Posted by Rick Denney on June 13, 2002 at 10:11:28:
In Reply to: Just noticed on St. Pete posted by Doug on June 12, 2002 at 01:00:17:
This is an old-fashioned design. Most rotary tubas have a bell with a large throat relative to the bell and bottom bow, with a smaller wrap and a taller bell. The throat on my Miraphone 186 is larger than on my York Master, despite that the YM's bell is 3.5" larger. The YM provides more higher harmonics than the Miraphone (which I've measured), but I think the bigger difference is in the directionality resulting from the bell shape. The tall bells act more like an exponential horn, throwing the sound directionally with a lot of energy. The wider bells act more like a bi-radial horn, with wider dispersion. Thus, the sound reaching the listener from a wide bell has more components from different paths, and the sound from the taller bell is more represented by a single central path. The multipath phase shifts from the wider bell seem to round out the tone. But this effect depends on room acoustics, and one shape may be more effective in a given environment than another. In a beer-tent situation, for example, the Miraphone has a carrying quality that cuts through high ambient noise without having to bounce off the walls. The wide-belled tuba that fills a concert hall with limitless bottom might be weak in that beer tent. The Miraphone recalls the older tall-belled designs--the St. Petersburg is a more direct example of them. Even rotary tubas have been trended to wider bells in the last decade or so, but that trend hasn't made it to Russia just yet.
Rick "who notes that the original tubas had almost no bell flare" Denney