almost no low range output to subwoofer

When I moved my Kenwood XXV-01D headunit to a new car, hardly any bass was going to my subs, even with the gain on my sub amp (Kenwood KAC-8152D) turned all the way up. So I decided to instead connect the front RCA channel to the sub amp (instead of the subwoofer channel) and all of a sudden I could hear bass again. Recently I blew the fuse on the + cable (the fuse closest to the battery). When I replaced it, all of a sudden I was having the same issue from the front RCA channel as I was from the subwoofer channel. Now I have to have my sub amp connected to the rear RCA channel to hear any bass. What I find weird is that when I hook up my 2-channel amp to any of the front or rear RCA ports, the midrange and highs play fine through my components, so it's just the bass that's missing. What is going on? Is it possible to blow out only the low range of the RCA-outs? I'm almost 100% positive it's not a crossover issue since I've played with the head unit's internal crossovers (even tried turning them off), as well as the one on the mono amp to no avail. The issue can't be with the source either because I've tried multiple sources such as satellite radio, AM, FM, CDs, and even my MP3 player to no avail. Besides, like I said earlier, the bass issue only occurs through the subwoofer (and now the front) RCA outputs, but not the rear.

i guess you could blow the subwoofer preout section only. does anything play when you have it hooked up to the subwoofer preout on the head unit? sometimes when you 1st install or move a HU the subwoofer output is turned off, de-equalized, cross-overs change or the bass boost is turned off. if you are sure it isnt a setting, then ... wait, the front preout did it too? hmm... try using only 1 RCA cable from the HU to different amps and see if they perform perfectly. Then you can eliminate that let us know any HU and amp settings so we can double check them

The most logical answer seems to be an issue with your head unit.  Perhaps a DSP is failing, perhaps the preamp is failing.  Whatever it is, it's time to get it looked at.  Is it under warranty?Support the12volt.com