actually it does work.... just not what u would expect.
@op
lets put it this way so u can understand easily. an amplifier is basically a power house to run the subwoofer. without an amplifier, the sub is just another speaker. Sub's work in a different frequency range and require more power to run (LOW frequencies). now if u do run the sub from ur stock pre, the low power will not damage the sub, however because there wont be enough driving force, the sub will only be making faint noises or no noise at all
