You SHOULD throw the speaker bar in the trash, get an AV receiver, hook all your sources up to the receiver and put in a nice 5.1 or better audio setup.
Short of that, the 685i only has an analog audio output connection, so you connect a long analog cable from your projector to your speaker bar, assuming your unnamed, random speaker bar has a 1/8" stereo or RCA stereo input.
If your speaker bar has a toslink or other digital input connection, then get a hdmi audio extractor and use that to provide surround sound to the speaker bar.
