There are many ways to connect the rca subwoofer cable, but in 99% of cases, this is the LFE connection type. Most subwoofers require a single long cable with RCA connectors. Connect it to the output of the AV receiver's preamp and the LFE (low frequency effect) port of the subwoofer. The right and left channels of some models are equipped with stereo inputs: they are usually connected to the appropriate output of the Hi-Fi amplifier preamp.
However, there are also subwoofers with high level connections. In this case, it is necessary to lay acoustic cables for the subwoofer and speakers, or use another set of cables to connect the subwoofer and amplifier.
Many stereo receivers and amplifiers are equipped with subwoofer output for LFE connection. In this case, use cables with RCA connectors on both ends ("male-male" type).
Some cables that come with the device usually have a specific standard length, but remember: the shorter the better. Short cables ensure less signal distortion. However, please do not choose a cable that is too short: the cable should be long enough to place the subwoofer in a different location to get the best sound (the location will affect the sound).