A loudspeaker is a device that converts audio-frequency electrical signals (approx. 20 to 20,000 Hz) into mechanical vibrations (sound). It is therefore used for sound reinforcement. As the name suggests, built-in loudspeakers are intended for installation in walls, fittings or similar.
Here you can buy built-in speakers from well-known brands like Canton, Pioneer, Bose, Magnat and others.