As in other aspects of life, change is the rule in the world of wireless. Since 2010, those who use wireless microphones and similar audio tools have lost 198 MHz of UHF spectrum to public safety networks and broadband services for data-hungry smart phones--and the DTV television stations that once were spread among those frequencies are being packed into the remaining spectrum. In Dallas or Orlando, for example, only two 6 MHz bands remain open between 470–608 MHz. By the end of this year, 600-MHz broadband services will be fired up across the country, and using mics in those frequencies becomes illegal.
So how has the latest generation of wireless microphones evolved to do more with less? For more than a decade, leading wireless manufacturers have been developing technologies to provide reliable audio performance in an ever more crowded RF environment, and working with the FCC to raise their awareness of the role that wireless plays in public events, including worship services.
Innovations include new ways of detecting and avoiding interference, increasing the discrimination of wireless receivers and refining the transmission signal, widening the operating range so that the equipment can encounter and tune to clear frequencies nearly everywhere, exploring other frequency bands such as 1.9 and 2.4 GHz, taking advantage of digital transmission and DSP, and increasing spectral efficiency so that more channels can fit into the smaller swath of available frequencies. Also, RF planning software and hardware is available to help determine the layout of larger multi-channel systems.
Finding space
Most of the midrange and high-end wireless mic systems will operate over an extended bandwidth--with a typical minimum of 5-10 TV channels (30-60 MHz) and in some cases the entire 470-608 MHz legal band in the U.S. Within that spectrum, the receivers have the capability to scan the local RF environment for potentially interfering signals, then automatically suggest and set channels that avoid the interference. Some professional systems even provide backup frequencies that can be switched manually or automatically when a new source of interference arises, and can be networked to monitoring software for real-time access.
Digital or analog transmission
The past decade has brought digital transmission to the forefront, embracing the innovations from the computer and telecommunications industries and applying them to professional audio. Many of the newer systems use a digital rather than an analog FM (frequency-modulated) signal between the transmitter and receiver, though some still use FM transmission--a seasoned technology that can deliver fine sound quality and in some cases extended range.
The more predictable bandwidth of a digital audio transmission, combined with methods to minimize intermodulation among transmitted frequencies, allows more channels to be placed in a given amount of spectrum, compared to FM.
Since the wireless signal is replacing a physical cable, says Joe Ciaudelli of Sennheiser, “interference-free transmission is a must” when designing systems--and other considerations such as audio quality, bandwidth, and range are necessary, yet secondary, to basic reliability. The best of the contemporary wireless offerings have achieved transparent, full-bandwidth audio within that secure connection.
The more predictable bandwidth of a digital audio transmission, combined with methods to minimize intermodulation among transmitted frequencies, allows more channels to be placed in a given amount of spectrum, compared to FM. Analog systems use companding (compression and expansion) to prevent overmodulation of the wireless carrier signal--unneeded with digital. Digital audio is typically full-bandwidth and accurate. However, in higher-end analog wireless systems, the quality of the companding, including dual-band companding and other circuitry, also yields excellent audio.
Digital signals retain their same audio quality until the user is out of range, and then the audio drops out; analog transmissions can become a bit noisier at extreme distances, though in some cases analog signals have more range. Digital transmission does introduce latency, though typically less than 4 ms of delay, whereas analog signals have virtually no latency.
Alternate bands
In addition to the greatly reduced UHF band, wireless microphone systems are offered in the 900 MHz ISM band, 2.4 GHz WiFi and 1.9 GHz DECT bands, and the VHF band between 174-216 MHz. Shure, for example, offers its ULX-D professional digital system in both the VHF and 900 MHz bands, and other brands can also be found in that spectrum. Fewer simultaneous channels can be run in the WiFi or DECT bands vs. UHF, yet they’re quite useful when several wireless are all that is required, or when adding a few more channels.
