Posted by Eric on November 18, 2003 at 16:13:19:
In Reply to: Bells and Timbre posted by Phantom Tuba chopper on November 17, 2003 at 17:40:29:
The bell flare does have a large impact upon the tone on any brass instrument. The job of the bell flare is the same as a similarly shaped loudspeaker horn: to efficiently radiate high frequency sound. It's a complex issue, but basically the more gradual the flare and the larger the diameter of the bell, the more efficiently the high frequencies in the tuba tone are radiated and the less high frequencies reflect back to interact with the lips.
The taper before the bell flare is important too. Basically the more conical the taper, as opposed to trumpet-shaped, the more bass is produced. A tuba can start with the same bore after the valves and have the same size bell and have a completely different taper in between yet still play in tune. The more conical flare ends up longer, however. A point halfway between the bell and the valves will have the greatest difference and thats where I look to compare tapers. Rotary tubas usually have the valves placed further down the bugle than a piston horn, further complicating the issue.
In terms of playing quality, it seems to me that the final flare influences that more than the taper of the body of the instrument. A King 1250/2341 has a very gradual taper for the final flare. It kills the high register but produces a broad, warm sound. A horn with a similar body taper and bore but with a more abrupt meinl weston or buescher shaped bell has a more focused sound and a much more solid high register because medium high frequencies are coming back to interact with the lips rather than escaping into the room. The King was really designed as a sousphone with the bell pointing at the listener, so it makes sense that they would use a gradual bell flare to approximate the sound of an abrupt bell flare pointing away from the listener.
Its all so complicated! Just play the thing and if it sounds good, great.