A simple mention of the word “wireless” these days is bound to bring up grumbling in the mind of audio production professionals. And with good reason, especially given the reality of dealing with the ever-shrinking landscape of available wireless frequencies. What was once a relatively straightforward process of selecting a few channels and doing your show has become increasingly complicated. Fortunately, pro audio manufacturers — particularly those who manufacture wireless systems — are by nature pretty smart, and have come up with some clever solutions, such as online frequency searching and intelligent systems that can quickly scan and lock onto open airspace.
Whole Lotta Technology Going On
A recent example of presenting real-world solutions to the issue of crowded airwaves comes from Shure, in the form of its new ULX-D digital wireless microphone systems. UXL-D first debuted earlier this year as half-rack, single-channel units, and at InfoComm, the company showed its ULXD4D dual-channel and ULXD4Q quad-channel receivers. On the surface, this may simply seem like a more convenient repackaging in a new form factor, but there’s a whole lotta technology going on that may not be apparent at first glance.
The features of the entire UXL-D line are impressive and include: predictive switching diversity; automatic channel scanning with IR sync; AES 256-bit high-security encryption; individual RF and audio meters; intuitive front panel LCD menu; and intelligent battery charging; and the ability to operate up to 17 systems within the space of a single 6 MHz TV channel.
Yet for a really big production, you might just require additional simultaneous wireless channels, and the new dual- and quad-channel ULX-D units take that a step (and a rather large one at that) beyond. “In standard mode, ULX-D can handle 17 compatible systems on one 6 MHz TV channel. In situations where you need more, you can switch to High Density Mode,” explains Shure’s Chris Lyons. “High Density Mode optimizes the digital transmission scheme and output power to squeeze 47 compatible systems into just one 6 MHz TV channel. So you can handle a full wireless installation with just 6 MHz of spectrum available.”
Essentially, the HD function is possible through the use of advanced RF digital filtering. That takes the signal from the normal 350 kHz to a narrow 125 kHz footprint while keeping intermodulation distortion to an absolute minimum. Unless IMD is kept in check, spurious harmonics of that 125 kHz RF signal would take up additional bandwidth, thus reducing the available channel count. The other key to successful operation in the HD Mode is switching the transmitter power to 10mW. When in non-HD Mode, a higher-power 20mW setting is available, for use in longer-distance transmission or difficult RF environments.
Another plus of the new ULX-D units is built-in Dante networking for low latency transport of multiple uncompressed audio channels over a single Ethernet connection, along with IT and control data.
Put to the Test
To check out the performance of the HD Mode, I recently attended a technology demonstration at Shure in Niles, IL. The test involved setting up 100 ULXD1 beltpack transmitters, each operating on a different frequency and placed about one meter apart (see Fig. 1). The idea here was to recreate the equivalent of an RF transmission nightmare with scores of simultaneous beltpacks operating, while walking among the various units and testing each for clear audio reproduction. The RF result is shown in the spectralyzer graph in Fig. 2, which indicates the real-time operation of 100 units within a 13 MHz spectral footprint.
The Dual and Quad ULX models (featuring the new HD Mode) will ship later this summer. But if you bought a single-channel version earlier this year, are you out of luck? Not exactly. “The good news is, it’s backwards-compatible,” says Lyons. “You can easily fit an older ULX-D single-channel receiver with the High-Density Mode feature simply by upgrading the firmware. Just attach it to your new Wireless Workbench software, download the firmware and the next time you synchronize the receiver and transmitter, you’ll have High Density Mode as an option.”
For more details, visit shure.com.
