Jump to content

Time alignment -UM400a and Boom mic


chris_bollard

Recommended Posts

  • Replies 56
  • Created
  • Last Reply

Top Posters In This Topic

I was responding to a 411/211 situation.

If you had 2 subjects on lavalier mics,

One being a 211 and the other 411 receiver, and they are close to each other there is a time/latency between the 2 signal paths.

Depending on the situation it will sound strange when the 2 are mixed.

Link to comment
Share on other sites

I was responding to a 411/211 situation.

If you had 2 subjects on lavalier mics,

One being a 211 and the other 411 receiver, and they are close to each other there is a time/latency between the 2 signal paths.

Depending on the situation it will sound strange when the 2 are mixed.

This is a NON-ISSUE. First of all, if you are mixing you should be using just the microphone that is on the person who is talking, then when the other person talks, use their microphone. Let's assume they are sitting right next to each other and they both have lavs on hard wired to analog board. If you had to actually mix (combine) these two signals, you would still have acoustical (space) phase/time issues to deal with (maybe). Now, if one of these two signals is delayed (we're talking miliseconds here) the actual result would be just as if they were sitting right next to each other as before but now ever so slightly further apart. What's the big deal?

Link to comment
Share on other sites

With respect to those who disagree-

If you are mixing a dramatic piece, sitting down, with 2 hands available to actually MIX, this is a non-issue.

If you are "run & gun", with a boom in one hand and trying to mix a bunch of RFs with the other, it is a definite issue. Having multiple open lavs close to each other (411 & 211 or any other mix of digital and analogue) will result in obvious and catastrophic phase issues.

Link to comment
Share on other sites

"If you are "run & gun", with a boom in one hand and trying to mix a bunch of RFs with the other, it is a definite issue. Having multiple open lavs close to each other (411 & 211 or any other mix of digital and analogue) will result in obvious and catastrophic phase issues."

 

If you are "run & gun" it is unlikely you will be able to "dial in" any delay or compensation that will help you in these fast moving dynamic situations. With "multiple open lavs close to each other" of ANY sort will/may result in "phase issues" (probably the wrong term). The only "solution" to this, in my opinion, is to have each source on its own track --- a credible mix directly to one or two tracks on a camera of this mess ("boom in one hand... mix a bunch of RFs") will not be any less "catastrophic" by introducing compensation for latency. Again, just my opinion.

Link to comment
Share on other sites

With respect to those who disagree-

If you are mixing a dramatic piece, sitting down, with 2 hands available to actually MIX, this is a non-issue.

If you are "run & gun", with a boom in one hand and trying to mix a bunch of RFs with the other, it is a definite issue. Having multiple open lavs close to each other (411 & 211 or any other mix of digital and analogue) will result in obvious and catastrophic phase issues.

Ok, your point may appear reasonable.  But think about it further....  Let's say you compensate for the delay dead nuts on.  First question: how do you do that with precision with any measurable assuredness?  What method?  How would you verify?

Thinking about it further, assume it is perfect when the 2 Lavs or the Lav and Boom are exactly 5 and 3/4" apart.  What happens when one source moves an inch?  Now you are running and gunning...  The 2 mics are going to be changing relationships constantly.  Both angle and distance.  What you are proposing is physically impossible.

 

It is also a non-issue.

 

 

Link to comment
Share on other sites

So presumably the delay between 211 and 411 is also not an issue?

 

Keep in mind, too, Robert (while others debate whether this is an issue or a non-issue), that if you're going through an analog mixer (you're still using the Solice?), that only the iso input for the 211 would be delayed, your mix would still incorporate the undelayed signal. 

 

Presumably, if post used the iso, it would definitely be a non-issue, as they likely pulled it to isolate it.

