KM 254c

Common name: Neumann KM 254c

Production Status: Discontinued / Vintage

The Neumann KM 254c is a special version of the KM54 c with an RF-shielded 7-pin Tuchel connector manufactured from 1964 to 1969. Powering requirements and microphone specifications are identical to the KM 54c. KM is the acronym for “kleinmikrophon” meaning “little microphone”. the KM 54c is the last improved circuit version of the KM 54. In 1953 Georg Neumann GmbH introduced the “KM” family with the KM 53, a miniaturized pressure (omnidirectional) condenser microphone. The professional market request was for microphones offering the same quality as the U 47, M 49 and M50 with a very small size. These microphones were aimed at television broadcast and similar applications. In 1954 a newly developed 21mm cardioid capsule, the KK 54 was manufactured. It had a great performance with 25 dB / 1 kHz rejection for back-side sounds. The microphone preamplifier was almost identical to the one used in the KM 53. It was designed around the Telefunken AC 701 k tube. The output transformer and all the necessary components were housed within a very small cylinder achieving a high grade of miniaturization for the times. The aluminium diaphragm was able to withstand the high heat coming from TV lamps better than a standard synthetic film membrane (e.g. PVC). The circuit received improvements during the time resulting in a KM 54, KM 54a and KM 54c exactly as it happened for the 53 and KM 56. The special “RF-proof” series are denominated KM 254, KM 254a and KM 254c. These feature a larger RF-shielded Tuchel connector and so are easy recognizable. Many accessories were available for KM’s such as different length capsule probes, in-line pad modules (Z 29) as well as standard, rack mount and battery-operated power supplies. The KM 54 microphone was used extensively for both pop-rock productions and TV shows. For decades it was the microphone used by the Pope in San Pietro. Many of them are still in use today although many have had their KK 54 replaced by the later KK 64 when they were discontinued.

Electrical Characteristics

Frequency Response
40Hz - 15 kHz
Output Sensitivity
1.2 mV/Pa
Self Noise (CCIR)
Self Noise (DIN/IEC)
Output Impedance
50 or 200Ω
Recommended Load
Proprietary unit
Supply Current
Alternative Powering
Tube Model
Telefunken AC 701

Switchable Options


Physical Characteristics

Tuchel 3469 (7-pin)
Connector notes
Available Colours
Matte satin chrome. Matte black
110 g
130 mm
Min diameter width
21 mm
Max diameter


Microphone box
NKMH power supply. BB9Kh battery operated power supply. Z38 elastic suspension. KC7 cable. KC8 cable. MF1 table stand. Z118 windscreen