The Microphone Man is back with another look at Electro Voice (EV); this time their revolutionary dynamic cardioids they called “Variable D”units. After EV had success with their “Slim Trim” omni mics, they went on to develop an excellent series of single-element dynamic cardioid mics that were unlike any others before them. In addition to the “Variable D” concept, which we’ll explore later, these were one of the first cardioid microphones to use the “end-address” rather than “side-address” design. Electro Voice “Variable-D” (D for distance) principle utilized multiple rear sound entrance points that varied the distance differing audio frequencies had to travel before reaching the rear of the diaphragm. This method of producing the cardioid or heart shaped unidirectional pickup pattern enabled the mic to be used close up without the usual “boomy”, bass boosting proximity effect of most cardioid mics. These mics had a very clean, crisp sound, especially on the human voice. EV used this new acoustic principle in three mics that they offered starting in the mid ’50s. The top of the line unit was the model 666 broadcast dynamic cardioid. This mic caught the eyes and ears of many top broadcast engineers and was used by CBS, ABC and other major broadcasters of that era. WABC radio in New York had a model 666 in its announce booth when they started their very successful top 40 format that began in Dec.1960. During this period WABC had the largest audience of any radio station in the country.
In addition to the model 666 EV also produced two less expensive versions, the 665 which was designed for broadcasting and the model 664 which was made for public address sound system use. The 665 had a very smooth frequency response very similar to the 666 whereas the 664 had a more peaked high frequency response and less bass. All three mics were high quality, rugged units and many thousands were sold. Many smaller market radio stations used the 664 because of its lower cost. Local stations using the model 664 in the ’60s were KTRB and KFIV.
In the mid ’60s EV came out with new models using this same Variable D principle but in much smaller size bodies. These newer versions, the models RE-15 and RE-16 were well used by big and small stations and networks for many years. EV still produced the original versions clear up into the late ’60s along with these newer units. Then in the late ’60s EV brought out the model 668 which had an improved “Continuously-variable-D” design that was larger and incorporated a large foam windscreen around the unit. This mic was specially designed for motion picture and TV overhead booms but also saw use in radio studios.
The model 668 lead to the development of the RE-20 model which became a radio industry standard that is in use to this very day. Disc jockeys loved the RE-20 for its “big” full bodied tone that made voices leap out of the radio speaker! Talk show hosts love the RE-20, too. Electro Voice Has become one of America’s top microphone producers, along with lots of other sound and electronic equipment.