Posted by Alex C on February 01, 2001 at 23:12:44:
In Reply to: 5th valve posted by Holton Question on February 01, 2001 at 22:05:17:
The real advantage is that the valve is bigger if placed after the valve cluster rather than in the leadpipe.
I won't argue about the possible problems created by having a rotor placed in the leadpipe, some work, some don't.
But if you notice, the Holton's fourth valve tubing is larger that 1-2-3. It is a fact that there is less resistance if there's less cylindrical tubing. Though not truly conical, compare the different effects on resistance using a combination for low Eb (3,4 and 5.) If all the valve's tubing had the same diameter, there would be a lot of increased resistance. With 4th tubing larger than 3rd, AND the 5th larger than 4th, resistance is reduced.
Additionally, if Pop Johnson and Mr. York thought it was a good idea, who am I to disagree. Mr. Jacobs claimed that it helped give the tuba "organ-like tones" in the low register. I noticed when he played my horn that it was true. Must be the 5th valve placement.