The digital revolution that rolled through audio mixing consoles over the past decade is now moving rapidly into the arena of wireless microphone technology. Today's digital wireless microphones not only promise improved audio performance at a comparable cost, they also could help your church better cope with the looming threat from new unlicensed “consumer white space devices” that soon will be operating in the same UHF frequency bands.
(Do I hear the theme music from “Jaws”?) Yes, the monster of FCC frequency spectrum reallocation returns to haunt us!
So, if you're shopping for new wireless mics, you should be considering a move to digital. If you serve a small church that needs fewer than a dozen or so simultaneous channels, you're in luck. You have a number of attractive and nicely affordable options. Or, if your Christian rock band is prepping for an arena tour that will touch down on three continents, you also have bountiful digital options—if you also have a bountiful budget. However, if your church is looking to replace a mid-line analog system of 15-20 microphones and spend less than $1,000 per channel, well, hang in there.
DIGITAL PLUSES
Perhaps the best way to understand the transition to digital wireless is to think back about five years to the demise of analog broadcast television. If you watched over the air (no cable), you probably had some strong stations with a good picture, some not-so-strong that were a bit fuzzy, and some weak ones that were very fuzzy and sometimes wavy—but you could watch them if you really had to.
Following the digital transition, those strong stations now look fabulous, and the not-so-strong look just as fabulous (but may take more futzing with the antenna). And the weak stations? Gone.
It will be much the same with digital wireless.
“Digital wireless microphone systems have the capability of providing better RF noise rejection, higher channel counts in a given bandwidth, and consistent sound quality throughout the entire operating range,” summarizes Mark Donovan, sales engineer for installed sound at Audio-Technica, Stow, Ohio.
“Digital wireless provides a cleaner audio signal due to full deviation and lower level signals to reduce noise during transmission,” adds Reimar Fochler, technical sales manager for Los Angeles-based AKG.
Tim Vear, senior applications engineer at Shure Inc. of Niles, Ill., notes that digital “potentially offers better audio quality, with a wider, flatter frequency response and increased dynamic range. It also offers improved RF performance for more simultaneous channels in a given bandwidth and reduced intermodulation effects.”
James Stoffo, chief technical officer at Radio Active Designs of Lincoln, Neb., and a noted authority on RF spectrum allocation, stresses digital's resistance to potential interference from new white space devices. “I've done a lot of testing of analog and digital systems, using purposely generated renegade interference, and I've found that digital systems are more tolerant. Often with an analog system, even at lower levels, it will go into mute. Digital will tolerate higher levels and retain full audio quality, though often with a decrease in range.”
BETTER, NOT PERFECT
In light of that testimony, it seems like a closed case. Yet unlike the TV transition, you control both transmitter and receiver, so you can stay analog for as long as it's working for you. And, there may be advantages.
Digital “… offers improved RF performance for more simultaneous channels in a given bandwidth and reduced intermodulation effects.”
“Analog systems remain viable, introducing little or no latency while maintaining very high performance,” says Audio-Technica's Donovan. And AKG's Fochler adds that there may be some instances “in the border zone of reception where with digital the signal instantly goes to zero, where with analog there would be an overlap from gradually degraded signal into mute.”
Shure's Vear also brings up latency as “the primary tradeoff.” To what extent this is any issue at all is open to debate, as digital wireless systems typically introduce between two and three milliseconds of delay. Some contend that, when combined with latencies from digital consoles and processors, cumulative latency could reach the audible threshold of 10 milliseconds—and perhaps cause annoyances with in-ear monitoring.
But as AKG's Fochler points out, high-end digital wireless systems “have digital outputs that allow the signals to stay in the digital domain through the mixer,” thus avoiding the latency-inducing D-A and A-D conversion cycle. And Stoffo has not found it to be an issue thus far. “I just finished two major events using digital wireless systems and IEMs, with analog connections to a digital console, and had no complaints at all,” he says.
PLAY IN WHICH BAND?
Digital wireless microphone systems fall into basically two categories: UHF, shared with TV stations and soon the fearsome new white space devices; and 2.4 GHz, shared with WiFi, cordless phones, microwave ovens, and a proliferating host of other devices. What's the difference?
Compared to 2.4 GHz, UHF is inherently more robust and versatile. “With digital systems in the UHF band, transmission works well through walls and around structures,” observes Karl Kussmaul, senior product manager for professional audio at Sony Electronics, New York. “Also, UHF offers a very large number of simultaneous wireless channels, often more than 100.”
Shure's Vear adds that UHF also benefits from “the use of standard antennas and distribution systems, and offers network capabilities. But the downside, compared to 2.4 GHz, is cost.”
