Your going to have to tell us a bit more to get an accurate answer . What equipment are you using to drive the speakers , Are the M-Audio's , Monitor Audio's , are they passive , active or both ? If your trying to hook up to the sub with a banana plug I take it that its a passive sub , ( no built in amplifier  ) ? Posting some pictures of the back of all your equipment would be helpful .

                                                                                                                                                            Regards  Tim

... you are using the self powered AV40’s driven by just your phone connected to the front input jack… there is no way to connect the F12 in stereo as the left AV40 is wired internally.  Best you can do is run speaker wire from the ‘output to right speaker’ on the back of the left av40, to the right ‘from reciever’ speaker line level input on the back of the F12.  Then run speaker wire from the right ‘out to speakers’ line level output on the back of the F12 to the ‘input’ on the right AV40.

The only way your going to get a stereo feed to that subwoofer is if you drive it with a separate source such as a receiver or computer soundcard that has a subwoofer out connector.

RG

I think you must have posted this elsewhere as it sounds kind of familiar.  What are you trying to drive these with?