Schoeps CMTS-501U (1979)
Two capsules, one rotating head, and a satin-chrome tube that put a full stereo image in a single mic body - for a price that made engineers wince.
Overview
The CMTS-501U is a tubular condenser in satin chrome, roughly 30mm across and 225mm long. It weighs around 320g net. You notice that on a stand, but a decent boom will hold it. It packs two independent capsule systems into one body, each switchable between omnidirectional, cardioid and figure-of-eight. That makes it a stereo microphone with full pattern control on both channels, which in 1979 was a serious piece of kit.
The upper capsule rotates through a full 360 degrees. Schoeps put a ring of coloured dots around the housing so you can read off each 45-degree increment by eye. That suits coincident and near-coincident stereo work. You can dial in the angle between capsules without dismantling anything, and the dots let you return to a setting you liked. The lower capsule stays fixed. Powering is 48V centre-point phantom, drawing roughly 2 x 0.65mA. The base carries a 5-pin connector with a short adaptor lead supplied, and connectors were offered in either Tuchel or Cannon form, or alternatively XLR or DIN.
Frequency range runs 40Hz to 16kHz. Sensitivity is approximately 1mV/µbar in omni and 1.1mV/µbar in the other patterns - 10 or 11mV/Pa respectively - into a load of 600 ohms or more. Self-noise is about 27dB in omni and 26dB in cardioid and figure-of-eight to DIN 45405, or 20dB and 19dB respectively to IEC 179. Signal-to-noise ratio is 74dB in omni and 75dB in the other patterns, A-weighted against 1Pa. Maximum SPL for 0.5% total harmonic distortion lands at approximately 125dB in omni and 124dB in the directional patterns. None of that is spectacular by modern standards, but it is consistent and usable.
Studio Sound (June 1979, p.94) put the CMTS-501U through the lab alongside six other microphones — the AKG C34 and C451/CK22, the Electrovoice 1777 and RE20, the Sennheiser MZK 431 Profipower and the Shure SM81 — measuring sensitivity with tone bursts to dodge wall and floor reflections, and plotting polar and frequency response in the anechoic chamber at the Polytechnic of North London. In that comparison the Schoeps measured a sensitivity of 1.0mV for 74dB SPL, an A-weighted equivalent noise of 26dBA, an impedance of 215 ohms at 1592Hz, and a power draw of 1.34mA at 48V. The same table rated its handling noise as poor and its pop sensitivity as medium — a fair cop for a body this size with two capsules stacked in it. The review also flagged the supplied elastic mount: a tubular clamp with plastic collets, a neat cable clamp and a swivel on the stand bush, but the swivel's friction was judged inadequate, so vibrating the stand could shift the mic's position no matter how hard the adjusting screw was tightened. That's the sort of flaw that shows up in a real session, and it's worth knowing before you go hunting for the original mount.
The price was £695 in the UK at launch, and the mic was distributed there through Scenic Sounds Equipment on Dean Street. Studio Sound ran a correction in its August 1979 issue (p.24) after the June review printed the wrong UK agent. The manufacturer was Schalltechnik Dr-Ing Karl Schoeps of Karlsruhe, West Germany, with Studer Revox America handling the US. At £695 the CMTS-501U sat well above the single-capsule CMC-series mics in the same catalogue, which started around £230. The extra money bought two capsules, a rotating head, and a single body doing stereo duty.
A pair of separate condensers gives you more flexibility in spacing and angle. A single stereo body with rotatable capsules gets you a coincident pair with matched electronics in one stand position, which helps in a tight venue or a session where the mic count needs to stay down. Recording-Engineer (August 1983, p.100) listed the CMTS-501U among the microphones with individually rotatable capsules suited to M-S and near-coincident work, alongside the AKG C-422, C-34 and C-33, the Milab XY-82 and the Neumann SM-69. It also got used. A 1985 Studio Sound piece on a classical recording operation lists a CMTS501U stereo mic in the equipment inventory as the main pickup, with other mics on the ends to widen the image.
Today the CMTS-501U is a specialist's tool. It suits engineers who understand pattern control and stereo technique, and it is a poor choice for a plug-and-play vocal mic. The period review noted handling noise and pop sensitivity, so it wants a proper shock mount and a bit of distance from close sources. The original elastic mount has a weak swivel, which is a known annoyance. The 5-pin connector means you'll want the adaptor lead, and a bare body without it is a hassle to wire up. Service and capsules are the usual Schoeps question, and the capsules are worth inspecting carefully. Prices for clean examples with the mount and lead tend to reflect a niche stereo tool rather than a collectible, so patient buyers can do well.
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