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SupercardioidAEA KU4

Supercardioid Ribbon Microphone

The AEA KU4 is a supercardioid ribbon microphone. It is based on the RCA KU-3A, an early directional ribbon mic. The KU4 has been in development at AEA for 4 years.

Ribbon transducers are natively bidirectional transducers. To produce a directional response, the acoustic path from the front to the rear of the ribbon element must be altered.

KU4The KU4 achieves this with an “acoustical labyrinth,” constructed of precision-milled aluminum. The rear of the ribbon element is obstructed by a tube that feeds into the labyrinth below the ribbon motor; the labyrinth delays the arrival of sound waves at the rear of the element so as to produce frequency-dependent phase cancellation.

In the RCA KU-3A, the labyrinth was stuffed with cow hair. The KU4 does not use cow hair, but there is some material packed into the labyrinth to aid the acoustical delay effect.

KU4 Polar PatternThe resulting pattern is supercardioid, with well-defined nulls from 120° to 150°, and 24dB of attenuation at 1kHz at 180° The mic’s rear lobe widens from 5kHz–7kHz, but even then maintains 10dB of attenuation at 180°


The ribbon element is AEA’s standard 1.8µ aluminum material. Ribbons are cut, corrugated, tensioned, and installed by hand at AEA’s facility in Pasadena.

AEA considers the KU4 to be especially well-suited to vocals and voiceover, brass, and drum overheads in spaces where an untreated or low ceiling can cause poor-sounding reflections.

AEA KU4 with RCA KU-31 (10001)The mic was announced in October, 2010, and officially introduced at the AES show in San Francisco in November.

Permalink: AEA KU4

The mic was released in 2010.


Pickup Patterns Pads & Filters
Supercardioid (2.8 mV/Pa; 30 - 20,000 Hz)
Ribbon Construction Impedance SPL/Noise
2.1mm x 28.6mm, 1.8-micron aluminum ribbon 300 Ohms (Low) Max SPL: 140 dB
Weight Length Max Diameter Interface(s)
2080g (73.37oz) 315mm (12.40'') n/a
  • 3-pin XLR male (1)
Power Specifications

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