If you don't hear sound coming out of the built-in speaker of your Nebula Mars II or Mars II Pro, try the following steps: 

1. Turn up the volume on your Mars II or Mars II Pro and play different videos in multiple streaming apps;
2. Update your Mars II or Mars II Pro to the latest firmware by going to Settings > Upgrade > Check Update;
3. Switch your projector to Bluetooth Speaker Mode (refer to How to Use a Nebula Mars II / Mars II Pro as a Bluetooth Speaker ). Next, connect your phone to the projector to play music and listen for sound;
4. While your Nebula Mars II or Mars II Pro is in Projector Mode, connect your projector to a Bluetooth speaker or headphones via Settings > Bluetooth to test the sound;
5. Reset your projector by selecting Settings > (General) > About > Recovery and try the built-in speaker again.

If you are still encountering the issue with the built-in speaker, contact us with the following information so we can find you a solution much faster:

1. Your Nebula's current firmware version. You can check this by going to Settings > (General) > About > System Version;
2. A short video that shows no sound coming from your projector's built-in speaker in both Projector Mode and Bluetooth Speaker Mode.