I've got a 5 1/2 ins red brass bell on my Taylor just so the guys in the wings can hear me.
No really...the sound is a little more diffuse than a narrower bell but we're not talking absolutes here, just comparatives. As with most things brass the effect is at the margins. The guys at the back of the hall don't complain either so I guess the sound gets there as well. I pretty well play most styles on it..some better than others of course, but that's the player not the horn.
Regards,
Trevor