As with any wireless spectrum, the microphone is potentially competing with other devices for those frequencies--and various methods have been developed to avoid interfering with them while still delivering several channels of clear audio. The DECT band was developed for cordless phones, and the WiFi band for data communication and Bluetooth, and the primary users of UHF and VHF spectrum are television stations. Your unlicensed wireless channels operate in the portions of that spectrum that are not otherwise in use in your area.
Seeking your level
Quite serviceable wireless microphones that will reliably provide a handful or two of high-quality audio channels are readily found for a few hundred dollars per channel. For critical productions requiring many channels operating flawlessly together, you may pay a couple thousand or more per channel. That being said, many of the key innovations in these premium systems have migrated to the mid-tier products.
Make a choice by starting with your particular situation. Do you need wireless mics for the pastor, a few other worship leaders, and the occasional pageant? Or are you presenting an elaborate production that is filmed and streamed?
Make a choice by starting with your particular situation. Do you need wireless mics for the pastor, a few other worship leaders, and the occasional pageant? Or are you presenting an elaborate production that is filmed and streamed, where the many participants are mic’d, musicians have in-ears, and the audio and staging staff are using intercom--all wirelessly?
Most wireless manufacturers offer several levels of wireless microphones, ranging from basic through professional. All have the basics of bodypack and handheld transmitters, and a companion receiver with audio outputs to your mixing console, while the upper range of systems might offer AES3 or Dante digital outputs, networking and control, sophisticated antenna systems, automated frequency detection and switching, and more. Some lines have a mixture of digital and analog offerings.
Here's a sampling of mid-level wireless microphone options.
AUDIX | PERFORMANCE 60
Audix Performance Series
Analog transmission in the UHF band, with 64-MHz tuning range between 522-586 MHz. Auto-scanning for available frequencies, with 207 pre-coordinated frequencies or selection of any desired frequency in 25kHz increments for up to 20 simultaneous channels. Single-channel/half-rack or dual-channel/1RU receivers, with adjustable squelch and analog outputs. Switchable transmitter RF output of 10 or 30 mW, with IR linking.
Starting at $700
AUDIO-TECHNICA | 3000 SERIES
Audio-Technica 3000 Series
With a 60 MHz tuning range, the 3000 Series wireless systems are available in two frequency bands – DE2 (470–530 MHz) and EE1 (530–590 MHz). Frequencies can be scanned and selected on the receiver and then synced with the transmitter via IR sync functionality. A backup frequency can be accessed by pressing the transmitter’s multifunction button in the event of unexpected interference. Both transmitters feature rugged, metal housings and are powered by two AA batteries.
Starting at $599
SENNHEISER | EVOLUTION WIRELESS G4
Sennheiser ew G4
Users of Sennheiser’s Evolution wireless G4 can daisy chain up to 12 wireless systems for simultaneous programming via an enhanced Easy Set-up function. The bandwidth rivals Sennheiser’s higher-end professional 2000 series, with bandwidths of up to 88 MHz and up to 32 channels. The RF output power is switchable in three steps (10, 30, 50 mW) to expand transmission range or adjust to difficult RF environments. An instrument set, a headmic set and two lavalier sets with either the ME 2-II (omni) or ME
4 (cardioid) and an on-camera version are available. All transmitters and the receiver are also available separately.
Starting at $829
SHURE | QLX-D
Shure QLX-D
Digital transmission in the UHF band, with 64 MHz tuning range; also available in the 174-216 MHz VHF band. Twenty-four-bit digital audio, with up to 17 channels in one clear TV band. Single-channel, half-rack configuration with automatic channel scan, analog receiver outputs, switchable trans- mitter output of 1 mW or 10 mW. Can be networked for monitoring and control.
Starting at $900
SONY | DWZ
Sony DWZ
Digital transmission in the 2.4 GHz band. Single-channel, half-rack receiver with scanning and automatic or manual channel selection. Full-bandwidth audio, with 24-bit/48kHz sampling rate. Analog outputs, with five-band EQ and intelligent feedback reducer via receiver menu, and supports up to six simultaneous channels.
Starting at $675
