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3 pin XLR and audio

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Zach Rohrer
3 pin XLR and audio
on Apr 3, 2011 at 4:09:21 pm

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!

Thanks!
-Zach


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Nick Griffin
Re: 3 pin XLR and audio
on Apr 3, 2011 at 8:19:50 pm

Zach-

Allow me to try to offer some basics and give you a little more direction.

1) Very few things in either film, video or, for that matter audio recording in general are recorded in stereo. Almost always individual sources/people/etc. are mic'd (or sometimes double mic'd to be able to choose the best sounding of the two) and either in a mixer going to the camera, or later in post production, are the individual tracks assigned to a space in the stereo spread via the pan function. The exception to this would be the attempt to capture an "environment," be it orchestra, waterfall, crowd scene, whatever where a pair of mics are used a specific kind of arrangement and one is assigned to the left channel and the other to the right. This captures actual stereo, but as stated above that's seldom done.

2) Some camcorder-mounted mics are stereo and, if they are professional "balanced" mics (see below) they will have 5 pins. Camera-mounted mics really aren't of much use except for news (my opinion).

3) XLR connectors with 4 pins are for power, ie.- a line going from a power supply that converts 110volt a/c (US) or 220volt a/c (Europe and much of the world) to 12 volt d/c so the camera can be operated without batteries.

4) There's more than stereo these days. Mixes are routinely done these days in 5.1 and 7.1 surround sound on high end projects like feature films, whether for the theatre or DVD/Blu-Ray. Certainly more complex than simple left-right stereo as it is assigning sounds in a 360 degree space around the listener.

5) Mics have three pins when they are "balanced." A professional, balanced audio line is able to go much further distances because one wire "shields" the other two which are in opposite phase of each other. Don't ask, you probably don't want to know anyway. Suffice it to say, a line is balanced to prevent hum and other interference caused by power lines, radio transmissions, etc.

For better, more comprehensive answers you should post this question on the Audio Professionals COW forum, because this is the best info you can get from me.


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Zach Rohrer
Re: 3 pin XLR and audio
on Apr 3, 2011 at 10:45:31 pm

My apologies for posting in the wrong forum, really new to the site and I didn't see the Audio professionals forum. I'll be sure to post over there as well. But I can't thank you enough for this response as I try to find my way through all the important details!


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Geoff Tirrell
Re: 3 pin XLR and audio
on Sep 8, 2011 at 1:16:23 pm

The way it was always explained to me when I was starting out is that many things you hear in the world are really not stereo sound. For example somebody speaking to you like in dialogue, interviews etc is only emanating from one point. While the fact that your ears interpret it in a stereo fashion it does not make it stereo.

Now for something like a band where the drummer could be positioned 20 feet or more from various other instruments it does make a difference in our perception of the sound environment. The reason I mention this is that during playback you have the same issue. If you record something in stereo but play it back on an old tv where the speakers are 3 inches apart is it really stereo? Now if you play it back in a home theater set up for surround sound you will defiantly hear it.


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