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3 pin XLR stereo/surround sound?

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Zach Rohrer
3 pin XLR stereo/surround sound?
on Apr 3, 2011 at 10:52:41 pm

I accidentally posted this in another forum, but since this one is Audio professionals I'm really hoping someone can give my an in depth answer to this situation.

I'm relatively new to a lot of the audio side of film production. But I've been doing a lot of research lately on types of Mics, what to get for a typical movie set, etc..

And I recently learned that 3 pin XLRs are not stereo, only Mono. Which I found surprising considering that, well, I honestly thought it was all stereo. (Sorry for the ignorance) Anyways, since pretty much every camera that I've looked at has only 3 pin XLR.

How do you guys work around the mono issue and make it stereo? Or even better, surround sound? It has me a little confused on how people are able to up the quality and any help would be appreciated!

Also, what if I was wanting to record a crowd, or maybe a live performance or something similar? What set up do you guys recommend to use to get a stereo or surround sound step up?

Thanks a bunch!
-Zach


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Ty Ford
Re: 3 pin XLR stereo/surround sound?
on Apr 3, 2011 at 11:44:21 pm

Hello Zach and welcome to the Cow Audio Forum.

Most sound is captured monophonically and mixed across a stereo or surround space during post production.

There are any number of stereo mics. They usually have 5 pin XLRs.

There are a few surround mics, but you have to be really well prepared to record good surround.

There are matrix boxes that encode LCRS surround into two channels.

Your question as to how to record a live performance in stereo or surround is a little too broad. There are different methods depending on what's being recorded.

Regards,

Ty Ford

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





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Eric Toline
Re: 3 pin XLR stereo/surround sound?
on Apr 4, 2011 at 9:10:38 am

A 3 pin XLR allows for a balanced signal path and also allows for 48 volt phantom power which all professional microphones require. The pin layout is: Pin 1/ground, Pin 2/positive signal, Pin 3/negative signal. Having a balanced feed helps to reduce/eliminate grounding issues and RF noise problems. Stereo & surround sound is created in post production. Dialog is always mono as it works better with subject placement in a shot.

Eric


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Jean-Christophe Boulay
Re: 3 pin XLR stereo/surround sound?
on Apr 4, 2011 at 3:32:31 pm

Hi Zach,

Beyond the pure technical aspects of your question, I think you're missing a much broader workflow question: camera sound is only one ingredient used in the production of the final sound track. The more focused the camera sound is, the more flexible it is for the mix and, normally, the better the final mix can be.

Recording audio in stereo on set is one great way to ensure your audio mixer hates you. We like focused recordings: each talent on his own lav mono feed, ideally, and a mono boom mic feed of the overall dialog. We can edit tightly inside a take with that, place stuff where it should be (as opposed to where it was when you taped it), take decisions on backgrounds and ambiances... If you record to stereo or, god-forbid, surround on set, any sound mixer will be stuck inside that perspective and will probably end up taking out a mono feed from your multichannel tracks so he can do his thing properly. You'll have wasted time and ressources on your multichannel recording.

Things that should be recorded stereo include ambiances, room tones... basically the canvas onto which we'll be placing the dialog and effects. For example, your crowd example would be a good stereo recording candidate.

Surround recording really should be left to experts and it's rather pointless to invest time and money for this on set. There's every chance the mixer would use a surround ambiance from a professional library, which requires much less work, so costs you much less money. Mind you, your stereo crowd would probably suffer the same fate, unless they are chanting something specific that I don't have in the 200-plus crowd sounds I have in my library.

As for your live performance example, if you're talking about a music performance, you're getting into highly specialized territory. That is much more in the realm of live music recording and is a whole other world. You really have to know your sound to start playing on that field.

IHTH,

JC Boulay
Technical Director
Audio Z
Montreal, Canada
http://www.audioz.com


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Andrew Rendell
Re: 3 pin XLR stereo/surround sound?
on Apr 4, 2011 at 7:52:52 pm

Not only is balanced sound, through XLR cables/connectors, much better quality than unbalanced/consumer wiring, you also need the phantom power ability of the balanced system to use the great variety of professional microphones available. Selection and positioning of the various sorts of cardioid, hyper-cardioid, figure 8, omnidirectional, shotgun, etc, microphones is an art in itself. And then you have to know when not to use the phantom power - 48V can kill the occasional very fine (and very expensive) microphone that isn't designed for it.


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Ty Ford
Re: 3 pin XLR stereo/surround sound? Phantom Power and RIbbon Mics
on May 22, 2011 at 1:58:11 pm

Andrew,

A good point. Let's take a look at that.

What mics do you have to be careful of and why?

Old ribbon mics are the only professional mics you need to be concerned about. You can fry any unbalanced mic if you somehow figure out how to wire it up to an XLR connector.

I own several old ribbon mics and have, upon occasion, plugged them into a preamp with the phantom supply on with no problem. The problem occurs in a few cases where the XLR pins connect in a specific order to allow the phantom power current to destroy the ribbon.

If you have a mixer that only has a global Phantom Power switch and you need it to power a condenser mic, but are also want to use an older ribbon mic. Turn the Phantom Power off, connect the ribbon mic, turn the phantom power on again.

There are a number of new ribbon mics that absolutely require phantom power to operate. Read the operations manual on each one to find out what they need. Most of these have a small IC amp onboard the mic that is powered by the Phantom Power. Without it, the mic won't work or won't work very well.

Regards,

Ty Ford

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





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Zach Rohrer
Re: 3 pin XLR stereo/surround sound?
on May 22, 2011 at 6:17:03 am

I have to say, I loved the response on this forum, but yours was the best! I can't thank you enough for this look into sound and how to handle it. To be honest I was a little baffled at how someone could only want mono. But now understand the technical side of it and how a lot of this fancy surround sound work is done in post, I totally understand the concept. Thanks a bunch!


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