Trends in Technology: Microphones - Radio Magazine

Trends in Technology: Microphones

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Microphones are, perhaps, one of the most taken-for-granted electrical devices ever developed for wide-spread use. They have been used to guide military troops in times of war, provide millions of play-by-play sports broadcasts, announce details of Presidential candidate races -- and Presidential passings, and for the transmission of trillions and trillions of telephone calls. Microphones have been used for Earth-to-space communications and Moon-to-Earth communications when Neil Armstrong first set foot on the Moon on July 20, 1969. Our world would certainly be a bit quieter and less informed if it weren't for the invention of the microphone. Throughout this article we will look at microphones of the past, present, and, with a bit of visionary imagination, the future. Because this publication is focused toward the radio broadcast industry, we will journey in that direction as well.

Past

A microphone is defined as an instrument capable of transforming sound waves into changes in electric currents or voltage as used in recording or transmitting sound. According to history, the term microphone was first coined by Sir Charles Wheatstone in 1827 and was used to describe a stethoscope-type device he had developed to amplify weak sounds. The word is Greek in origin with "micro" meaning small and "phon" meaning sound. In 1876 Emile Berliner invented a microphone that was used as a telephone voice transmitter. The patent rights to that invention were then sold to the Bell Telephone Company for $50,000.

Inventor David Hughes is credited with inventing the carbon microphone in 1878. Early carbon microphone development supported the telephone and broadcast industry through the first several decades of the 20th century. While carbon microphones were widely used in broadcasting until the late 1920s, they continued in use in the telephone industry up until the 1980s when the use of miniature electret condenser microphones began.

Ribbon microphones came into play in the 1920s when the RCA Company developed its first version known as the PB-31/PB-17. These were replaced with the Model 44A and then later an improved magnetic material brought about the Model 44-B/BX. Early ribbon microphones used field coils and permanent magnets. Later models used double ribbon elements. In later years, the RCA Model 77 ribbon microphone became the most popular model for recording and broadcast because of its smooth sound and directional pickup patterns. The company went on to produce many other ribbon microphone models that have to this day remained staples of the early broadcast and recording industries and are dearly cherished by collectors worldwide. RCA terminated production of their microphones in 1973. Ribbon microphones of various brands have enjoyed a recent revival in the vocal and instrument recording markets with over two dozen new models showing up in the past two years.

Over the expanse of time, dynamic microphone elements have become one of the more popular types. Invented in 1897 by Ernst Siemens, the first commercially available dynamic microphone was the Western Electric Model 618-A introduced in 1931, a mere nine months before the RCA 44A.

In 1964 Bell Laboratories was awarded a patent for their creation of the electret microphone. That technology allowed for the manufacture of microphones of greatly reduced size, lower cost, improved reliability, and much-improved frequency response. Improvements to electret condenser microphone technology occurred over the following decades. The two most popular microphone technologies in use today are dynamic and condenser.

Condenser microphones, when compared to their dynamic cousins, are more sensitive to sound, typically have a greater sound output level, higher frequency response range, and lower noise output content. Because of their lighter weight elements, a condenser microphone will more quickly and accurately react to rapid changes in sound dynamics such as volume and rapidly changing music transients. On the down side, condenser microphones are more sensitive to incoming volume. Their output may become distorted if placed too close to a sound source whereas most dynamic microphones can typically be placed up against a source without creating sound distortion. Most professional condenser microphones require a +48V phantom power source while dynamic microphones do not. The phantom power source is usually derived from an audio mixing device to which the microphone is connected, although external phantom power sources are available. Care should be taken to assure the manufacturer's recommended phantom power voltage is reaching the microphone in order to avoid poor microphone performance -- typically in the form of lower output and higher noise level.

Condenser microphones typically come in two forms: large or small diaphragm. Whereas large diaphragm condenser microphones are known across the industry for creating a warm sound, the small diaphragm microphones will typically provide a better response to musical transients and an overall smoother and somewhat wider frequency response.

