Essential Features of Wireless Microphones

Wireless microphones are a core element of live events today, for music, theatrical performances, and even events like presentations and panel discussions. It would be almost unthinkable to have a concert or stage a play without wireless mics, yet wireless is one of the most mysterious and misunderstood parts of audio. Many universities are laboring with outdated wireless mics or just don’t have enough of them to meet the needs of the different venues on campus that require them. Even schools that are well-supplied can be overwhelmed by the monthly battery costs related to wireless mics.

Higher education institutions are faced with a tough challenge: Audiences today have been raised on a diet of professionally-produced media and expect live presentations and performances to be slick and professional. Delivering professional-quality audio that makes audiences glad they came isn’t easy. This article offers five features of wireless microphones that can make the difference between “good enough” and “great.”

Crystal Clear Digital Sound

Even mid-priced wireless systems are now digital, providing better sound quality with less effort. Analog wireless systems had limited dynamic range, which required careful adjustment to avoid hiss or distortion and necessitated planning and testing during sound check to make sure the settings are right for each performer. Digital systems can handle a wide range of sound sources—from whispering actors to screaming singers—without constant tweaking.

Using Spectrum Efficiently

One of the biggest challenges for wireless mic users is how to operate many systems in larger spaces. Having more systems in one room requires the ability to pack frequencies closer together in the spectrum without interfering with each other. With wireless spectrum continuing to become more crowded and TV channel assignments changing regularly, having the ability to switch frequencies is increasingly valuable. Buyers should look for systems with a tuning bandwidth of at least 20 megahertz; systems should also be able to operate at least ten units in one open TV channel, which is all that may be available in some metropolitan areas.

Working the Room with Wider Coverage

Larger spaces like an auditorium or theater demand thoughtful placement of receiving antennas to guarantee coverage throughout the performance area; these spaces also require distribution of the antenna signals to the receivers which may be in the wings, under the stage, or in a control room at the back of the room. Fortunately, modern wireless systems typically offer a selection of available antennas for both medium- and long-range pickup, and an optional antenna distribution system that feeds one pair of antennas (and DC power) to multiple receivers.

The signal from the transmitter on stage weakens considerably as it travels, so it’s important that the receiving antennas are located so that they can harvest as much of the remaining signal as possible. Mistakes involving antennas can easily result in 80% of the signal being lost, causing intermittent audio dropouts that the audience will notice.

Making Connections with Networking

Running audio cables through walls and ceilings from the stage to the control room can be expensive and labor-intensive. Upscale wireless receivers offer digital audio networking in addition to standard analog audio outputs. Digital networking allows hundreds of audio channels to be carried over one standard ethernet cable, even for considerable distances. This ability means that the receivers can be located backstage—where signal pickup can be stronger—even if the mixing board is in a remote control room. The audio signals take so little bandwidth that they can even share the same network used for data and building functions. Networkable wireless receivers also make frequency coordination much simpler. Wireless system management software can monitor performance in real time and upload new frequencies if interference is detected. These capabilities can all be done remotely from the control room.

Maximizing Power with Rechargeability

The insatiable appetite for seemingly infinite numbers of batteries can be a shock to wireless users and purchasing agents. It’s also a huge headache for AV technicians, who must err on the side of caution and throw away batteries that may still have considerable use left. It’s not uncommon for universities to dispose of thousands of alkaline batteries every year. Smart lithium-ion rechargeable batteries for wireless mics provide the same performance as alkaline batteries but can cost about one-fourth as much per operating hour. In addition, the remaining operating time of a rechargeable transmitter can be measured accurately in hours and minutes, so there’s no doubt about whether it will last through the event. When the curtain closes, the microphone or bodypack simply drops into a charging dock to be sure that it will be ready to go when needed. Best of all, rechargeable batteries support university environmental goals by preventing hundreds (or thousands) of alkaline batteries from being disposed of in landfills.
Technical advances have made wireless microphones better sounding, more scalable, less expensive to operate, and even greener than ever. Investing in quality wireless systems can deliver better-sounding, more reliable performances to audiences for years to come.

About the Author
Chris Lyons, Senior Manager / Integrated Systems Marketing, Shure Incorporated, is a 36-year Shure veteran who has filled a variety of different marketing and public relations roles. His specialty is making complicated audio technology easy to understand, usually with an analogy that involves cars or food. He doesn't sing or play an instrument, but he does make Shure Associates laugh once in a while.