Electro Voice Slim Dynamics
Electro Voice (EV) has a long and illustrious history in the electronics industry. Starting as a relatively small company near the start of the Great Depression. Check Wikipedia for a brief history of the company. EV began manufacturing inexpensive carbon and later crystal microphones mainly for PA systems and ham radio operators.
Like several other smaller manufacturers, EV had a tough time breaking into the broadcast and recording markets. In the mid 1930s EV designed a line of inexpensive but quality ribbon mikes to go along with their carbon and crystal models. These ribbon mikes had a shape similar to RCAs design yet at a much lower price. EV continued this line of ribbon mikes into the 1950s. Modesto’s KMOD used an EV ribbon in their control room in the early 50s as seen in photos on this website. Modesto station KBOX also used the EV ribbons.
EV really began to try to crack the broadcast market in the late 40s when they began to build high quality dynamic mikes. The development that really gave EV a boost was their “Acoustalloy” nonmetallic diphragm. This diaphragm was made from mylar plastic material and proved to be excellent at translating sound waves into electrical signals.
In 1950 EV came out with three revolutionary omni-directional dynamics that caused quite a stir in the audio industry. These mikes were one inch in diameter, which was much smaller than previous dynamic units.  As we related in our previous article on the American Microphone Company…American came out with their one inch diameter mikes at about this same time.
There were three “slim-trim” long barreled models. The top of the line was the model 655 [3,3A] which had the widest frequency response and was designed for TV and radio broadcasting. Then next was the model 654 designed for both TV and radio or high quality sound systems and recording…but with slightly reduced high end response and a lower price. The third unit, the model 636, was especially for PA use…but was excellent with just a slightly narrower frequency range. [6,7]
The two “broadcast” models came in black and chrome finish…then later available in “TV gray” finish. The model 636 came in bright satin chrome. All three of these mikes continued in production through the 1960s. Electro Voice continued to improve and make changes in the bodies of these mikes as time went along. EV shortened the length of the 1 inch barrel design to make their lavalier mikes used in TV and anywhere freedom of movement was important.
I remember that CBS and ABC networks began using these EV models in TV and radio in the early 50s. NBC, of course, refused to use anything but RCA mikes until sometime in the 60s…because of being owned by RCA at that time. I recall seeing the model 655 on the Arthur Godfrey TV-Radio simulcast in the early 50s.
Dick Clark on “American Bandstand” used the EV model 654 starting when his show was broadcast from WFIL-TV in Philadelphia over the ABC-TV network.[4C] Jack Bailey, MC on “Queen for a Day” on ABC used an EV 655. Local stations, as well, used the EV Slim-Trim dynamics on both radio and TV for many years.
Large market radio stations like WMCA in New York, KMPC and KNX in Hollywood were big users of the EV “slim-trim” omni dynamics back the day.
While attending the Don Martin Radio/TV school in Hollywood in 1959 I had the opportunity to tour CBS/KNX Columbia Square studios. KNX’s morning man at the time was Bob Crane, later of “Hogan’s Heros” fame, Bob used an EV 636 “Slimair” attached to a harness around his neck. This allowed him freedom of movement so he could operate 4 turntables on which he played his “drop-in” sound effects and voices on his popular show.
I remember wondering why this big 50,000 watt CBS station would use a “PA” mike like the 636 in their big Hollywood studio! Actually the model 636 was an excellent mike for voice use like interviews or any voice work. [6,7,7A,8]
KMPC’s long time midday personality, Ira Cook, used an EV model 655 in his studio. This was another station I was able to visit while attending broadcasting school in Hollywood. KMPC was another 50,000 watt station that was owned by Gene Autry for many years and featured some top name radio personalities like Gary Owens, Robert W. Morgan, Johnny Grant, Dick Whittinghill, Roger Carroll [4A,4B] and many others.
Electro Voice became a major factor in the sound industry as the years went on and even down to the present day. In addition to mikes…EV designed and built phonograph pickups, amplifiers, loudspeakers, and many other electronic products. 
In upcoming articles we will look into EV’s unique cardioid microphone units that highly impacted the broadcast industry.