Determine whether you can use the existing subwoofer to connect to active speakers. Collaboration both audio devices must have dual stereo output channels and power. Otherwise your idea will not succeed. It should be noted that active speakers do not require additional software when you connect to the subwoofer directly.
Get on the radio or in a specialty shop acoustic audio cable "pigtail" with dual RGB connector, which is popularly called the "Tulip". At the same time on the second side of the cable should be represented by bare wires.
Connect RPG leads to the speakers and the subwoofer. Active speakers are connected through the "Tulip", and the subwoofer via a special socket for connection of passive speakers. It is necessary to observe polarity |R|L||R|L|, otherwise the system will not function. If the subwoofer channel is not represented a type of "latch", and connector "Tulip", then used a double audio cable double RGD connector on both ends.
Turn on the subwoofer in the network, while the active speaker will work in passive mode. Otherwise, if the powered speakers may be a conflict of amplification systems, which will lead to the background sound playback or failure of the acoustic devices.
Connect the subwoofer to the PC through the special outlet and test the acoustics. If the sound does not appear, then go to "volume Settings" or "configure mixer" and check if the indicated audio device, as well as other volume parameters. Can also verify that the sound drivers under "system Properties" - "device Manager".