unless you're riding in a covered wagon with wooden wheels and no suspension, i can't see how transporting your cabs laying any which way isn't an order of magnitude less "violent" than the speakers get hit with just setting them on stage and playing through them!
magnets might get shifted when you drop cabs, that's about it.
Funny, I Just ran across this discussion while looking for something else...
When I was a teenager, I worked at a music store and the electronic technician there told me that the only consideration he'd make for transporting speaker cabinets would be to transport them facing down. He said it's most unlikely, but once he saw the magnet assembly break loose from the frame, shifting over, freezing the voice coil, and rendering the speaker useless. That could possibly, maybe happen if the cab was transported on its back (magnets down), but he also said that the owner probably dropped the cab in its back. Past that, he said he wouldn't worry about that too much.
Over the years, I've seen the magnet assemblies on a couple of JBL drivers, of all things, let go, shifting over and ruining the driver.
But speaker guys in the know tell me that it takes a severe drop for that glue between the magnet and the frame to let go. Of course, none of the shop guys or technicians
ever dropped a cabinet, right?
