Philips EL-7500
A microphone that arrived as a box of parts and a soldering iron - and, by most accounts, actually worked.
Overview
The EL-7500 was Philips' build-it-yourself microphone kit. It made its public debut at the 1966 Audio Fair at the Hotel Russell, where Studio Sound (July 1966, p.28) spotted it among the third-floor exhibits, listed at 7 guineas. It sat in the same listing as an £800 helical-scan video recorder. For that price you got a genuine moving-coil capsule, a matching transformer, a stand, a lavalier cord and a switch, sold as a carton of parts for a home constructor to assemble.
The kit is more thoughtful than the price suggests. The capsule is a lightweight moving-coil unit with its own acoustic filter. The body is moulded in impact polystyrene in medium and dark grey. The main housing is split into two sections joined by a small hole, which makes a pair of resonating cavities that extend the bass response. That is a real acoustic trick, not decoration. A sub-assembly carrying the on/off switch and matching transformer is held by two screws, so it can be pulled for changing impedance or fitting new leads. Source impedance is selectable at 200 ohms, 500 ohms, or high. The transformer provides the 500-ohm and high (25K) taps around a nominal 200-ohm capsule.
Versatility was the selling point. Philips designed it to serve in four configurations, and the kit ships with both a clip-and-cord lavalier arrangement and a desk stand. The same microphone can be worn, stood on a table, or handheld as a stick. Amateur Tape Recorder (December 1966, p.21) called it a unique conception - a microphone and accessories bundled to cover every use, saving the buyer money by arriving as a kit.
The EL-7500 is a consumer microphone that doubles as a small lesson in acoustics and impedance matching. Its survival rate is probably thinned by the fact that it was meant to be soldered together rather than kept in a box. Complete, assembled examples with the stand, clip and cord intact are the ones to look for.
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