Question about Sennheiser g4 and AVX sensitivity settings

A

Ahab

New member
Hi all, pretty basic question here: I'm often a one-man crew for observational documentaries, filming with a Canon C300. In order to capture dialogue from two subjects I want to try a new setup, which is to have the AVX hooked straight into my C300 recording the main speaker and the g4 plugged into a Tascam DR-40 recording an independent audio track of the 2nd speaker.

My question is this: for filming a typical indoor conversation, at "normal" volume, what is the optimal sensitivity settings for these mics? I'm reading different things online about the g4, for example, so I thought I'd check in here about what people are setting for their transmitters and receivers.

Any info would be much appreciated.

Thanks.
 
Whatever prevents the transmitter from clipping at the highest expected sound level. It will vary between mics, subjects, and environments.
 
I wouldn't mix those two different systems. The AVX has 19ms of delay since it encrypts the signal. Although that's not even a frame, you'll hear it like an echo when combined with an analog RF system like the G4. The G4 has no latency. Also, the AVX has a built in system that compresses the wav to keep it from clipping. Works surprisingly well but it will sound different than the G4 if your audio peaks. The G4 will just clip if you haven't gain staged it properly or if the speaker shouts. Is there a reason why you want to shoot dual system and direct to camera? The preamps on the C300 are much better than the DR40 preamps. Very adequate for dialog. It would be easier to go direct to camera on both channels.
 
19ms would be unacceptable in my audio DAW, quite noticeable, and as video editors work in frames, what happens if both mics hear the same source? A voice perhaps and you cannot align them on the timeline? Horrible phasing and artefacts. Sertainly enough to make impulse sounds such as bangs and clicks appear as two separate peaks next to each other. You're going to get fed up going into the audio editors, sliding it a bit there then going back into the video editor. 19ms is a long time in sound. I can hear it. My audio system works at 9ms which I cannot hear.
 
I thought I had posted kind of the same suggestion of not going dual system since you do not need to.

Depending on what DAW you are using you might be able to sync the tracks if there is enough crossover. If there is almost no crossover then the lag should not be a big issue, just make sure to drop the level of the audio you are not using. The auto sync features in the DAW will work at subframe resolutions, but it will only work if there is a fair amount of shared audio.
 
DNN said:
I wouldn't mix those two different systems. The AVX has 19ms of delay since it encrypts the signal. Although that's not even a frame, you'll hear it like an echo when combined with an analog RF system like the G4. The G4 has no latency. Also, the AVX has a built in system that compresses the wav to keep it from clipping. Works surprisingly well but it will sound different than the G4 if your audio peaks. The G4 will just clip if you haven't gain staged it properly or if the speaker shouts. Is there a reason why you want to shoot dual system and direct to camera? The preamps on the C300 are much better than the DR40 preamps. Very adequate for dialog. It would be easier to go direct to camera on both channels.
Click to expand...

The reason is that I'd like to lav up two people for many of these doc shoots and the C300 only has two XLR jacks, one of which is occupied by the shotgun mic. So I figured I would have a seperate system recording a 2nd lav track independently of the C300, and went with the DR-40 (over the H4N) because it can record a safety track which is important since I'm manning the camera and therefor unable to moitor the levels. I did hear that the 19ms delay can cause that echo issue, but can't that be fixed in post?

In any case, I'm totally open to other solutions as long as they don't involve spending hundreds of dollars more in gear.
 
The latency delay can be fixed in post relatively easily ... providing the NLE can move audio in sub-frame increments. Some NLE's can, others can't. Vegas Pro for instance, can shift audio down to the sample level (typically 48,000 per second).
OTOH, If only the one audio source is heard, a 19ms delay is usually not noticed on dialog.
 
Fixing things in post should be a last resort. Depending on how far away your camera is you are going to have three audio tracks that are all at different sync points so that could be a mess. I would stick the G4 on the camera and the AVX on the portable recorder. You are going to have to post sync that track anyway. If you are fairly close your on camera mic may not be noticeably off from the G4. Not altogether sure why you are using it except as a safety backup, in which case it's small offset should not really be a problem.

As to post syncing. You really want to do that on the clips before you edit. If you send edited footage to sound post and they have to guess which clips are out it is going to waste a lot of time. That time comes out of the time they could be polishing up the tracks. NLE's like Resolve will auto sync based on the audio track and that will "fix" any lag issues. You do want to have your "hero" tracks on the camera or you will have to spend time unlinking the audio and relinking to the "hero" track. With out going too far down the rabbit hole you can shift audio by small increments but video only by whole frames, so you want the audio that you do not need to shift married to the video and the audio you need to shift on it's own.
 
I'd put both talent channels on the C300 and use the external recorder as your backup/ambiance track since the recorders you mention have phantom power for the shotgun mic. If you have a lightstand or c-stand and a pole or even an arm, boom the shotgun mic to get it as close as you can to the speakers. You can also mount it low and out of frame, though both speakers may be slightly off axis since you're using one mic to capture both. But you'll get better sound closer than on camera. Then just monitor the sound from your C300 while you're shooting. Don't trust that the system will do it for you since you can suddenly get rf hits during the recording or dozens of other problems. You have to monitor or be prepared to shoot over. Also, you should probably try to match the levels of the two systems. The AVX allows you to change input volume on the transmitter and the G4 allows you to do it on both the transmitter and receiver. You can download a tone generator app to help.
 
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