According the Amazon, these are self-powered L+R speakers with optional passive hookups so your have 2 options:
1. Your source component (PC?) has a separate SUB OUT JACK, then yes, hookup your powered sub there.
2. If SUB OUT not available, then you have to buy a powered subwoofer with built-in CROSSOVER, and you know this when you look at the back of the sub, it has LINE IN, as well as OUTPUT for the L+R speakers. In this scenario you are powering the entire system via the amp inside the sub and bypassing the amp of the Mackie.