Microphones

Future mics need to be more digital and more controllable.
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In an audio world that seems to be all about digital streams, format conversion and file manipulation, two pieces of equipment remain firmly entrenched as analog devices — the input and the output. Why? Because no matter how much technology is applied within the signal path, the simple fact is that actual audio is a real-world phenomenon of sound waves traveling through the air and reaching our ears.

Reproducing that sound requires transducers — devices that transform sound into electrical information (input) and vice versa (output). On the input side, the capture and transduction of real-world sound sources has been accomplished by microphones for more than a century. The first microphone patent was granted to Thomas Edison on an application filed in March of 1877. So, to say that the microphone is a mature technology is an understatement.

Yet, new and better microphones are announced constantly, begging the question: What possible new variations on this age-old theme are truly needed? Are today's microphones truly better, or is this all puffery designed to boost sales while recycling and recombining a bunch of tired ideas in shiny new packages?

Application-driven design

As broadcast workflows change to take advantage of today's computer-driven advances, microphone manufacturers continuously adjust their offerings. The realities of networked audio, digital recording and surround sound have created needs and opportunities resulting in purpose-built designs that pull mature, proven transducer designs into the 21st century.

While household usage of full surround sound continues to lag, the production side of the industry has adopted it almost universally. Deploying traditional mics to capture stereo and surround information is problematic, so manufacturers have produced a wide range of microphones and mounting systems to make the job easier.

Surround mics modeled on the human skull use an array of individual mic capsules to provide discrete outputs for center, left, right and surround channels. Other systems use a more traditional form factor, using multiple mic capsules paired with remote electronics to deliver simultaneous mono, stereo, mid-side (MS) stereo and surround information. Even the classic Decca Tree stereo recording system has also been updated and adapted for the needs of surround sound capture.

The whole concept of “in the box” computer recording and mixing is similarly reflected in new microphone designs. Professional-quality mics are now available with USB outputs, enabling them to be plugged directly into a laptop, desktop or tablet computer. Similarly, the use of traditional low-impedance XLR mics is now accommodated by USB interface boxes. This allows professional production standards to be met virtually anywhere, including office cubicles and home studios.

In the field

Microphones have evolved and adapted to the needs of video capture in the field. Camera-mounted versions of shotgun, stereo and surround microphones have become commonplace. More importantly, today's field production recording devices now enjoy high-quality preamps, and many studio-quality microphones now have the ruggedness required to deliver incredibly clean, detailed recordings under virtually any conditions.

For the more common ENG application of voice recording, the ubiquitous smartphone looms as a possible game-changer. Traditional field packs of recorders, mixers, microphones and the batteries to power them are a bulky assemblage. But with a smartphone and a few well-chosen apps, the same job can now be done with a single handheld device. The only issue is the lack of quality microphones to interface with them.

Because smartphones and computers are designed for the consumer market, audio is something of an afterthought in such devices, with the on-board microphones being cheap condensers. Naturally, however, after-market upgrades are available. To date, high-quality professional recording via smartphone remains elusive. But, looking at overall trends, it's only a matter of time before a high-quality microphone and/or preamp emerges to make the concept of a single-device, field-production setup possible.

Digital microphones

With the concept of analog broadcasting already near extinction, every part of the signal chain has moved into the digital realm. Traditionally, microphones transduce the sound they capture into an electrical signal. Getting that signal into the digital realm has to happen, so it's no surprise that digital microphones are beginning to appear.

Digital microphones perform their analog-to-digital (A-D) conversion immediately after the mic capsule, with an output stream that (typically) conforms to either AES/EBU or AES 42 standards. The idea is to move the audio signal to the digital realm as soon as possible. Because each conversion operation (A-D or D-A) adds latency, the optimal situation is to keep the signal digital from the point of capture all the way through the audio chain to actual broadcast. Ideally, that audio would not be converted back to analog until being sent to a loudspeaker.

Today's digital mics offer exceptional quality, with 24-bit conversion, wide dynamic range and sampling rates up to 192kHz. With the audio information in the digital domain, the addition of on-board DSP opens up enormous control possibilities as well.

The bottom line on digital microphones is that the market is simply not yet ready to embrace them. Familiarity and tradition die hard, and the enormous installed base of analog inputs to sound systems will need to be replaced before this next generation of products can proliferate. That's why most digital wireless systems on the market today still rely on analog outputs.

During my days working at a major microphone manufacturer in the 1990s, the market demanded a better headworn microphone for music, driven by artists like Madonna and Janet Jackson and enabled by the emergence of wireless. Based on user input, we created a specification for the “ultimate headworn microphone.” It would fit any size/shape of head in total comfort, keep the mic element in a stable position, and would also be weightless and invisible. Oh, and it would have full-range frequency response while never messing up anyone's hair.

Have we gotten there? Obviously not. But comparing today's headworn microphones to those of, say, the mid-90s, is an eye-opening exercise. My point is this: For any given circumstance, there is an optimal microphone design. As long as applications keep changing, microphone manufacturers will keep striving to optimize that critical first link in the audio chain. So, don't dismiss these new microphones. While there is truth to the idea that a mic case full of classics like the SM57 or RE10 will get you through pretty much anything, the bottom line is that striving for excellence requires a broader view.

Modern materials and design have given us non-fragile ribbon microphones and headworn mics that weigh under an ounce. Upgraded industry standards and advances in electronics have brought us mics with miniscule noise floors. Wireless mics now rival cabled versions in sound quality. The move to surround sound has created huge advances in multichannel pickup systems.

So, while the microphone is a mature technology, the fact is that today's designs are light-years ahead of their predecessors. Microphone manufacturers as a whole are clearly dedicated to evolution, using the lens of changing industry needs to focus on innovations that will meet the ever demanding needs of tomorrow's pro audio world.

Jack Kontney is a regular contributor and authors the “Audio Technology Update” e-newsletter.