Testing audio recordings at DVinfo.net

Go Back   DV Info Net > The Tools of DV and HD Production > All Things Audio

All Things Audio
Everything Audio, from acquisition to postproduction.


Reply
 
Thread Tools Search this Thread
Old July 17th, 2015, 02:23 PM   #1
Major Player
 
Join Date: Oct 2010
Location: NY, NY USA
Posts: 466
Testing audio recordings

Hi,

I am in a process of improving my audio recordings and have some questions. I have recorded a person reading something random for testing purposes. I recorded using a boom mic and a lav mic. I used both mics at the same time. I recorded them to different channels. From Final Cut I exported the stereo file which obviously has both recordings one on each channel, then I exported just the lav mic and then just the boom mic and then dual mono. I like the stereo best. Let me know what you think of these recordings.
Here is a question, I don't want stereo for voice recording I want dual mono but how do I control how much of each mic I get in the dual mono audio? Is there a way to control it?
Here are the files:
https://www.dropbox.com/s/uen79drs2p..._Boom.wav?dl=0
https://www.dropbox.com/s/rdkubcciyv...lMono.wav?dl=0
https://www.dropbox.com/s/bznho1m11f...t_lav.wav?dl=0
https://www.dropbox.com/s/cbdi7q4hx9...tereo.wav?dl=0
Kathy Smith is offline   Reply With Quote
Old July 18th, 2015, 06:48 AM   #2
Inner Circle
 
Join Date: Jan 2004
Location: Boca Raton, FL
Posts: 2,979
Re: Testing audio recordings

If I understand you correctly, this is a question for the Final Cut forum. In FCP 7, you take each audio channel (Left and Right) and set the PAN to 0. That makes that channel what you call Dual Mono. That is, the channel appears equally in both left and right. You can then adjust the LEVEL using key framing. for certain parts or set the level for the whole track.
Les Wilson is offline   Reply With Quote
Old July 18th, 2015, 10:45 AM   #3
Trustee
 
Join Date: Aug 2008
Location: New York
Posts: 1,844
Re: Testing audio recordings

Dual mono serves no useful purpose other than doubling the file size.
I would NOT mix both mics together at the same time, phase issues are likely
Rick Reineke is offline   Reply With Quote
Old July 18th, 2015, 01:21 PM   #4
Major Player
 
Join Date: Oct 2010
Location: NY, NY USA
Posts: 466
Re: Testing audio recordings

Quote:
Originally Posted by Les Wilson View Post
If I understand you correctly, this is a question for the Final Cut forum. In FCP 7, you take each audio channel (Left and Right) and set the PAN to 0. That makes that channel what you call Dual Mono. That is, the channel appears equally in both left and right. You can then adjust the LEVEL using key framing. for certain parts or set the level for the whole track.
I'm working in Final Cut X and I know how to make them dual mono, pan etc. The question is how do I control each channels levels when they are in dual mono
Kathy Smith is offline   Reply With Quote
Old July 18th, 2015, 01:24 PM   #5
Major Player
 
Join Date: Oct 2010
Location: NY, NY USA
Posts: 466
Re: Testing audio recordings

Quote:
Originally Posted by Rick Reineke View Post
Dual mono serves no useful purpose other than doubling the file size.
I would NOT mix both mics together at the same time, phase issues are likely
Rick, why not? If you do not have phase issues, why wouldn't you do it if it makes it sound better? Just curious. As far as dual mono goes, what do you mean it doesn't serve useful purpose? Do you mean you would leave it in stereo mode for just vocals? Why? That makes no sense to me. Can you explain?
Kathy Smith is offline   Reply With Quote
Old July 18th, 2015, 02:30 PM   #6
Trustee
 
Join Date: Aug 2008
Location: New York
Posts: 1,844
Re: Testing audio recordings

A dual-mono file (two channels, assigned or panned hard left/right) sounds the same as a single mono panned to center, the center-panned single-channel file comes out of both channels/speakers equally.
Phase issues are likely I didn't say 'for sure', but 9 out of 10 times with say, a lav and boom, abnormalities happen.. if it sounds better with the two mixed together (in mono of course), sure, why not.
Rick Reineke is offline   Reply With Quote
Old July 18th, 2015, 06:04 PM   #7
Trustee
 
Join Date: Jul 2003
Location: Burlington
Posts: 1,961
Re: Testing audio recordings

I'm not familiar with Final Cut, but in the NLE software I am familiar with, you would put the two original audio sources on two separate tracks with each panned to center and grouped so they stay in sync while moving or trimming the audio regions.

That gives you complete and separate control of how each original source gets into the rendered file.

In addition, if your software allows it like Vegas, you could slip one track in extremely small increments to change the sync relationship between the two sources if needed.

