If there is no sound when the projector playing videos like , turn off Dolby sound on your connected devices or apps. If there is no sound when it connected to the DVD, select the "PCM" sound input mode to ensure that the sound works. For an optimal viewing experience, we recommend that the best projection screen size be 40-120 inches. We do not recommend it for business presentations (such as PPT, Excel) in the bright scene.The connection will cause a certain delay in the projection picture and the sound. So this mode is not suitable for games.Much higher brightness than ordinary portable projectors, bring you a better performance on the picture.You don‘t need to connect it with any other speakers.System: Display Multimedia System mirroring for: Supported( version above 4.2)for screen mirroring: SupportedUSB Plug-Play Mirroring for : SupportedEmploying four times as many pixels as 720P, it creates amazingly clear images for the ultimate in cinematic enjoyment.