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HVX-300p- Audio distortion on lav mics

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Megan Evans
HVX-300p- Audio distortion on lav mics
on Sep 9, 2009 at 6:14:37 am

I am working with some interview footage that was shot on an HVX-300p, using a field mixer and in some cases, 2 or 3 lav mics were used. In the scenes where 2-3 mics were used, as opposed to 1 mic scenes (which are fine), the audio is way over-modulated and distorted. These mics were ran through a field mixer and sent back to the camera as left and right channel inputs (Ch. 1 and 2). The camera levels were set to Auto. Testing the mics and mixer back in the office today, it was determined that the mics and mixer are fine, isolated from the camera. Is there some audio setting we're overlooking on the camera, or has anyone had a similar problem when using this camera?

We're somewhat newbies on this camera... coming from Beta SP and the analog world...

Any help would certainly be appreciated.

Thanks!


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David Jones
Re: HVX-300p- Audio distortion on lav mics
on Sep 9, 2009 at 3:33:16 pm

Hi Megan,

Without seeing how you actually set up the gain structure with the camera, it's hard to say what you might need to do differently.

Are you using wireless mics? Is the limiter set to "on" on the mixer? What's the audio gain level set to (in the audio set-up menu)?

I hate to be "that guy" but this is why you need to monitor the audio in the field, using headphones plugged into the camera, or send a return to the mixer. Meters on these cameras can tell you the levels are correct when you're actually recording distorted or clipped audio.

Sorry about your recording.

Dave


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Megan Evans
Re: HVX-300p- Audio distortion on lav mics
on Sep 9, 2009 at 4:06:45 pm

Hi David,

Thanks for your help. I will check the gain settings in the camera (we're new to this camera) and see. We monitored audio through headphones in the field, both on the camera and on the mixer. This distorted audio was caught in the field, albeit too late, but the rest of the shoot (2 days) went smooth with great audio. The guys shooting it say they did not change anything to correct the bad audio in the field, so it's kind of a mystery...

Thanks again!
M


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Megan Evans
Re: HVX-300p- Audio distortion on lav mics
on Sep 9, 2009 at 4:19:03 pm

Hi again David,

Some updated info on your questions:

The Rear Mic inputs (ch. 1 and 2) are set to -60Db in the camera audio settings menu. Those are the two channels we were using in the field.

I did notice that our firmware is 9.19 and I've seen that we need to upgrade to 9.28. Could this be a factor for our audio issues? Also, yes, the mixer limiter is ON.

Thanks again,
M


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Dave LaRonde
Re: HVX-300p- Audio distortion on lav mics
on Sep 9, 2009 at 5:08:08 pm

[Megan Evans] "...In the scenes where 2-3 mics were used, as opposed to 1 mic scenes (which are fine), the audio is way over-modulated and distorted. These mics were ran through a field mixer and sent back to the camera as left and right channel inputs (Ch. 1 and 2)..."

It sounds like the Mic inputs on your camera were set to Mic Level, but the mixer's output was set to Line Level. This Mic/Line mismatch will indeed overmodulate the audio, and there's no way to fix it. Sorry. Oh, you can try taking it to an audio guy and it will cost a lot... but the results won't be anywhere near what you hoped for.

If you absolutely HAVE to use the footage -- for example, one of the interview subjects had to catch a plane to some out of the way place like Mars or Neptune -- it's going to be an ordeal to listen to it. Otherwise, a reshoot is in order, and it's a hard lesson learned.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Noah Kadner
Re: HVX-300p- Audio distortion on lav mics
on Sep 9, 2009 at 7:40:16 pm

And this is why you hire a sound mixer and do what they say... :)

Noah

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Ned Miller
Re: HVX-300p- Audio distortion on lav mics
on Sep 10, 2009 at 2:26:49 am

I too come from the betacam world and when I first moved to digital I learned that there is less head room, meaning hot audio breaks up. Or it could be the Mic/Line mistake a poster above alluded to.

So here is what you do from now on, and many of the TV shows I work on, like Dr. Phil, etc. demand:

Before the shoot even starts roll some bars and tone BUT then a little human voice and play back. Just takes a minute. INSIST the audio guy is listening off the camera, some only monitor their mixer. Especially if the audio guy is going wireless to the camera, they tend to not check the REAL camera audio.

So...lesson learned, we all learn by our mistakes. You should offer a reshoot at your expense and if the sound guy is ethical he will offer you many days of freebies to help make up for it.

Good luck,

Ned


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George McMorrow
Re: HVX-300p- Audio distortion on lav mics
on Oct 2, 2009 at 8:49:26 pm

All previous posts are correct, you probably need to reshoot. I also do audio and had the same problem when the the cameraman switched from line to mic level when he moved his position. Lesson learned, ALWAYS have the mixer send 1k tone to camera to set levels and repeat this every time the camera moves and ALWAYS monitor audio from camera headphone jack. if it is sent back to mixer as a confidence line, do a quick pull and reinsert of cable from headphone jack to make sure that it is the camera audio that you are listening to, and not the audio from the mixer.
I worked a corporate job yesterday that had the mixer levels sends set one side to mic and other to line. I figured this out quickly when I sent the 1k tone.
The lessons learned under stress are never forgotten
George McMorrow
Cinecall Productions
cinecall.com



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