Car Stereos: Adding a Sub To 2002 Trailblazer LTZ with Bose, noticeable gap, passive crossovers

Question
I have an amp that will go to the sub and i got a LOC and attached that to the low level signal coming from my head unit but I don't know if that is the right way to do it in order to get all the low frequencies out of the system.

Answer
Normally, I just tie into the speaker leads in the rear of the car.  Run those speaker level wires to the amplifier.  Then I use the low pass filter built into the amp to cutoff the highs at the desired range that best suits the listening requirements of the owner.  Some want a well-rounded bass sound, so I raise the filter level.  Some want all out bass.  For those, I lower the filter to the lowest frequency, so there is a very noticeable gap between the mids and the amplified lows.  If you want to put some sort of crossover in before the amplifier, that is fine, but I would be sure you use an active crossover, not a passive.  Passive crossovers will lose valuable power.  Hope this helps, Scott