No sound only base at my door speakers

I have an aftermarket HU an android touch screen it was a cheap radio. I also upgraded to jbl stage 3 door speakers. Now on the adapters they gave to connect to the new HU there is a pink wire that is marked “amp DET” idk where to hook that up to. Now with out it i get sound at my front dash speakers but nowhere else the door speakers just have bass. If i fade the setting to play sound only to a specific side it does not work and gives me no sound. Before i go an purchase an amp or anything i need a little help or some guidance to what i need to do.

 

Did you ever figure this out? your the only other person I have found with this issue that I now have.