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Where do you measure a tubas bore size and what is the meaning of it? Just thinking because I ordered a Jupiter JCB-780L which has a bore size 16.8mm and I'm currently playing a Melton Spezial maybe model 25 (not my own) and don't know it's bore size (picture from behind: https://picasaweb.google.com/1178935548 ... 6114668530" target="_blank" target="_blank).
Link to Jupiter: http://www.thomann.de/fi/jupiter_jp_780l_bb_tuba.htm" target="_blank

Hi!
I believe bore is measured after the last valve circuit before the main bugle. Piston horns generally seem to have smaller bores in relation to Rotary models. My experience has been that larger bore instruments are harder to "overblow" in relation to smaller bore Tubas of the same valve type! An old piston valve King recording Bass might have a bore of .689", compared to .830" of a St.Pete 202.

Al

Bore size measurements are typically taken at the second valve slide (i do not understand the history of why at this point). The issue with using bore size to compare horns is that lead pipe design / valve design (rotor vs piston) places this measure at an arbitrary place in the bugle of the instrument. Rotary horns tend to have long lead pipes proportional to their piston (especially "grand orchestral" designed) brethren. Total volume displacement of the horn would be the best measure of size comparison of horns, but this would be a challenging (physically and technically due to weight and leaks).

I would say it is safe to say, the only people concerned about bore size are the technicians with they are repairing and replacing parts... For the rest of us, if it plays how you like it, why worry?!

+1. For example: I have a King Silvertone cornet with a .458 bore and small bell that has a wonderful low range, almost like a tenor horn, but sounds stuffy in the upper register. I also have a Besson 2-20 trumpet with a .464 bore that is stuffy in the lower register, but absolutely screams in the upper register. This is completely against the "conventional" wisdom that a larger bore can help the lower register, and vice versa.

Ben wrote:Bore size measurements are typically taken at the second valve slide (i do not understand the history of why at this point). ....

Some manufacturers used to make their bores progressively larger all the way through the valve section. Taking the measurement inside the 2nd valve slide was sort of a way to average the bore size.

bloke wrote:This thread has become both large and a bore.

Only six responses and you're already bored?

I'm glad charvette1000 asked because I wondered myself what bore size was, how it was measured, and how it affected play and voice.

Jim

acjcf2 wrote:I'm glad charvette1000 asked because I wondered myself what bore size was, how it was measured, and how it affected play and voice.

Jim

Yeah... it's not a bad topic and folks should be encouraged to ask questions no matter what. Maybe some day someone could come up with a list of "most frequently asked questions" that could be posted at the top of the forum main page.

This is one of the things that never got covered (and many other things related a horns construction) when I studied tuba playing at local conservatorium.
I am almost fifty and most of the students are 7-18 or so and I guess that the teaching focused on the playing and theory. And I am an engineer too...

I have calipers all over the house, I just don't know where to measure...

charvette1000 wrote:I have calipers all over the house, I just don't know where to measure...

It can be done in any room with sufficient light and space.

Klaus

charvette1000 wrote:I have calipers all over the house, I just don't know where to measure...

I think the answer was given up this thread. Anyway:

The standard place for measuring the bore of a brass instrument is the inner diameter if a male branch of the 2nd slide.

This makes sense for instruments with a uniform bore through all, or at least through the first three, valves. If the bore increases through the valve block, you have to measure the respective valve slides to specify the bore progression.

The old B&S F tubas used to have a 5 step bore through it valve block.

Some Miraphone rotary baritones have one bore for the first two valves and a slightly larger bore for the two next valves.

3+1P compensating euphoniums and tubas have one bore for the 3 first valves and a larger bore for the 4th valve loop and hence for the compensating loops. At least the Yamaha YEP-641 euph has a conical crook in its 4th valve loop.

There are many other permutations of bore progressions, but it may be worth noting that the Conn 40K and the large York Master like many other BBb basses have a uniform bore through all four valves, 0.732" and 0.750" respectively.

Klaus

And along that line, Miraphone 186's have constant .770 bore through the block as well. Kings have a constant .687 bore, and have had that bore for a century or more, as have the Conns.

Proper design and bracing so that nothing gets in the way of a node or antinode is much more important than bore.

imperialbari wrote:

charvette1000 wrote:I have calipers all over the house, I just don't know where to measure...

It can be done in any room with sufficient light and space.

Klaus

My group measures outdoors. Has anyone tried lexan calipers? I heard they don't burn your hands.

charvette1000 wrote:I have calipers all over the house, I just don't know where to measure...

Pull your 2nd valve slide and measure the inside diameter of one of the legs. Here's an image of me measuring the bore size on my YEP-641:



The advertised bore size for YEP-641, 642, 842 is .591... or 15mm.

Rick F wrote:

charvette1000 wrote:I have calipers all over the house, I just don't know where to measure...

Pull your 2nd valve slide and measure the inside diameter of one of the legs. Here's an image of me measuring the bore size on my YEP-641:



The advertised bore size for YEP-641, 642, 842 is .591... or 15mm.

Great post by Rick!

Also hinting towards that smart invention of the digital calipers with a wireless numeric keypad (not in the photo) allowing you to write in the exact desired measuring result!

And the photo also is an implicit warning: Please do not measure the bore too often! As you see the left leg has been measured so often that it has been worn short.

Klaus

imperialbari wrote:And the photo also is an implicit warning: Please do not measure the bore too often! As you see the left leg has been measured so often that it has been worn short.
Klaus

charvette1000 wrote:And I am an engineer too...

That is an unfortunate disease for a tuba player. It tempts one to measure dimensions rather than music.

Rick "severely afflicted with same" Denney