You plugged a car speaker into your zenith allegro sound system through the headphone jack and you think you shorted the system out can you fix the sound system?

The headphone jack is actually wired with resistors so the headphones don't get the full amplifiers output. The only way you can fry the speaker system, is to send voltage back through the headphone jack and/or crank the volume all the way up with a short or no speaker connection. Check speaker fuses!