Posted by Not rick, but on May 24, 2002 at 09:03:30:
In Reply to: Re: Re: Re: Re: Re: Basses and Contra B. posted by Doug on May 23, 2002 at 22:56:46:
No, Klaus is on the right track. The measurement that is the primary determinant of pitch is length. Double the length and the pitch descends an octave. Bore does not affect pitch and bell flare does only to a minor extent. What I'm not sure of is the relationship of bore to the scaling. Should one scale the bore by multiplying cross-sectional area or the diameter of the bore?
Let's assume it's the bore diameter and take a typical fluegel horn (which the tuba most closely resembles), a Bach 183. 0.401" bore (Where DO they get these numbers? What genius came up with the idea of adding .001" to the bore spec?), 6" bell. Scaling all measurements by 4 to create a BBb version results in an instrument with a 24" bell and a bore of 1.604", a behemoth with a bore bigger than the water line that feeds my house.
If we scale the bore by cross-sectional area, however, we end up with a more reasonable 0.802, still larger than most BBb piston tubas, but smaller than a St. Pete. Cross-sectionally, the bell would be scaled to only 12". Now THAT would be a funny-looking tuba!
FWIW
Chuck(G)