Obviously, once you have mixed two sources together in a rendered file, if you need to make a change for one source you have to go back to the software to make a new adjustment and then re-render. This also requires having access to the original files as well (or at least a file where they aren't mixed together, like an archive render where the two audio tracks are still separated but all the heavy lifting for the video portion is completed and doesn't need to be re-done).

Last edited by Jay Massengill; July 18th, 2015 at 06:57 PM.
Jay Massengill is offline   Reply With Quote
Old July 19th, 2015, 07:00 AM   #8
Major Player
 
Join Date: Apr 2008
Location: Chicago, Illinois USA
Posts: 660
Re: Testing audio recordings

Kathy

Bring those dual mono tracks into your project in FCP. You should see your track(s). The horizontal black line in each track is the level control. Move those up or down accordingly.

If your audio is in the storyline (part of your originally recorded video, then right click on that clip, and choose "expand audio components" or select clip and control-option-s.

Jonathan
Jonathan Levin is offline   Reply With Quote
Old July 19th, 2015, 07:06 AM   #9
Major Player
 
Join Date: Apr 2008
Location: Chicago, Illinois USA
Posts: 660
Re: Testing audio recordings

If the mics were kept at least 3 feet (three to one method) from one another, would phase issues still apply regardless?
Jonathan Levin is offline   Reply With Quote
Old July 19th, 2015, 08:11 AM   #10
Trustee
 
Join Date: Aug 2007
Location: Portland, Oregon
Posts: 1,177
Re: Testing audio recordings

Quote:
Originally Posted by Kathy Smith View Post
Rick, why not? If you do not have phase issues, why wouldn't you do it if it makes it sound better? Just curious.
Not clear exactly which practice Kathy is asking about here.

The reason for not COMBINING mics is that there will ALWAYS be phase issues, so the theory "if you don't have phase issues" doesn't even apply in the Real World.

Quote:
As far as dual mono goes, what do you mean it doesn't serve useful purpose? Do you mean you would leave it in stereo mode for just vocals? Why? That makes no sense to me. Can you explain?
Oh, there are so many pitfalls here I don't know where to begin and my head is swimming with problem cases.

I have genuinely lost count of the number of people coming through this forum (and several other similar forums) who plugged a monaural microphone into their TRS stereo mic input thinking that they are recording "dual mono". It sounds OK during editing, etc, and then they discover when it is played back in the board-room (or the film festival, or whatever) that the dialog just completely DISAPPEARS because the "dual-mono" turned out to be two opposite-polarity signals which completely cancelled each other. The solution, of course is to NEVER NEVER EVER use BOTH channels. Pick ONE and ABSOLUTELY DISCARD the other one.

For that matter, I have virtually discontinued even creating STEREO mixes for non-music video productions. IMHO, there is VERY MINIMAL "advantage" (if any??) and HUGE disadvantages in many cases where you don't know exactly what the playback/exhibition situation will be.

Even big-budget films with 7 or 15-channel delivered sound tracks ALWAYS record dialog in single-channel MONAURAL and PAN each track somewhere along the panorama. Processing dialog in stereo has ZERO BENEFIT and ALMOST ALWAYS causes problems with diffusion and significantly lowering the intelligibility of the speech.

There are so few "benefits" and such a huge pile of disadvantages that I have simply eliminated the practice completely so that I can think about things that would actually benefit from production decision-making.
Richard Crowley is offline   Reply With Quote
Old July 19th, 2015, 08:14 AM   #11
Trustee
 
Join Date: Jan 2011
Location: Pennsylvania
Posts: 1,359
Re: Testing audio recordings

The 3:1 rule applies when there are TWO speakers, one mic on each speaker.

When speaker #1 is talking, mic #2 will be so far away that it will pick up that speaker at a much lower level than mic #1. If the two mics are mixed (at approximately equal gain), the contribution from mic #2 will be much lower than the contribution from mic #1. Therefore, although there will be phasing issues in theory, they will be at an insignificantly low level.

The situation Kathy is talking about is entirely different, because there is just one speaker. Regardless of the difference in distance, she is presumably mixing the two mics at roughly equal level ... not equal gain. Therefore, yes, the phasing issues could be significant. If the difference in distance is roughly three feet, the phasing issues will extend down to a few hundred Hz, which is in the middle of the vocal energy region.

Of course maybe that "phased" sound is what Kathy likes. But in theory it should be avoided.
Greg Miller is offline   Reply With Quote
Old July 19th, 2015, 10:00 AM   #12
Major Player
 
Join Date: Apr 2008
Location: Chicago, Illinois USA
Posts: 660
Re: Testing audio recordings

Richard great advice as usual.

Greg-

OK. Now I am confused.

