I'm thinking about an Axiom subwoofer, but I'm not sure about how to make one work in my setup.

My audio out is an Apogee Duet, and my speakers are active monitors Adam A7. The Duet is stereo out only, and the Adam monitors are audio in only.

My guess is I need some kind of splitter, but not sure how it would work with Axiom subs having a single RCA input. Splitting one channel doesn't seem like a good solution. I'm curious if anyone here has figured out a solution to a similar setup? Keep in mind the Adam monitors are active and have their own built-in amplifiers.