Using Unity3D with Dolby Atmos

I am currently developing a project where it is mandatory that the user can distinguish wether a sound is coming from behind or from the front. I bought a pair of surround headphones which is connected to its own AVR, supporting several Surround formats. I tried using them with the Dolby Access App and the receiver detects the Multichannel Sound. When I am using Unity, the receiver stays in surround mode, eventhough I changed the audio settings to 5.1... Several sources suggested to use the MS Spatizilizer Plugin provided by the DolbyDeveloper site for Unity. But neither does this work. The sounds stays in Stereo

Is there anything I need to take into account when trying to realize Dolby Atmos or Multichannel Sound in general using Unity? I changed the settings under Edit -> Project Settings -> Audio, followed the PDF instrutictions from the plugin, changed Audio Output in Windows to several different Audio Modes. Nothing helped..