I have a 2018 Taurus Limited, added a custom 2 X 10" woofer box driven by an Alpine M500. I tapped into the 2 6X9 drivers on the rear deck and use the speaker level inputs on the Alpine amp. The subs sound great! However I just noticed that if I move the fader all the way to rear, there is almost no sound at all. If I turn the volume all the way I can barely hear any sound. If I set the front/rear fader to center, then all the speaker work. I don't quite know what to look for, or is this "normal" for these cars? I also installed a set of Focal 5x7's in the front doors and installed the focal tweeters in the pillars. Very nice improvement.