In the past year or so, several major players have introduced digital wireless microphone systems, ranging from entry level to professional units. While generally maintaining the traditional form and functions of the products, engineers have adapted concepts and techniques from computer networking, cellular telephones, and digital signal processing to enhance their performance.
Expect this trend to continue, since the new technologies can provide advantages in dense RF (radio frequency) environments, as well as generally excellent audio quality. And in some cases, they also offer ability to maintain the signal within the digital realm from the mic capsule through the console and beyond.
Digital RF requires a lower signal-to-noise ratio in order to deliver a usable signal to the receiver, compared with analog wireless. As well, the signal is either on and with undiminished audio quality, or off and silent. The “noising up” and other audio artifacts are rare with these systems. Typically, a lower transmission power is required from the digital system’s transmitter to achieve the range found with a 50 mW analog unit.
Digital wireless systems have a wider audio bandwidth, at both ends of the spectrum, than analog. A good analog system may boast a response from 50 Hz to 15 kHz, while the digital ones are close to flat from about 20 Hz to 20 kHz. Digital systems also don’t require companding circuitry that has the potential to affect audio quality. From my listening tests using several of these systems with voice and instruments, I’ve found the audio to be quite accurate and uncolored, even with the entry-level wireless.
Allowing the signal to remain digital is a feature of many of the professional units, which offer AES /EBU digital outputs as well as the standard analog XLR and quarter-inch connectors. Also, encryption schemes are easy to apply to the digital signal and decode at the receiver for pristine audio. Even without encryption, the signal is much less likely to be intercepted and decoded when in the digital domain.
Greater resistance to interference is another hallmark of the new digital wireless systems. However, we’re still talking about radio systems, and an interfering signal falling on a transmission channel can diminish range (since they’re all frequency agile, moving to a clear frequency will provide the solution) – but having an interfering signal break in and be reproduced as audio noise is unlikely. This characteristic makes frequency coordination and channel spacing easier; a few of the new digital systems make close, even spacing of channels possible.
Receivers often have a much wider tuning band than analog units, in some cases covering 150 MHz or more of spectrum. Using the new digital systems, you’ll have less need to carry several RF “splits” while touring in order to deal with crowded spectrum in locations with many DTV stations and other radio sources. Many of these systems operate in the UHF band between 470 – 698 MHz (for the U.S.), as well as in the 2.4 GHz region.
Finally, networking and computer monitoring/control that has been a feature of many professional systems has been expanded in the new systems. Remote control of the transmitter parameters as well as the receiver is often possible. These control capabilities can even be performed via a tablet computer or smart phone. Some systems can act as a spectrum analyzer, presenting a visual representation of the RF environment.
Take our Photo Gallery Tour of recent wireless systems from a number of manufacturers, highlighting key features such as transmission method, frequency band, audio bandwidth and sampling rate, transmitter power, and more.
Gary Parks has worked in pro audio for more than 25 years, including serving as marketing manager and wireless product manager for Clear-Com, handling RF planning software sales with EDX Wireless, and managing loudspeaker and wireless product management at Electro-Voice.