Do you know why the factory amplifier is not sending a flat bass signal to the subwoofer? In my testing, there's a large dB boost in the 70 Hz area and it sounds awful - really boomy bass at times as a result. Doesn't matter what I set the head unit EQ to, the signal is still molested by the time it gets to the sub.
I know this because I charted the frequency response and actually went through the trouble of buying a small Kicker amp and a PAC AP4-CH41. The PAC hooks up in-line behind the screen and sends a true flat audio signal to the Kicker amp, which I then wired up to the factory subwoofer, thus removing the signal/power from the factory amplifier in the process. Everything sounds MUCH better just by feeding the factory sub a flat signal, which you can then EQ with the PAC or Kicker amp as you please. I really don't understand how the audio engineers let the system pass this way. It's one of the worst audio systems I've ever heard because of the drastic bass boost to some frequencies in the factory amp. An amplifier software update needs to be released to fix this.
This is not a one-off thing either. I've had multiple 5th gen Limited trucks and they've all had the issue on the current amplifier software (unless something changed in the last few months).