Need technical help

I have a Sony mini home theater system DAV-X1 which uses two small speakers and one subwoofer. The speakers/sub are connected to the receiver via special cables that are supplied with the unit. The issue: I don't have the subwoofer that came with the system. The cable that attaches to the sub is a special plug with 4 prongs.
I checked the output of the prongs with an ohm meter and they all seem to move the meter. I'm trying to figure out how to hook up a generic subwoofer. Not sure which wires go where or how to "jump" it. Also not sure if any of those four prongs supply power to the designated sub.
I am attaching a link in case you want to have a look.
Any help would be appreciate.
Just a guess here: This sub has a dual voice coil (right and left channels). The 4 wire cable has +/- for the right side and the left side. The amp for the sub is built into the sony. If it is this way, you could easily hook up any "passive" (non powered) sub. It could probably attach to a powered sub also, just make sure you use the speaker level inputs and not into the rca jacks.
Thanks Elevick, In reading your info I believe you are correct. I took a trip to the local Sony outlet and had a good look at the subwoofer that is supplied with the DAVX1.
I think there may be two woofers in the cabinet. One firing downward and the other inside the cabinet.
Also noted that the output is 6 ohm. I found a similar model at the Sony store DAVX1V which uses the same special interconnect cables but the subwoofer looks a little different and is a 4 ohm speaker. I may be able to get one of those and was wondering if the difference of 2ohms would matter at all?