First of all, it is necessary to understand that the set-top box is the output device, and the projector and active speakers are the input devices. Therefore, the set-top box is connected to the projector through HDMI, and the set-top box is connected to the active speaker through an audio cable. What audio cable is used to connect the set-top box and active speakers? This depends on the input interface of your active speaker. It is certain that the set-top box has a red and white lotus interface. Active speakers generally have a red and white lotus interface, but some active speakers have a 3.5 interface. If it is a 3.5 interface, you need to use 3.5 to red. White Lotus interface to connect devices. Some projectors also have speakers, but the sound of this projector’s speakers is very poor, but HDMI outputs audio and video signals synchronously, that is to say, the projector will also make sounds. At this time, set the projector’s volume to zero or turn it off. Projector sound. Otherwise it sounds uncomfortable.