnishing published in 1688.[5]

In 1921, 3M invented a sandpaper with silicon carbide grit and a waterproof adhesive and backing, known as Wet and dry. This allowed use with water, which would serve as a lubricant to carry away particles that would otherwise clog the grit. Its first application was in automotive paint refinishing.[6]
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Re: Bore roughness and tone

Post by david_h »

Thanks Terry.

There are horsetails on a road verge near us that is normally cut before now. This year it is being 'managed for wildlife' (cynics say to save money) and won't be cut till autumn. Maybe I will remember to take some to try out with before they do.
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Re: Bore roughness and tone

Post by chas »

david_h wrote: Wed Jun 16, 2021 1:10 am
Terry McGee wrote: Tue Jun 15, 2021 5:07 am And perhaps they would have even used the sandpaper of the day - rushes - to polish the bore further if they felt the need.
How did they use rushes Terry? (it's a search that sends Google off in several more obvious wrong directions).

Edit: Ah, OK, Equisitum, I hadn't thought of that as a rush
Cool, I'd never heard of that. As one who likes to investigate the history of tools, I just might have to get some.
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