With a supercardioid polar pattern, rich ribbon tone, and extended top-end, the KU4’s directionality allows it to be positioned almost anywhere without capturing room tone and bleed, making it one of the most flexible ribbon mics in production today.

Where To Buy

KU4 Microphone Overview

  • Supercardioid polar pattern, rejecting bleed and ambient room reflections
  • Extended top end with classic ribbon smoothness
  • Near-field ribbon mic with reduced proximity effect for close-miking
  • AEA’s redesign of RCA’s legendary KU3A
  • Made in the USA

A Ribbon Without Room Tone

AEA’s KU4 is one of the most useful and unique ribbon microphones in the world. Its supercardioid polar pattern rejects bleed from other instruments and reflections in the room while retaining matchless top-end clarity. As the brightest mic in the AEA line, it retains the full spectrum sonic range that has made ribbon mics a staple in most of the world’s great recording studios.

The KU4’s minimal proximity effect and accented mid-range make it an exceptional vocal mic that captures the presence and detail of a performance. Its near-field nature also lends to the close range recording of kick drums, strings, and woodwinds, providing a welcome brightness and balance in the mix.

The Near-Field Supercardioid

The KU4’s supercardioid polar pattern enables it to capture direct sound from a vocalist or instrument without room tone. This is an advantage when tracking musicians live in the same room or when used live on stage. With most figure-of-eight patterned ribbons, mic positioning can require a finesse to avoid other sources using the microphone’s nulls. The KU4 has none of these limitations.

Being a near-field ribbon microphone, the microphone was designed to be positioned between one and 18 inches from the source. The mic’s proximity effect kicks in six inches away from the sound source. It can be placed close to an instrument while retaining a balanced frequency response.

Unlike most traditional ribbon mics, think the KU4’s placement should be thought in terms of inches instead of feet. Of course, the KU4 can also be positioned at some distance from the sound source. It will just have a more balanced sound from up close.

The KU4 can handle 140+ dB SPL at 1 kHz. That means it will not be hurt by loud sound sources.

Hear the KU4

"AEA has definitely captured the right amount of clarity and vintage character with the KU4. This will be a permanent part of my drum rig, so much that I'm considering buying a second KU4 to move around the studio for other applications.”

- Ali Shaheed Muhammad (A Tribe Called Quest, Luke Cage)

An Alternative to Sibilant Condensers

After getting used to bright condenser microphones, sometimes traditional ribbon mics sound darker than desired. The KU4, with its unique bright character, has the best elements of both condensers and ribbons– specifically, a smooth midrange that doesn’t accentuate sibilance in the same way that condensers often do.

The mic’s supercardioid polar pattern, bright voicing, and near-field design offer the flexibility to use it in the exact same way as a condenser. This problem-solving microphone can be used in virtually any recording situation.

The KU4 In Action

A mic made for singers

Watch David Ryan Harris sing into a KU4 in this performance of “Shelter”.

See More KU4 Videos

A Reinvention of a Classic Motion Picture Microphone

The KU4 is a redesign of the legendary RCA KU3A, a unidirectional microphone originally designed for boom use in Hollywood motion picture studios. It was RCA’s most expensive ribbon microphone and fewer than 600 units were ever manufactured.

The KU3A combined the smooth ribbon sound of the classic RCA 44 with a unidirectional pattern, a wide sweet spot, and reduced proximity bass boost. It expanded the engineer’s range of placement choices and became a standard at film studios throughout the world.

Today, the KU3A is a rare collector’s item and only a handful of studios or rental houses own them. Original KU3As are notorious for their sonic inconsistencies due to production tolerances that included the use of the thick hair of English cows as a damping material.

At AEA, we engineered our KU4 from the ground up in order to recreate this seminal design while ensuring flawless consistency from unit to unit.

Yes, There’s a Matching Preamp

Since the KU4 is a classic passive ribbon microphone, the preamp is critical for optimum performance. Preamp gain should be at least +60dB or higher and the preamp should have a very high impedance. It’s the same requirement with all passive ribbon mics.

To guarantee consistent, full-range ribbon sound, we recommend AEA’s RPQ2, RPQ500 and TRP2 preamps, which were specially designed for ribbon microphones. However, preamps with above a 5K ohm impedance found in many live soundboards are adequate for guitar amps and other louder instruments. On quiet sound sources or for distance recording, an AEA preamp is highly recommended.


Ali Shaheed Muhammad / A Tribe Called Quest

“This [KU4] will be a permanent part of my drum rig, so much that I’m considering buying a second KU4 to move around the studio for other applications.”

Colin Stetson / Arcade Fire, Bon Iver, Tom Waits

“For close miking the bell and upper stack area, the KU4 is the best mic I’ve used on Bass and Baritone Sax.”

John Hill / Sia, Eminem, Portugal. The Man

“The KU4 has been our go-to mic on everything since it arrived. Love it!”

“The KU4 is honest, exactly where it needs to be while retaining a euphoric quality that’s hard to replicate with anything else. It’s truly a great experience hearing anything through that microphone. I know I’ll be excited about the results every time I reach for it.”

Josh Block (Leon Bridges)

Recording Mag

“Almost as important is that this is not just a microphone, it's a legend, and it's an RCA legend of very long standing. Don't underestimate the power of the legend; sometimes it just makes people perform better. I know, it's silly, but that's how the studio is. The KU3A was made by hand for a special job, and became a legend much the way the Stradivarius did. The KU4 makes it possible to actually own the legend.”

– Scott Dorsey read the full review

Sound On Sound

“The combination of classic ribbon smoothness with a near-cardioid pattern is a very beguiling permutation that enables the use of ribbon mics in situations that are normally inappropriate or too challenging. ”

– Hugh Robjohns read the full review

Mix Mag

“It's hard not to rave about this mic. Yes, It's expensive, but the feeling you get when you hear the KU4 in front of anything is the reason audio engineers get out of bed in the morning...The KU4 has an intimate quality that I've not heard out of any other ribbon. Using the mic is a joy”

– Kevin Becka read the full review
The AEA Sessions

AEA’s own recording series featuring our favorite artists.

Ribbon Recap
AEA’s KU4: Myth, Cow Hair, and a Supercardioid Legend
Jack White Performs Acoustic in Fargo With Five KU4s