Link to comment
Share on other sites

I agree that this is a non-issue. I do what Jeff said – when I'm alone I run my lavs directly to my tracks and only run one through my 302, with the boom always through the 302. If I had direct outs I'd probably just leave lavs mixed onto one track and recommend picking out the isos where needed, although this could just be a waste of samples. If I'm mixing I always have the boom on one, and ride two lavs on track two, and then isolate additional lavs because they can't be run through the mixer. If I'm in doubt I'd rather track the lavs and let post flip them and chop them about than mix them than have a mix track with phase and delay issues. Because I drop lavs quite a bit (I don't know exactly how much but it's probably on the order of 12-20dB) if talent isn't delivering a line I don't come across phase issues.

 

Most people can't perceive a delay below a good 25-30ms, so your talent would have to be 30ft apart to create an audible delay between the talent, and then they'd have to somehow overcome the inverse square law to create any issue. As for delays in hybrid transmitters, 3ms is negligible when a frame is 41ms long, and I'd still be mixing as above if I had digital hybrids, so they wouldn't be mixed together that often unless both people are talking at the same time.

Link to comment
Share on other sites

Phase issues can even occur when there is only one microphone. What do you delay then? When in a run and gun situation, and you can actually hear phase issues, just move your boom, if it's involved. If it's to lavs, there's not much you can do as others have pointed out. Even if the perfect delay could be dialled in, the next moment someone moves and it's now all different. Maybe now there are phase issues because a delay was dialled in

Link to comment
Share on other sites

Incidentally, I read a 2009 article a while ago about Matt Jepson who mixes (or at least did for a long while) Mythbusters. He uses up to five channels of Lectros (411s from the image) into two daisychained 302s, with the boom mixed left and the radios mixed right, and then these sent to camera wirelessly. I don't know if he still uses this system, but if he does I've never heard any delay or phasing issues, and I can't imagine he mixes these in and out since he's essentially doing run and gun work.

Link to comment
Share on other sites

Congratulations,

That is a good buy!

When you receive it and have time,put it side by side with a 411 and no delay, 2 transmitters with lavs on 2 people side by side in let's say an interview situation, and mix both to a mono track.

Keeping in mind that this would be unscripted so both faders would need to remain open or at least mostly open so as not to clip any words.

I would be interested to hear your thoughts.

Link to comment
Share on other sites

+1

Congratulations,

That is a good buy!

When you receive it and have time,put it side by side with a 411 and no delay, 2 transmitters with lavs on 2 people side by side in let's say an interview situation, and mix both to a mono track.

Keeping in mind that this would be unscripted so both faders would need to remain open or at least mostly open so as not to clip any words.

I would be interested to hear your thoughts.

Link to comment
Share on other sites

" I think the threshold is somewhere around 2-3ms. "

that would mean you would perceive a delay between lips moving, and hearing the words of someone only about 3 feet away from you.

I suppose an "it depends" goes here, as what exactly is meant by "perceive a delay"?  of we play two mixed sounds of the same thing, but one is delayed, we will notice it pretty easily, depending on the sound, but if we are comparing an image with a sound, it may take longer, but as has been mentioned, we will notice more quickly if the sound is early (compared to image) as our "ear-brain/eye-brain processing" is used to real life, where sound is normally a slight bit after than the image...

Edited by studiomprd
Link to comment
Share on other sites

I suppose an "it depends" goes here, as what exactly is meant by "perceive a delay"?  of we play two mixed sounds of the same thing, but one is delayed, we will notice it pretty easily, depending on the sound

 

That is with a delay above 30ish ms we hear two distinct sounds, with a delay below that we hear the two sounds as one.

 

Having a boom at 1ft and a lav at 1ft where the lav has a 3ms delay could cause phase issues, but there would be no audible delay between the two until the boom were a good 25 feet away at least. 

Link to comment
Share on other sites

Sorry to veer a bit off-topic from the original boom vs. digital wireless discussion, but this raises an interesting issue, however, when using digital camera hops. If I understand this correctly, then the 3ms delay (UCR411a/UM400A) is cumulative. Therefore, at the camera end of this hop, the wireless transmission delay from input to output would be 6ms? Is anyone uncomfortable with THIS amount of delay?

