I have a different question posted in the audio forum with no responses because the forum has been dead for awhile, so I'm posting this one here.

I've taken the output from the stock sub-amp and used it as a line input to a good-known-working amp powering a good-known-working sub. Without running an actual check frequency by frequency, I can tell that the bottom end is missing. On bass heavy tracks (electronic, rock or whatever usually bottoms out at 40 hz or so) where I know there is sound down low ~20-~35, it is missing. If I turn up the volume and the sub output all the way, I can feel it a little.

This tells me that there is a crossover blocking the low fq. This makes sense as the factory 'sub-woofers' (which is completely incorrect terminology for them) probably would have launched their cones trying to play a 22hz tone. Where is this bass-blocker?

Does anyone have any idea what can be done to get a full range of output from the stock 12 or so channels?

As a personal rant, I think it's absurd that car manufacturers boast about how many lousy speakers they can cram into a car, when for a few bucks, I could put 3 or 5 (for front and back passengers) that can play much clearer, and truer with full frequency response. "Oh you want an inadequate sub-woofer, that will be a $2400 add on, but it still won't play lower than the door speakers because it's still a 6.5!"

Unfortunately, with the crazy fiber-optic set up, and with the car's systems reliant on the stock head unit, I'm not sure how to bypass the problem component (that which is doing the crossing over), even if I can find it.

PS, my DSP is set to Front.