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Shure’s Axient wireless mic system

In this week's feature Professor Rumsey looks at the clever technology inside Shure's new Axient wireless microphone system

If you operate wireless microphones on a regular basis you’ll know that the airwaves are increasingly thick with congestion. So-called “white spaces” that used to be available for wireless mics are gradually being squeezed by other services such as wireless internet, security systems and other data transmissions. Governments have enthusiastically sold off parts of the spectrum and audio engineers have to work hard to operate their systems in the remaining gaps. Shure’s recently launched Axient wireless microphone system introduced a suite of tools designed to ease the process. By intelligent use of software, coupled with remote device control, networking and spectrum management, the company aimed to improve the reliability and quality of wireless audio systems under challenging conditions. What, then, is some of the technology behind the scenes? Quite a lot of wireless microphone systems can use what’s called “diversity reception” to improve the consistency of coverage. Essentially, how this works is that the receiver has more than one aerial, and sometimes more than one radio-frequency (RF) receiver module. The aerials are spaced apart, so that if one of them experiences a drop-out in signal strength (say as a performer moves around), the other one probably doesn’t. An intelligent receiver monitors the signal strength from the two modules and may either switch or cross-fade between them to ensure a reasonably seamless coverage as the signal strength changes. Shure takes the step of introducing frequency diversity into the equation, which means that the microphone can transmit on two different frequencies at the same time. This improves the options open to an intelligent receiver. For example, if interference screws up the signal on one channel the receiver can instantly switch over to the other one. Coupled with advanced interference detection and spectrum management, this is a powerful tool to increase system reliability. Rather than sticking to one constant transmission frequency, the system continuously scans the available RF band and selects the best and most compatible alternative frequencies on which to operate. By scanning the RF spectrum at a particular venue, the system can determine where potential problem regions lie and can rank backup frequencies for suitability in case it needs to switch. Because there is remote control of the microphones and transmitters, the switch can be done without the operator having to intervene manually. A display of the RF spectrum is shown on the front panel, or alternatively one can employ the more sophisticated Wireless Workbench software on a laptop, to undertake more detailed evaluation of the current environment. Axient wireless systems can also be networked using a rugged Ethernet switch that has nine ports and a dedicated DHCP server to assign IP addresses to individual units. All in all, Shure seems to have come up with a wireless system designed to meet a number of the most pressing challenges faced by those trying to keep their show on the road.