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Old September 9th, 2011, 10:16 AM   #1
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Problem with my lav mic

Please can you watch the lined file and if you have an explanation help me as it is driving me mad.

I have had this problem repeatedly where I get a massive spike in sound - a loud pop/click/crack or as here - however you want to describe it! I am using old but otherwise very reliable Senheisser EW100 wireless mics (first generation) an have just replaced the antennas and mic to rule them out and it is still happening. Any advice/help gratefully received. Thanks.

Further info - I expect it to happen at least twice in an hours recording either in a church or a reception room.

- password is audio
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Old September 9th, 2011, 10:25 AM   #2
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Re: Problem with my lav mic

Either someone rubbed against the mic, or interference.
Who was wearing the mic? Certainly not the speaker at the lectern and I didn't see the groom move, however I did see someone else move at the time of the noise. (left, almost out of frame @ 00:05) If this person was wearing the mic I would suspect mic contact.
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Old September 9th, 2011, 10:52 AM   #3
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Re: Problem with my lav mic

sounds like rf interference to me. try a different channel or decrease the distance between transmitter and receiver.
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Old September 9th, 2011, 11:45 AM   #4
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Re: Problem with my lav mic

Because you've mentioned that this is not the first time you've had this happen; i've ruled out the contact with wind screen of the mic.

This sounds like radio interference or a signal drop, is there a chance that the guy who moved his arm in the left of the frame was wearing the mic? It's possible that your transmitter was located in the drop zone, any movement or contact with the device will cause this.
I dont think there is anything wrong with your wireless mic system... I had the same thing happened to me, the next day I found a better location for the mic and had no issues with sound.

Have you tested the location of the transmitter before the shoot? did you find any drop/"dead" zones?
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Old September 9th, 2011, 12:32 PM   #5
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Re: Problem with my lav mic

A couple of things. The speaker isn't wearing the lav, so why use this audio? Did you not have a backup camera mic? You really need backups for a wedding. Sorry for the lecture, but just saying.

I'm betting the lav is on the officiant who appears to be sitting just out of frame. The noise clearly lines up with the movement of his arm (which Rick also pointed out). If this mystery person is indeed the one who is wearing the mic, I think we can say with near certainty that he bumped the mic with his hand when he was scratching his nose or whatever he was doing. It does sound like that.

By the way, if you have only one wireless unit you would have done well to actually put the lav on the venue's own mic stand there. You could have taped the lav alongside their mic and wound the cable around the mic stand, taping the transmitter at the base.

I've done a fair number of weddings, and we always have lavs on the officiant and groom (the groom's mic is crucial for getting the bride's vows). We also have a backup camera mic getting the room and another mic (usually wireless) on the PA. I would feel really nervous with anything less than that.
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Old September 9th, 2011, 01:34 PM   #6
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Re: Problem with my lav mic

Sounds like a sudden drop in signal strength. You mentioned you had the aerials replaced? a pair of portables close in can usually work quite well with one of the aerials physically snapped off - until something soft and squidgy gets in the way - like a body!

The first thing to do is set up a test to check if the pair are functioning as they should. Open air is best. Simply hold the transmitter up in the open, mount the receiver where there's no obstruction and move apart - see what kind of distance you can get. With nothing in the way, an original system should get 40m. Obstructions will limit this, but if you do it outside getting this sort of distance is common. It's not reliable distance of course, and have a few people stand in the way and it will drop off, but it means that used at 10m, signal strength should be perfectly good enough to get noise free reception. Closer still and totally solid.

If you do this test and get the range - then the cause of your problem will be local - is there still a dry joint on the receiver or transmitter that when under clothes breaks the contact and reduces the range, suddenly?

Or you may not get the range, indicating very low power output or a permanently faulty connection - even a simple dry joint on the pcb can do this.

It's an RF problem of some kind, but it's going to need some work tracking it down. Do you know anybody who has a similar system? Then you can compare item for item to track down which one it is?
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Old September 9th, 2011, 02:31 PM   #7
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Re: Problem with my lav mic

I'm not familiar with Sennheiser wireless systems as I'm a Lectrosonics and Sony guy, but noticed something. In both Lectrosonics and Sony, if signal strength was weak or if interference was present, the audio would mute rather than go nuts like your sample. Does Sennheiser always do this if the signal drops? It sounds like a squelch problem to me, rather than brushing the mic.
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Old September 9th, 2011, 05:39 PM   #8
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Re: Problem with my lav mic

Sounds very much like an RF dropout to me, definitely not the sound of something touching or scraping over the mic capsule or cable. First thing to check is that the transmitter and receiver antennas are parallel to each other and not bent or scrunched up. Make sure that the mic cable isn't touching or crossing the transmitter antenna. Insure the transmitter antenna is in free space, not touching the wearer's body.

