I'll run you through different scenarios and you can decide which one applies to you.
If you are using the
original AV cable, you'll need an extension for the audio to the chair. You have a few options. You can either use two
Y-adapters (if you want the audio from both the TV and the chair) or a
coupler (to run the cable to just the chair. Regardless on whether you decide on just the chair or both the chair and TV for audio, you'll then need an
audio cable.
The same process applies if you are using the
component cable, as it uses the same audio process.
If you are using the HDMI from the PS3 to the TV, find the
original cable that came with the PS3. Plug it into the PS3 and then the red and white ends into the seat. Go into audio settings and change it from HDMI to composite.
Also, If your TV has it, you could also use the audio output to the chair. You'd still need the audio cable.
If any of that doesn't make sense or you need further info, feel free to ask.