Neumann KM84

The @neumann.berlin #KM84 was introduced in 1966 and built until the early nineties, and is still one of the best FET cardioid small-diaphragm condensers of all time.

I have two of them, they are ex BBC and have very close serial numbers.

The KM stands for Kleine Mikrofon, German for small microphone, the 8 means it is phantom powered and the 4 that it is fixed cardioid polar pattern.

KM84s are based around a gold-covered mylar diaphragm. This diaphragm is supported in front of a metal backplate, and these two conductive 'plates' form a simple capacitor — a device which can be used to store electrical charge.

The amount of charge that can be stored is proportional to the distance between the two plates. Consequently, when sound waves vibrate the diaphragm closer or further from the backplate a difference in charge is created which can then be converted to an audio signal.

Small diaphragm capacitor (or condenser) microphones are usually chosen over their large diaphragm counterparts in a few different scenarios but usually when you want a more natural sound over the more coloured LDC.

While SDCs tend to have a slightly higher noise floor than LDCs, in use this tends to be negligible because most modern mics are very quiet, SDCs usually have an excellent transient response due to the ability of the small diaphragm being able to follow the wave more accurately.

They also have a very consistent pickup pattern meaning the directionality of the mic remains more uniform across the frequency spectrum (When the capsule diameter is similar to or larger than the wavelength, the mic becomes more directional which means in LDCs the pickup pattern gets thinner in the higher frequencies).

The result of this is that the off-axis response tends to be more accurate in SDCs, this has benefits when recording a source where bleed from other sources is unavoidable for example when recording a snare drum the hi hat bleed still sounds good with a KM84 (not the case with an sm57).

I love to use my KM84s on piano, acoustic guitar and other stringed instruments as well as drums (overheads, snare, hi-hat). It also sounds good on accordion, reeds and woodwind. It sounds great on my double bass too. It has a very firm and tight lower mid range which I find quite unique.

The KM84 has been replaced with the KM184 which uses the same capsule but with a transformerless impedance conversion circuit which, to my ears doesn’t sound as good. Fingers crossed Neumann do as they have done with the U47fet and U67 and reissue this mic, along with its sibling the multi-pattern #KM86.