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!
I don't have my manual handy, but recall reading somewhere(possibly in the manual, possibly on the ACI website) that the speaker level adapter had a "built in resistance". The only question is how much resistance? I would like to find out too since I would like to fabricate a speaker level adapter for mine too (I bought one used, without the adapter). I'm using the low level connection now.

Maybe there is someone out there who can put a meter on their Speaker level adapter and tell us what the resistance is??

In your case you may want to just get an RCA Y adapter to use for the time being with your preamp.
I could use a RCA Y adapter but was wanting to find an option for using the sub with an integrated amplifier and as such need the speaker level adapters or the ability to manufacture some. Let me know if you find anything out as to the resistance. I have an electronics repair guy who I have confidence in who could make the adapters if I have the specs.
Go to aci and look at the sub set up section. If not email mike d at aci, he still answers

I have three and love em