Electro-Voice Model 676 Dynamic Cardioid
A hundred-dollar microphone with a tapered tube in its tail that solved the cardioid's oldest problem.
Overview
Turn a Model 676 around and the first thing you see is the backbone - a slotted, tapered metal spine running down the rear of the body. It looks like industrial design showing off, and Electro-Voice's own advertising played it up, billing the 676 as "the only microphone with backbone." It wasn't decoration. The tube is the acoustic heart of the microphone, and it's the reason the 676 earned a reputation as a problem solver in the mid-1960s.
The problem is one that has plagued cardioid microphones since the beginning: a single fixed rear path can only cancel sound arriving from behind at one frequency. Ask most cardioids to reject a monitor wedge or a loud audience and they'll do it well across a narrow band while everything else bleeds through. E-V's answer was patented under U.S. Patent 3,115,207 and trademarked Continuously Variable-D. The rear path is a tapered tube whose effective acoustic length changes with frequency - long for lows, short for highs, with no moving parts anywhere in the chain. According to E-V's literature, that gave a useful cardioid pattern across the entire response range rather than at a single tuned point, plus more uniform rear cancellation and smoother off-axis behavior than the common fixed-path designs of the day.
In a real room, the 676 is unusually resistant to wind and handling shock for a microphone of its type. It also shows almost none of the proximity effect - the bass boost that appears when a performer works the grille up close - that afflicts most cardioids. The frequency response is specified as flat from 40 to 15,000 cps. A recessed switch on the body lets the user tilt the bass down 5 or 10 dB at 100 cps to fight reverberation, low-frequency feedback, or room rumble at the source.
Inside sits E-V's Acoustalloy diaphragm, a low-mass alloy the company described as effectively indestructible — a claim backed by a warranty with no time limit at all. E-V's copy stated plainly that if a microphone failed, you could send it back, and if there were even a hint that workmanship or materials were at fault, the repair would be free, decades later if necessary. That's a striking promise from any manufacturer, and it says something about how confident E-V was in the 676's build. The diaphragm's low mass is credited with the microphone's smooth, peak-free, wide-range response and its unusually high output for a body this small. Dual output impedances — high or balanced low — are selectable at the cable, and the element is protected by high-efficiency dust and magnetic filters.
Physically, the 676 is short and finely balanced, and it slips into a 1-inch stand clamp for quick, positive mounting. It has no on-off switch. That is deliberate: E-V positioned the 676 for hand-held and suspended applications where a switch is one more thing to bump or fumble, and the company's literature calls out the shorter length and balance as making it ideal for those uses. Buyers who wanted the same performance with a standard mounting stud and an on-off switch were pointed to the Model 674, which E-V described as identical in performance. At introduction the 676 listed at $100.00 in satin chrome or non-reflecting TV gray, or $110.00 in gold, with the companion 674 at the same $100.00. The optional Model 420 desk stand added $20.00. These were list prices before normal trade discounts. The microphone was advertised in the audio press through the middle and late 1960s - Audio (October 1965, p.53) ran the "microphone with backbone" pitch, and High Fidelity (September 1967, p.111) carried the same message, with HiFi/Stereo Review running it in 1966 and again in 1968.
Those magazine appearances are advertisements, not independent lab tests. The technical claims - the CV-D behavior, the 40 to 15,000 cps response, the absence of proximity effect, the Acoustalloy diaphragm - come from Electro-Voice's own marketing and product literature, not from a reviewer's measurement bench. That doesn't make them false, but they are manufacturer claims, not third-party verification. The period advertising does show that the 676 was a sustained, heavily promoted part of E-V's line for years, with the CV-D concept at the center of the pitch.
The 676 is a dynamic cardioid with selectable high or low impedance at the cable, so it can drive a vintage high-impedance input or a modern balanced low-impedance preamp without a transformer swap. The bass roll-off switch is useful in untreated rooms. The lack of an on-off switch suits hand-held work and is a minor annoyance for anyone who wants to mute at the mic. The small size and high output make it easy to place in tight spots where a larger dynamic won't fit.
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