Link to comment
Share on other sites

I think what it all comes down to is our confidence in post (if any) to "fix" any phase or delay issues from delivered isolated tracks.

Phase issues can occur with or without any system delay, as people and microphones move. That obviously can affect the mix if you have multiple mics open. This is why in the modern era of "wire everyone", it is critical to be able to deliver ISO tracks and have post in place to use them.

It's simply too much to expect us to be perfect on the fly. But we sure can try!!

Robert

Link to comment
Share on other sites

I think what it all comes down to is our confidence in post (if any) to "fix" any phase or delay issues from delivered isolated tracks.

Phase issues can occur with or without any system delay, as people and microphones move. That obviously can affect the mix if you have multiple mics open. This is why in the modern era of "wire everyone", it is critical to be able to deliver ISO tracks and have post in place to use them.

It's simply too much to expect us to be perfect on the fly. But we sure can try!!

Robert

+1
Link to comment
Share on other sites

That is with a delay above 30ish ms we hear two distinct sounds, with a delay below that we hear the two sounds as one.

Having a boom at 1ft and a lav at 1ft where the lav has a 3ms delay could cause phase issues, but there would be no audible delay between the two until the boom were a good 25 feet away at least.

Have you tried this in practice? I seem to remember that only 10 ms were needed. But it'd be interesting to actually try this.

A good way to find out about delay/phase this is to put two identical audio clips on adjacent tracks in a daw at the same starting point and start nudging one of them. It works well with drums, because you can easily hear the difference between phasing and delay. Phasing will start almost immediately

Link to comment
Share on other sites

Wow. There's a lot here. Some of the questions have been answered correctly, and some of the answers have muddled the information.

 

 

First off, YES you can easily perceive "a delay when your mics are merely a foot apart". As has been said already, this is comb filtering, and is obvious if you've ever placed a microphone on something, and moved another microphone around it while listening to the blend of the two.  And as has been stated already, the 20ms figure is the threshold at which we perceive two similar sounds to be different. Look up "Precedence Effect" (and it should be noted, the figure changes with the type of sound).

 

If you feel the need to delay your close mics to "match" the distant mics, go right ahead, but as long as either microphone is moving, you're doing yourself no favor. Your best bet is to choose one microphone as your main sound, and if you need multiple microphones, 3:1 rule it.

 

Additionally, "phase issues" as we are discussing here cannot happen with only one microphone, unless you are talking about picking up slapback echo from somewhere. This is about comb-filtering that results from two microphones picking up the same source.

 

Oh, what else... Someone mentioned something about a distant mic not picking up the same waveform as a close mic because the "phase relationships will change". The phase relationship of particular frequencies doesn't change over time. Sound all propagates at the same speed regardless of frequency, so theoretically, in an anechoic chamber, a distant mic WILL pick up the same signal as a close mic on the same axis.

Link to comment
Share on other sites

 

 

Oh, what else... Someone mentioned something about a distant mic not picking up the same waveform as a close mic because the "phase relationships will change". The phase relationship of particular frequencies doesn't change over time. Sound all propagates at the same speed regardless of frequency, so theoretically, in an anechoic chamber, a distant mic WILL pick up the same signal as a close mic on the same axis.

Sorry, but this is not correct.  Waveforms certainly do change with distance and time.  A source sounds quite different when you are 10 feet from the source as opposed to say 150 feet from the source.  

 

 

If you feel the need to delay your close mics to "match" the distant mics, go right ahead, but as long as either microphone is moving, you're doing yourself no favor. Your best bet is to choose one microphone as your main sound, and if you need multiple microphones, 3:1 rule it.

 

 

 

Also, the 3:1 rule is multi micing multi sources, not ONE source.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...