The Shure Unidyne I Model 556 – This variation of the Unidyne I is one of the most recognizable microphones Elvis used early in his career. According to the 1947 Shure product data sheet, “The Model 556 is a dynamic, unidirectional moving coil, super-cardioid type microphone providing high quality sound reproduction over a wide range.
The true unidirectional characteristic of the ‘Unidyne’, obtained by the ‘Uniphase’ principle, offers very satisfactory operation in adverse acoustic conditions where a conventional microphone would be practically useless.
The microphone features a new acousto-mechanical circuit containing a moving coil element, which works in conjunction with a high flux magnet, provides high efficiency and a peak-free response from 40 to 15,000 cycles. Rear response is down about 15 decibels (dB) due to the “single-phase” one-way acoustic network.
The new voice coil unit comes with a double windscreen to ensure quiet outdoor operation. As a precaution against mechanical vibration, the unit is spring-suspended inside the microphone housing, which, in turn, floats in rubber under tension in the stand connector.
The case is modern in design, with attractive streamlining and a grille treatment. The swivel allows the microphone to be aimed at the sound source for better sound pickup.
Shure’s iconic Unidyne microphone featured on the special edition “Elvis” stamps issued in 1993.