Meeting Topic: Making Wireless Work Today
Moderator Name: Tom Levno
Speaker Name: Michael Abbott of All Ears, Inc. and Jonathan Novick of Alteros, Inc.
Meeting Location: The Ivar Theater at the Los Angeles Recording School, 1605 Ivar Ave., Hollywood, CA, 90028
Wireless solutions have transformed modern productions. They give performers incredible freedom to move around and help keep stages clean. Wireless solutions also give the production crew incredible headaches. Finding available spectrum is one of the main sources of frustration. Spectrum needs keep growing. In addition to the wireless mics, and instrument packs, there are also in-ear monitors and crew comms. At the same time, the FCC keeps reallocating spectrum for other purposes. We are currently in the middle of a huge spectrum reduction and the next reduction is just a few more years away. Two industry veterans, Michael Abbott and Jonathan Novick, discussed the realities the industry faces today and a unique solution that helps mitigate the problem.
Jonathan noted that common problems include lack of clear spectrum, coverage area, audio quality and battery life.
Michael said most of these problems are dealt with in large scale shows by a dedicated wireless vendor like Soundtronics. On the Grammys, 48-56 RF mics were used along with 48 frequencies for in ear monitors and up to 300 production wireless com belt packs. On top of that, many of the 22 acts bring their own wireless mics, in ear monitors and walkie talkies. Soundtronics does the frequency coordination and sometimes training and maintenance with some of the touring crews. Sometimes the noise floor in part of the RF spectrum rises and makes some of the equipment unusable. Sometimes these noise sources mysteriously go away and sometimes not. It is essential that everybody using RF equipment do coordination so interferences can be sorted out to the best extent possible.
Jonathan described the squeeze that has come from the FCC's National Broadband Plan that is in the process of reallocating spectrum for broadband use—movies on your cell phones. He described the history of the shrinking UHF TV band since 1949. Now, T-Mobile is putting up 150 cell sites a day using the 600 MHz band. It has been proposed that by 2023, the 500 MHz band will also be sold. Thee is less RF spectrum for audio production but more demand for RF services with wireless mics, in ear monitors and wireless coms. The fine for using the old spectrum after the transition date is $10k per channel per day of violation. The FCC went after some churches in 2010, so beware.
After the spectrum repack, the frequencies in use are closer together causing intermodulation, another pesky type of interference. The job of RF coordination is difficult. Not many schools are not teaching the science of RF technology. The total cost of ownership used to be the cost of the equipment. Now, to assure your equipment will work, if you are doing a major show, you need an RF coordinator.
The FCC has not opened up any new bands of spectrum for use by modulated carriers of audio. Digitally modulated wireless would seem to offer some opportunities but with the necessary latency, it is not useful for live production.
Jonathan discussed range and controlled coverage and the complexities of designing a multiple antenna system, often used in large scale productions. Michael described such a system used in a resent show at Staples Center.
A new technology is available from Alteros. With up to 24 mic channels in a system, it runs at 6.5 GigaHertz UHB (Ultra Wide Band) and offers full dynamic range audio over purely digital links with no processing. Because of its high frequency and low power, it's range is fairly short and it is easily blocked. This can be an advantage. If the signal is contained in a space, there is higher security for the signal, less chance of interfering with neighboring productions and possible reuse of channels in separate rooms/zones. The system is license free. The transmitter can be synced to the house clock allowing for digital audio to be delivered in time with house digital audio. Learn more at https://www.alteros.tech/
Michael discussed encryption and how signal security and privacy are increasingly called for in both corporate and broadcast productions, of microphone and intercom signals.
The UWB communication is based on pulses and timing. The receiver looks for pulses at periodic times. All of the pulses are identical. When there is no pulse, the digital information is 0. When there is a pulse, the digital information is 1. All of the pulses are the same frequency. All pulses are 2.5 nanoseconds in duration. There is no phase or amplitude information. The control unit, capable of receiving 8, 16 or 24 channels depending on licensing, outputs on MADI and Dante at 48kHz 24 bit audio.
The applications and limitations of the Alteros wireless mic system were discussed. When the area of performance is clearly definable such as corporate situations, houses of worship, television studios, tennis matches, or dressing room interviews, the system works well. Jonathan noted that it is not the universal solution, but it creates 24 channels of breathing space and can work along side other technologies.
To review the meeting, go to vimeo.com/LAFS and scroll down and select the slide of the meeting.
AES-LA thanks Michael Abbott and Jonathan Novick for an excellent presentation.
Written By: Tom Levno