Neumann KM 85
A small-diaphragm FET condenser built around a bass rolloff switch. The studios that bought it knew why.
Overview
The KM 85 is the least discussed member of Neumann's fet-80 family. The KM 84 gave the world the default cardioid and the KM 83 the omni. The KM 85 took the same small body and capsule lineage and added a low-frequency rolloff. In plain terms, it is a cardioid with a built-in high-pass. Contemporary price lists treated the three as siblings: Neumann's UK distributor F.W.O. Bauch quoted the KM 83, KM 84, and KM 85 at the same figure, £95 in late 1977 and £77 in the spring of 1976 listing. Nobody paid a premium for the rolloff.
That rolloff is the whole pitch. Audio (January 1978, p.82) documented the KM 85 as a cardioid with a frequency range of 40 Hz to 20 kHz and a maximum SPL for 0.5% THD of 133 dB with the sensitivity switch set at −10 dB. The capsule is the KK-85 and the preamp is the KMi, running on 48 V phantom at 0.4 mA. Those numbers describe a microphone that will sit on a snare or a tom all day and never flinch, and that's where working engineers put it. It's the drum mic, not the vocal mic or the string mic.
Close-miking a drum kit loads a cardioid condenser with proximity-effect bass that has to be carved out downstream. A microphone that does some of that carving at the capsule saves an EQ move on every channel. It is the same microphone as the KM 84 with one decision already made for you.
Physically it is the fet-80 body: small, unglamorous, and built to be clamped onto a drum rim. It belongs to the subset of the series that accepted interchangeable capsules, which is why the KM 84's cardioid, the KM 83's omni, and the KM 85's cardioid-with-rolloff could share a preamp body. Studio Sound (June 1995, p.18), looking back at the family when the KM 184 arrived, described this as a small subset of the fet-80 line that did have swappable capsules. The 184 would abandon that flexibility entirely.
Collectors note that the fet-80 series passed out of favour quietly. The 1995 Studio Sound retrospective observed that the KM 84's discontinuation in favour of the fet 100 series "went curiously unmarked." If the famous KM 84 went out without a send-off, the KM 85 went out with even less. KM 84s command attention and prices, KM 83s have the omni crowd, and KM 85s trade among people who specifically want the rolloff. Scarcity is real but demand is narrow, which keeps prices lower than the model's quality would suggest. Buyers should confirm the KK-85 capsule is present and original. The interchangeable-capsule design means bodies and capsules get separated over four decades, and a KM 85 body wearing a KM 84 capsule is just an expensive KM 84.
What the KM 85 asks of an owner is patience and a phantom supply. The 48 V, 0.4 mA draw is trivial by modern standards, and the 133 dB SPL ceiling means the mic will survive anything a drummer can throw at it. The −10 dB sensitivity switch gives extra headroom on the loudest sources. It is a tool microphone in the best sense: unromantic, reliable, and specific about what it's for. If the KM 84 is the fet-80 everyone knows, the KM 85 is the one the engineers who mic drums for a living quietly kept in the case.
eBay Listings
As an eBay Partner, we earn from qualifying purchases. This helps support our independent vintage technology research.