Just when you thought it was safe to go back to a hard-wired connection for your favorite microphone or guitar, here comes some new wireless technology. Undaunted by the recent restructure of wireless frequency allocation by the FCC, at least two manufacturers are rethinking their approach to wireless audio. Rather than transmitting analog audio via conventional methods, new systems from Line 6 and AKG refine wireless transmission of digital audio, providing resistance to interference in busy RF environments.
Digital Modeling Technology
At the beginning of this summer Line 6 (line6.com) announced their new line of digital wireless microphones, the XD-V series. The XD-V system includes two handheld cardioid mics, the XD-V30 and XD-V70, both of which incorporate Line 6's digital modeling technology.
The XD-V30 provides a single microphone model based on the Shure SM58, while the XD-V70 provides users with a choice of several different microphone models including the Shure SM58 and Beta 58A, Sennheiser e835, Audio-Technica AE4100, Audix OM5 and Electro-Voice N/D 767 (though this makes me wonder… if you ask for an Audix OM5 on a rider, and you get a model of the OM5, has the rider been met?).
Two belt pack systems are also available: the XD-V30L and XD-V70L, both of which feature internal antenna, quarter-inch input and condenser lavalier mics. All of the transmitter bodies are constructed from metal; the receivers for the XD-70 and 70L each have a half-rack metal chassis while the receivers for the XD-V30/30L are desktop units constructed from polycarbonate.
XD-V wireless units operate in the 2.4 GHz band, well away from digital TV, cell phone and "white space" device frequencies. Line 6 claims a frequency response of 10 Hz to 20 kHz with a dynamic range of 115 dB or better.
The XD-V70 incorporates Line 6's exclusive L6-DC7 (removable) capsule capable of emulating the aforementioned models. A variety of capsules from Shure, Audix and Heil Sound can also be used with the XD-V70. The XD-V70/70L operates on 12 channels with a range stated as 300 feet, while the XD-V30/30L operates over six channels with a 100-foot range. All models employ Line 6's DCL (Digital Channel Lock) technology that encodes the digital transmission to prevent unwanted interference. The systems also incorporate Line 6's PDP (Proprietary Data Placement) technology frequency diversity, hybrid frequency-hopping spread-spectrum technology in which each user channel is split into four frequencies before being transmitted. The receiver reassembles the signal, resulting in reliable operation even in hostile RF environments. XD-V systems may be operated internationally without need for a license.
Scanning the Spectrum
From halfway across the world, AKG has unleashed their new DMS 700 Digital Microphone System, calling it the first digital wireless to meet worldwide transmission regulations. This system features several components including the DSR 700 digital, true-diversity rack mount receiver, DHT 700 handheld digital transmitter and DPT 700 body pack digital transmitter, which can be used with almost a dozen different AKG microphones including HC 577, C 520 and C 520 L and C 555 L headsets as well as an instrument cable. The DMS 700 system is available in two frequency ranges (548.1 to 697.9 MHz or 710.1 to 864.9 MHz) allowing operation of up to 100 channels simultaneously. Tuning range is across 155 MHz with pre-programmed frequency groups supporting up to 40 channels of intermodulation-free operation. Users may also manually tune channels in 25 kHz increments. Audio bandwidth is spec'd at 20 Hz to 25 kHz.
DMS 700 system components utilize AKG's proprietary audio encryption for secure transmission as well as resistance to potential sources of RFI. A digital data stream carries battery reserve and mute status information from the transmitter to the receiver. The DSR 700 can scan the local RF spectrum, find an unused channel and transmit that frequency data to the transmitters via infrared link. An Environment Scan function turns the receiver into an RF spectrum analyzer, scanning the receiver's frequency range for active RF and displaying the results on a frequency spectrum chart. Built-in DSP includes a low-cut filter, semi-parametric EQ and dbx compression and limiting.
DHT 700 handheld and DPT 700 belt pack transmitters are capable of up to 50 milliwatt RF output (user selectable) and run eight hours on two AA batteries. Backlit LCDs on each unit show frequency data, output power and battery status. Digital conversion is 44.1 kHz/24-bit with a latency of less than 4ms. Audio connection to the DPT 700 is via mini-XLR, and a jack is provided for an external mute switch, enabling the system to be muted even when the transmitter is not easily accessible.
The DHT 700 handheld wireless mic is available with either AKG's D5 supercardioid dynamic or C5 cardioid condenser capsule. Both transmitters feature charging contacts for use with AKG's CU 700 fast charger. The CU 700 can charge two DPT 700 or DHT 700 units without removal of the batteries, achieving maximum capacity in two hours' time.
With the addition of an optional HUB 4000 Q Ethernet interface, the DMS 700 system may be interfaced with Harman's HiQnet, enabling network control and monitoring of DMS 700 system functions. Optional accessories for the DSR 700 include the AB 4000 antenna booster, SRA 2 B/W active and SRA 2 W passive wideband antenna. An optional (free) iPhone application enables control and monitoring of DMS 700 wireless systems from an Apple iPhone or iPod touch via wireless router.
These are some of the most recent developments in wireless technology. It will be interesting to see how wireless audio manufacturers continue to negotiate the ever-crowding RF environment over the next few years.
