The thread that was comparing/contrasting tubas vs. Sousies seems to be closed now ... *tear*... so I guess I'll start another to ask my question.

Physically, how does the size of the bell affect the sound of a tuba? First off, tubas (generally) have a smaller bell, while Sousaphones have this huge windbreaker to splay sound all over the field. Now when it comes to tubas, I've seen some bells that flare out wildly such as these two:
http://www.rickdenney.com/old_king_and_Conn_24J_filtered.jpg

then I've seen tubas with tiny bells and no flare, like this shiny Jupiter:
http://www.rickdenney.com/images/Jupiter582_and_York_Master.jpg

All other things aside, such as bore profile, taper, size, etc., how does the size of the bell actually affect the sound of the tuba?

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But wait, another question! Has anybody ever heard that it takes however many feet in distance for the sound of a tuba to "develop"? This explains why many concert halls and band rooms have high ceilings, so that the sound can develop before it is projected off some object (ceiling, an acoustic shell... ) Somebody said this to me before at a state band festival and it sorta seems to make sense, but I'd really like to know the physics behind it. What's going on?