Tip for hiding compact electronic gear 'in' a room yet have it be effectively invisible.

Install a return air ventilation grill, but behind the grill is a hollow wall cavity. The grill is sized to match the cavity wall opening. Frame the cavity within the wall structure as needed and run speaker/input/control wires to wherever needed.

Creative AC outlet locating (per local codes) and you have the electronics equipment hidden in the wall but fully accessible from the room via the grill panel.

Use screws as per normal to attach the vent grill over the equipment cavity or install vent with a hinge. The vent grill provides plenty of ventilation for the equipment yet can be painted to match the wall color, melding it into the wall visually.

Essentially a small equipment closet right in the room.