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Canon XH-A1 issues, where is the bad chain link?

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Michael Cummins
Canon XH-A1 issues, where is the bad chain link?
on Aug 6, 2009 at 3:33:22 pm

Just finished shooting in one of our factories that had a LOT of ambient noise from nail guns, metal stampers, saws, etc. Now, before you roll your eyes, let me say that this isn't about removing background noise or sweetening audio.

I knew this was going to be an interesting endeavor when I saw our locations were two manufacturing facilities. One of them is known corporate-wide as their loudest plant in the United States. We also needed a second lav. We currently have a Sennheiser EW-100 G2 kit for our wireless setup. I had the mic clipped onto the talent's bra underneath her cotton shirt (first few inches of cord taped up, etc), and was getting pretty good audio. I was monitoring through the camera with full-covering headphones and couldn't detect any peaking whatsoever. Furthermore, the VU meter on the XH-A1's LCD didn't read any overdriving or constant peaking. Everything seemed good.

I started capturing the footage yesterday and found that the audio on her mic is consistently overdriven, with just enough distortion to make me wonder why I didn't hear it through the headphones. Bringing the clip into an FCP timeline, the program's VU meter shot the audio peaking at about -12dB, with it usually riding between -13dB and -15dB. So at this point, I figure it's a problem with either the transmitter or receiver. Going through the settings I see that the transmitter is set to -10dB for sensitivity. I tweaked this a bit at the beginning of the shoot and anything above that was too much (0db yielded noticeable distortion).

Check me on these settings. Under the XH-A1's audio menu (Menu\Audio Setup\XLR GAIN UP\) the setting is switched to 12dB instead of off. The camera's physical MIC ATT switch is set to off (switching to on during the shoot yeilded too much noise).

Where is my broken link here, and why can't I rely on the VU meter on the camera's LCD?


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Ty Ford
Re: Canon XH-A1 issues, where is the bad chain link?
on Aug 6, 2009 at 5:14:12 pm

Hello Michael and welcome to the Cow Audio Forum.

I think what you have here is not uncommon in situations in which you go directly from mic to camera. Let me talk it through, though without the mixer.

Mics can, themselves, overload before getting to a transmitter or camera. If the mic too sensitive, you have to use a less sensitive mic.

The input of the transmitter could be overloaded by what the mic is picking up , even if the mic is not distorting. That's an adjustment on the transmitter.

The fact that your FCP footage is a -12 means you probably weren't overdriving the camera input, but with no way to calibrate the receiver to the camera, you could have been sending line level from the receiver to a mic input on the camera. The receiver output could have overloaded the front end of the camera before it even got to the camera input controls.

The term is "gain staging" you need to know that each stage is properly set to get the loudest audio that doesn't get too loud and distort somewhere along the chain.

How's that work for you?

Regards,

Ty Ford



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






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Michael Cummins
Re: Canon XH-A1 issues, where is the bad chain link?
on Aug 6, 2009 at 5:28:40 pm

That sounds exactly like what was happening. Is there a process I can go through to get all the devices in line with each other to prevent this on other shoots? Or is this a "goes to show you" moment where I need to pick up some sort of mixer? Usually I'm the guy running the A camera, monitoring sound, and checking/moving lights around, while the other crew member helps setup and does what I tell him, so running another device (mixer) is going to be difficult, especially since the other crew member is hard of hearing.

Funny thing is, I had the exact opposite problem with the other mic. I had a wired lav on the other talent that sounded like it was overdriving before it even hit anywhere near zero on the LCD's VU. So I had that audio pulled back so it wouldn't continually peak, but in post it's clean but a little quieter than what I hoped for.


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Ty Ford
Re: Canon XH-A1 issues, where is the bad chain link?
on Aug 6, 2009 at 6:55:50 pm

[Michael Cummins] "Is there a process I can go through to get all the devices in line with each other to prevent this on other shoots? Or is this a "goes to show you" moment where I need to pick up some sort of mixer? Usually I'm the guy running the A camera, monitoring sound, and checking/moving lights around, while the other crew member helps setup and does what I tell him, so running another device (mixer) is going to be difficult, especially since the other crew member is hard of hearing.

Funny thing is, I had the exact opposite problem with the other mic. I had a wired lav on the other talent that sounded like it was overdriving before it even hit anywhere near zero on the LCD's VU. So I had that audio pulled back so it wouldn't continually peak, but in post it's clean but a little quieter than what I hoped for."


A process..sometimes. On some wireless you can see the audio input level on the transmitter so you can make sure the input sensitivity of the transmitter is good. Some receivers have peak lights or metering to let you know how they are doing. The output of the receiver is USUSALLY mic level, bit not always.

You sort of have to know what to expect (pandemonium) and how to finagle things to get the levels sorted out.

