What is a Low Pass Filter

Otherwise, your subwoofer would also be receiving midrange signals full force, which would make it much easier to hear its location. Your ears would know that it is not blending as well as could be with your main speakers, as it should 'disappear' when set up well. And as far as a sub trying to do high frequences like cymbals, well, that's really funny to hear.

Hope this adds to your understanding.