English: An audio engineer in the control room of a professional sound recording studio. In front of him is the mixing console with a plurality of linear potentiometers for regulating the recording level of the different instruments/voices playing in the live room behind the glass window. In front of the engineer are two large 30 cm bass driver monitor loudspeaker boxes (outwards, details see further below) and two smaller loudspeaker boxes, so that persons in the control room can listen to the sound recording or to different channels (instruments/voices), which is called monitoring.