Indeed, the new digital UHF systems are impressive examples of powerful, sophisticated, high-performance technology. Some features (not all found in all systems) include very wide tuning range for maximum frequency agility; 256- or 512-bit signal encryption for security and stability; Ethernet networking for system setup; compatibility with third-party (AMX/Creston) control systems; AES3 and networked digital outputs; remote control of transmitter parameters (via 2.4GHz!); handheld transmitters with switchable capsules; and modular receiver racks for two, four or eight channels.
Essentially, the UHF digital options available today are high-end systems designed for broadcast production and big-budget touring. They meet the demand for rock-solid performance, high channel counts, and a level of frequency agility that allows worldwide touring and navigating very dense RF environments with random interference.
If that doesn't sound like your church, or your budget, then the new 2.4 GHz systems are for you.
SHARING THE ROAD WITH WIFI
“The chief advantages of 2.4 GHz transmission are freedom from interference from TV broadcasts, new white space devices, cell phone towers and other such transmitters,” maintains Steve Devino, live sound product manager for Calabasas, Calif.'s Line 6 Inc., a pioneer in developing this technology.
That and the attractive price tags pretty much sum up the inherent advantages. This “WiFi” neighborhood employs a widely used technology, with all the cost efficiencies that come with mass production of basic components. That's good.
Not so good is the fact that WiFi and other 2.4 GHz devices are multiplying, so the background noise level in your church in this spectrum already could be fairly high. But because the signals are all digitally encrypted, they are “looking for each other” and will still get through—up to a point.
“You want to keep your transmitters as close to the antennas as possible,” warns Stoffo. “The system can only process so much extraneous signal while seeking its own data, and if it gets overwhelmed you could have dropouts.”
The other limitation in this band is simultaneous channel counts, usually 4-10. But manufacturers are working hard to stake a solid claim in this spectrum. Line 6, for example, approaches the problems with “a number of tools to maximize the operational range, including high-power mode, channel scanning, selectable RF schemes, remote antennas, and a maximum channel count of 14 on some systems,” according to Devino.
DIGITAL IS READY
Without question, the new 2.4 GHz digital systems are a good choice for small churches needing only a few wireless channels, or for larger churches looking to add “safe” channels that will not interfere with existing analog UHF systems.
Basic systems available in the $300 to $500 range (for a handheld transmitter and receiver) are the DMS 70 System from AKG, System 10 from Audio-Technica, XDV-35 from Line 6, and GLX-D from Shure. Performance of the underlying wireless technology is likely to be largely equivalent, so your choice may depend on mic capsules available, as these will not be replaceable.
Two step-up systems in the $600 to $700 range are the Sony DWZ and the Line 6 XD-V75. The Sony's handheld does offer replaceable capsules, and the receiver has built-in graphic EQ and switchable wide- and narrow-band modes to minimize interference. The Line 6 model is the channel count champ (at 14) and also features advanced microphone modeling to emulate “the competition,” and sturdy rack-mount receivers accommodate loop-through remote antenna distribution.
SKIPPING THE MIDDLE
As of this writing, there is no digital equivalent to the “mid-priced” UHF analog systems popular in many churches. This may change in the future, but for now you take a big leap from basic, budget-friendly 2.4 GHz models up to fully loaded, touring-friendly rigs that start around $1,700 per channel.
Although pricey, these systems satisfy most stringent large church standards, not to mention arena shows in the RF density of New York or London. In addition to the features outlined above, all have 24-bit encoding at sampling rates at 44 or 48 kHz (except Sennheiser which offers options from 44 to 96 kHz.) Most also will offer digital outputs (AES3 or Dante network), variable transmitter output power (10 mW to 50 mW) and an Ethernet connection for setup using proprietary computer software.
Systems in this category include the AKG DMS700, Beyerdynamic TG 1000, Sennheiser 9000, Shure ULX-D and Sony DWX. We'll also include the unique Lectrosonics Venue platform, which falls into the same price and performance category but is not purely digital: it encodes the audio signal into digital but then carries it over analog FM. The company's argument for doing this is complicated, but rather convincing if you check it out on their website.
Of course, for any expenditure of this magnitude, you need to be checking all the relevant websites—in depth. But I expect you'll find, with the degree of frequency agility and computerized spectrum management they all offer, you'll be prepared for the coming onslaught of (cue “Jaws” again) horribly invasive consumer white space devices.
And that impending change—of vital interest to all churches, large or small, whether using analog or digital—is worthy of a dedicated article. Watch for it in am upcoming issue of CPM.
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