What kind of amp did you use?

 

Would it be better to tap into the rear door speaker wires left and right channels to the line level converter? I tried just the old sub wires with a horrible sounding result. Just curious what the guys who added an aftermarket amp did to get great sound from their sub. Also if anyone else has a 98 did you use preamplifier signals or the signal from wires going straight to the speakers from the amp?

 

The system is splitting the lows from the mids & highs, all your low frequency signal is being sent to the sub, your door speakers are mids & highs only, so there's nothing to 'tap' into. I'm not sure where your stock sub amp would be located at, but if you're install is good it's possible the old amp is shot as well. If there's an adjustment on the input levels of your new line level amp I'd play with that first. But if your old stock amp is in the trunk and you can find the pre-amp input, run that to your new amp and bypass the old amp entirely. Also make sure your new amp is getting enough DC power, it's a long way from the battery to the trunk and light gauge power wire is gonna add a lot of loss.

 

Helpful tipster here. If you pulled that 8 inch factory woofer out and left the grill cover in tact, you would see an Sound pressure level increase from your subs into the cabin of the car from your 12's. It can be a pain to pull the seat and rear deck lid, but if you're already planning to pull the factory sub out, you can add a little Dynamat to the edges of the rear deck while you're in there, and that will really reduce unwanted chassis vibrations.

 

I strongly recommend leaving the rear door signals alone as their signal levels are terrible! Instead, I came off the old sub line and into an Audio Control AC2 module that corrects and puts back in ALL the signal you could want for your sub amp. Worked awesome for &200, just saying ...