A question on a B&W high pass filter

I have a B&W 800 series variable high pass alignment filter for my 803 matrix speakers. I have never used it & wondered if I need to? What would I be expected to hear? Or should I just sell it & forget it? Also, what is the thing worth? New, in box. I never hooked it up since i had no idea of why I would need to. If you can help me understand this question, please answer. Thanks.....