Shure SM10A
Seventy-eight grams of head-worn dynamic microphone that turned a performer's whole head into a mic stand.
Overview
The first thing anyone notices on picking one up is how little it weighs. The SM10A's net weight is 78 grams, less cable and connector. That number only means something once you've worn a microphone on your head for a two-hour set. Shure built this as a low-impedance, unidirectional dynamic for close-talk head-worn work. The manual names the applications plainly: remote-site sports broadcasting and corporate intercom systems, plus singing drummers, keyboard artists, and any performer who needs a head-worn vocal mic with strong noise rejection and a smooth, natural-sounding frequency response.
The capsule is a moving-coil dynamic with a cardioid polar pattern. The manual's specification puts the frequency response at 50 to 15,000 Hz with rear cancellation of 15 to 20 dB. That rear rejection is the whole point of a headset mic in a loud room. It keeps a drum kit or a monitor wedge from bleeding in from behind the performer's head. Shure rates the impedance at 150 ohms nominal for connection to inputs rated 19 to 300 ohms, which is about as forgiving a load as a dynamic mic can present. Output is specified at -65.0 dB where 0 dB = 1 volt per 10 microbars. The French-language section of the same manual gives the open-circuit sensitivity as -65.0 dBV/Pa (0.45 mV) at 1000 Hz measured at 8 mm. That's a low-output, close-work design. It wants to be near the mouth, and it expects a decent preamp.
The mounting hardware is where the SM10A earns its keep. It rides on a supplied steel headband assembly, and an adjustable pivot lets the boom move 20° in any direction. The boom also slides out, so the microphone can be positioned up to 89 mm (3 1/2 in.) from the pivot housing. That's enough travel to get it in front of a mouth without clamping the headband down hard. A foam windscreen comes in the box to tame wind noise and explosive breath sounds. A belt clip that fits over the XLR connector hooks onto a belt or waistband to provide cable strain relief.
The connector end is a professional three-pin male XLR on a non-detachable 1.5 m (5 ft) two-conductor shielded, plastic-jacketed cable. Polarity follows the modern convention: positive pressure on the diaphragm produces positive voltage on pin 2. The overall microphone measures 203 mm (8 in.) in length with a maximum height of 44.5 mm (1-3/4 in.) at the pivot housing. The mic housing itself is 15.9 mm (5/8 in.) in diameter by 14 mm (9/16 in.) in height. Packaged weight runs 950 grams (2 lbs., 1 1/2 oz.), most of which is headband and box. The unit is eligible to bear CE Marking, conforms to European EMC Directive 89/336/EEC, and meets the applicable tests in EN55103 (1996) parts 1 and 2 for residential (E1) and light industrial (E2) environments.
One quirk: as supplied, the SM10A has no on-off switch. Shure's manual explains that one can be constructed using a Switchcraft T3F 3-pin female professional audio connector (or equivalent) with an integral switch, wired into the cable between mic and PA. It adds a caveat: for the switch to be silent, phantom power must not be active on that input channel. The intended user is someone comfortable building a cable, not someone expecting a mute button on the capsule.
The SM10A shows up in Shure's mid-1980s print advertising alongside the 520D "Green Bullet" and the SM98, in a campaign built around the line "So you thought Shure only made vocal mics." Studio Sound (September 1986, p.9) ran the spot. It pitched the SM10A/12A/14A family as the hands-free operation drummers and keyboard players demand, with noise-reducing construction. That's Shure's own marketing, not an independent verdict on how the mic sounds. The same ad block repeats across several issues of the magazine in 1986 and 1987, which says more about Shure's media buy than about the microphone.
The SM10A is a purpose-built tool rather than a studio generalist. The 50 Hz to 15 kHz cardioid dynamic, the 150-ohm load, the 20° pivot and 89 mm of boom travel, the 78-gram body all point at the same job: put a directional dynamic close to a moving performer's mouth and keep the rest of the stage out of it. Collectors and working players tend to encounter these still attached to their headbands. A bare SM10A is harder to deploy than a complete assembly, so the headband and belt clip matter as much as the capsule. The non-detachable cable is the weak point on any survivor of this age. 1.5 m of plastic-jacketed two-conductor is not a lifetime component, and a cracked jacket at the XLR end is the usual failure. Buyers should confirm the windscreen and belt clip are present, because those small parts are the ones that go missing.
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