Posted by Rick Denney on October 23, 2003 at 10:42:41:
In Reply to: Re: Re: Re: Tuba MP Throat Size vs. Bass Trombone posted by Mary Ann on October 23, 2003 at 10:14:49:
Yes, Mr. Jacobs had an airflow meter and also measured the pressure of what I recall were various CSO performers on trumpet, trombone, and tuba.
I don't know how he normalized the resulting output, but I assume he did, so that comparisons were made at the same volume levels. The C you mention would probably have to be played fairly softly on a tuba not to be much louder than the same pitch on a horn.
But I suspect that the tests were conducted on notes more within the usual ranges of the instruments, such as around middle C. This would put the notes still near the middle of their broad characteristic mouthpiece impedance curve, while the low C on a horn must be well outside the impedance curve for a horn mouthpiece. This curve is like a the hump of a camel, covering basically the entire "cash" register of the instrument. That impedance curve is superposed on the impedance of the instrument, which has a series of sharp resonant peaks (unlike the mouthpiece). The mouthpiece therefore adjusts the relative strength of the various resonant peaks of the instrument, which is what gives it its characteristic sound. Thus, a euphonium with a tuba mouthpiece sounds like a really stuffy tuba (but nonetheless a tuba), while a tuba with a euphonium mouthpiece sounds like a really flatulent and uncentered euphonium. The performer can override these effects by imposing yet another impedance curve which forces a musical shape on the resulting resonance peaks, but it seems to me that doing so takes really strong chops.
I think it's important to note that Jacobs was comparing world-class professionals in his test; performers who have a similar efficiency of sound production on their respective instruments. For example, he was comparing Herseth (or Schilke--I don't know) on trumpet and himself on tuba, not Jacobs on both tuba and trumpet.
Rick "who could not make a low C on a horn with any amount of air" Denney