Dynamic microphones are traditionally more durable physically and far less susceptible to moisture when compared to condenser microphones. While dynamic microphones do not have the wide, smooth frequency response of a condenser mic, they are capable of withstanding far greater incoming sound levels making them a good choice for miking very loud vocals and instruments.

Condenser and dynamic microphones both have similar sound pickup patterns. An omni-directional pattern will allow sound to enter the microphone from any direction (360-degree acceptance angle). A uni-directional cardioid pickup pattern microphone typically allows sound to enter into the front of the microphone (180-degree acceptance angle) but minimally accepts sound from the back. A hyper-cardioid pattern allows even less sound to enter the front of the microphone and practically no sound to enter into the back of the unit.

There have been many microphones introduced throughout history that have become industry favorites. Models such as the Electro-Voice 635 in earlier days and the RE-20 in later times are well established in the broadcast industry. And, for stage and high-level vocal recording, the Shure Model SM58has become a tasty favorite of vocalists throughout the World. And Sennheiser's Model MD-421 dynamic, now celebrating 50 years in the marketplace, has long-served as a studio standard.

Present

Modern day applications have driven the market toward the creation of new styles and types of microphones. For podcasting and computer recording, microphones with a USB output for connection directly to a computer are now in high demand. Available models include Audio-Technica's AT2020 USB side-address cardioid condenser, Shure's PG42USB large diaphragm condenser microphone, Blue Microphone's Plug 'n Play, Snowflake Portable USB, and Yeti microphones, Samson's CO1U condenser, its G-Track, and Go Mic models, the Rode Podcaster large diaphragm model, and AKG's Perception 120 to mention but a few. Just like standard microphones, not all USB output microphones are created equally. USB converters can and will sometimes cause unwanted audio artifacts such as digital noise and other unusual sounds, so always be cautious when purchasing a product. Many standard microphones can now be adapted to having a USB output with the addition of an external XLR-to-USB adapter such as Tascam's US-122mkII which offers two microphone inputs, two line inputs, on-board phantom power, a high impedance instrument input plus MIDI in and out. Shure offers the X2u, featuring a headphone jack with volume control, integrated preamp, monitor mix control, 16-bit 48kHz sample rate and +48V phantom power. Others such as M-Audio's Fast Track Pro offer two front panel mic or line inputs, on-board phantom power, inserts for outboard effects, balanced or unbalanced analog audio outputs, S/PDIF digital in and out, MIDI in and out, and more.

Another application for a standard dynamic microphone is with JK Audio's BlueDriver, a Bluetooth device that attaches to a microphone's XLR connector. When paired with a Bluetooth-enabled cell phone, the device's 3.5mm jack provides a mic level signal suitable for recording along with cell phone audio. Devices of this type provide versatile and economical field operations for news gathering -- especially when paired with one of those long-time resident dynamic microphones that have been lying around radio stations for many years.

Future

As we spend the present day venturing through the maze of microphones, we come to the end of the trail where we catch sight of Holophone's unique and interesting lineup of surround sound recording microphones that range from their 7.1 channel Model H2-Pro to the H4SuperMini and the PortaMic 5.1 portable units. And, peeking beyond the trail's end towards the future of what many microphones might someday become, we see the recently announced Squarehead Technology AudioScope, an array of 315 microphones that can hang high above major sporting events to be used to pick out one voice or event-related sound source from within an environment of thousands of persons. The company uses sophisticated signal processing algorithms to isolate and process the sound bringing it into crystal clear clarity.

My hope is that you have enjoyed our journey over the road of microphone history that led to a drive through the fields of present day trends in technology and on to a peek into the future. Microphones of all types and sizes, including some not yet invented, will continue to be used to bring us day-to-day news and information, entertainment, and, most importantly, for documenting today's events for tomorrow's history books.

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