Electro-Voice Model 911 Mercury (c. 1955–1956)
A crystal microphone built for the tape-recording boom, sold on bass response and a $27.50 price tag.
Overview
The Model 911 Mercury is a crystal microphone, the kind of pickup that defined home recording before affordable condenser mics existed. Electro-Voice built it for general-purpose work. The company's own catalog copy promised "excellent bass response" and "smooth, wide-range reproduction of music," which tells you who it was for: the tape-recording hobbyist cutting parties, recitals, and family gatherings onto reel-to-reel. The Mercury was one of several crystal models E-V advertised side by side in the mid-1950s. It sat above the budget Model 915 Century and below the cardioid Model 950 Cardax.
The published specs are modest by any modern standard. Response is listed as 50-8000 cps in one E-V catalog, but a different printing of the same catalog gives 30-8000 cps. That's either a running production change or plain catalog inconsistency. Output level is rated at −50 dB, the pickup is omnidirectional, and it uses a metal-seal crystal element with high impedance (Hi-Z) output. Hi-Z crystal mics were designed to feed the high-impedance inputs common on domestic tape recorders of the era, not the low-impedance balanced inputs of professional gear. Plug a Mercury into a modern low-Z input and you get thin, rolled-off sound.
The physical package is practical. The head tilts, and there's an on-off switch on the body, which is handy when you're juggling a tape deck and don't want to reach for the transport. The cable connects via a built-in connector rather than a captive lead. The finish is satin chromium.
Two catalog variants carried different prices. The Model 911-8, supplied with a 6-foot cable, listed at $25.50. The Model 911-20, with an 18-foot cable, listed at $27.50. That's a two-dollar premium for twelve extra feet of cable. Other E-V advertising from the same period lists the Mercury at $27.50 flat with an 18-foot cable included, and at least one dealer classified from the era shows a used example changing hands for $10.
Period coverage is thin. Tape-Recording (April 1956, p.3) ran Electro-Voice advertising promoting the crystal microphone line for tape recording work, and the same magazine's August 1956 issue (p.3) carried the campaign again. So the Mercury was actively marketed through at least the middle of 1956. These are manufacturer advertisements rather than independent reviews, so treat the performance language as E-V's claims, not measured results. The archive has surfaced no lab testing, no independent frequency-response measurements, and no service documentation for the Model 911.
A general-interest recording guide of the period noted that a crystal microphone of this type has an average range response of roughly 60 to 8000 cycles and becomes fairly directional at higher frequencies. So despite the omnidirectional rating, the top end behaves differently than the bottom. The same guide suggested owners request a directivity pattern diagram with the microphone at purchase and test it themselves by rotating the mic through 360 degrees while recording. Crystal mics were understood to interact with the room, and the manual literature of the day spent real space explaining how reflected sound changes what a microphone captures.
Crystal elements are the Mercury's weak spot today. The Rochelle-salt crystal material inside these pickups is hygroscopic. It absorbs moisture over decades and degrades, which is why so many surviving crystal microphones are dead or drastically reduced in output. A working Model 911 is a survivor, not the norm. Test the output before buying, and know that crystal replacement is a specialized repair, not a routine one. E-V advertised the metal-seal construction as a defense against exactly this failure, but seventy years is a long time.
The Mercury dates from the point where tape recording became accessible enough that a family might own a machine, and a $27.50 microphone was a considered purchase rather than a professional expense. It isn't a studio piece, and it's priced accordingly on the secondary market when it appears at all.
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