December 17, 2013, by Craig Leerman
Microphones as we know them date back to about the mid-1800s, when many different inventors were trying to electronically transmit sounds from one place to another.
Before then, the term microphone was used to describe an acoustical device (like an ear trumpet or stethoscope) that helped amplify sounds.
One of those inventors was German physicist Johann Philipp Reis (1834-1874), who designed a sound transmitter consisting of a metallic strip resting on a membrane with a metal point contact that would complete the electrical circuit when sound waves moved the membrane (a.k.a., diaphragm).
A bit later, American Elisha Gray, an inventor and one of the founders of Western Electric, formulated a liquid transmitter that immersed a rod connected to a diaphragm into an acid solution. A second fixed rod was also immersed in the liquid, and a battery connected the two rods. As the sound waves moved the first rod, the distance between it and the second rod varied in proportion to the sound, producing corresponding changes in the electrical resistance flowing through the cell.
While Gray may have actually invented the liquid microphone first, history recognizes Alexander Graham Bell as the inventor of the telephone because he filed for a patent a few hours before Gray.
A replica of the Bell liquid telephone circa 1876. Looks similar to a microphone…
As children, we were told the story of Bell accidentally spilling some acid and calling for his assistant, saying “Watson, come here, I need you.” Watson heard Bell’s voice over the system, and it’s noted as the first “phone call.” Other inventors who contributed significantly to early microphone technology include Emile Berliner, David Edward Hughes and Thomas Edison.
As a self-confessed “mic geek,” I find the history of these devices fascinating, and thought it would be interesting to share some of the highlights of mic development. Note that this is by no means intended to be comprehensive, but focuses on what I see as many of the notable design breakthroughs through the years.
Western Electric 618A (Credit: John Schneider, Flicker
By the late 1920s, Western Electric developed the first practical dynamic microphone, the 618A, which became a very popular with broadcasters. According to the company’s instructions for use, the 618A sported a “thin duralumin diaphragm of low mechanical stiffness” and a magnet made from “high-grade cobalt steel.”
The document goes on to state that “a number of air chambers and slot openings connecting them have been associated with the diaphragm in order to obtain substantially uniform response over a frequency range from 35 to 9,500 cycles per second.
One of these acoustic elements, in addition to exerting a control on the motion of the diaphragm, allows air to be transferred from the front to the back of the diaphragm. This eliminates effects due to changes in barometric pressure.”
beyerdynamic was founded in Germany in the mid-1920s, initially developing loudspeakers for the motion picture industry. By 1939 the country introduced its first dynamic microphone for studio use, the M19, which also became a favorite of broadcasters.
Neumann unveiled the CMV3 in 1927, arguably the first commercially available condenser mic for broadcast. Later, the U47—although perhaps not the first multi-pattern condenser—was certainly a marquee product, becoming a standard in the 1950s and by 1960 largely replaced the ribbon mics used for recording.
Meanwhile, in 1932, RCA introduced the massive 77A. Designed by Dr. Harry F. Olson, it featured two vertical in-line ribbons and an acoustic labyrinth inside the case which enabled it to be unidirectional.
According to the manual, “The figure 8 pattern of the velocity-actuated part of the ribbon combines with the circular pattern of the pressure-actuated half to provide an overall cardioid pattern.” The 77A was no handheld model at 11.5 x 3.75 inches and weighing in at 4.5 pounds, it used a 1/2-inch pipe thread for mounting.
In the 1940s, RCA would introduce the classic model 77D, an Art Deco beauty with adjustable pattern control.
A tube connected the ribbon to the labyrinth in the mic’s body and the tube had an adjustable shutter that could be adjusted by the user that closed off portions of the tube openings allowing patterns control from omnidirectional to bi-directional (figure 8).
In the mid-1920s, Sidney Shure founded a radio parts supplier in Chicago named the Shure Radio Company, later changed to Shure Brothers when Sidney’s brother Samuel came onboard.
