Microphones Phase Cancellation?

Hi all -

sound engineer for a musical in which there are many occasions where two actors (of the 20+) will sing very close to each other, or facing one another (love song, argument, etc.) Each actor is mic'd with a headset, all but one with omni capsules - since it's a high school production, people are not always so careful to not lose my cardioid capsules.

When the actors are close to each other, the mics actually cancel each other out (I'm assuming they phase between the two of them?), and I loose both actors until one backs away or I lower the level. Aside from riding the faders (which I've been doing thus far, and it leaves room for a fair amount of error seeing as I'm not always so quick on the draw) what's the best way to combat this?

anyone else run into this sort of thing?

Thanks!
 
This is the constant battle for musical theatre mixing. You might try swapping the polarity of one of the mics to see if that helps. Riding the faders really is the solution solution, unless you have a huge budget to implement an a/b speaker system.

I always say mix is a verb. So many people like to think they can "set it and forget it" when it comes to mixing a musical (NOT saying that is that is the case here). Some of the best production sound engineers I have observed are always on the move with faders, making adjustments for every syllable in some instances.

Oh, and be sure to stop by the New Member Board and introduce yourself.

~Dave
 
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This is the constant battle for musical theatre mixing. You might try swapping the polarity of one of the mics to see if that helps. Riding the faders really is the solution solution, unless you have a huge budget to implement an a/b speaker system.

I always say mix is a verb. So many people like to think they can "set it and forget it" when it comes to mixing a musical (NOT saying that is that is the case here). Some of the best production sound engineers I have observed are always on the move with faders, making adjustments for every syllable in some instances.

Oh, and be sure to stop by the New Member Board and introduce yourself.

~Dave
I've heard this before. :lol:

-Chris
 
This is the constant battle for musical theatre mixing. You might try swapping the polarity of one of the mics to see if that helps. Riding the faders really is the solution solution, unless you have a huge budget to implement an a/b speaker system.

I always say mix is a verb. So many people like to think they can "set it and forget it" when it comes to mixing a musical (NOT saying that is that is the case here). Some of the best production sound engineers I have observed are always on the move with faders, making adjustments for every syllable in some instances.

Oh, and be sure to stop by the New Member Board and introduce yourself.

~Dave

Tried that last sunday - to no avail. Thanks for the suggestion though!
 
It can be frustrating. Often time you really do get to a point that you are at the best you can get it with out a bigger budget, better talent, or more gear.

~Dave
 
Along with riding the faders, try brining the gain down a little. If that doesn't help, then I would try to pick up both off of one mic; but again, this is the same as riding the faders.
 
Along with riding the faders, try brining the gain down a little. If that doesn't help, then I would try to pick up both off of one mic; but again, this is the same as riding the faders.


I think the best thing I've ended up discovering is to carefully crank the gate threshold on the two singers during their song. Since they're projecting quite a bit It hasn't caused any issues thus far - as long as I can remember to set them back when I'm done. It does also get a bit tedious because there's something like 6 different songs (all with different singers) in which I've had this happen during the course one show. Is there any major downside with this that you guys can see?

If only I had that Yamaha LS9 that I've been asking for (I could store compressor/gate snapshots)... sigh. Unfortunately my yearly tech budget is around $500 a year. I had to write a grant myself to buy an old soundcraft ghost so I could finally have mute automation.

thanks for all the help.
 
I think the best thing I've ended up discovering is to carefully crank the gate threshold on the two singers during their song. Since they're projecting quite a bit It hasn't caused any issues thus far - as long as I can remember to set them back when I'm done. It does also get a bit tedious because there's something like 6 different songs (all with different singers) in which I've had this happen during the course one show. Is there any major downside with this that you guys can see?

If only I had that Yamaha LS9 that I've been asking for (I could store compressor/gate snapshots)... sigh. Unfortunately my yearly tech budget is around $500 a year. I had to write a grant myself to buy an old soundcraft ghost so I could finally have mute automation.

thanks for all the help.

Yay for playing with the gain! The only downside I can see is forgetting to dial it down and having the entire house hear your mistake via feedback. I'm one of those ops (when I get to op) that never ceases to quit playing with every dial and fader on the board because I'm always searching for that perfect sound. Personally, I think that separates a good op from a great one. Just keep your attention held during those moments and keep trying everything.

Would panning one to each speaker help? Off the top of my head I can't remember how it would react, but it's worth a shot imho.
 
