KU-3A

Common name: RCA KU-3A

Production Status: Discontinued / Vintage

The KU-3A is  unidirectional ribbon microphone which used an acoustical labyrinth (a folded pipe with internal damping) to achieve the necessary delay to the rear port. The microphone was introduced in 1948 and largely intended for boom use. Operational instructions advised suspending the mic at 45° to the floor, though the ribbon is mounted on the vertical axis, not parallel with the sloping grille. The brochure amusingly (by modern standards) claims small size and light weight. The horizontal cardioid polar pattern was remarkably even for such a design and an improvement on earlier techniques which employed twin pressure and velocity ribbon elements. An output transformer provided 30, 150 and 250 ohm taps. An F&E 3 pin connector to open ends was provided.