phase question - please help

A

allieminute

Member
If I use two separate recording systems would I run into any mic phasing problems? Example - if I had the same two recorders, two mixers, and 2 mics. Audio is my only priority. I want the best I can get, audio wise. My audio package now is roughly 17k I'd like to double or triple it. There's a whole lot of scenes that require multiple use of microphones and it's my first time running into that and I was worried about any phase problems and figured I would just do it this way. Money and the crew isn't an issue I have everything I need so, please help. Thank!


By the way I'm a director / producer not an audio guy, but I like to cover my ground.
 
allieminute said:
If I use two separate recording systems would I run into any mic phasing problems? Example - if I had the same two recorders, two mixers, and 2 mics. Audio is my only priority. I want the best I can get, audio wise. My audio package now is roughly 17k I'd like to double or triple it. There's a whole lot of scenes that require multiple use of microphones and it's my first time running into that and I was worried about any phase problems and figured I would just do it this way. Money and the crew isn't an issue I have everything I need so, please help. Thank!


By the way I'm a director / producer not an audio guy, but I like to cover my ground.
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Not sure I understand what you're asking. Are you saying you want to use two mics, two mixers, and two recorders to simultaneously record the same audio source? Or is it a scene where you have multiple audio sources, say the dialogue of two characters, and you're going to mic and record each source separately?

In general, phasing problems can arise when two different mics pick up the same audio source and the mic placement violates the 3:1 rule which says that the distance between the mics must be at least three time the distance of the closest mic is from the source. Of course, the reverb effect of the differing arrival times can still be a headache but that's not a phasing issue. If you're micing separate sources and recording isolated tracks, whether on the same recorder or different recorders, phasing shouldn't be an issue. And of course, if phase issues were going to occur it would be when the two signals are mixed - no mixing, no phase problems.

Gotta be careful though - phasing problems can sneak in unexpectedly. Was watching the "Things That Move" episode on locomotives on National Geographic Canada HD last Friday evening and all the narration and host dialog was completely missing for the entire half-hour episode. Audio in commercials was fine and the program's music and FX stems were there (although reduced a bit in level) but all of the host dialog, interviews, and voice-over was stone cold dead. Obviously the dialog stem was dual mono (as it should be), the music and FX stems were stereo, but somehow the left and right channels in the final mix were inverted with respect to each other and somewhere along the line it was getting mixed down to mono. Result, partial cancellation of the M&E stems and total cancellation of the dialog. Can't say if the foul-up is in the mix, producer's quality assurance of the deliverables, somewhere along the broadcast chain at National Geographic Channel, or at the cable system head-end but someobody certainly was alseep at the switch. Can't believe people actually get paid for this level of incompetence!
 
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thanks for the reply, sorry I should of made it more clear. I do want to record with two separate mics, mixers, and recorders at the same time on each person. In an interview scene I want each to be on a mic (boom). So I shouldn't have any problems with phasing? If I'm doing that should my mic guys still follow the 3:1 rule or should it not matter?

Yeah I agree, that's pretty bad, and I would think they would have more than one guy right?? So I guess they were all sleeping lol
 
allieminute said:
thanks for the reply, sorry I should of made it more clear. I do want to record with two separate mics, mixers, and recorders at the same time on each person. In an interview scene I want each to be on a mic (boom). So I shouldn't have any problems with phasing? If I'm doing that should my mic guys still follow the 3:1 rule or should it not matter?

Yeah I agree, that's pretty bad, and I would think they would have more than one guy right?? So I guess they were all sleeping lol
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Two mics on EACH person for a total of 4 mics or 2 mics in total, one on each person? I can;t imagine why you'd want to deal with 4 mics on two people so unless you tell me otherwise, I'm going to assume you mean you're going to have two booms, one following each person. I wouldn't think you'd have a phasing issue in that situation. If it occurs, phasing problems are created by mixing the signals from two mics but in that situation you won't (or shouldn't) actually be mixing the two mics together, you would be checkboarding them in post. You'd have two tracks ...

Track 1: Question 1 .............. Question 2 ............... Question 3 ..............
Track 2: ................. Answer 1 ................. Answer 2 ................. Answer 3

When you mix those two into a single dialog track, each track is muted where you see the dots in the above two lines, crossfading between them in the transitions. So you don't have the sound of question 1 on track 1 actually mixing with the bleed of question 1 that was picked up by the mic for track2.

If you are going to put a lav on each person AND ALSO have a boom on each, for a total of 4 tracks, you'll never mix the booms and lavs together. In that scenario you decide in post whether to use the boom or the lav and discard the other one. If you do try to mix the lav with the boom on the same person you may well encounter phasing problems.
 
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