A speaker unit with a speaker frame and two membranes arranged in the speaker frame. A first membrane radiates in a major acoustic radiation direction substantially perpendicular to a major plane of the speaker unit. A second membrane has a secondary acoustic radiation direction different from the major acoustic radiation direction. Two drive units are positioned within the speaker frame, attached to the two membranes, and positioned coaxial to each other at the same height in the speaker frame. An acoustic duct provides for a closed acoustic channel from the second membrane in the secondary acoustic radiation direction to a secondary surface of the speaker unit in a same plane as the major plane of the speaker unit.