AEA KU4 Ribbon Microphone


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Product Code: 9999-08706
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The AEA KU4 Unidirectional Ribbon Microphone, a contemporary realization of the RCA KU3A classic, a mic many engineers consider to be the best ribbon microphone ever made!

The AEA KU4 celebrates the legendary RCA unidirectional KU3A, a high-sensitivity microphone designed for the Hollywood movie studios. Also known as a M-10001 for its manufacturing number, it was RCA's most expensive ribbon microphone. Fewer than 600 were ever manufactured. What made the KU3A special? It combined the smooth ribbon sound of a 44 with a unidirectional pattern, a wide sweet spot and less proximity bass boost. It expanded an engineer's range of placement choices and became a standard at film studios around the world. Although condenser mics became the new standard by the end of the 1960s, ribbon mics are still appreciated today by experienced music recording engineers. However the KU3A is a rare microphone, a collector's item, and few studios or rental houses own them. Opportunities to work with a good KU3A are limited.

How is the KU4 different from other ribbon microphones?
The KU4's supressed rear lobe is useful when the back of a figure-of-eight would pick up undesirable sounds. The KU4's reduced proximity bass boost facilitates closer micing and its low-tuned ribbon delivers solid, undistorted bass. These characteristics make the KU4 well suited for modern studio production. Its lightly-tensioned, ultra low mass ribbon has a frequency response out to 40 kHz and fast, accurate transients. There is no upper midrange ringing common to large condenser mics. The KU4â??s ribbon is well protected and its field-tech replaceable pole piece and ribbon assembly is a real convenience if an accident occurs. The KU4 is your ticket to discovering why the KU3A has been part of high-end studio life for over 60 years. AEA is honored to play a part in its history, and invites you to listen to the KU4 and claim your part of this legacy.

AEA KU4 Unidirectional Ribbon Microphone Features

  • Contemporary realization of the RCA KU3A classic
  • Supercardioid pattern for excellent rear rejection
  • Reduced proximity effect
  • Smooth, high-bandwidth frequency response
  • Authentic New Old Stock RCA ribbon material
  • High-quality anodized & nickel-plated finish
  • Custom AEA transformer, neodymium magnets
  • Consistent Quality
  • Field-tech replaceable ribbon assembly
  • Hand-crafted in Pasadena, California

AEA KU4 Unidirectional Ribbon Microphone Applications

  • Close-mic vocals
  • Brass
  • Upright bass
  • Drum overheads
  • Anything where the bidirectional rear pick-up can be problematic

AEA KU4 Unidirectional Ribbon Microphone Specifications

  • Operating Principle: Velocity microphone
    • Frequency Response: Below 30 Hz to above 20 kHz
    • Maximum SPL: 140 + dB SPL above 200Hz for 1% third harmonic
    • Output Sensitivity: 2.8 mV/Pa into unloaded circuit
    • Output Impedance: 300 Ω nominal
    • Recommended Load: 1.2 KΩ or greater
    • Phantom power: Not required or recommended (pair with the AEA TRP or AEA RPQ preamps for optimal impedance matched performance)
    • Polarity: Pin 2 high for positive pressure at the front of the microphone.
    • Connector: XLR-3M wired to a 1.5 meter captive cable
  • Off Axis Response:
    • Polar Pattern: Supercardioid
    • Relative Output at 180° (dB): -12
    • Angle of Maximum Rejection: 135°
  • Transducer element
    • Ribbon Thickness: 1.8 microns ( .0000018 meter ) of pure aluminum
    • Ribbon Width: 0.082"Â? (2.1 mm)
    • Ribbon Length: 1.25" (28.6 mm)

AEA KU4 Unidirectional Ribbon Microphone Includes

  • AEA KU4 Ribbon Microphone
  • 1.5 Meter Microphone Cable (Attached)
  • Custom Storage/Shipping Case
  • Stand Adapter
  • Manual
  • Manufacturer Warranty

1 Review Hide Reviews Show Reviews

  • 5
    Beautiful ribbon sound in a directional format
    Stuart Martin

    I often use the standard fare of Neumann, AKG, etc. large and small diaphragm condensers, and I've always been happy when the mix includes a couple of sources recorded with AEA's R84 or R88 (or even a couple of Royer R121's). However, a recent jazz session left me feeling like the room was too prominent in the sax and trumpet tracks (recorded with an R84 and an R121, respectively in a "live" room situation). Alan Moon suggested the KU4, and the matched pair I received has been a great investment. Compared to the R84 (or R121) the KU4's sound mitigates the proximity effect while providing a richer experience in the 2k to 10kHz region with a reduced sensitivity to sounds from behind the mic. While some may feel the mic is expensive, it has a very worthy and useful sound coupled with a very high-quality fit and finish (at almost five pounds).

What We Think


All of the folks here at Front End Audio are really excited about the new AEA KU4 Supercardioid Ribbon Microphone - winner of the 2010 Pro Audio Review PAR Excellence Award. While figure-8 ribbons afford some really positive attributes in regards to placement (using the null points of the microphone to optimize rejection of unwanted bleed), sometimes it's desirable to be able to get the sound of a ribbon while also getting the rear rejection of a supercardioid pattern. Based on the RCA 44, RCA engineers originally developed the KU3A to be a boom microphone to catch dialogue - hence the need for the supercardioid pattern (no need to catch rear ambiance of the rafters, right?). The increased width of the forward pickup pattern over the traditional Figure-8 pattern of traditional ribbon mics made the RCA KU3A a much loved microphone of vocal-stylists who had the good fortune to have used one. It is in the spirit of making something that has been most difficult to acquire available again to artists and engineers alike, that Wes Dooley and the folks at AEA bring you the KU4 - And Front End Audio is happy to help you acquire yours.

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