After further testing I was able to get signal to the subwoofer during AirPlay playback. Without making any Speaker Setting changes I played around the surround mode settings. There are 3 buttons on the remote, AUTO, SURR, and ADV. I hit the auto button just to see if it was already there, but heard a click and it showed AUTO SURROUND on the receiver display and the subwoofer just suddenly kicked in.
With AirPlay music I was able to switch between the different sound modes and they worked correctly. For example the ACTION setting would send voices to the center channel and add a slight echo; all the SURR modes worked like Dolby Surround, Neo 6 Cinema/Music, etc.
One weird thing though, is when switching back to the Xbox, you can only choose a few different HDMI audio output modes. You can choose Stereo, 5.1, or 7.1 uncompressed (PCM) out or Bitstream with sub options of Dolby Digital or DTS. With the 5.1 uncompressed or either of the Bitstream options and playing back sling tv (which is now only available in stereo), the ADV modes (Action, Drama, Adv Game, etc) will show that they are on, but no sound comes to the center speaker or surrounds from what I can tell. The SURR button only gives me the option of STEREO or EXT STEREO and EXT STEREO will
force sound to come out of the center channel. No other modes will do this.
The stereo uncompressed option will show stereo on the receiver and allows the ADV modes and SURR modes to work correctly and output sound from the center speaker.
I miss my old Pioneer that would apply the surround affects to any and all audio formats...