ACI Titan subwoofer hookup options

I just recently purchased an ACI Titan II LE subwoofer and I am unsure what my hookup options are with regards to hooking it up to an older amplifier (no subwoofer HT output) for stereo music play. The manual shows a speaker level addaptor that runs from the speaker terminals to the RCA inputs on the sub. Is this just a matter of converting L/R speaker wire to one RCA male connector? If so, I'm sure I can secure the necessary parts from a source like parts express. Or would this adapter be doing something else to the signal before it goes into the subwoofer. Probably a dumb question, but someone out here probably knows. Emailed the company for these adaptors (they were originally supplied with the sub) but they are no longer in business. Please give me advise on plan B!