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Adam Benn
Sennheiser
on Jan 8, 2009 at 3:34:25 am

Maybe you could help me.

I'm doing a documentary shoot with a singer. I have 2 Sennheiser G2100 wireless transmitters and receivers. I've used them in a lot of situations with a lot of luck. Recently we we've been shooting with this singer over several weeks. He is talking to his band during rehersals and then going into full on singing with piano, drums, horns and other instruments. When he sings with the piano it becomes distorted, sounding overmodulated.

Now ordinarily I would obviously check and change the frequency, the levels on the on the camera, the xlr's are in Mic with no phantom power. The AF out levels on the receivers are at at least -24 and the Sensitivity on the transmitters is at -30. The mic is placed conservatively midway down his coat jacket lapel.

So then, this seems like it's still over modulated... new batteries, camera tested with other mics...


Testing individual components of the band to try and root out the problem resulted in only the weird overmodulation coming when the piano, a baby grand is playing. It's miked, but going to speakers that are far away and not as loud as the drums, or horns.

We cannot take away the piano and mike it later because we're recording live performances.

Any thoughts?


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Ty Ford
Re: Sennheiser
on Jan 8, 2009 at 2:49:34 pm

Hello Adam and welcome to the Cow Audio Forum.

I think you're overmodulating the transmitter. This is a very common problem when changing levels from normal talking to singing. No adjustment after the transmitter will fix this problem, you have to turn down the input to the transmitter or get a less sensitive microphone. Of course, that'll mean the talking sections are too quiet.

Yes, I imagine the baby grand is not helping. His lav is sitting right in front of it when he's playing, right?
In most cases like this, people use one mic for interviews and another for performances. There are some high-end wireless that allow remote adjustment of the transmitters input sensitivity, but they are not cheap.

Regards,

Ty Ford

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






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Adam Benn
Re: Sennheiser
on Jan 8, 2009 at 3:29:40 pm

I have the sensitivity of the mic turned all the way down so that when he is talking I have to boost the levels all the way up to hear him when he's just talking... Also the over-modulation ONLY comes from the piano, not his voice or any other instrument.



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Ty Ford
Re: Sennheiser
on Jan 8, 2009 at 4:30:49 pm

Adam,

Same problem; source (piano) too loud for the system. Odd though. How loud does he play the piano? Are there other instruments or monitors with piano or other source?

Regards,

Ty Ford

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






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Rodney Morris
Re: Sennheiser
on Jan 9, 2009 at 12:50:28 pm

It's very possible that what you are hearing isn't overmodulation caused by high levels. Some mics just aren't good at reproducing an accurate piano sound. The piano, as you know, has a very complex sonic "footprint" if you will. There are so many harmonics that sound with the playing of a single note. When multiple notes are played simultaneously there are crazy amounts of harmonics floating around and I've heard some pretty weird signals coming from cheaper mics that sounds somewhat similar to mild distortion, but different from that caused by simply too much gain. I don't know if there is a term for it, but I would call it "harmonic distortion". I wouldn't be surprised if it occurred with the G2 systems. However, this is speculation at this point and I'd be very interested to hear what Ty and others have to say about this.

Maybe I'm just crazy. I'm no longer drinking caffeine these days so...

Rodney

Freelance Sound Technician/Mixer


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Ty Ford
Re: Sennheiser
on Jan 9, 2009 at 1:38:13 pm

Rodney, if you're crazy, I'm crazy. You're one of the brighter guys here at Cow and I really appreciate that you're here.

You make an excellent observation. Technically, what you're talking about is some sort of distortion that happens when a frequency range larger than expected is put through a system not designed to handle it.

It may be just the mic itself or something in the circuitry of the transmitter. I don't think it's happening in the receiver, but it's not impossible.

I occasionally run into sub-harmonic problems with my wireless. We were going from one location to another at NASA/Greenbelt last month. I was fully rigged with mixer, two lavs and a boom, had my headphones on was listening to the wireless. While we stood waiting for the elevator, the meter on my Sound Devices 442 mixer started showing something and I was hearing the compander in one of the wireless get a little wacky. I took off my headphones and I could hear/feel this very low frequency resonance; the kind you get in some buildings. I'm not sure what the source was, but this sort of structure-born sound can play havoc with a wireless system.

I've even run into it outside. It isn't usually constant, but something somewhere made a noise and the waves roll out from it. It the same thing when you're sitting still on a boat and another boat goes by. Eventually their wake will pass under you.

If I had mics with a high-pass filter to scrape that stuff off, it wouldn't have modulated the compander threshold.

Not all wireless are the same, Adam. What you may have found might be the Achilles Heel of the Sennheiser system. Maybe they didn't design it to be used near a sound source like a piano. In trying to get the circuit right for voice, they might have ignored the possibility that the system would be used around a piano.

Or, (now for something completely different) I have heard that the ME2 lav that comes with the G2 wireless is not so good. People have said that trading up to a MKE2 made a noticeable improvement. They weren't even talking about piano.

Rather than condemn the transmitter, I'd be interested to hear if the problem went away if you tried a different lav. The MKE2 is good. Other very good lavs are the Countryman B6, EMW and Sanken COS11. You can order the Countryman mics with the right plug to work on the Sennheiser. I suspect you can do the same with the Sanken.

There are a few hinky (two wire or three wire) wiring problem that do exist among mics and transmitters, but a knowledgeable shop should know about that.

I have EMW and B6 mics and I had them made with cables so that I could switch and use the mics with my wireless or connect them through an inline XLR power supply and use them hard wired. Sometimes hardwired is the easiest way to go.

Hope this helps and do let us know what you find.

Regards,

Ty Ford

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






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Adam Benn
Re: Sennheiser
on Jan 9, 2009 at 2:48:52 pm

Thank you guys so much for your input. I'll try some new mics maybe and I'll let you know. Maybe next time I'll have some footage to post for specifics. Thanks again.



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