I did a very similar set up as Kathy did to record a single person's dialog in my studio. I had a Lav running into input One of my mixer, and a boomed shotgun above frame feeding into input Two of the mixer. Lav was panned hard left, Boom was panned hard right. Approx. distance between the two mics was 3 feet.

My intent was to have the lav as main audio with the boom being mixed in at a very low level to add ambience. With the two seperate tracks in my editor, I can adjust one or both to my liking.

Should I avoid this in the future? It seemed to sound great to me, but the complete cancelation thing has me wondering now, even though the levels of my two tracks are not the same.

Jonathan
Jonathan Levin is offline   Reply With Quote
Old July 19th, 2015, 10:23 AM   #13
Trustee
 
Join Date: Jul 2003
Location: Burlington
Posts: 1,961
Re: Testing audio recordings

There is some confusion because of various terminology being used here, but essentially from what I am reading, everyone is actually correct in what they are saying in response to the OP. It's just mostly semantics.

Jonathan, you are correct in your workflow for a single person with two mics. The key is you're controlling the level of the boom mic in relation to the direct lav sound when you do the edit. If both mics were mixed together at full volume, you would hear the potential problems very clearly.

And controlling the level of both mics individually is what the OP is asking about. I think your guidance on the key strokes to achieve this in Final Cut should help.
Jay Massengill is offline   Reply With Quote
Old July 19th, 2015, 11:00 AM   #14
Trustee
 
Join Date: Jan 2011
Location: Pennsylvania
Posts: 1,359
Re: Testing audio recordings

Jonathan,

No, if you are mixing in just a little of the boom (for ambience) then the phasing issues will be minimal. The problem arises when the levels from the two mics are nearly the same. I assumed (perhaps incorrectly) that Kathy was going to mix the two mics at approximately equal levels.

And while you won't have complete cancellation, you may have "comb filtering" which defines cancellation at certain frequencies. Even so, it may not be complete cancellation at those frequencies, the amount of cancellation depends on the relative levels from the two mics ... the closer the levels, the greater the cancellation.

I just did a quick search and I found that Wikipedia has a rather exhaustive entry under "comb filter" although with a lot more detail and a lot more math than is warranted by our present discussion. I'm sure you can find a lot of other articles if you look.
Greg Miller is offline   Reply With Quote
Old July 19th, 2015, 05:10 PM   #15
Major Player
 
Join Date: Oct 2010
Location: NY, NY USA
Posts: 466
Re: Testing audio recordings

Quote:
Originally Posted by Jonathan Levin View Post
Richard great advice as usual.

Greg-

OK. Now I am confused.

I did a very similar set up as Kathy did to record a single person's dialog in my studio. I had a Lav running into input One of my mixer, and a boomed shotgun above frame feeding into input Two of the mixer. Lav was panned hard left, Boom was panned hard right. Approx. distance between the two mics was 3 feet.

My intent was to have the lav as main audio with the boom being mixed in at a very low level to add ambience. With the two seperate tracks in my editor, I can adjust one or both to my liking.

Should I avoid this in the future? It seemed to sound great to me, but the complete cancelation thing has me wondering now, even though the levels of my two tracks are not the same.

Jonathan
That's exactly what I'm doing. I'm using lav as main audio and I just want to add some ambiance from the boom mic. I did't say I want to use both mics at the same level, that's why I asked how to adjust the gain of each mic separately.
My idea was inspired by this article from B&H, here is an excerpt:

"If you have a wired or a wireless lavalier microphone, you may want to consider using it as well as the mounted shotgun microphone. It may seem like overkill to use both mics at the same time, but doing so will deliver a richer, fuller sound. Also, if your subject moves out of the sweet spot momentarily, the lav mic will keep their dialog from being lost. You can hear for yourself what this combination sounds like because these miking techniques where used in the production of this B&H web video."

I still don't understand what the problem is with this logic. I just did a test, posted it in this thread stating that I like the effect. Does anyone hear any phase out issues in my recordings?
Kathy Smith is offline   Reply
Reply

DV Info Net refers all where-to-buy and where-to-rent questions exclusively to these trusted full line dealers and rental houses...

Professional Video
(800) 833-4801
Portland, OR

B&H Photo Video
(866) 521-7381
New York, NY

Z.G.C.
(973) 335-4460
Mountain Lakes, NJ

Abel Cine Tech
(888) 700-4416
N.Y. NY & L.A. CA

Precision Camera
(800) 677-1023
Austin, TX

DV Info Net also encourages you to support local businesses and buy from an authorized dealer in your neighborhood.
  You are here: DV Info Net > The Tools of DV and HD Production > All Things Audio

Thread Tools Search this Thread
Search this Thread:

Advanced Search

 



Google
 

All times are GMT -6. The time now is 10:02 PM.


DV Info Net -- Real Names, Real People, Real Info!
1998-2017 The Digital Video Information Network