Bass waves don't open up until after about 15 feet or so. That's where the volume is and the idea behind folded cabs. If a bass wave has to travel X number of feet to get loud, the folded horn makes the bass waves travel some of that distance from within the cab creating the louder results sooner. How close do you stand to your rig during practice vs. stage?
at practice I'm about a foot and a half from my cab, on stage it will vary but it's usually quite a bit further, maybe 4-10 feet. having said that during practice i'll move around, and if i stand facing my cab about 10 feet away, i can barely hear the bass at all, and there is hardly any room-filling low end. on stage when i'm 10 feet way it sounds way better and i can hear everything plus more low end.
it must be how we set up at the jam space. we kind of form a triangle with the drums at the top and the guitar and bass pointed towards the drums from the other two corners. not a lot of space between us, maybe 6-8 feet...
Sometimes it travels differently. I'm sure it has to do more with my deafened ears or the room / set up since it's my understanding that bass is not unidirectional. I'm sure someone has a much more technical answer though