Posted by Joe S. on July 06, 2000 at 19:47:21:
In Reply to: graduated bore size posted by Karen on July 06, 2000 at 19:17:54:
Some of the B&S (aka. Perantucci, VMI, et al) rotary valve tubas have "graduated bores".
The first valve past the mouthpipe will have the smallest diameter tubing connected to it, and by the time one encounters the 5th or 6th valve, the bore size of that valve's tubing is quite a bit larger.
Some PISTON sets have 1-2-3 one size, the 4th piston's tubing larger, and the (#5) rotor PAST all of the pistons has even larger tubing. That would also be considered "graduated bore".
I have no idea if there are any disadvantages. I have played some BAD tubas with graduated valve bores and some GREAT tubas with NON-graduated bores (and visa versa, of course).
"Graduated bore" is a very old concept. Some trombones have a smaller bore top slide tube and a larger bore bottom slide tube, with the crook at the bottom expanding in size from one to the other.
A tuba that I am currently "building" (out of parts from other old tubas) has a NON-graduated bore through its four pistons, and it plays VERY "open" (in the low register) and smooth...I would not change a thing, regarding its valve bores. I believe that the expanding branches of the tuba have more to do with "response" and "open-ness/resistance" than whether or not a tuba has graduated bore sizes in its valves' tubing. An exception (possibly) is a tuba in Eb or F equipped with a LOT of valves (5 or 6). Since those tubas are fairly SHORT in overall lenghth, it is probably a pretty good idea to make each valve's tubing have a slightly larger size.