Audio-Technica SpectraPulse Review
Mar 19, 2010 12:00 PM, By John McJunkin
A high-tech wireless microphone system for the boardroom.
The radio frequency spectrum is getting very crowded, and the scarcity of bandwidth is being compounded by legislation that is chopping up the available spectrum between more and more government agencies and other commercial bands. It continues to get harder and harder to find a clear frequency, and the more frequencies are required for a job, the more complex and difficult it gets. Contractors are in need of solutions that overcome these difficulties, and Audio-Technica has obliged with its SpectraPulse system. This is the only true ultrawideband (UWB) system in existence, and it brings some pretty high science to bear to solve the problems that contractors face. I spent time with a SpectraPulse system, and I was wowed by that high science but also impressed from a pragmatic standpoint. The system is simple to use and works exactly as advertised.
I'm not going to pretend to understand in great depth the technical workings of the SpectraPulse system, but allow me to offer a simplified explanation: The system is based upon time division multiple access (TDMA) channel access, the same technology used for most 2G and some 3G cell phones. The TDMA architecture allows 15 time slots of information per millisecond, and during the first of these time slots, the Audio-Technica drm141 digital receiver module transmits to synchronize and send status and control. Each of the system's 14 transmitter channels then has an opportunity of one time slot in duration to transmit its data to the receiver. Each transmitter sends its data sequentially during its respective time slot, and during the other 13 time slots, it queues its data for transmission during its next slot. This limits latency to less than 1.5 milliseconds. This system facilitates fast bidirectional communication between transmitter and receiver, which in turn helps to avoid sync loss, and much faster reacquisition if sync is lost, typically 3 milliseconds or less. Basically, this is digital over the air, which provides ipso facto encryption and allows for the transmission of a multitude of signals with much less bandwidth. Since the system does not use a single carrier frequency per se, it's virtually impossible to isolate and intercept the signal unless the signal thief has a UWB system of their own, and in that case, 128-bit encryption is available.
The system's transmitters are the mtu101 microphone transmitter unit and the mtu201 XLR desk stand transmitter. The mtu101 incorporates a boundary microphone and is roughly trapezoidal in shape. It is about 3"x5"x2". On its underside are a sliding power switch and a recessed rotary switch to determine on which of the system's 14 channels the unit will transmit. I used a standard tweaker tool to make the necessary adjustments. Atop the unit are LEDs to indicate power and link status. Additionally, the power LED will blink if the unit's batteries are failing. I like this a lot. It can use NiMH batteries or standard AA alkaline batteries, and Audio-Technica includes a pair for each transmitter—a nice touch if a contractor needs to get the system up and running immediately. A soft-touch button on each transmitter can be configured as push-to-talk, push-to-mute, or in toggle mode. This microphone/transmitter cuts a low profile and is therefore nice for installs that require clear lines of sight. The mtu201 is virtually identical to the mtu101 in topology and operation, but it's just a bit "taller" as it were. It offers an XLR input intended for use with an included gooseneck microphone, but any signal can be connected to the mtu201's XLR input. It struck me that these could be useful in a multisignal cart scenario, for example, a drum kit on a wheeled platform.
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