Microphones, History of Radio, Broadcaster, Broadcasting

How Were Radio Microphones Invented? (Live365 History of Radio)

Microphones: we wouldn't have talk radio without them. They pick up on our every word, and broadcast those words to the whole wide world. Microphones are an essential part of being a broadcaster, and for today's Live365 History of Radio, we're going to give you a short history lesson about the radio microphone; who came up with the idea, how it was invented, and how it was improved for the airways.

There are many different kinds of microphones used today, but the history of the radio mic specifically is a fascinating one. Testing, testing - it's time to check your mic knowledge! Keep reading to learn more about the history of the radio microphone.

The Early History of the Microphone

Unsurprisingly, we can attribute the invention of the microphone to Alexander Graham Bell. (You know, that guy who invented the telephone?) Bell patented the first version of the microphone in 1876. His microphone consisted of a wire which conducted electrical direct current (DC). Audio signals were generated and received by a moving armature transmitter and its receiver, and transmission was possible from both directions. Bell later improved upon his microphone, making his second transmitting device utilize a liquid transmitter.

Bell first demonstrated his microphone at the Philadelphia Centennial Exposition of 1876. This microphone utilized a variable contact principle to provide a more effective method of electrical signal modulation than his first microphone design. In 1877, inventor Emile Berliner patented a design based on Bell's liquid transmitter idea. Berliner's device used a steel ball placed against a stretched metal diaphragm. Soon after, Francis Blake also improved upon Bell's design, patenting a module that used a platinum bead impressed against a hard carbon disc as the variable resistance element. Blake's device fell short of the desired frequency range, but became the standard of Bell's telephone system for years because of its efficiency in modulating telephone signals.

Then came carbon microphones. Blake eventually developed a microphone transmitter that used loose carbon granule elements. This early microphone design was the precursor to the carbon microphone: the most widely used microphone type from its invention to the present day. David Edward Hughes independently developed a carbon microphone in England, while Thomas Edison is credited with revolutionizing the communications industry in America with his carbon button microphone. This device allowed voice signal to be converted into alternating current which was passed through a transformer, therefore allowing higher voltages to be used to send the signal over a long distance.

The invention was no sweat off Edison's back, because before his carbon button microphone, he had already designed a more simple "mechanical" mic. It would engrave foil or wax to record voice and music. In 1877, he developed a system which would imprint signal as bumps on tin foil. Edison, his team, and competitors worked over the years to develop a better microphone for those wax cylinders. (At the time wax cylinder recorders were called - you guessed it - "records.") The carbon button microphone was the design he needed to perfect his wax cylinder recording work.

Bell quickly adopted the use of carbon microphones into his telephone system. Because early radio was being developed around the same time, some pretty swanky carbon microphone designs came into play during the Golden Age of Radio that began in the 1920s. You can see one design, made by Shure, in the video below.

Microphones in Early Radio

The carbon microphone was readily used in early AM radio transmissions and could be used as an amplifier. This was because the microphone was relatively cheap to produce, had a long life, and was robust and portable compared with liquid microphones.

The carbon microphone dominated from 1879 until the 1920s when it was replaced by more advanced variable resistance microphones. Since the telephone system was large, slow to change, and had a profitable monopoly, there was little pressure to move away from the inferior sound quality of the carbon microphone. Seriously, they lasted a long time. Rotary dial telephones were manufactured with carbon microphones all the way up until the 1980s!

Anyways, with the advent of commercial broadcasting in the early 1920s, the need for better microphones arose. Western Electric, the manufacturing branch of Bell Telephone, eventually developed what was then called the "electrostatic" microphone, as well as the "electrodynamic" microphone. These later came to be known as the condenser (or capacitor), microphone and the moving coil microphone, respectively. The Western Electric Model 7A was an improvement on Edward Christopher “EC” Wente's initial condenser model made in 1916. The Western Electric Model 7A was manufactured in 1927.

Following the invention of the condenser microphone were the inventions of two very similar types of microphones; the aforementioned moving coil (or dynamic) and the ribbon (or velocity) microphones. During the 1930s and 1940s, the microphone manufacturer Radio Corporation of America (RCA), made a number of ribbon microphones. They were EVERYWHERE in radio. Below is a video of a man repairing a 1930s Amperite ribbon microphone, as well as a clip showing off a classic 1940s RCA mic.

Radio Microphones in Modern Times

While the popularity of the ribbon microphone eventually died by the 1960s, the condenser microphone eventually dominated the airwaves. Not because of the microphone itself, but due to changes in the way voices and music were recorded.

Ribbon microphones have an inherent, high-frequency roll off that is similar to the way people hear. Between the 1930s and 1990s, the majority of people were recording voice to tape machines through consoles which both had a high-frequency roll off. Those tapes were then put on vinyl which also had a high-frequency roll off. Then those vinyls were played on radio, which also had a high-frequency roll off. By the time the original source track hit the home listener, much of the high-frequency content was totally lost.

Until the late 1950s, condenser microphones could not compare to the ribbon’s frequency response. But condensers steadily improved and swept the recording and radio industries. They became the “go to” mic for many recording studios. Because of their high-tuned system, frequencies in condensers in the top-end were exaggerated and hyped. Sometimes these condensers were so hyped, monitoring vocals directly through the console would sound harsh. But by the time the condenser was recorded to tape and then transferred to vinyl and then played back on radio, the top end was greatly rolled off and sounded smooth.

Now, the most common type of studio microphone is the electret condenser microphone. Some broadcasters also choose dynamic microphones, as they have grown over time as well. With the digital age, the quality of sound microphones can record has improved drastically. And they still continue to improve today!

And that's about it for the history of microphones so far. We hope this article has amplified your knowledge on the subject. (Not our best joke, but we tried!) Thanks for reading and happy broadcasting!


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Article Image: A retro ribbon microphone stands in front of a green background. (maxxyustas via DepositPhotos.)

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About Kathryn Milewski

  • New Jersey