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Wireless Mic interference

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Michael Frank
Wireless Mic interference
on Jan 15, 2010 at 1:49:23 am

Hi guys,

I've been shooting some lectures recently, using the Sennheisser evolution G2's into the XLR inputs on a Z1U. Have shot in the location before but not until this past time that there was an issue with static or RF interference. I'm looking for advice on two areas:

1) Is there anything I can do in audio-post to remove the static when it is only a light interference? What would be the best way to tackle this?

(I know the best answer is to reshoot.. unfortunately this isnt really the kind of situation where I can stop the whole show just for the sake of the video.)

2) How can I avoid the interference? Please hand hold me here if you're willing.. I'll admit that I'm not an expert in this area and I'd love to know how to make sure I'm doing this right.


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Ty Ford
Re: Wireless Mic interference
on Jan 15, 2010 at 11:43:39 am

Hello Michael and welcome to the Cow Audio Forum.

Apple's Soundtrack Pro and Izotope's Rx noise reduction along with some cutting and pasting room tone in quiet spots may help.

For the future, nope, not much you can do. Try......

1. Before the event, fire the wireless up and walk test everything to see what's going on. If you hear problems, try different frequencies to see if it goes away. The pros use spectrum analyzers to look for open frequencies and problem areas.

2. Once everyone gets into the venue with their Blackberries and other personal communicators, your audio still might be messed with. You can try asking that people turn them COMPLETELY off and not just in standby, but they probably won't and you can't tell who the guilty party is.

If it's a live show, you can't stop the flow and ask again that everyone turn off their gear. I was on a shoot for Apple last year and we kept getting hits while trying to shoot. I kept having to say "phone noise" after each ruined take. Even after asking people to turn them off several times, they'd all look at their devices and poke them, so they had to be turning them back on again.

These devices are like crack cocaine to some people. If they turn them off, they feel, deflowered, disempowered and incomplete. It's very weird. It makes me think of the old Star Trek; specifically, the Borg Continuum. Humans with hardware implants. We're starting to look like that now with the Bluetooth headsets. But I digress.

Also be aware of any other wireless gear, or ask about it. I've recorded in some halls fine one time, but had real problems the next. I asked the house guy if his wireless gear was on, even though he wasn't using it. It was. He turned it off. I was fine.

Regards,

Ty Ford

Want better production audio?: Ty Ford's Audio Bootcamp Field Guide






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Jordan Wolf
Re: Wireless Mic interference
on Jan 15, 2010 at 11:41:13 pm

Sennheiser (and many other wireless microphone manufacturers) has a frequency finder that will help get you in the ballpark. After that, you will be much less likely to have interference from surrounding TV stations.

As Ty mentioned, it is possible (and quite likely) that you will get interference from devices that the audience brings into the space. Nextel is notorious, from my experience. The only way to truly solve the actual problem is to have everyone turn their devices off (unlikely). I make it a habit to do so when I attend events where RF is used (microphones, IEMs, Comm. packs, etc.).

Of course you could build a Faraday cage for the presenter to stand in, but...that might not look too nice.

Then, there's my favorite option: a wired microphone. Is there any reason that you cannot use a wired microphone to pick up the audio?

Wolf
<><


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Ty Ford
Re: Wireless Mic interference
on Jan 16, 2010 at 1:58:53 am

Audio Technica, and others, have spent a lot of money over the last few years to redesign their mics with better shielding to protect from the increase in personal wireless gear. So far, it seems to be working.

Poorly shielded connectors are a common entry point for interference.

Regards,

Ty Ford

Want better production audio?: Ty Ford's Audio Bootcamp Field Guide






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Richard Crowley
Re: Wireless Mic interference
on Jan 16, 2010 at 7:25:15 am

"Then, there's my favorite option: a wired microphone. Is there any reason that you cannot use a wired microphone to pick up the audio? "

Yes, that is my BKM! (Best Known Method). It is no longer practical to get 100% audience (and even crew) compliance with turning OFF all their little pocket jammers.

My favorite solution was the movie producer who took offending cell phones, etc. from cast and/or crew and nailed them to the door frame (or the fencepost). Probably not practical for most of us. :-((


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Ty Ford
Re: Wireless Mic interference
on Jan 16, 2010 at 2:07:36 pm

Hi Richard,

Thanks for stopping by with your good idea. Where I am, even hardwired mics are susceptible. I have found some help using new connectors and better shielded cable.
Neuntrik EMC connectors and Gotham GAC-5 cable.

Regards,

Ty Ford

Want better production audio?: Ty Ford's Audio Bootcamp Field Guide






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Jordan Wolf
Re: Wireless Mic interference
on Jan 16, 2010 at 6:21:22 pm

Yeah, RF can get in anywhere there's enough metal to make an appropriate-length antenna or certain fraction of the wavelength of the original (I think it's 1/20th when you take into account the entire run of cable from source to input).

Those Neutrik connectors seem to work well - I don't know if I've ever used them.

Wolf
<><


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Michael Frank
Re: Wireless Mic interference
on Jan 17, 2010 at 2:57:09 pm

Guys thanks for all of the tips and suggestions. I really appreciate it.

Will be doing some post cleanup over the next couple of days, so we'll see how that goes.

Moving forward getting a wired mic might be the best option.. I'll have to discuss the pros and cons of both approaches. The only thing I can see is them not wanting to be limited in how they walk around the room.. but its either be limited or run the risk of the interference I guess.


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Richard Crowley
Re: Wireless Mic interference
on Jan 17, 2010 at 8:53:25 pm

"Moving forward getting a wired mic might be the best option.. I'll have to discuss the pros and cons of both approaches. The only thing I can see is them not wanting to be limited in how they walk around the room.. but its either be limited or run the risk of the interference I guess."

Everything is a tradeoff decision. What is more important, a clean recording, or the spontaneous wandering of the presenter? You can make a case either way.

"Will be doing some post cleanup over the next couple of days, so we'll see how that goes. "

Cell phone RFI noise is particularly tough to eradicate. It is not that different from the intentional jamming done behind the Iron Curtain during the bad old days of the Evil Empire (USSR).


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Ty Ford
Re: Wireless Mic interference
on Jan 17, 2010 at 10:18:23 pm

Richard,

If you get a hardwired lav, see if you can get one that terminates into your current wireless as well as into a hardwired power supply. That way you can get double duty out of it.

If you/they can handle the idea try a countryman E6 over the ear and get it with two cords one wireless, one hard wired.

See/hear it in action here: http://www.vimeo.com/5330259

Regards,

Ty Ford

Want better production audio?: Ty Ford's Audio Bootcamp Field Guide






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Bob Kessler
Re: Wireless Mic interference
on Jan 19, 2010 at 6:18:39 am

Just curious...

How far away was the receiver from the transmitter? I don't do live or production sound very often any more, but one thing that always worked well for me was placing the receiver as close to the speaker as I could and running a long cable to the mixer; it seemed to help A LOT.


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