By 1932, the company was producing microphones to fill a rapidly growing market, and debuted the model 33N, a 2-button carbon microphone model that was the first lightweight, high-performance product in a field largely dominated by bulky units.
Shure went on to release the iconic model 55 in 1939, the first single-element unidirectional mic. The design is called UNIDYNE (short for “unidirectional dynamic”) and it revolutionized the field.
Before the 55, attaining anything other than an omnidirectional pattern meant using more than one diaphragm and combining their outputs, which resulted in a large mic head that usually didn’t sound all that good because the elements were spaced apart and usually had different frequency responses.
Shure 55 Unidyne
Shure solved this by using small ports that allowed sound waves to reach both sides of the diaphragm at different times, resulting in a more linear frequency response compared to using different diaphragms.
And to reduce handling noise, the capsule was suspended on springs dampened with foam to isolate the diaphragm from vibrations. Because the design only required a single diaphragm, the mic became smaller and less expensive. Factor in the timeless aesthetic design of the housing, and it’s no wonder that the 55 is still a popular model after all these years, with the current Shure catalog offering two updated models.
About 100 miles to the east in South Bend, Indiana, Al Kahn and Lou Burroughs converted their business from servicing radios to developing mics, and in 1930 incorporated under the name Electro-Voice. By the mid-1930s the company was up and rolling, producing a steady stream of innovations.
In 1934, while going through some old technical journals, Kahn came upon what he called “an ancient watt meter – patented in 1892 or thereabouts” which had a balanced winding to cancel hum from the stray 60 Hz fields that the watt meter might pick up.
As Kahn described it, “A little light bulb went off above my head, and I rushed back…got some tin snips, cut some laminations out, and I made a transformer and put it in and it worked.” Thus, the humbucking coil was born, and solved a major problem for mic users.
The company moved to larger facilities in nearby Buchanan, MI, and also diversified its product offerings into loudspeakers, phono cartridges, and consumer electronics. Still, mic work continued, with the model 664, a.k.a., “The Buchanan Hammer,” hitting the market in the mid-1950s. The nickname derived from legendary durability, but the single-element cardioid, dynamic type mic was also the first model to incorporate the company’s patented Variable-D (Variable Distance) design still found in several EV mics to this day, including the RE20 and the recently introduced RE320. Variable-D uses multiple rear and side ports to achieve pattern control.
Dr. Fritz Sennheiser founded Laboratorium Wennebostel in Germany in 1945 and started producing mics the next year. Later the company would change its name to Sennheiser, and by 1960 produced one of the most enduring models in pro audio, the MD-421.
While it currently sports a glass composite body, the original 421 body was made of DuPont’s Delrin polymer resin, one of the first mics to feature a molded body. The MD-421 also offers a user-adjustable bass roll-off filter, and is still extremely popular with live and studio engineers.
Next door in Austria in 1947, Dr. Rudolf Görike and Ernst Pless started AKG, supplying movie equipment to theaters in post World War II Vienna.
Just a few short years later, AKG had introduced new mic technologies that include an early (and perhaps the first) high-quality condenser, the first remote-controlled multi-pattern capacitor mic, and one of the first dynamic cardioid models.
The D12 was highly coveted by sound engineers for its great sound and cardioid characteristics, and 1971 saw the introduction of the 414 series, a large diaphragm condenser with multiple variable pickup patterns that is still a staple of studio and stage work.
Shure stepped up again in 1959 with Unidyne III, the first high-quality unidirectional design that is used by speaking into the end rather than the side of the microphone.
It was the predecessor to the SM57 and paved the way for modern handheld designs.
By the mid-1960s, the SM58 (for “studio microphone”—bet you didn’t know that!) launched, delivering a combination of sound quality and rugged reliability that’s made it the standard for live vocal use to this day.
Hideo Matsushita founded Audio-Technica Corporation in Tokyo in 1962 and since that time the company has developed a wide range of designs. My favorite comes from 1985 with the UniPoint Series of ultra-compact condenser mics.
