Shure ES615
A plain omni dynamic that sold as a calibration tool and decades later found a second life as a studio room mic.
Overview
The ES615 was never meant to flatter anything. It was a measurement microphone - the sensor half of Shure's M615AS Equalization Analyzer System. The little omni dynamic came bundled in the analyzer's rigid plastic carrying case, along with a long cable and a fistful of connectors. Shure sold it separately as well, and that's the version most people run into today: a small dynamic capsule with no switches and no obvious reason to exist unless you own the analyzer it was designed to feed. In its intended role it's a frequency-response probe. The M615 has a rear-panel switch that introduces low-frequency compensation tailored to the ES615's own roll-off, so the analyzer reads flat when the mic is doing its job. Audio (July 1978, p.90) listed the ES615's pink-noise frequency response as within a 4 dB envelope from 125 Hz to 13 kHz, with roll-off below 125 Hz.
Collectors and engineers like the mic now for the same reason it was boring in 1977: it's omnidirectional and it's a dynamic. Omnis have no proximity effect, so you can put one close to a source without the bass ballooning, and a dynamic omni is about as un-fussy as a transducer gets. Electronic Musician (undated excerpt, p.7) described a session where an ES615 served as the "room-equalization" mic opposite an AKG C 451 B on acoustic guitar. Shure never had that use in mind.
The system was aimed at working sound engineers on a budget. DB Magazine (June 1977, p.46) framed the M615/SR107 pairing as gear for the engineer "who lacks a big budget for sophisticated analysis gear," a low-cost route to a fine degree of speaker-and-room correction. The ES615 is the part of that system that outlived its host.
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