Well, almost two years later, and three different speakers later, no more speaker pop when I turn off the car!! It must have been both speakers I installed before this latest one today were no good and caused the speaker to pop. It's only been one day though, hopefully it holds up!
BMWCCA Member# 451235
(Summer) 2001 330Ci - ZSP
(Winter) 1994 530i "Greenie" - PARTING OUT! (PM for details)
(Grocery Getter) 2002 525iT