Seconding Marco's comment ... even without the interference this audio is unacceptable, completely unusable. While it's important to track down the source of the noise burst so it doesn't happen in the middle of an otherwise usable track, if this is typical of what you've been recording you really need to re-think your audio strategy from the beginning.
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Old September 10th, 2011, 10:11 AM   #9
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Re: Problem with my lav mic

Thanks all for the feedback. I guess I should have given you all a few more facts instead of getting you all to shoot blind. The groom was wearing the mic. The mic was on his lapel (outside), and the transmitter in his inside pocket. The spare mic cable was wound around the transmitter (is this not the right thing to do?). The areal was not scrunched up, he was only 5 meters away and I have tested the kit and all is good out to 70 meters. I was not planning on usng this audio as I did have the lecturn miked up seperatly, I just happened to find this clip while editing and as it has been driving me nuts for a while now, grabbed it for the purposes of trying to find an answer. It happened 5 more times during this 1 hour service. I am now sending them back to Senheisser for a full service with samples of the faulty audio.

Thank you all for your valuable time and help
Ian.
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Old September 10th, 2011, 11:16 AM   #10
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Re: Problem with my lav mic

Quote:
Originally Posted by Ian S Lewis View Post
Thanks all for the feedback. I guess I should have given you all a few more facts instead of getting you all to shoot blind. The groom was wearing the mic. The mic was on his lapel (outside), and the transmitter in his inside pocket. The spare mic cable was wound around the transmitter (is this not the right thing to do?). The areal was not scrunched up, he was only 5 meters away and I have tested the kit and all is good out to 70 meters. I was not planning on usng this audio as I did have the lecturn miked up seperatly, I just happened to find this clip while editing and as it has been driving me nuts for a while now, grabbed it for the purposes of trying to find an answer. It happened 5 more times during this 1 hour service. I am now sending them back to Senheisser for a full service with samples of the faulty audio.

Thank you all for your valuable time and help
Ian.
Wrapping the excess mic cable around the transmitter is not a good thing to do. Coil it up and put it in the wearer's pocket or stuff the coil under his belt. Keep it clear of the transmitter antenna. As he was sitting down, the antenna could have become pressed against his body - you want it in free space. If by 'inside pocket' you mean the wallet pocket inside the breast of his jacket, that too would have pressed the antenna tightly against his chest, just from the pressure of the fabric. Best place for the transmitter is usually on his belt.
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Old September 11th, 2011, 02:23 AM   #11
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Re: Problem with my lav mic

Thank you so much - armed with new info I will do some tests and see if I can recreate the problem and if your solution fixes it - I think you may have just hit the nail on the head. I had coiled the spare mic cable around the transmitter body and it was pressed against his body inside his jacket! I did not realise this was a no no. The next wedding I filmed, for whatever reason, I decided to have the spare cable coiled up, away from te transmitter and I only suffered one glitch the whole day - however, the transmitter was still placed in an inside jacket pocket. I will only ever mount on a belt from now on.
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Old September 11th, 2011, 03:29 AM   #12
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Re: Problem with my lav mic

It sounds more like the mini plug or other contact is loose. Check the mike socket on the transmitter and the receiver contacts. You might also try a non lav mike on you camcorder to see if you have a camera audio problem. Rule out all the permutations.
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Old September 11th, 2011, 06:13 AM   #13
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Re: Problem with my lav mic

If you wrap the mic. cable round the transmitter you can strain and break the cable as it comes out of the plug. This is definitely NOT the thing to do.

If the antenna touches the body you will get about a 70dB reduction in transmission.

If the squelch was set to "low" you would have gotten a mute instead of a glitch if low signal was the problem.
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Old September 11th, 2011, 06:33 AM   #14
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Re: Problem with my lav mic

@Ian, I had a 1st generation EW wireless bodypack die during travel back home from an international trip... even in carry on. When I went to the Sennheiser website about out of warranty service, I discovered they no longer service the G1 EW products. FYI
http://www.sennheiserusa.com/service...t_Wireless.pdf
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Old September 11th, 2011, 10:59 PM   #15
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Re: Problem with my lav mic

Sounds like a RF interference to me... I had a similar problem with my ew100 G2, while recording a medical conference in NYC a few years ago. Almost every MD there had a Blackberry, many of them were on call, and I noticed them coming out of the room to respond to the call right after I heard the RF interference... Good thing, I had also Zoom-H4n set up on a podium, which gave me clear audio I finally used.

When I shoot weddings I always place a transmitter into inside (wallet) pocket of the groom, loose cable is coiled and placed next to it. I have never experienced any loss of signal, even when the antenna in the pocket is in vertical position, and my receiver's one is in horizontal...
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