Im using a high-low converter to install a system without a head-unit, do I have to connect both rear speakers?

I am installing a high to low converter to hook up subs and a amp on my chrysler 300. I thought I had everything connected, but im not getting anything to the subs? I have power to the amp, a good ground, good acc connection. Now do I need to connect both rear speakers to the hi low converter? Shouldnt it still give me something if I only use 1 rear speaker?|||You can just connect one wire from the rear speaker to the high low converter and to your power amp.