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I need a wireless expert

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Chris Babbitt
I need a wireless expert
on Aug 17, 2009 at 6:24:42 am

I shot a seminar this week in a classroom at a university. My Sennheiser wireless transmitter kept dropping audio. The audio would keep cutting out for like a milisecoond, but consistently about every ten seconds or so. I tried changing frequencies, but had the same problem. So, I substituted my old trusty Samson U1. I didn't get the dropouts with the Samson, but the compander circuit was going nuts, so that when the speaker was talking at lower volumn, the Samson lowered the level way down, as though it was trying to suppress some kind of noise. In all the years I've been using both these systems, I've never seen behavior like this. What do you think could possibly be going on in that bulding that would cause these problems? I don't think there were any other classes or activities taking place while we were there.



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Ty Ford
Re: I need a wireless expert
on Aug 17, 2009 at 11:42:45 am

Hello Chris and welcome to the Cow Audio Forum.

With all due respect, you would be one of the few people on the planet that consider Samson wireless "trusty." :)

Wireless is a wiggly thing. Your description of what each mic was doing makes me think there were at least two problems; one for each mic.

I've not experienced the problems you have with the Sennheiser, but having the transmitter on someone who's wearing a wireless communicator, blackberry, etc, can PROFOUNDLY mess with a wireless mic transmitter. I like to hold the person's gear at my station until they are finished speaking. That way I'm sure they won't "turn it in to check for messages" during the event and hammer my wireless.

The compander issue (if that's what it was) could have been caused by extreme low frequencies. I have had this in industrial and office buildings. The last time while waiting for an elevator inside a building at NASA, in the Maryland suburbs of DC.

The possibilities are many. Wireless mics use primary transmitting and receiving frequencies, but also have intermediate frequencies that can be interfered with. A spectrum analyzer could probably find the culprits. The compander issues are more likely related to the actual audio picked up by the mics.

Regards,

Ty Ford



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






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Chris Babbitt
Re: I need a wireless expert
on Aug 17, 2009 at 3:17:28 pm

Thanks for your quick response, Ty. Although I can't say the same for other Samsons I've owned, this one (with a Sony ECM-44 capsule) has been a rock-solid performer over hundreds of events.

The seminar was attended by around 80 people, and I'm sure that every one of them, including the speaker, had some sort of wireless device. But, I've shot over 30 hours with this same group at another location, with the Sennheiser mike, with no dropouts or hits whatsoever.

Your theory of extreme low frequencies causing the companding makes sense, as there is no audible noise in the recording. Do you know what could possibly be the source of the low frequency noise? Some sort of alarm system maybe?

I guess I'll have to resort to a wired mike, if we have to shoot at this location again.



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Ty Ford
Re: I need a wireless expert
on Aug 17, 2009 at 4:10:20 pm

Chris,

Structure-borne noises from other places in the building, typically heavy machinery in the basement for HVAC or other things.

Regards,

Ty Ford


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






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Sam Mallery
Re: I need a wireless expert
on Aug 19, 2009 at 5:10:11 pm

The next time this happens with the Sennheiser G2, you can try turning off the pilot tone in the system. The pilot tone turns off the audio when it detects interference. The thinking behind it is that you would rather hear silence than hear static. You never know, you could have turned off the pilot tone and perhaps there may not have been static there at all.

I always pack a wired option in any given situation.



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Chris Babbitt
Re: I need a wireless expert
on Aug 19, 2009 at 5:21:08 pm

AhHa!

Good advice! I did have the Pilot Tone turned on.





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Jordan Wolf
Re: I need a wireless expert
on Aug 27, 2009 at 12:52:32 pm

Download Sennheiser's IM Prevention software to help see where the pronlem frequencies will be. Also, make sure to use their Frequency Finder to pick appropriate and open RF for the area.

Wolf
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