No Sounds from Subwoofer

[smms25 10+ year member]

Hey guys looking for a little bit of help on my install. On the first try, I tried to keep the original headunit and used an LOC to give the signal to my amp. But I got some weird sound from my sub(almost muffled or something like that, but sound nonetheless).... then I decided to go with a in-dash DVD Pioneer AVH-P4000, ran the RCA from there to the amp... now I get no sound from my subwoofer at all.

The sub is a MTX T4512-04 and the amp is an Alpine MRD-301 (or whatever the mono block alpine is)

Any help appreciated towards my diagnosing this problem

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