i have a 2005 KIA optima lx and my friend recently put two large speakers(made in the 70s)in my trunk and there hooked to my rear speakers with speaker wire...it sounds pretty good and the bass slams but having it the way i do will i run into any problems?
It would be better if they were hooked up to a separate apmlifier.if they are just connected to the rear speakers you can possibly have an impedance mismatch and burn up the amplifier in the car stereo. http://hyperphysics.phy-astr.gsu.edu/hbase/Audio/imped.html
