ok, so you have 2 12s, lets say audiobahn, lets say tuned at 40 hz, your bumpin and one blows, does this mean the working sub is seeing a bigger, lower tuned box and could also be damaged because of this
if they share the same chamber then yes the working sub will have the whole box to its self, which will lead to the sub haveing to much excursion and eventually breaking most likely. but if they have seperate chambers then no nothing will hapen.