SoundField ST-250
A stereo microphone that puts the whole control room on a cable — capsule angle, polar pattern, M-S or X-Y, all adjustable after the stand is clamped down.
Overview
The ST-250 is the microphone you set up once and then argue with from across the room. Everything that matters — the effective angle between capsules, the polar pattern from omni through every cardioid to figure-of-eight, the switch between X-Y and M-S formats, the choice between vertical and end-fire orientation, even a left-right invert — lives on a separate Control Unit rather than on the mic body. That means a engineer can place the thing in a hall, walk back to the desk, and reshape the stereo image without touching the stand. Collectors who have used one describe the experience as closer to operating a console than to positioning a microphone.
The capsule array itself is a coincident design, and the manufacturer's own literature claims it produces "the most accurate stereo image of any microphone available" — marketing language, to be sure, but the underlying approach is the real story. Because the capsules are coincident, the mic is mono-compatible by design, and the polar patterns are described as linear both on and off axis. The frequency response is quoted at 20 Hz to 20 kHz. Surface-mount construction is used throughout to keep the body compact, which is the sort of detail that matters more to a repair tech than to a buyer.
Where the ST-250 gets interesting is in the format switching. In X-Y mode the capsule angle sweeps from 0 to 180 degrees, so the user can dial the stereo width from a mono point source out to a crossed figure-of-eight — and setting the angle to zero gives mono outright. In M-S mode the angle control affects only the sides, leaving the centre image untouched, which is precisely what a broadcast engineer wants when the same recording has to fold down cleanly for a mono listener. A separate switch flips the mic between vertical and end-fire use, and the two controls combine: M-S or X-Y, end-fire or vertical, in any of the four combinations. There is also a four-channel "B format" output available through the optional ST-CB3 cable, which taps the raw capsule signals for surround work.
Power is refreshingly flexible. The mic runs from mains (110–250V), from phantom power, or from standard C cells in the control unit, with the manufacturer quoting up to 40 hours of battery life. A headphone monitor on the control unit lets the operator check the signal in X-Y format regardless of which mode is engaged, though it only functions on mains or battery power. An attenuator pads the input for very hot sources, a bass roll-off trims from 120 Hz to tame wind and room rumble, and the invert switch corrects the left-right swap that happens whenever a stereo mic gets hung upside down.
Mix (June 1992, p.3) framed the ST-250 alongside the SoundField MkV as going further toward resolving the practical difficulties of stereo miking than any microphone then made, singling out the patented encoding process that lets the recorded image be reworked in post production. That post-production flexibility is the pitch, and it is a real one: a stereo image captured with a coincident array can be re-angled, re-patterned, and re-balanced after the fact in a way a spaced pair never can. Studio Sound (March 1991, p.11) described the mic as remotely switchable between left/right and M-S formats and between vertical and end-fire positions, aimed at studio recording, film location work, and broadcast.
The kit as shipped included a foam windshield, a 3-metre cable, a stand adapter, and a field carrying case. Optional extras ran to a shoulder case for the control unit, 20-metre and 100-metre cables (the long one on a drum), the ST-CB3 B-format cable, a shock mount, and a Rycote windshield with pistol grip and mount.
A note on battery life: the manual's 40-hour figure assumes C cells in the control unit, while at least one period write-up suggested a much shorter real-world runtime under normal conditions. Treat the manual's number as a best case and plan on carrying spares for location work.
The ST-250 sits in the SoundField line as the stereo microphone that brought the company's multi-capsule approach into a self-contained, remotely controllable package. It is not a simple point-and-shoot mic, and it rewards someone willing to learn the control scheme — the angle and pattern interactions in M-S mode in particular take practice to use musically rather than just technically. For a collector, the appeal is the same as it always was: a microphone that behaves like a small system, with a control surface that lets you fix a stereo image you got wrong without striking the stand.
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