1. X7s plus default player don't support AC3, need firstly switch to Android source, then download AC3 player, such as "Kodi","BS player" and "VLC android";
2. X7, X7sd, X7A don't support AC3, some video files if the audio format is AC3, there isn't sound;
3. Android 6.0 version compatible with more applications, such as Netflix, CPU update to A53, faster than Android 4.4. Android 6.0 version support 4K video file.
4. Android 4.4 version build in Google remote control, you can use Android phone(Download "Google TV Remote" APP) control the projector as remote control (Android 6.0 version need download other remote app).