.488 bore vs .500

[wesleyrubim]

Hey everyone

I’m about to change my horn and I have some questions about bore sizes.
I know that in terms of sound it doesn't make that much difference but in terms of feel, what do you feel is the difference between a .500 horn compared to .488 or smaller?

Thanks

[ithinknot]

"no"

... or rather, it depends. The feel and sound both come from the whole design, and if you're comparing two different designs all (or at least most) bets are off. If you have to generalize, the smaller bore may be fussier about inputs, and might not be quite as "pure dB loud" (as opposed to "projecting") at full tilt. But it's also possible that the conceptual/artistic "size" of the sound might be larger, and it might handle being pushed quite hard in a more accommodating/comfortable way. In those respects, some Bach and Holton .490s are "larger" than some 3Bs.

Or are we talking changing slide bore but keeping the bell section the same? Then, yes, the horn will probably "take more air" and the sound will be somewhat wider. But it can also feel "more" or at least "differently" resistant. (Bach 12 slightly louder and punchier than the 8, but also potentially "tighter".) It's all about system balance. A bigger slide can make you encounter the resistance points in the bell section sooner. Sometimes that's good and develops tone color in an interesting way, and sometimes it crosses the line into "stuffy". Same way that things can go wrong opening up bass trombones infinitely... take a design that works (albeit within certain constraints), then remove resistance somewhere specific, only to start chasing your tail with new localized headroom limits that weren't apparent before.

[MrHCinDE]

I wouldn‘t rely too much on bore size to guide on how a horn feels. Best to judge on an individual horn-by-horn basis.

I have a .481/.491" 2B Silvertone which plays with just as much sound as my .508“ 3B/F and is arguably more open. This would go against any simplified logic that such a small horn could be quite stuffy for those not used to it but other factors such as leadpipe, materials, condition and build/tolerance are probably more important.

I have experienced some tendencies and even some pretty direct links, e.g. that my 3B+ plays a lot like a slightly larger 3B, but there are so many factors so best just to get out there and try lots of horns.

[hyperbolica]

To me bore size is all about the blow. I usually play 525, and can learn to play .500 bore, but .48x I usually wind up exhaling at the end of phrases. I sometimes run out of steam because I think I can play longer phrases than my oxygen supply allows.

[Finetales]

All other things being equal (just swapping out slides on a Shires for example), a .485" will have a noticeably smaller/tighter blow than a .500". It's essentially twice as big as the difference between .500" vs. .508", which is a drastic difference in feel. .491" to .500" is about the same distance.

However, usually your comparison will be between two different horns, which as already mentioned have a lot more going on to differentiate the feel/blow than just the slide bore. Every horn is different.

That said, while some 2Bs do play huge, they would play even bigger if you threw on a .500 slide with the same specs and leadpipe.

[harrisonreed]

Don't forget "pizza mathematics". The smaller you go, the bore size will become much smaller in volume. So the difference is likely much greater than .508 vs .500

[baileyman]

Funny that one would use less air on a somewhat smaller slide diameter, as in both cases that air has to squeeze through the much smaller mouthpiece throat. It seems the throat should dominate. Perhaps there is something else going on.

[ithinknot]

Perhaps there is something else going on.

acoustic impedance ≠ fluid dynamics

[harrisonreed]

Funny that one would use less air on a somewhat smaller slide diameter, as in both cases that air has to squeeze through the much smaller mouthpiece throat. It seems the throat should dominate. Perhaps there is something else going on.

It comes down to the volume of air you are applying energy to and the volume of air that can be compressed into the tube.

(Before anyone says it, yes, of course it's not a closed tube.)

[hyperbolica]

Funny that one would use less air on a somewhat smaller slide diameter, as in both cases that air has to squeeze through the much smaller mouthpiece throat. It seems the throat should dominate. Perhaps there is something else going on.

Well, I don't know, try it. Sub-500 horns just use a lot less air than large bores. Play some long notes. I can put the same mouthpiece into a 525 and a 500 bore that I have here. I can hold a tuning Bb for 16 seconds on the 525 and 22 seconds on the 500 bore. I'd be able to hold even longer on a 488. And if I can hold my breath for say 30 seconds, there will be some point at which the limiting factor of how long I can play a note is my ability to hold my breath, and at the end of the note I will have to exhale before inhaling again. This is part of the reason why trumpet players don't worry about bore as much, because how long you can hold your breath doesn't matter for larger bores. It's a practical problem when you play bass for a while and then switch back to smaller bore. You can get dizzy playing tuba.

[baileyman]

Perhaps there is something else going on.

acoustic impedance ≠ fluid dynamics

Yup, for sure. And even in fluid dynamics a venturi can almost disappear in flow. Not quite sure how impedance should affect flow, since the impedance is there at zero flow, too.

Maybe you have a thought on this. That the vibrating lips act as a metering device, where the flow seems like it should be a function of pitch and volume. For a freebuzz, there is some rate of flow through the flapper valve. It can then be hooked up to a horn. I think we must be saying then the feedback from the horn changes the behavior of the buzz, where the buzz flow varies with horn bore. I can easily imagine this is an impedance effect, but I have to say I can no longer do the math on these things so I can't show it one way or the other. However, I think it's true that one can make a bigger and bigger horn, till it has infinite diameter, where it becomes equivalent to a freebuzz. I suppose then freebuzz should take the most air of all.

I can't answer this. But my own freebuzz will go for longer than any trombone note I need.

[Doug Elliott]

There are very open feeling sub-.500 bore horns, and there are very tight feeling .500 bore horns. The leadpipe, end crook, and neckpipe can make more difference than the slide bore.

And the mouthpiece.

[ithinknot]

Maybe you have a thought on this. That the vibrating lips act as a metering device, where the flow seems like it should be a function of pitch and volume. For a freebuzz, there is some rate of flow through the flapper valve. It can then be hooked up to a horn. I think we must be saying then the feedback from the horn changes the behavior of the buzz, where the buzz flow varies with horn bore. I can easily imagine this is an impedance effect, but I have to say I can no longer do the math on these things so I can't show it one way or the other. However, I think it's true that one can make a bigger and bigger horn, till it has infinite diameter, where it becomes equivalent to a freebuzz. I suppose then freebuzz should take the most air of all.

I can't answer this. But my own freebuzz will go for longer than any trombone note I need.

Maybe substitute can for will in the final sentence? The lips act as a metering device, but not via a single variable... I can make a freebuzz go long, but I can also maintain the same pitch and volume while choosing to modify the aperture in a way that empties the tank much faster. Is one of those a "tpt buzz" and another a "tuba buzz"? I'm talking about increasing the vibrating "reed width", not just introducing vertical leaks.

Anyway, agree re feedback, and if not an impedance effect, what else? It seems logical that the feeling of "efficiency" as an achievable ideal (across horns of different sizes, and equally dependent on soft machine changes) must involve some degree of impedance matching (and subsequent coupling phenomena?).

Honestly, though, I'm interested in this stuff but semi-understand it at a, let's say, "flowchart" rather than "can do the math" level. If I married and/or housetrained a physicist I could probably get some vaguely sensible questions answered for free, but as it is I'm probably barking up the wrong lamp post beyond a certain point.