A mixer can help because at least you get the mixer to camera audio calibrated. Then you can jump back to just finagling the other stuff. Good mixers also have good limiters that let you run mic a little hotter without fear of distortion, so you're recording farther above the noise floor of the camera.

The Sound Devices 302 is my strongest suggestion for an entry level mixer. Please don't ask me if there's a cheaper one. Yes there are cheaper ones. They don't do what a 302 does, so don't bother.

Regards,

Ty Ford

Ty

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






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Greg Curda
Re: Canon XH-A1 issues, where is the bad chain link?
on Aug 7, 2009 at 1:53:09 am

Additionally, unless Canon fixed this on the XH-A1, all XL style cams had line level inputs that were -11dB (consumer line level). If you were to put a +4 output (pro line level) into that, there would be distortion, no matter what your meters read, because, as Ty pointed out, you are overdriving the front end of the camera.

With a mixer, at least you can run a tone through the system to line up the camera. This wont help you in the above scenario, though. I have either used a variable pad (Shure makes them) with line level (-15dB), or mic level to the camera to avoid that problem.

You are still correct to monitor through the camera, because that's your recorder, and that's what is being recorded. Even with a mixer, if you are listening only to the mixer, you have no idea what is being layed down.

The high noise environment may have prevented you from hearing the subtle distortion in your track. If you're going to do a lot more of this, I recommend HN-7506 from Remote Audio. These are aircraft-style "blockout" phones with Sony 7506 drivers in them. Originally designed for the NASCAR circuit, they would provide the isolation required to hear your track properly.


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Ty Ford
Re: Canon XH-A1 issues, where is the bad chain link?
on Aug 7, 2009 at 1:58:03 am

Um, well, my Canon XL2 has mic level inputs ONLY at the XLRs.

Regards,

Ty Ford

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






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Greg Curda
Re: Canon XH-A1 issues, where is the bad chain link?
on Aug 7, 2009 at 2:21:21 am

Really? Hmmmm... I know XL1 and XL1a had that prob...Mic only on the XL2? Hmmm... I know there's no mic/line switch, right? Someone told me once that the inputs were auto-sensing. I thought, wow, how advanced...hahaha!!

OK, Ty... thanks for the correction... Do you have any intel on XH-A1 inputs specifically? for my failing memory banks? hehe!!


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Ty Ford
Re: Canon XH-A1 issues, where is the bad chain link?
on Aug 7, 2009 at 2:27:20 am

Greg,

I don't, but I'm sure it's online somewhere.

The XL2 also has line inputs via unbalanced RCA jacks on the side of the camera. I've been told they are better than the XL inputs, but I've never really had a problem with the XLR inputs and my Sound Devices 442 mixer.


Regards,

Ty Ford

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






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Michael Cummins
Re: Canon XH-A1 issues, where is the bad chain link?
on Aug 7, 2009 at 2:23:07 am

Thanks for your help, guys. Yeah, the XH-A1 has a switch for both mic and line for the XLR inputs. It also has an option in the menu for a +12dB boost. I think what might've happened was I increased the transmitter's sensitivity from the usual -20db to -10db, but didn't feel the need to adjust the AF OUT on the receiver because I couldn't pick up any distortion at all.

Honestly, I've been hearing a lot lately about the Sound Design 302, and would get it if we had another dedicated crew member on our shoots. But for now it looks like noise canceling headphones are going to have to work.

And $1,300 isn't much in my mind for a good field mixer. We, of all people, should know that you get what you pay for.


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Greg Curda
Re: Canon XH-A1 issues, where is the bad chain link?
on Aug 7, 2009 at 2:44:50 am

The 302 is a steal at 1300, as are all SD products, in my opinion. If the line inputs of the cam actually pan out at +4, then you might consider the MixPre... limited flexibility (mic in only, +4 out only), but it can go totally unnoticed on your belt, and give you that great SD sound.


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Sam Mallery
Re: Canon XH-A1 issues, where is the bad chain link?
on Aug 7, 2009 at 1:15:42 pm

"Where is my broken link here, and why can't I rely on the VU meter on the camera's LCD?"

Perhaps next time give yourself more headroom when setting levels.

Did you set the audio levels when the loudest noises were happening?



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Michael Cummins
Re: Canon XH-A1 issues, where is the bad chain link?
on Aug 21, 2009 at 7:50:00 pm

Well, gentlemen, you're advice has been taken. I just received the Sound Devices Mixpre from B&H today. Had a bit of play time with it going over the features in the manual. The PortaBrace for it will arrive next Tuesday. *does little dance*


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Larry Vaughn
Re: Canon XH-A1 issues, where is the bad chain link?
on Dec 19, 2009 at 11:27:35 pm

There is or was a good tutorial online at dvcreators.net regarding the Sennheiser EW110-G2 system. I have the XH-A1 and although I normally stay away from wireless if possible, I got good results by setting it up the way the video suggests.



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