Miniature mics in broadcast

Without microphones, there would be no sound to broadcast. This is equally true for both traditional TV broadcast media as well as modern content creation situations. However, given the importance of mics in image-carrying broadcasts (TV), much effort is made to keep them out of the picture. Here, the miniature microphone is preferred because it is almost invisible, easy to carry and place, fits with wireless transmitters, and produces easy-to-process sound if it is a good-quality microphone.

At the beginning of microphone history, nobody cared about the size of a microphone. However, as broadcast production also encompassed television, a need for small-footprint microphones gradually arose. So, manufacturers followed up on this demand by downsizing wherever possible. When the electret microphone was developed in the 1960s, it became possible to make small microphones. This process has been refined and used in broadcast (and hearing aid manufacturing) ever since. In television, the demand has been strengthened as the news crews have been diminished, often consisting of just one VJ (video journalist) who then must manage all equipment, set up interviews and do everything in between.

Specs of small mics

Making an extremely small microphone is a challenge. However, excellent specifications can be obtained with a clever design: high SPL at low distortion, perfect frequency response and self-noise acceptable for the microphone's purpose. Also, efficient accessories are often available: easy-to-handle clips and jammers to reduce wind noise. On top of that—and above all—the construction must be robust for long-lasting performance.

The lavalier

The miniature microphone is often referred to as a “lavalier microphone” or just “lav”. The microphone can be placed on a person's chest by clipping on a tie, jacket, or collar to pick up that person's voice. In these positions, the mic is close to the sound source, providing a suitable SPL for the input. However, the placement also has some implications, as the sound of the voice is very much dependent on the position where the voice is picked up. A neutral position would be in front of the person, one meter from their mouth. When the voice is picked up at another position, the sound is somewhat colored or at least different from the neutral recording [1].

Need for processing

One thing to consider is that you might have the world's best microphone, but you still have to correct the sound. Usually, this involves raising speech intelligibility by gaining frequencies between 2-4 kHz [2].

If the microphone tends to create a harsh sound, processing the microphone signal seldom does any good. So, to enhance the audio for speech intelligibility and better spectral balance, a microphone with a smooth frequency response and extremely low distortion is needed.

BLM

Sometimes, miniature mics are used to capture sounds other than a single voice. This might be when a group of interviewees are gathered around a table. Who should carry the microphone, then? Here, it is possible to use a boundary-layer microphone by attaching it to the tabletop (even just using tape for the fixation). By applying this method, you gain 6 dB in all directions, and there is no comb-filtering.

In other cases, you may apply the same method by attaching the microphone to a wall or to the ceiling, for instance, to pick up acoustical music or vocals. The microphone's light weight makes it easy to position it perfectly [3].

Mics and wireless transmission

In broadcast, miniature mics are usually connected via a wireless connection – i.e., a bodyworn radio transmitter and a receiver. The transmitter also provides power for the microphone and a decent input that can handle all the signals generated by the microphone [4].

Various brands have different solutions for adapting the microphone to the transmitter. Some solutions seek to linearize the microphone signal because the active component, the FET (Field Effect Transistor), is not entirely linear. Therefore, additional resistors can be found in the connectors or in the transmitter.

2061 Miniature Microphone

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2061 Omnidirectional Miniature Microphone

Lavalier

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DPA suggests a miniature microphone for broadcast use (and other fields of content creation): the 2061 Miniature Omnidirectional Microphone. This microphone fulfills the requirements of IP57 for prolonged life when exposed to water, dust and makeup. The housing is designed with advanced sweat-repelling capabilities for uninterrupted operation. And finally, an easy-to-handle clip and efficient windjammer goes with the microphone.