Do I need an amplifier or subwoofer?

In my 04 TL I replaced my old subwoofer with a used OEM factory one. When in used it rattles slightly. Is the subwoofer the problem or the amplifier. All the other speakers in the car perfectly fine. I also want to mention that I took out one of the speakers in the door panel as it blew. So the amplifier is... show more In my 04 TL I replaced my old subwoofer with a used OEM factory one. When in used it rattles slightly. Is the subwoofer the problem or the amplifier. All the other speakers in the car perfectly fine. I also want to mention that I took out one of the speakers in the door panel as it blew. So the amplifier is powering all but one speaker cause theirs nothing connected to it.
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