So i have searched all over the forums about replacing the sub and adding an amp to the sony 700 watt system but my question is why is everybody splicing the loc to the door speakers? Can i not just install the loc right where the wiring comes into the sub?

 

Apparently at higher volumes to line to the sub actually stops, or at least slows down, the volume increases. So if your volume is at a "15" to the door speakers, you may only be sending a "12" to the sub and the difference is greater the higher your volume is.

Jumping a signal from the door speakers by-passes that.