Two Mics Through A Mixer - New, please help!

[Michael Clark]

I film with a Canon T2i using Magic Lantern. I just recently got a JuicedLink cx231 mixer. I will take the example of a music concert to ask my question. If I plug a wireless transmitter into the sound board at the venue, I can transmit the main output to the receiver plugged into my camera. From what I've read, this is not desired as it is unbalanced, but after shooting one concert this way, it worked out all right for my purposes. I wondered if, with a juicedlink box with 2 XLR inputs, it is possible to receive sound from a wireless transmitter and an on-board shotgun mic (Rode NTG-2) simultaneously? If so, are there issues with a delay from the wireless or do they sync up pretty well. I wasn't sure if it would drift over time.

[Edward Carlson]

Wireless from the house mixer to your camera isn't desirable because of the potential for RF interference, dead batteries, etc. It would be much better to use an XLR cable. You can absolutely use two mic inputs with the mixer, that's what it's designed for! If you do use the wireless, it would never ever "drift" since it's a live signal being transmitted only a few hundred feet. You would need to be a few thousand miles away to notice the delay of a wireless audio signal.

[Paul R Johnson]

It would be great to be able to get a cable from the house mixer to the cameras, but running a length of cable that long in many venues means it has to be properly installed by the house tecs so it doesn't cross walkways and become a hazard. Handing the audio guy a zoom or similar, or the Sennheiser XLR plug in works for me - unless I have an hour or two spare, and have very helpful house tecs who don't mind doing the work.

[Michael Clark]

Thanks to both for the insight. Another application for this would be a wedding, in which case I would have a wireless lapel on the groom. Sorry for the really obvious question - I assumed using both was possible - I just only ever thought about the other benefits of a juicedlink box and hadn't considered that!

[Les Wilson]

There are a couple pitfalls to the wireless sound board transmitter approach but once worked out, can do the job for you. The previously mentioned dropouts are one such problem. I was in a venue were the mixer was over 100' from the alter and my Sennheiser sk100 units had some ugly dropouts at that range. One tip is to pay attention that the antennas on transmitter and receiver are both horizontal or both vertical and not one of each. Also, monitor your input. The sound operator could accidently change re-route the inputs to your mix or silence the aux output feeding your transmitter... especially if it's an aux they don't use often....

[Steve House]

Originally Posted by Michael Clark

I film with a Canon T2i using Magic Lantern. I just recently got a JuicedLink cx231 mixer. I will take the example of a music concert to ask my question. If I plug a wireless transmitter into the sound board at the venue, I can transmit the main output to the receiver plugged into my camera. From what I've read, this is not desired as it is unbalanced, but after shooting one concert this way, it worked out all right for my purposes. I wondered if, with a juicedlink box with 2 XLR inputs, it is possible to receive sound from a wireless transmitter and an on-board shotgun mic (Rode NTG-2) simultaneously? If so, are there issues with a delay from the wireless or do they sync up pretty well. I wasn't sure if it would drift over time.

They won't drift with respect to each other but they might not sync up well either. Sound travels roughly about 1000 feet per second. Imagine a singer on stage with a mic in his hand wired to the soundboard, his voice then transmitted wirelessly to your camera which is in the back of the room. The sound leaving his mouth arrives at your camera at the speed of light since that's what electricity and radio travel at - it's essentially instantaneous. But if you have a mic on your camera feeding the other channel, sound hitting THAT mic has to travel through the air, say, 100 feet. It will arrive at the camera 1/10 of a second LATER than the sound coming through the radio link. If you try to mix 'em you will get all sorts of reverb and comb filtering effects. As far as sync to picture, the sound through the radio would be in sync but the sound coming directly to your camera mic will be about 3 frames later than picture, an out-of-sync condition that is certainly noticable and a level that is completely unacceptable for any professional work.

[Tom Morrow]

Wireless transmitters are analog, so there is no digital delay like many other audio devices these days. It's possible there could be delays from digital processing in the signal chain before the mixing board, and of course there is sound propagation time as mentioned above. You'd probably end up choosing one or the other recorded track rather than mixing both signals together, to prevent the reverb/phasing/combing issues.

[Jay Massengill]

It's easy to split the tracks and nudge one of them in extremely small increments to re-align any difference in delay using modern editing software. So it's not a deal-breaker if you have to record two sources that have a delay difference. You just have to be careful in editing and mixing them in post-production.

I recently shot a parody of a "recording session". The 3 performers were closely huddled and very active around a cheap large diaphragm mic for the video. I had that mic on one channel, but I actually used a hypercardioid on a boom just out of frame on channel 2 for the actual audio, sending both mics to camera and audio recorder. Since I was double-recording I used a slate clapper for sync. Magnifying the waveform in extreme detail, you could see the delay in the sharp slate clap between the visible mic only inches away from the slate and the overhead mic that was about 3 feet away.

[Karl Winkler]

Originally Posted by Michael Clark

I film with a Canon T2i using Magic Lantern. I just recently got a JuicedLink cx231 mixer. I will take the example of a music concert to ask my question. If I plug a wireless transmitter into the sound board at the venue, I can transmit the main output to the receiver plugged into my camera. From what I've read, this is not desired as it is unbalanced, but after shooting one concert this way, it worked out all right for my purposes. I wondered if, with a juicedlink box with 2 XLR inputs, it is possible to receive sound from a wireless transmitter and an on-board shotgun mic (Rode NTG-2) simultaneously? If so, are there issues with a delay from the wireless or do they sync up pretty well. I wasn't sure if it would drift over time.

If you set up your wireless properly (i.e. choose a clean frequency, have your antennas line of sight to each other, set your gain properly), you should not have any problems at the range you are talking about, assuming you have a decent wireless system. There *will* be a delay of the acoustic signal from the speakers to your camera-mounted microphone, so the two signals (wireless and on-camera mic) will not be synched. As a rule of thumb, think 1ms of delay per foot of distance. If you are 50 ft. away from the PA speakers, there will be 50 ms of delay on your camera-mounted microphone signal.

As others have pointed out, you can re-synch them in post. However, be aware that if you move around and the distance between the PA speakers and your camera changes, the amount of signal delay between the wireless (which stays constant) and the on-camera mic will vary, thus making your life difficult in post. That said, if you were to re-locate for each shot, but then stay put once you got there, you could again re-synch in post, but between shots, the amount of time you are adjusting for may vary.

[Michael Clark]

Because I am still in the hypothetical phase now and have not yet been able to try this out (will do so before wedding Saturday), when you say I can re-sync the two in post, I was under the impression the T2i would save it as one audio/video file and the two would not be separate.

[Edward Carlson]

Depending on the NLE, you will probably be able to see the right and left audio channels separately. In this case you would just have to slip one of the two tracks a few frames to get it to sync.

[Michael Clark]

Ahh, you're right. Sorry - couldn't visualize that at first. I'm in Premiere CS5, so that will be no problem. Thanks!