Electro-Voice Model 664
A chrome-finished cardioid dynamic that Electro-Voice's own advertising called the world's best general-purpose mike. The Variable-D porting behind that claim is why it still shows up in studios sixty-odd years later.
Overview
The first thing you see on a 664 is the finish. It's satin chrome, per the original announcement, though Electro-Voice's own ad copy from the period simply says "chrome finish." Either way it's a bright, hard, reflective body that photographs badly and feels solid in the hand. The second thing you see is the holes. There's one on top, slots on each side, and another near the rear. If you don't know what they're for, they look like a manufacturing accident. They're not. They're the entire point of the microphone.
Electro-Voice built the 664 around its Variable-D principle, and the company's own literature explains the scheme in unusual detail. Behind the side slots sit small acoustic "windows" that lead straight to the back of the Acoustalloy diaphragm. The path is short and tuned so only high frequencies get through - and by the time those highs arrive from behind the mic, they've been cut by almost 20 dB. The top hole handles midrange, with a longer path and additional filtering. The rear hole handles lows, with the longest path of the three. According to E-V, rear rejection stays as uniform as front pickup, with no loss of sensitivity. The company was blunt about the competition. Most cardioids of the day used a single cancellation port for all frequencies, which E-V called a compromise that left many "single-hole" designs effectively omnidirectional at one frequency or another.
That's a marketing claim, and it should be read as one. But the critique under it is a real engineering problem. Single-port cardioids can have inconsistent off-axis behavior, and they suffer from proximity effect, where bass response climbs as you crowd the grille. The multi-port Variable-D approach was E-V's answer. The company claimed the design eliminated proximity effect "completely."
Frequency response is quoted at 40 to 15,000 cps in the ad copy, and at 60 to 13,000 cps in the original product announcement. That's a discrepancy. The narrower figure comes from the launch notice. The wider one appears in the later advertising that ran in the tape and hi-fi press. The safest reading is that the 664 covers roughly 40 Hz to 15 kHz in its advertised band, with the tighter numbers coming from the initial spec sheet. Either way it's a wide-range dynamic for its era. Audio (July 1963, p.52) pitched it to readers as the starting point for turning home "sound snap-shooting" into professional-quality recordings, noting that the 664's design allowed wider range without compromise at either the top or the bottom end.
Output level is listed at 55 dB, at 150 ohms. In practice that's a healthy signal that will drive a tape recorder or amplifier input at normal gain settings, without cranking the preamp and dragging up its noise floor. E-V's advertising made exactly this argument, noting that the mic's high output let recorders run at ordinary gain. The 664 can be used on a floor stand, a desk stand, or carried in the hand, and it has an on-off switch.
Impedance is selectable. The period advertising describes a multi-impedance arrangement covering low, medium, or high impedance, changed at the cable by moving a single wire. The original announcement lists 150 ohms specifically. For anyone patching a 664 into a modern interface, the high-impedance setting is the wrong match for most contemporary gear.
Two more details from the original announcement. The 664 uses a pop-proof filter to cut wind and breath blasts, and it's shielded against dust and magnetic particles. It ships with an 18-foot cable. List price at introduction was $79.50, which rose to $85.00 in the advertising that followed. High Fidelity (August 1963, p.15) quoted the $85.00 list figure and described the 664 as putting out a healthy −55 dB signal to match any modern amplifier or tape recorder, with high or low impedance selectable at the cable.
That price put it at the top of E-V's general-purpose line. The same 1963 Audio advertisement that ran the 664 also listed the omnidirectional Model 611 at $45.00, the general-purpose slim dynamic Model 623 at $57.00, and the "Slimair" Model 636 at $72.50. The 664 sat above all of them, and E-V positioned it that way, calling it the world's best general-purpose cardioid and guaranteeing it would outperform all others. The company's pitch to broadcast and TV engineers was that Variable-D mics record what you want to hear and nothing else, with no unwanted background noise and no boom even from close talking. That's ad copy, not a test report.
What independent voices said is harder to pin down. A 1957 piece in Tape Recording (October 1957, p.3) presented the 664 alongside the Model 951 as the choice of broadcast and TV engineers. A separate technical article in the same publication (the L. L. Farkas piece on microphone characteristics) used the 664's directivity pattern as its illustration. It noted that a good dynamic of this type will pick up tones to around 15,000 cycles and is considerably less directional than the other microphone types discussed. So the 664 was treated as a reference example of what a competent cardioid dynamic could do, not as an exotic outlier.
Now the caveats. The 664 is a dynamic, and dynamics of this vintage don't have the airy top end of a condenser. The 15 kHz figure is the advertised ceiling, not a description of how it sounds on a cymbal. The Variable-D porting is genuinely effective at rejecting rear sound, but it depends on those ports staying clear. A 664 that's been stored in a dusty case or handled carelessly can have its acoustic windows partially blocked, and the pattern degrades. The on-off switch is a known wear point on any microphone of this age. And the chrome finish shows every fingerprint and every scratch. None of that is disqualifying. It's the normal condition of buying a sixty-year-old dynamic.
Collectors and working engineers chase the 664 for the same reason they chase most good vintage dynamics. It's a cardioid that behaves predictably in a bad room, it doesn't need phantom power, and it has a voice. The Variable-D design separates a 664 from every generic single-port cardioid of the period, and it's the reason the model stayed in the catalog and in the advertising for years. Prices have firmed up as the studio market rediscovered vintage E-V dynamics. A clean example with an intact switch, clear ports, and the original cable is worth meaningfully more than a parts-unit with a seized switch and a dented grille. Buyers should test the impedance wiring before trusting it, and should budget for a cable replacement regardless of what the listing claims.
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