A rare matched pair of vintage Neumann KM 88i small diaphragm condenser FET microphones sitting in front of their original cases.

At the Vintage King Tech Shop, we see our fair share of rare and historic microphones pass through our doors. But when a matched pair of vintage Neumann KM 88i small-diaphragm FET condensers arrived in their original boxes, even our most seasoned technicians paused to admire them.

"These mics are really rare," says Vintage King Microphone Technician Tim "Timmo" Johnson. "In my 28 years as a microphone technician, I’ve only seen about six of these. A matched pair? That’s something special." 

A rare matched pair of vintage Neumann KM 88i small diaphragm condenser FET microphones sitting on bubble wrap on top of a stack of schematics.

Neumann KM 88i Small Diaphragm Condenser FET Microphone

Released in 1969, the Neumann KM 88i was born out of necessity. "Neumann had an abundance of KM56 capsules," Timmo explains, "so they designed the KM 88, which was a FET version of the KM56 that used the KM 84 amplifier circuit."

Like its tube-powered sibling, the KM 56, the KM 88i featured a unique double-sided nickel capsule—a design originally developed for the KM 54. This capsule gave the KM 88i a unique character. 

The KM 88i featured three selectable polar patterns. In cardioid mode, the rear capsule was disconnected, while in omni and figure-eight, both diaphragms came into play. Despite the pattern changes, the mic maintained consistent sensitivity and noise performance—a testament to Neumann’s engineering.

A page from the Neumann KM 88 manual with a photo of the KM 88 imt and a paragraph about the KM 88i.

The output circuit utilizes Neumann's BV-107 transformer—the same model used in the KM 83, KM 84, and KM 85. Its solid-state design delivers a unique tonal character compared to the tube-based KM 56. 

"As far as sound, it behaves more like a KM 56 than a KM 84," Timmo says. "It doesn’t have the warmth of a tube, of course—it’s more surgical. These mics are great for acoustic guitars, room mics, or anything, really. And with three polar patterns, they’re very versatile."

A rare matched pair of vintage Neumann KM 88i small diaphragm condenser FET microphones sitting in front of an open piece of vintage studio gear.

What made this pair of KM 88s particularly remarkable was their condition. "These mics are in immaculate shape," Timmo says. "They came in the original boxes, which is almost unheard of for something this old."

Over a few short years, Neumann released the following variations of the KM 88: 

  • KM 88 i - Standard version with 3-pin male XLR connector (170mm length)
  • KM 88 i mt - 3-pin male XLR connector, dark matte finish (170mm length)
  • KM 88 - a special-order version with a male 3-pin connector compatible with “Binder 09-0006-00-03 or Tuchel 3261001 female connectors” (165mm length)

A page from the Neumann KM 88 manual detailing the different versions of the KM 8x series microphones.

"Neumann didn’t make too many of these mics, and they didn’t make them for very long," Timmo notes. "All of the KM 88s were produced within a few years to work through their surplus of KM54 capsules." By 1986, the model was discontinued, making well-preserved examples like this pair increasingly hard to find.

Vintage King Microphone Technician Tim "Timmo" Johnson sitting at a workbench working on a rare matched pair of vintage Neumann KM 88i small diaphragm condenser FET microphones.

A close up of a rare matched pair of vintage Neumann KM 88i small diaphragm condenser FET microphones, showcasing the serial numbers on the back.

A rare matched pair of vintage Neumann KM 88i small diaphragm condenser FET microphones sitting in front of a rack of outboard gear.

Akane NakamuraIf you’re interested in purchasing a vintage microphone for your studio, we're here to help! Contact a Vintage King Audio Consultant via email or by phone at 866.644.0160.