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Low audio levels


BradTheSoundGuy

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Here's the issue:

I recently worked on a show with another sound guy. We each had a couple of people wired, we each sent sound to camera wirelessly via Zaxcom. Multiple times a day I checked my levels. Sent tone, -20, mixed on my 552 between -4 and +4.

Now it's come to my attention my audio is extremely low. They're cutting on FCP. His audio is fine, mine is not.

The camera's were XD cams.

I also recorded a backup on my 552. I've brought the files into ProTools, and the level's are consistently in the green - very rarely reaching pre-clipping in the yellow. He did not record a backup, and used a different mixer (which one escapes me now).

The editor has told me my audio sounds muddy as well as very low. I've gone in and seen and heard for myself. There is obviously a difference in our audio. I brought in my backups which were brought into FCP and there is no difference - the same issue.

I'm not sure what to think here. I've mixed like this for years with no problems. The audio sounds fine to me in ProTools. I don't know anything about FCP. Why would the other guys audio be fine, and mine be so low? Could the camera's be set differently in regards to sample rate and bit depth? Could it be a transfer issue from the raw file to however it gets into FCP? Why would only my audio be affected? Could there be different settings for each track in FCP where one is compressed and one isn't?

Also, about halfway through the shoot my Zaxcom had issues and I switched to hardwiring to camera. They're telling me the issue is throughout all the episodes, so I don't think it was a Zaxcom issue.

Finally, I remember noticing recently that the master output knob on my mixer had been brought down a little. I thought it was weird, fixed it and continued on. While this could very well be the problem, I always send tone many times in a day to check my levels. I don't remember if it was this shoot that this happened on, but even so, setting tone on the camera at -20 is -20 no matter what right? If my master had been low and unnoticed for the whole series, I was still mixing to 0, and the camera was still getting audio at the proper reference level right? I doubt this was the problem, as the camera's audio pot's were in their normal position's to achieve -20 and not maxed crazy to make up for a lower output from me.

I'm baffled. Did I F up?

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do your backups sound fine?

did you check what the camera was recording?

what output were you using from your 552 - i know the 442 TA3 outputs dont play nicely with the zaxcom, someone else will hopefully say if this is the case with the 552.

were you comparing your colleague's audio and yours on the same computer running FCP - has the editor done something to the global audio outputs like a poorly set limiter etc?

can you play the files on the edit machine with another program? like quicktime.

what were you sending to camera? radios ch1 boom 2? if you are using hardwire boom and radios with a delay like the lectros, is it possible that when the tracks are imported into FCP and tracks 1 & 2 are summed to mono, you are getting cancellation.

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another review...please...

you sent a "0" tone to the camcorder from your mixer, and calibrated it to -20 on the camera?? or did you send -20 tone from your mixer to the camcorder and calibrate that to -20 on the camcorder...?? remember tone is an average signal level, not a peak signal level.

mixing at -4 to +4 on your mixer after you calibrated your "0" to -20 on the camcorder would result in low-ish levels of -24 to -16 on the camcorder. If those are your peaks, rather than average levels, you are pretty low.

I'm not sure about the "muddy" issue, but as you said that you worked both wired and "hop" with similar results tells me the hop is not the issue, but...

Edited by studiomprd
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First off, do you know the difference between peak and average levels? Since you didn't specify in your original post and your levels turned out so low, I'm guessing that may be part of the problem.

Generally speaking, your average levels should be around zero (-20 on the camera) and your peaks should be around +10 to +12 (-8 to -10 on the camera). This may vary some depending upon the program material.

The differences between the two is one of the most basic things anyone should know about audio before ever daring to call themselves professional.

So, if your average levels (use the VU characteristics on the SD mixer) are around zero you should be okay. The peaks need to be watched because if they ever hit true maximum they will annihilate your sound. The SD limiter can help you get louder with less worry here. However, don't use the limiter to squish the sound at all, just to protect the tip-top peaks from overmodulating.

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another review...please...

you sent a "0" tone to the camcorder from your mixer, and calibrated it to -20 on the camera?? or did you send -20 tone from your mixer to the camcorder and calibrate that to -20 on the camcorder...?? remember tone is an average signal level, not a peak signal level.

mixing at -4 to +4 on your mixer after you calibrated your "0" to -20 on the camcorder would result in low-ish levels of -24 to -16 on the camcorder. If those are your peaks, rather than average levels, you are pretty low.

I'm not sure about the "muddy" issue, but as you said that you worked both wired and "hop" with similar results tells me the hop is not the issue, but...

You've been learning from my posts again, Senator.

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sucks. interested to find out what happened here. i hate sending audio to camera but realize that sometimes its what the production wants to avoid sync in post. the bad thing about that though is the cam op could "f" up your sound if you're not careful. and we all know how much camera guys care about us.

anyway, curious to find out the result. would like to avoid something like this in my future...

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Has anyone listened to the audio directly off the disc in a playback deck? That would be the first thing to check. If its ok listening directly from the disc, then the problem has been introduced while ingesting or even further down the chain.

As far as the cam op messing with the audio, I always put some tape over the camera's level pots to ensure they dont get bumped up or down. With more and more Easy Rigs in use and shooting "off the hip", the cam op's body can bump the pots on the camera. The tape also tells them to "dont touch" without actually saying it!!!

But I have to say, most of our cam ops here in Australia are pretty good. They dont touch the audio settings and they actually listen to the program send from our mixer. Most guys here wear earphones plugged into the camera and they say it helps them listen for story etc etc.

Anyway, dont mean to digress, go check the original discs!!

Good luck

Peter Mega

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Thanks for all the responses everyone. They've since come back to me saying things are ok, it's not muddy and the audio post guy's are happy with it. I was on set all day today, so I only have one email to go off. Will be investigating further on Monday at a production meeting.

To answer a few questions tho:

Average level's were at 0, peaks up around +10

Tone sent at 0, camera set at -20

No tape on the pots - will from now on for sure tho.

There are no discs to go back and check. This was all shot on cards that were dumped to harddrive throughout the day, then wiped and used again. Horrible stuff.

I was baffled, am relieved a little now, but still in complete awe as to how it was messed up so bad in the first place.

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