Crossover subwoofer response


Nov 25, 2015
Hi everyone. Before I start this thread, I'm sorry for my bad english, because I'm from Quebec and I speak French as a primary language. I'm installing a new audio system in my car and I've got a Kenwood Car Radio, which is the KDC-158U. I have Pioneer Speakers to go with it, and a subwoofer. I simply don't have the money for an amplifier, and I absolutely need to drive the subwoofer from the rear speakers output, because I only have front speakers anyway. The question is : on the website of my radio, and I'm not sure of the frequency response of the system. What are those?. I can't find them! Also, if you find them, could you say my which cutoff I need for a low pass crossover to drive the subwoofer on the rear speakers output? Thank you very much guys, hope you can help me!