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Thanks to a recent change in regulations, a new class of wireless systems is revolutionizing live sound, theater, and broadcast: Wireless Multichannel Audio Systems, or WMAS.
Using broadband multiplexing to transmit more audio channels over the same airwaves used by traditional narrowband systems, WMAS technology presents a more efficient, streamlined, and scalable solution for managing wireless mics, bodypacks, in-ear monitors, and crew communications. Systems like Shure’s Axient Digital PSM and Sennheiser’s Spectera represent a new paradigm in wireless audio.
This article will provide an overview of Multichannel Wireless Audio Systems, how WMAS technology works, and the many benefits it brings to productions of all sizes.
In February 2024, the Federal Communications Commission (FCC) put into place new regulations permitting the use of “a new, more spectrally efficient wireless microphone technology” in the United States. Similar regulations were issued by the European Telecommunications Standards Institute in 2021, but the FCC’s announcement officially opened up the U.S. market.
According to the FCC’s press release, “The new rules will allow WMAS to operate in the broadcast TV bands and 600 MHz duplex gap on both a licensed and unlicensed basis, and in other Part 74 LPAS frequency bands on a licensed basis.” Essentially, these rules allow the use of wider spectrum blocks that make WMAS possible.
Companies like Sennheiser and Shure had already been developing WMAS products in Europe and the U.S.; the loosened regulations simply allow consumers to use these systems legally. Now that WMAS is officially sanctioned, these products are sure to become the new standard in wireless audio.
A Wireless Multichannel Audio System is any wireless transceiver that uses broadband multiplexing to transmit and receive multiple channels of audio over a single RF bandwidth. Compared to traditional narrowband systems that require separate equipment and careful coordination of frequencies to send and receive audio from different devices, WMAS represents an all-in-one solution that is more efficient and flexible than anything else.
However, WMAS doesn’t refer to any specific technologies—it simply denotes a new class of devices that are allowed to operate under the new FCC and ETSI rules. Different manufacturers may use their own proprietary codecs and protocols in their WMAS platforms, but they all accomplish the same feat of packing more channels into less space on the RF spectrum.
The basic principle behind WMAS involves combining (or multiplexing) multiple digital audio signals into a single RF channel. Instead of the older “link-based” approach, wherein each transmitter sends audio to a corresponding receiver, WMAS gear transmits and receives all of your mic signals, IEM mixes, and crew comms at once. This also includes bidirectional data channels that allow devices to talk to the base station.
Abandoning the link-based approach means that WMAS can dynamically adapt and scale to make optimal use of available spectrum space, comply with local regulations, or operate alongside traditional narrowband systems. Unbound by specific frequencies, a WMAS system can make full use of the available airwaves.
WMAS also avoids the issue of intermodulation distortion (IMD) artifacts that has historically plagued narrowband systems. Instead of requiring extra space between channels to account for IMD, WMAS equipment cleverly isolates IMD products in their own dedicated channels on either side of the operating band.
An Overview of Wireless Multichannel Audio Systems (WMAS) from Shure.
Wireless Multichannel Audio Systems solve a number of problems that hinder traditional wireless systems. Some of the benefits of WMAS include increased spectrum efficiency, flexibility, resiliency, and simplicity.
The biggest benefit of WMAS is its ability to squeeze more audio channels into the same amount of bandwidth used by narrowband systems. The increased spectrum efficiency of WMAS allows operators to use more wireless mics and bodypacks on stage, give performers more dedicated IEM mixes, and use the same system for talkback and crew communications.
When operating at the full bandwidth allowed by the FCC, WMAS theoretically supports up to 64 channels of audio. However, this would require sacrificing some amount of audio quality, range, or latency. In practice, Shure specifies a maximum of 40 channels within 8 MHz: still plenty more than is possible with narrowband systems.
WMAS equipment can be easily reconfigured for various situations using several different operating modes. Switching modes can allow you to maximize channel count, minimize latency, extend range, or dynamically balance these parameters for optimal performance. Users can even adjust the fidelity, operating range, and latency of each audio channel individually, meaning that critical channels, such as lead vocals, can be given preference over utility channels, such as crew comms.
When it comes to fighting interference, WMAS has a big advantage over link-based narrowband systems. Cutting-edge WMAS transceivers are capable of constantly scanning the airwaves for interference and “working around” problematic overlaps. Instead of taking a minute or more to manually switch a channel to a new frequency, you’ll only hear a short dropout while the system automatically adapts.
The RF bandwidth used by WMAS depends on the number of channels needed (and the required fidelity and latency), so it’s easy to scale up or down as needed. Whether you have the full 8 MHz available to work with or you’re sharing the airwaves with nearby users, WMAS always makes the most efficient use of the available frequencies.
For example, if you’re using WMAS alongside a narrowband system, you can limit its bandwidth to avoid interference while still getting the most out of the available space. If that space becomes free, you can expand the bandwidth to accommodate additional channels or achieve better fidelity with the same channel count.
Because WMAS supports bidirectional audio, you no longer need separate systems for transmitting and receiving audio. Instead, one WMAS base station can act as a transceiver for all of your wireless mics, IEMs, and communication channels. This translates to smaller racks, fewer antennae, easier troubleshooting, and speedier setup.
But less gear doesn’t have to mean less redundancy. Professional WMAS systems include features like mirrored Dante ports and secondary power supplies to ensure continuous operation even if a cable comes loose or a power supply fails. In fact, Sennheiser has published an article outlining solutions to a number of potential problems ranging from broken cables to unexpected interference (see below).
Like any new technology, WMAS comes with a bit of a learning curve. Fortunately, leading brands like Shure and Sennheiser have created some very useful resources to help you understand WMAS and get the most out of their products:
If you’re interested in upgrading your wireless system, get in touch with one of our Audio Consultants to get the full scoop on WMAS and find the right products to meet your needs.
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