In March of 2023, Sennheiser launched a press release about their upcoming vision for the future of wireless audio. They presented their concept of the Wireless Multichannel Audio System or WMAS. It is primarily aimed at applications that require a lot of channels in the air, such as theater productions, large sporting events, major tours and broadcast.

Right now we are living in a world of one transmitter to one receiver rule. RF channels use 200kHz of bandwidth for broadcasting, there is little to no bi-directional communication between the devices and coordination of multiple frequencies is becoming mission impossible for events on the largest scale (consider the Super Bowl, or Broadway theaters), because we are being squeezed in a corner due to larger and larger demands for wireless on one hand and less RF space on the other. Frequency coordination requires a lot of planning, measurements, personnel, time and money. WMAS promises to eliminate most of these issues, by providing a single rack unit device that can process 64 channels of audio over RF and combine a microphone, an IEM signal and bidirectional communication into one broadband RF channel.

The project started as research on how to combat RF fading, which is the natural loss of signal on stages. RF fading can cause signal dropouts, and is usually dealt with by means of diversity, where 2 antennas are deployed and the system decides which signal is stronger. Until now, this was the only way to deal with RF signal reflections that can, just like in audio, cause cancellation of the signal and compromise the integrity of the transmission. In addition to that, the amount of transmitting power grew with the use of multiple systems. If one system transmits at 50mW, and you are using a large number of systems in one location, then the power on air gets a massive increase, which can cause intermodulation issues for not only wireless audio systems, but also for other surrounding devices.

The author running a monitor mix - on the right, there are two antennae, one for the IEM system, the other for the microphones (one half of a diversity pair). With WMAS all these systems get combined and only one antenna is used.

So how does Sennheiser propose to tackle all of these problems? WMAS is a bidirectional system-based device, where multiple on-air units are combined into a single system that transmits on one broadband channel. Instead of 200kHz, WMAS is using 6 or 8 MHz, which is the bandwidth of a single TV channel. As stated in their press release, “the audio engineer simply selects a carrier frequency for the broadband RF channel to be configured, and the system will coordinate itself, with the quality and range that the engineer chooses for the individual audio devices.” So not only will there be minimal need for frequency coordination, but the system also provides the ability to define allocation of spectrum resources for each channel individually. Your lead singer will have the best audio definition and lowest latency setting, while a guitar tech can maybe get away with lower audio definition and slight latency increase for their in-ears.

All of these RF channels will operate on a total of 50mW of power. This means that there is going to be less transmitting power in the air and an increased ability of reusing channels for larger outdoor festivals. This is great news for Broadway where theaters that currently disrupt the RF spectrum of a neighboring venue can have their wireless footprint reduced, resulting in less need for frequency coordination between venues. Also, larger festivals can possibly reuse the same channel to transmit on stages that are sufficiently spaced apart.

Until now, we had to use separate frequency ranges for microphones and IEM systems to achieve best results. With WMAS, not only do they reside in the same TV channel, they coexist in the same beltpack unit. Since WMAS is bidirectional, Sennheiser is designing a transceiver unit, which performers can use for microphones and IEM systems in the same pack. This also means that Sennheiser is expanding their range of IEM systems with a digital range, which means that this technology will probably be more widely available in the following couple of years.

Source: https://en-us.sennheiser.com/wmas (Sennheiser press release)

The feature I am really excited about is the dynamic resource allocation. Since all devices in the system talk to each other through remote control and communication, it will be possible to create “scenes” for your resources. Imagine a festival where one band is playing and the other is setting up. The resources go to the performing band, while the units of the artist setting up can be discovered by the system and just confirm that they are turned on and give you a battery check status. When it is time for a changeover, the operator can simply swap the allocated resources, giving priority to the new band on stage. This is huge in terms of coordinating systems on festivals between performers and prevents issues where someone accidentally turned on their systems too soon, affecting the performer on stage.

Another really important factor is the omission of the diversity system. All of the bidirectional transmission and communication will be done with a single antenna, because the broadband transmission channel is much less susceptible to signal drops due to the 30-fold diversity on 6 MHz and over 40-fold diversity on 8MHz. During an online presentation of the system it was also mentioned that the rack unit will have multiple antenna connectors, but rather than using them for diversity, the unit will provide zones for easier deployment on larger stages.

Setting up an IEM system will be faster and easier. The reduced physical footprint will be a welcome benefit in terms of rack space and weight.

Here comes the disclaimer: I got all this information by reading their press release and attending an online presentation and am in no way affiliated with Sennheiser (just a fan). Since the actual devices are still in development, all technical specifications are subject to change until the official release, which I suspect will happen either by the end of this year or in the next year. Sennheiser is currently advocating with the FCC to clear the use of broadband transmission for these devices, but since this change has already happened in many of the countries in Europe and Asia, I don’t think the FCC wants its users to be left behind with this new technology.

This new technology promises to drastically change the way the RF world will look in the future. Instead of racks and racks of gear, it provides a compact solution that saves truck space, weight and time for the operator to set this up. I don’t see this being adopted on smaller-scale productions in the beginning and this new technology will have to coexist with the current systems for quite some time. But I am excited to see how they will tackle all of the demands that the touring life brings. One thing that is on my wish list is a complete redundancy solution with an automatic fail safe switch. Since all wireless signals will be handled by a single unit, this now becomes a single point of failure that can bring down an entire show. I am hoping to see some sort of a solution that resembles the Waves server technology, where a secondary unit seamlessly takes over in case of the primary unit’s failure.
For more information, check out Sennheiser’s press release on the technology: https://en-us.sennheiser.com/wmas And if you are from the US, check in with your local Sennheiser dealer to see if you can provide a letter of support of the changes to the RF transmission rules that the FCC has yet to approve.

The Future of Wireless Audio is Even BETTER Than You Think