Thanks for the replies.
The problem is that the pics on the website and in the instructions are totally different from the subwoofer Axiom actually shipped me.
On my EP350 there is no "XLR 1/4 PHONE IN" connection (or out connection for that matter).
There is only a connection labeled "Low Level Input" (and Low Level Output). And of course the "High Level Input" connections.
If I could figure out how to attach a picture I'd attach it.