Airplay query

[stickytape]

So we've got a bit of a conundrum! We often download movies and TV shoes and have this on Dropbox on the iPad and then beam them to the Apple TV. However, now we are exporting the sound to the Sonos one via Airplay from the Apple TV, this appears to cancel out when we share the actual picture. Essentially, we get the option of playing the movie on the iPad with sound from the Sonos, or vice versa! Is this how it will be, or am I missing an obvious setting where we can beam from the iPad to the apple TV and still get the audio from the Sonos?

Thanks in advance!