Violent sounding car speaker blow out - any danger?

As I was driving home tonight the stereo in my car cut out several times for short intervals, over rougly a five minute period. This was the first time I've ever observed this behavior. This finally climaxed in the music cutting off completely and my left-rear speaker letting out a LOUD hum with crackling & popping. The hum went on for a couple minutes, even after I ejected the CD and turned off the stereo. Most concerning was the burnt smell and crackingly that continued for the rest of the drive home (about another 10 minutes, again with the stereo off). I think I've had speakers "blow-out" on me before but it is typically a gradual process. Am I naive here in thinking this is highly unusual and perhaps dangerous (ie the speaker in question continuing to receive current and "burn")? Or does this sound like a more run-of-the-mill car speaker blow-out? I don't intend to turn the stereo back on, but I'm concerned if this is something that needs to be serviced right away.