The presence of a subwoofer is a must in any multi-channel speaker system. Without this component, it is impossible to call the soundstage full.
Passive subwoofers need to be powered by an external amplifier. The biggest advantage of a passive subwoofer is that it gives you the ability to work with different amplifiers according to your needs and required characteristics, which is not possible for active subwoofers. And a connection to the amplifier seems to convert passive subwoofer to active.
Ways of connection
Connect the RCA cables
RCA cables will be used to connect the subwoofer to the amplifier. The output from the subwoofer can be mono or stereo. You can find them on the subwoofer main unit (rear side). In the case of the mono output, only one cable will be required for the output. For stereo output, you will need two cables.
Understanding the subwoofer
The subwoofer can be a Single Voice Coil or a Dual Voice Coil. A Dual Voice Coil subwoofer offers multiple cabling options, such as parallel, series, or independent. With a single voice coil, a single set of terminals would include positive (red) and negative (black), while the dual voice coil has two of these sets of terminals.
Connection to the amplifier
Make sure the amplifier is turned off before starting. Connect the RCA cables already connected to the subwoofer input jacks to the amplifiers. The jack on the amplifier would be labeled LFE or subwoofer output. This is where the RCA cable is plugged in. Connect the amplifier to power and double-check all cables before turning it on.