Re: Bells and Timbre


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Posted by Rick Denney on November 17, 2003 at 18:36:04:

In Reply to: Bells and Timbre posted by Phantom Tuba chopper on November 17, 2003 at 17:40:29:

Response has to do with how readily the instrument reflects a pulse back to the lips from the end of the bell. I would expect that anything that damps that return pulse will make the instrument less responsive. Lots of bends in the tubing, and so on, would damp that reflection and make the tuba sound stuffy. A taper design can be so wide that the instrument doesn't resonate well on the right note, and that also will damp that return pulse. If the vacuum part of the return pulse arrives at the lips just at the right time for the next parting of those lips, the vacuum will help them part, and that's what makes it feel responsive.

I therefore suspect that the whole instrument affects responsiveness, not just the leadpipe and valves.

I've always had the feeling that the bell does quite a bit of tone shaping, by controlling which frequencies reflect from which points of the flare, and by controlling dispersion into the room. Thus, I like the notion of putting a really nice-sounding bell on a responsive body. How much it helps in any particular case depends, I think, on the relationship between the shape of the bell and the body.

But that doesn't mean a great bell will make a bad-sounding tuba much better. There is still a lot of tone that happens before the sound reaches the first ferrule. I don't think it's just the bell on, say, the CSO York that makes it sound as it does (in the right hands). But there aren't that many options of taper design once you have laid out the valves and have sized the bell, so maybe the bell is having a secondary effect by dictating what is possible in the body of the instrument.

The bell on my York Master is not as fast a taper as most vintage American instruments, and I think that is because of the restriction imposed by the attachment ring. I might someday experiment with a Miraphone 186 bell on that instrument. It has a wider taper, and when trimmed to the right length will fit the ferrule properly (the joint would be about three inches closer to the bell than it is on the Miraphone). A former owner pitched the idea to me. We both wonder what effect it might have on the intonation of the instrument, and we both think it might loosen it up a bit and make it more like other B&M instruments without the interchangeable bell. It's just too far down on the list of projects right now, though. The .750-bore piston set and awesome fourth-valve might be a great match for the strong-sounding Miraphone bell. Someday I'll try it (reversibly, of course).

Rick "who thought the CB-50 bell was already a copy of a York bell" Denney


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