With more wireless microphones and other RF equipment being used on sets across the country for HD productions that use both stereo and 5.1 channel audio, the need to locate and secure useable frequencies has become a problem for many production crews on location.
James Stoffo, a principal at Professional Wireless Systems, in Orlando, Florida (a division of Masque Sound), is one of the country's most sought-after wireless technology specialists. He specializes in coordinating spectrum frequencies for some of the highest profile events, including the NFL's Super Bowl and NBA's All-Star Game telecasts. Stoffo says crews will find it increasingly hard to avoid interference if they re not careful setting up their equipment.
Q: Do you see a lot of true 5.1 audio being captured for HD productions?
A: Not really. The only 5.1 production I have been involved with so far was last year's Super Bowl telecast [on Fox]. We had a single Holophone 5.1 surround-sound RF microphone from DPA Microphones, which we put into five transmitters. For the most part, true multichannel audio is not the norm for most production in the U.S. I handled the pre-game, halftime and national anthem production at this year's Super Bowl and we didn't do 5.1 surround sound.
Q: What are some of the issues to be concerned with when micing surround sound for HD production?
A: Everything on set has to be quieter in HD, that's for sure. Multichannel audio picks up things you don't hear with stereo, so that's one reason producers tend to avoid it when they can. You have to watch your noise floors and your gain settings. A lot of that gets buried with analog audio. You can't make any mistakes with HD audio production.
Q: What types of equipment should producers be aware of when micing an HD production?
A: They should choose systems that are "frequency agile," allowing them to find frequencies that older systems cannot. They usually give you about 30 MHz of frequency to locate a good channel. Remember that most of the wireless mic systems on the market are analog FM systems. Most people think that FM sounds better than digitally encrypted systems.
Q: What about the issue of decreasing spectrum available for things like wireless mics on location?
A: In another year or so, we're going to be down to less than half of the space we now have available for wireless production devices to operate in. And if you look ahead to 2009, we'll have about one-quarter of the frequency space. The amount of RF out there now makes coordination that much more difficult, because production people still want to have all of their intercoms systems, microphones, IFBs, etc. in place. That requires spectrum to do it. It's a problem people have ignored for too long.
The problem is caused by the fact that HDTV broadcasts take up double the amount of spectrum—the same spectrum where wireless mics operate. Plus, the FCC gave away another portion to telcos at auction and to emergency services. Television productions are considered 'secondary users': so we have to work around what the FCC does. We've lost a lot of spectrum that production crews have relied on forever. It's just not available anymore.
I've been working on frequency coordination for years, but working on large productions like the Super Bowl is getting more challenging because crews are using more equipment. Production managers have to start thinking about putting their IFBs and intercoms on lower spectrums, where there is more bandwidth available, and putting the wireless microphone transmitters, which generate lower power, on the higher bands so that they don't step on each other.
On site you should test each receiver separately first and look at the signal strength. Usually, I find about 15 percent of my mics are stepping on each other and I have to readjust to another frequency to enable them to co-exist on the same production. Obviously, this interference problem is worse outdoors than inside a studio.
Q: What type of tools do you use to help find useable frequencies?
A: I wouldne't go on any project without a radio spectrum analyzer, frequency scanner and counter, and an intermodulation software program on a laptop that does the millions of calculations for you.
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