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Author Topic: Phase Reversal use on Theatrical Lavs.  (Read 16043 times)

Ryan Tolzmann

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Phase Reversal use on Theatrical Lavs.
« on: October 30, 2013, 08:41:18 PM »

Hey guys,

So I know when you have panel mics, you reverse the phase of every other one for better feed back control, which is very easy due to the mics being for the most part stationary.

But my question is if you do the same thing for wireless lavs in theatrical use,  is it even effective? 

My thoughts are, since the mics are constantly moving..  does it just cause unnecessary cancellation at times when actors are in close proximity of a reversed phased mic?

Any suggestions or discussion would be great! Thanks guys!
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Ryan Tolzmann
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Ivan Beaver

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Re: Phase Reversal use on Theatrical Lavs.
« Reply #1 on: October 30, 2013, 09:11:45 PM »

Hey guys,

So I know when you have panel mics, you reverse the phase of every other one for better feed back control, which is very easy due to the mics being for the most part stationary.

But my question is if you do the same thing for wireless lavs in theatrical use,  is it even effective? 

My thoughts are, since the mics are constantly moving..  does it just cause unnecessary cancellation at times when actors are in close proximity of a reversed phased mic?

Any suggestions or discussion would be great! Thanks guys!
First of all you cannot reverse the phase-on the POLARITY.  BIG difference-even though a large majority of this industry cannot get it right-INCLUDING the manufacturers :(

Automatically reversing the polarity of every other mic is not necessarily a good thing.

It depends on the particular situation-placement of the mics-placement of the loudspeakers-pattern control of the loudspeakers and so forth.

Sometimes you can get more gain before feedback-but at the expense of sound quality-which makes you turn up the level and need that extra gain.

Sometimes it does not make a difference.

Simply being able to push a fader up higher does not mean that it is any "clearer".  It may be louder (or not) but is it as easy to understand?  Ultimately that is what we are after-NOT just SPL.

A clearer sound does not have to be as loud to be understood.

Sometimes it does not make a difference.

Every situation is dependent on many factors
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Ivan Beaver
Danley Sound Labs

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g'bye, Dick Rees

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Re: Phase Reversal use on Theatrical Lavs.
« Reply #2 on: October 30, 2013, 09:23:22 PM »

Hey guys,

So I know when you have panel mics, you reverse the phase of every other one for better feed back control, which is very easy due to the mics being for the most part stationary.

Really?  Please explain how this works.

Quote


But my question is if you do the same thing for wireless lavs in theatrical use,  is it even effective? 

My thoughts are, since the mics are constantly moving..  does it just cause unnecessary cancellation at times when actors are in close proximity of a reversed phased mic?

Any suggestions or discussion would be great! Thanks guys!

I don't flip the polarity on any lavs/earsets unless it's needed.  If you hear the sound start to degrade when two miked performers get close, go ahead and flip one of them.  But as you point out, when the sources are mobile, you have to react in real time rather than rely on some pre-determined formula.

Auto-mix will help...
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David Simpson

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Re: Phase Reversal use on Theatrical Lavs.
« Reply #3 on: October 30, 2013, 09:36:05 PM »

I do a lot of theatre mixing. I do not, as a rule, swap the polarity on mics unless it helps remedy a specific issue I am having. Often times I find that it is one tool to help reduce comb filtering experienced when two actors are singing face to face (as directors often stage them to do). However, riding the faders and reducing one of the mics could be just as helpful. As Ivan and Dick have said, it depends on many factors.

~Dave
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Ryan Tolzmann

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Re: Phase Reversal use on Theatrical Lavs.
« Reply #4 on: October 30, 2013, 11:45:01 PM »

Hey thanks for the replies.. im on mobile so bare with me..

To Ivan Beaver,  I suppose I should have been more technically correct in my original post.  I do know that the "phase" button on consoles, is really changing the polarity of the mic, which in turn changes the phase. If im not mistaken?

I also dont do this automatically at every gig.  I do however agree with the rest of your post %100.

As far as doing a panel of however many table mics, if you did switch the polarity of every other one, would that not help kill any feedback issues?  Or would delaying every other by 1ms be an alternative? 

And to Dick and David, I think you are very right regarding reversing the polarity with lavs in theater.

I only ask about this, because I met a seemingly experienced A1 at a theater who told me she did this with all her lavs to cut feedback problems.. and it didnt really make sense to me. So I turned to you guys on this site!

I personally think if you can properly ring out your mics witb your geq, you shouldn't be having much to worry about..
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Lee Buckalew

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Re: Phase Reversal use on Theatrical Lavs.
« Reply #5 on: October 31, 2013, 07:01:23 AM »

Hey thanks for the replies.. im on mobile so bare with me..

To Ivan Beaver,  I suppose I should have been more technically correct in my original post.  I do know that the "phase" button on consoles, is really changing the polarity of the mic, which in turn changes the phase. If im not mistaken?

I also dont do this automatically at every gig.  I do however agree with the rest of your post %100.

You are mistaken.
A polarity reversal does nothing to phase as phase is a shift in the starting point of a given frequency.  If a long enough sinusoidal wave is involved then it may be the same as a time offset.

Lee
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Ivan Beaver

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Re: Phase Reversal use on Theatrical Lavs.
« Reply #6 on: October 31, 2013, 07:09:49 AM »


I only ask about this, because I met a seemingly experienced A1 at a theater who told me she did this with all her lavs to cut feedback problems.. and it didnt really make sense to me. So I turned to you guys on this site!


There are many "experienced" people in this industry who don't have a basic understanding of what is going on.

They have all sorts of "vodoo" and "wives tales" that they keep passing on to others-and never stop to think or understand what is REALLY going on.

Yes they may have done something in the past-and it made a difference-but was it better?

Many people associate something that is different (that they created) as somehow "better".

ALWAYS QUESTION when it does not make sense or seems strange
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Ivan Beaver
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Keith Broughton

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Re: Phase Reversal use on Theatrical Lavs.
« Reply #7 on: October 31, 2013, 08:32:25 AM »

Quote
Really?  Please explain how this works.
I think the concept is that with multiple mics open, it will help reduce low frequency feedback as the wave lengths are longer and might partially cancel out if polarity of some mics is inverted.
Tried it myself and the results were inconclusive.
I use a high pass filter for best low freq control.

If it's multiple open mics, you could try putting a gate on the channels with just 6 or 10 db of gain reduction, fast attack and slow release.
I do that with panel mics and it works great.

However, if it's just one mic and not a group of open mics that is feeding back, polarity or gates won't help.
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Nathan Salt

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Re: Phase Reversal use on Theatrical Lavs.
« Reply #8 on: October 31, 2013, 10:23:21 AM »

The concept is that the mics hear similar background noise so reversing the polarity on half of them will cancel out the background noise.
In practice it does pretty much diddly squat since the mics each hear something slightly different so doesn't null.

After seeing how awesome the dugan mixers are, I can't wait to actually get to use one. How well do they work on musicals?
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Nathan Salt

Tim McCulloch

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Re: Phase Reversal use on Theatrical Lavs.
« Reply #9 on: October 31, 2013, 10:38:41 AM »

After seeing how awesome the dugan mixers are, I can't wait to actually get to use one. How well do they work on musicals?

They're great for dialog.  No experience with the "music" mode, but some users report they're an improvement and other users say they're too fiddly and manual mixing is better for their workflow.  Obviously, YMMV.
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ProSoundWeb Community

Re: Phase Reversal use on Theatrical Lavs.
« Reply #9 on: October 31, 2013, 10:38:41 AM »


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