View Full Version : A Step by Step Guide to Audio

09-19-2009, 03:56 PM
Been doing a bit of reading for about an hour or so on the audio capturing options/issues with the 7d and I guess i need some help. For me and the way my brain works, I wondered if someone could make two lists for me.
On the first list would be "things needed to buy" for audio on the 7d. This would include software as well. Ideally, I would like to be able to run lavs and boom into the camera for documentary work, but still be able to see my meters.
On the second list would be the "process" of "how to" capture audio on the camera. By this I don't mean smart arse responses like hold boom but something to the effect of setting up the camera and then how to use FCP to capture (I have watched the Phil Bloom about plural eyes on vimeo by the way too).
I am doing all this to try and figure out what I need to buy for a shoot in Nov. Right now I have a camera on order and that is it.
thanks a ton guys

J Davis
09-19-2009, 04:09 PM
Until a hack arrives to disable the in built AGC (auto gain control) in the Canon 7D the aim of the game is to avoid it.

For those that don't know, the in built AGC will raise the volume on quiet sounds including background ambience which results in unbearably loud hiss.
Here is an example of AGC hiss from a GH1 link (http://vimeo.com/6551914) , listen to how the hiss fades when he talks and then comes back in between. The 7D AGC will be similar.

One method to avoid AGC is to use the Beachtek x5a which emits a high pitch tone to fool the AGC. The method I prefer is to record the audio separately to
the Zoom H4 (or similar) and then use the on-camera audio for sync purposes during editing. This is known as two system audio.
I'm not going to go into the sync process as you can read plenty of threads about it plus you already saw mr blooms plural eyes vid.

A typical audio shopping list would be ...

shock mount (I use Rode)
shotgun mic (I use Rode NTG2)
xlr cable
mic pre amp (I use Sound Devices MM1)
audio recorder (I use Zoom H4)

here is an example of two system audio after it goes thru sync in post (using the equipment above) link (http://www.dvxuser.com/V6/showthread.php?t=182763)

if you were going with the beachtek x5a then it would replace the mic pre amp and audio recorder in the above list.

I'm sure others will chime in with similar setups but this should get you up and running.

09-19-2009, 04:27 PM
so j_davis, am I understanding correctly that the Beachtek x5a would only be used if i am planning for the audio to be captured with the camera? meaning that if i capture the audio with your recommended Zoom H4 there would be no need for the x5a?
to me this means, i still shoot the scene with the 7d and just have the camera itself pick up what it can while a boom is running to the Zoom H4. then i take the files from the H4 into FCP and sync them with the files from the 7d (using mr. bloom's tutorial)... does all that sound right? did i just repeat what you said above- lol?

Rakesh Jacob
09-19-2009, 06:04 PM
Both the zoom H4 (old model) and H4N (current model) have built in preamps and phantom power. I'm sure they're aren't high end but should be fine for most, and atleast comprable to Beachtek stuff.

J Davis
09-19-2009, 06:09 PM
Both the zoom H4 (old model) and H4N (current model) have built in preamps ...

The pre amp in the zoom is 'functional' at best, but by no means comes anywhere close to pro, use it only if you are on a budget. Zoom operates well when it is recording at line level.
EDIT: @jrod81 ... yes you understand correctly!

Peter J. DeCrescenzo
09-19-2009, 07:06 PM
Hi Jared: I'm not sure from what you've posted here, but in case you're not familiar with the other important reason to record sound on an external recorder instead of using the 7D (or GH1) mic jack ...

Audio _monitoring_ is even more critical than microphone or preamp sound quality. Because these cams don't have a headphone jack, if a high-quality mic or preamp isn't connected correctly or reliably to the cam's mic jack, you won't know about it until playback, which is often too late. _No_ sound or screwed-up sound [disconnected/badly-connected/overdriven mic] is _much_ worse than solid but lo-fi sound [cam's built-in mic].


But if you're already familiar with this aspect of the DSLR video production audio puzzle, apologies for this slight detour.