The W3 is a great to make your S8 subwoofer, or any other self-powered subwoofer, wireless.
The W3 kit comes with a sender unit and receiver unit. For use with an AV Receiver or Stereo Amplifier, you'll need to connect the sender unit to the SUB or LFE output of your AV receiver. This is usually done with a 3.5mm stereo-mini to RCA "Y" cable. You can connect either RCA to the SUB / LEF out, and just leave the other side unplugged. Then, you'll connect the W3 receiver to your S8 Powered Subwoofer, using a 3.5mm stereo mini to RCA "Y" cable, normally. If you're using a different sub that only has a single RCA, connect the same color RCA that you used for your AV Receivers SUB / LFE out, and leave the other unplugged. Both W3s will need power. In this configuration you will need a USB AC adapter for each W3 unit.
You can also do this using powered speakers like our A5+s, A2+s, HD6s, or HD3s, instead of an AV Receiver. For this, you'll connect the W3 sender to the RCA output on the left speaker, using a 3.5mm stereo-mini to RCA "Y" cable. Then connect the W3 Receiver to the input on your S8. You can either use a 3.5mm stereo-mini to stereo-mini cable for this, or another 3.5mm stereo-mini to RCA "Y" cable; either will work fine. Both W3 units will need to be powered from a USB port. You can use USB AC power adapters, or if the powered speaker you're using is an A5+, you can use the USB port on it's rear panel for the W3 sender.