Simultaneity in the AirPlay Universe

Most Apple products support the streaming of audio (and some even video) data through the network to AirPlay enabled devices like Apple TV, AirPort Express or third vendor products. Apple advertises the AirPlay technology with:

[...], you can stream your tunes to more than one room simultaneously, [...]. AirPlay works over Wi-Fi or an Ethernet connection, or a combination of both.

But how simultan can these devices stream under real world conditions? I tried to address this issue with two 2nd generation Apple TVs and an iMac Streaming through Wi-Fi and Gigabit Ethernet. It proved to be a difficult task to measure this precisely! Continue reading