… delivering high-quality audio. And the #1 reason that someone is not satisfied with their audio visual provider is because of audio issues.
So how do you ensure the highest quality, audio? Well, you plug a cable into your microphone and run it to your audio mixer. But who wants to do that?
Of course, nearly every live production these days relies on wireless audio, reducing cost and setup time by eliminating long cable runs while at the same time giving on-stage talent the freedom to move around. However, wireless audio is not without its potential issues, the biggest one being radio frequency (RF) interference.
To understand RF interference, we first need to understand a little about wireless microphones. Wireless microphones rely on radio frequency transmission to send an audio signal from the transmitter used by on-stage talent to the receiver operated by the audio / visual team. Here in the United States, wireless microphones operate unlicensed in the TV band spectrum, which is generally between 400 MHz and 600 MHz*. More specifically, Shure’s Axient Digital A product line supports a tuning range of up to 184 MHz and can operate between 470 MHz and 636 MHz while Shure’s ULXD G50 line supports a tuning range of up to 64 MHz and operates between 470 MHz and 534MHz**.
There are a couple of important things to note here. First is that wireless microphones operate unlicensed, which means that anyone can use these frequencies. Second, these frequencies are part of the TV band spectrum, which means that some of them are used by high-powered transmissions from television broadcasters, and the frequencies used vary from city to city, broadcaster to broadcaster. In combination, both of these factors mean that there is good potential for interference for your wireless audio transmission.
As if these potential issues were not enough, there are a multitude of other factors that can cause RF interference for wireless audio transmissions. Microwave ovens, power generators, electrical equipment, and power cabling are just a small fraction of the types of devices that can generate RF interference and cause less-than-optimal wireless audio performance.
So how do we manage this potential RF minefield and provide robust, high-quality wireless audio for our events?
Well, there are several things that we do, starting with wireless spectrum management.
At many venues, and in particular hotels, there is typically a person in change of wireless spectrum management. They will assign frequency blocks to AV providers to use during their productions, helping ensure that when multiple events are taking place, they are not using the same frequencies for wireless audio.
The next step is to perform a frequency scan. Most mid-range and high-end wireless audio systems have frequency scanners built-in, and they will scan available frequencies to find which are currently the best to use. However, these are only the best frequencies at the time of the scan… what happens if someone turns on a power generator somewhere in the building after the frequency scan but during the live performance?
Well, here is where it pays to plan ahead. There are several approaches to mitigating this risk, and the first starts with something as simple has having wired microphones on stand-by up on stage. If the RF interference is significant, an on-stage presenter can simply pick-up a wired microphone and continue. Next, a speaker can be directed to a podium microphone, if available, in the event that their wireless microphone goes out. Of course there is also the option of having backup wireless microphones on different frequencies to ready to go as well.
While all of these backup scenarios are perfectly fine for the overwhelming majority of use cases, there are some use cases where any interruption of audio would be considered a failure, even picking-up a backup microphone. For those cases, Shure’s Axient AXT600 Digital Spectrum Manager is the best option. When the AXT600 performs a frequency scan, it not only selects the best frequency as the primary frequency for each wireless microphone, it also ranks and stores backup frequencies, and can automatically switch between primary and backup frequencies on the fly if it detects there is a problem. For critical performances, such as keynote presentations, concerts, and corporate all-hands meetings, the AXT600 is a critical component in ensuring the highest possible recoverability from RF interference for your event.
So the next time you are preparing for a live event, ask your AV provider what they are doing to ensure robust and reliable wireless audio. If they don’t have a plan for spectrum management and dealing with the very real possibility of RF interference, they may not be the right AV company for you.
* As a result of rules adopted buy the Federal Communication Commission in 2014 to reorganize the UHF television band, most of the 600MHz frequencies (617-652MHz and 663-698MHz) were repurposed for wireless licensing. As of July, 13th 2020, a license will be required to transmit on these frequencies.
** Shure has different versions of their Axient and ULXD lines of wireless audio products which support other wireless frequencies available in other parts of the world.