Low output from sound-bar to powered sub

[Hydrobluedaytona]

I have the 7 inch radio, and wanted to augment the sound, since I don’t have a factory sub. Ended up ordering the Cerwin Vega VPAS10, due to price and size. I tapped into the two twisted pairs of green/gray wires in the B-pillar on the passenger side, however, I’m barely getting any sound at all from the sub. Eq, gain and everything cranked up to max on the sub. I connected my phone directly to the sub, with an RCA connection, and it’s a 100 times louder, so I assume I have a signal issue. Is there a filter or anything somewhere, that prevents the lower frequencies to reach the sub? Or am I missing something else?

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