Downward firing subwoofer


I have a downward firing box with 1 sub & 1 passive sub. Can I remove the passive sub and put an actual sub, or will this cause issues as far as clarity.
rickregal
Probably not.  The passive sub is designed to work within the cabinet volume and the subwoofer driver.   Removing the passive will really muck things up.   If you need more bass, get another sub, preferably the same as the one you currently have.   
Who makes it? Why would you want to? Is the passive in bad order?

Regards