Whats the biggest difference a valveset can be from the bugels bore.

[LargeTuba]

What's the biggest difference a valveset bore can be from the bugles bore without causing problems. how bad would it be to have a . 5" taper between the mts and the valveset.

[bloke]

Assuming you're referring to reverse expansion...
If this is a concern, you can probably find small-side inside/outside tubing that matches your valveset bore, and it's not that difficult to expand the small side of a (usually: tapered) main tuning slide bow by half a millimeter (only about 20/1000ths of an inch) and blend that expansion into the overall taper of the main slide bow (annealing the bow, and forcing three or four balls through the bow until one that is 20/1000ths larger is forced through - to the point in the tapered bow that the 20/1000ths-larger bore size is already realized).

As far as swapping out the small-size main slide tubing with half-millimeter-larger tubing, probably (??) using the outside slide tube as the inside slide tube - and finding another tube that fits over that one - would do the trick.

rules for bore expansion? Based on the vast variation that we've all seen in tuba shapes/sizes, there obviously are none, but there is certainly experimentation, along with trial-and-error. There is also "going to war with the army you have".

What's the biggest difference a valveset bore can be from the bugles bore without causing problems. how bad would it be to have a . 5" taper between the mts and the valveset.

[LargeTuba]

Thanks for the reply

Assuming you're referring to reverse expansion...

I’m thinking About using a Conn 12j Valveset (658″ bore) with an older boosey And hawkers 3v Eb tuba. The seller of the Boosey and Hawks Tuba says the short end of the MTS is 24mm and the First valve bore is 18mm (.709”).

[iiipopes]

Respectfully, I believe this is the wrong question. For example, Flugelhorns traditionally have a .410 to .430 bore, but a huge expansion after the valve block to the throat. French horns have small bores and 12 feet of tubing, the same as an F tuba, and generally play in the upper octave with very little conical expansion of the tubing until the bell throat. Modern Bach trumpets have at least three rates of taper in their different bell throats, as do Schilke trumpets, but play with similar intonation characteristics to their respective brands.

It's not so much the absolute taper, but the balance of cylindrical tubing and conical tubing, of whatever taper, all in the right places. Cylindrical tubing tends to expand the sonic distance between overtones and conical tubing tends to compress the sonic distance between the overtones.

So to me, the real question is what is the proper relationship, since all brass instruments, at the very least, need some conical tubing to temper the overtones to our Western ears, and some cylindrical tubing, if for nothing else, for tuning and valve slides.

[bloke]

Martin 6/4 B-flat tubas (which play in-tune, and play well) typically feature an epic bore expansion immediately after their conservative-bore-sized valvesets.