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AEA KU4 - Unidirectional Ribbon Microphone

AEA KU4 is modern interpretation of the original RCA KU3A,which many engineers consider to be the best ribbon microphone ever made.It combined the smooth ribbon sound of a 44 with a unidirectional pattern.Top-quality ribbon microphones handmade in U.S.
AEA KU4 - Unidirectional Ribbon Microphone
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AEA KU4 - Unidirectional Ribbon Microphone
AEA KU4 - Unidirectional Ribbon Microphone
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The Legacy of the RCA KU3A

The KU4 is AEA's modern interpretation of the original RCA KU3A, which many engineers consider to be the best ribbon microphone ever made. The increased rear rejection of the supercardioid pattern reduces the amount of room sound, which is often desired in modern production applications, particularly vocal recording. With a custom transformer, strong neodymium magnets and a low-tuned RCA new-old stock ribbon, the KU4 continues AEA's legacy for wide-bandwidth, top-quality ribbon microphones handmade in Pasadena, CA.

The KU4 celebrates the legendary RCA unidirectional KU3A, a highsensitivity 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.

We are proud to expand your opportunities with the AEA KU4 featuring an RCA ribbon, interchangeable KU3A parts and consistent performance.

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 KU4’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.


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

for unidirectional ribbon microphone AEA KU4

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
  • 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” (2.1 mm)
  • Ribbon Length: 1.25” (28.6 mm)

  • Included: Custom storage/shipping case, stand adapter, manual and attached 1.5 meter microphone cable

Limited Warranty:
  • Three years parts and labor

  • KU4 weight with cable: 4.7 pounds (2.15 kg)
  • KU4 weight with case: 7 pounds (3.2 kg)
  • Length: 12.65” (32.4 cm) Width: 4.62” (11.7 cm) Depth: 3.75”(9.5 cm)

AEA KU4 Wins 2010 PAR Excellence Award!

"The editorial staff of Pro Audio Review is pleased to announce the 25 recipients of the 2010 PAR Excellence Award. This award is presented to professional audio companies that exhibited a particularly significant new product at the 129th AES Convention in November 2010."