After a lifetime in sound and lighting I can answer pretty definitively. They don't care. I've had gear in badly heated warehouses, in trucks at -20, outside on loading docks for hours. They come thru every time. Cables, on the other hand, cannot be unwrapped frozen. The rubber insulation can break, and crack off. I ruined a few VERY expensive snakes over the years trying to lay them frozen. Let them warm to room temp. I always let amps warm a bit first to avoid condensation. My sub zero routine, open all the cases, but don't disturb for half an hour.
Your bass cab can freeze, but to be safe, give it some defrost time inside before firing up.