How to Fix No Sound from the Built-in Speakers on the BenQ MOBIUZ EX2780Q

Causes

• The wrong audio output device is selected — the EX2780Q outputs audio over its HDMI/DisplayPort connection, but many PCs default to the graphics card's own HDMI/DP audio device (named after the GPU, e.g. "AMD High Definition Audio" or "NVIDIA High Definition Audio") instead of the monitor. The image shows on the BenQ but sound goes nowhere or to no active device.
• Monitor volume muted or set to 0 in the OSD — the built-in treVolo speakers have their own volume control in the monitor's on-screen display. If it was muted (often accidentally via the remote's mute button) or set very low, the 2.5W speakers are effectively silent even though the PC is sending audio.
• Audio not carried over the connected input — on this model reliable speaker output comes over HDMI or DisplayPort. The single USB-C port is primarily for video/data and does not deliver power; depending on the laptop, audio over USB-C may not be routed to the treVolo speakers at all, leaving the built-ins silent.
• Audio device disabled or set as default on the wrong endpoint — after a Windows update, the monitor's audio endpoint can be disabled, or Windows can hand the default to a different device with nothing plugged in, so the EX2780Q speakers never receive a signal.
• Stale or corrupt GPU audio driver — the HDMI/DP audio driver bundled with the graphics driver can break after an update, dropping monitor audio while display keeps working.

How to Fix

1. Set the BenQ EX2780Q as your default playback device — in Windows right-click the speaker icon in the taskbar → Sound settings → Sound control panel → Playback tab. Find the EX2780Q / BenQ MOBIUZ endpoint, right-click it, choose Set as Default Device, and set Set as Default Communication Device. Raise its volume slider and unmute it (speaker icon should not show a cross).
2. Unmute and raise the OSD audio volume — press the joystick on the back or the remote's menu button, open the Audio menu in the OSD, and confirm Volume is up and Mute is Off. Turn on the treVolo sound mode for the fuller built-in audio, and double-check you did not mute it with the remote.
3. Connect over HDMI or DisplayPort for speaker audio — the built-in speakers are driven over the HDMI/DP link. If you are connected via USB-C, switch to an HDMI or DisplayPort cable (or plug the audio device into an HDMI/DP input) and reselect that input in the OSD so audio is routed to the treVolo speakers.
4. Play a test tone to confirm the endpoint — with the monitor selected, play any video or run a sound test. If nothing is audible, open the OSD audio menu again and confirm volume is at a reasonable level while playback is active; the small 2.5W drivers can sound very faint, so raise volume to 50%+.
5. Update or reinstall the GPU audio driver — in Device Manager expand Sound, video and game controllers. If the BenQ/AMD/NVIDIA High Definition Audio device has a warning or is old, update it, or uninstall it and restart so Windows re-enumerates it. A fresh install of the latest graphics driver also restores the HDMI/DP audio stack.
6. Check the cable for HDMI/DP audio support — some budget adapters or old cables pass video but drop the audio return channel. Try the included DisplayPort or a known-good HDMI 2.0 cable, and confirm the audio endpoint re-appears after reseating it.