Posted by Kram Kazam on March 10, 2000 at 22:18:13:
In Reply to: Re: Re: Re: perceptions posted by Joe Baker on March 09, 2000 at 15:28:25:
I'm real doubtful that a conversion from Eb to C will work as described. Adding a yard of CYLINDRICAL tubing to a not-so-long Eb is going to dramatically change the overall profile (the 'unwound' theoretical version of the tuba which most plainly illustrates the total taper of the horn).
The most you can probably 'get away with' is a whole step. (Getzen G-50 is the only commercially successful horn I know of to pull off this trick)
The likely result, at the very least, will be funky intonation. The proportion of cylindrical to conical length of any brass instrument is what largely determines the sound quality and intonation of the finished instrument.
As an illustration for your consideration: A .500 bore Euphonium (non-compensating) and a .500 bore Valve Trombone have identical 'bore' and same total length. Can you tell them apart blindfolded? You bet.
Although a less fair comparison, it's interesting to know that a french horn (on the 'f' side) and the fattest F tuba also have essentially the same length! Aside from the bore & bell differences, the F horn is proportionately much more cylindrical than the mostly conical F tuba. The valve & branches, leadpipes, etc, etc are carefully designed to compensate for the particular taper of that instrument.
This is why 'cuttting' a BAT from BBb to C is especially an ART. --Because doing so really screws with the taper. Try this: Make a representative paper sillouette of a 'Herald Tuba' about 18' long. Make the first 3 inches or so relatively unchanging in width (kinda representing the leadpipe & bore through valves & maybe main slide.) flare the remaining 15" to mimic the BAT of your choice. Now just try to chop out 2" somewhere after the valves without the flare looking really goofy to ya. Although what you 'see' is an over simplification of what the sound wave in the horn actually experiences, it's a good illustration of how radical the change actually is. to complicate matters, the actual 'conical' portion of tubas isn't perfectly conical. The sound wave behaves differently in the bends, and must be compensated for... Yadda yadda yadda.
If this Eb to C conversion really works - producing good intonation and all - then color me crazy; I'll rush in next time some old Eb pops up on ebay so I too can have a lovely playing C tuba for under $700, plus some tubing & solder.
I'll bet a lot of pride out there has kept us on this BBS from hearing all the 'true confessions' of botched efforts at tuba cuttin' & lengthening. Let's get the truth out there, folks. If they could talk, A lot of (formerly) nice ol' horns out there might be suing for malpractice!
~-o^o-~ Mark
PS- I'm still thinking about cuttin' down my 12J & adddin' a fat ol' 4th valve (rotary) somwhere. I must be sick. Just like in AA, I need your anecdotes to keep my impulses in check ! . . .