Over the years the line has grown to include more than 30 models, including hanging, boundary, gooseneck and even handheld microphones.
Audio-Technica UniPoint U853A
The UniPoint Series continues going strong as a contractor and sound operator favorite.
About the same time, beyerdynamic introduced the M88, incorporating a new low-mass diaphragm element that offered fast transient response coupled with the ability to handle high SPL levels. It caught on with engineers around the world, and a version of the M88 is still a current item in the catalog more than 50 years later.
In 1964, Bell Labs received a patent for the electroacoustic transducer, an electret microphone. Electret condensers offered greater reliability, higher precision, lower cost, and a smaller size that anything available at the time.
During this period, AKG launched the world’s first 2-way cardioid microphones. One of these was the D202, a handheld model that with two diaphragms, one for the lows (20 Hz - 800 Hz) and a second one for the highs (800 Hz - 20 kHz).
AKG D202, nicknamed the “rocket” for obvious reasons
The mic sported a sintered bronze grill on the front, rear ports at the cable end and a 3-position bass cut switch. Another model, the D202ES, moved the crossover point to 500 Hz.
Carl Countryman incorporated the family business in 1978 and since that time has been making innovative miniature mics for people and podiums. In the 2000s, the E6 earset mic was developed and has become a favorite earworn miniature model.
And, introduced a few years ago, the model B2D is the smallest directional lavalier available, with a capsule diameter of only 0.1 inch (2.5 mm).
Sennheiser decided to go small in 1983 and came out with two significant advances. The first was the development of the first directional clip-on microphone, the MKE 40, followed smallest studio clip-on microphone available at the time, the MKE 2.
More than 25 years later, the MKE 2 is still extremely popular with broadcasters and corporate audio folks.
With VLM technology first deployed in the OM Series that debuted in 1986, Audix put itself on the map just a couple of years after its founding. VLM (“very low mass”) is based on using a lightweight diaphragm that allows for extremely fast, accurate processing of incoming signals, while still offering extended frequency response and high SPL handling.
In the late 1980s, David Blackmer founded Earthworks Audio in New Hampshire with an initial goal of designing and manufacturing audiophile loudspeakers. He was dissatisfied with the measurement tools of the day, and set about to improve the situation.
The first tool he designed was an omnidirectional mic, which led to the manufacture of the OM1. He wanted to get back to designing loudspeakers, but his colleagues begged to differ, persuading him to design other mics as well as preamps.
The overall design philosophy is extended frequency response, very fast impulse response, near “perfect” polar pattern and pure signal path, with the goal of better emulating the time resolution of human hearing (10 microseconds or better). This is now provided in a wide range of condenser models for vocals, instruments and measurement.
Speaking of precision, DPA Microphones (originally Danish Professional Audio) was founded in the early 1990s by two former employees from high-end measurement tool manufacturer Brüel & Kjær.
Sennheiser MKE 40
Headquartered in Allerød, Denmark, DPA was first recognized for the 4011 cardioid followed by two headset designs—the 4066 cardioid and 4088 directional—that have helped shape the popular market genre we enjoy today.
In the late 1990s, Neumann forever altered the landscape with the introduction of the KMS 105. This condenser model proved a watershed mic for live performance, “breaking the ice” for other high-performance condensers in the live market such as the Shure KSM9, Audix VX10, Rode S1 and others.
As we moved along to a new millennium, Milab went digital with the DM-1001, a mic microphone with AES/EBU and S/PDIF outputs. The DM-1001 uses two large diaphragms, each with its own AD converters, with the polar pattern calculated in the DSP from a mix of the front and back signals from the elements.
A separate programmable control offers a choice of standard or user configures patterns. Neumann also entered the digital realm with the Solution-D, a studio-oriented design with integrated DSP processing and an A/D converter that allows for gain adjustments to be made digitally inside the mic.
Craig Leerman is senior contributing editor for Live Sound International and is an avid collector of vintage microphones. Read about more about some of his mics here.