If only I had that Yamaha LS9 that I've been asking for (I could store compressor/gate snapshots)... sigh. Unfortunately my yearly tech budget is around $500 a year. I had to write a grant myself to buy an old soundcraft ghost so I could finally have mute automation.

thanks for all the help.
Just got an LS9... our old console got hit by lightning... anyway, I'm not sure what console you are using, but the LS9 and some other boards have options built in that will reverse the phase of a mic signal from within the board.
 
So does the ghost. Fairly sure it's standard (or at least gotten to be one) on most boards nowadays. Struck by lightning? oof!

Also I would pan L + R, save for the fact that I'm running a mono house system. Also, not the gain mind you, the gate threshold, so that it won't open unless really quite loud signal is near it.
 
Even with unlimited budget and resources, the "right" way to handle two mics in each other's faces is to ride the faders as you follow along in the script. Consider it a learning experience -- it's easier than you think.
 
Keep in mind that when you pan left or right in a stereo system, you create other issues. Half of your audience will not be able to hear the mic that is not panned in their direction.

~Dave
 
Keep in mind that when you pan left or right in a stereo system, you create other issues. Half of your audience will not be able to hear the mic that is not panned in their direction.

~Dave

It depends on the size of the house, but yes; more problems.

Sorry, I mis-read the previous comment about the gate. Lets call it lack of sleep.
 
Phase can be eliminated by having a 18dB difference between the two microphones. You can even delay one of them a few milliseconds and see how much that affects the phase relationship between the two mics. A slight delay helps surprisingly well.

Phil
 
Is phase cancellation that common of an occurance when mixing musicals or is it largely dependent upon equipment? I'm curious because we run our high school musical each fall with 20 body packs/E6 mics along with 10 AT 853s overhead and have never had that problem.
 
Is phase cancellation that common of an occurance when mixing musicals or is it largely dependent upon equipment? I'm curious because we run our high school musical each fall with 20 body packs/E6 mics along with 10 AT 853s overhead and have never had that problem.

Comb filtering and cancellation can happen when two or more actors are close by each other. Facing each other makes it worse. Each actor's voice is picked up by two mics. Since the two signals have phase differences due to the differences in path length to each mic, the tonal character or volume changes due to some cancellation.

Typically, the trick is to drop the level of one of the mics a few dB, which reduces the effect. If you know the lines, you can dip the fader for the actor not speaking at the moment. It's better to turn down the unused mic as opposed to turning up the used mic.
 
I've learned (especially in a duet) to leave the faders alone (equal) and adjust the gain. Typically characters sing at different levels on any given night. If they're close keep one off.
To the poster w/ 20+ body mics and 10 hanging mics you have comb filtering/ phase issues, you just don't know what to listen for.

Phil
 
Phase can be eliminated by having a 18dB difference between the two microphones. You can even delay one of them a few milliseconds and see how much that affects the phase relationship between the two mics. A slight delay helps surprisingly well.
An important factor, although technically it is relative rather than absolute phase that is the issue and the relative phase is the same regardless of the relative levels, it is the resulting effects that vary.

What happens is that the a sound is picked up by two microphones, one close and one some distance away. Since it takes some time for the sound to travel and sound reduces in level over distance, it arrives at the further microphone both reduced in level and at a later time.

If the difference in the time arrival at the two microphones equates to a full wavelength the two signals are in phase relative to one another and will coherently sum when combined. If the difference is half a wavelength the two signal are out of phase relative to one another and will cancel when combined. Since wavelengths vary for different frequencies that means that any particular difference in distance will cause certain frequencies to sum, others to cancel and most to be somewhere between those two extremes. Change the distance, and thus the relative time arrivals, and the frequencies that are summed or cancelled change.

The results when the signals are combined are also dependent on the relative level of the signals. Full summation or cancellation only occurs if the signals are of the same amplitude or level. If there are differences in the levels then the effects are reduced until at some difference in relative level the resulting relative phase effects become negligible.

What happens with duets and similar is that the relative levels and path length differences between the microphones are such that when the microphone signals are summed in the mixer the relative phase effects on the frequency response can be audible as may changes in the response due to movement. When that happens, reducing one of the microphone levels will reduce the resulting summation issues and frequency response anomalies. Adding delay is also a common trick however all it really does is change the relative phase and thus what frequencies are summed or cancelled, it does not actually reduce or eliminate the interactions.
 
I Agree with the above post :)

Reversing the polarity or delaying the mics may fix the issue at some frequencies, but it'll cause a whole new set of comb filtering issues.

Sadly there is no magic solution.

The easiest thing in my experience is to start pulling one mic out as the actors move closer to each other, for kissing scenes or hugs or whatever, pull one out entirely, and manage the placement of the headsets / lapels so you can pick them both up off the one mic without losing too much level from either performer.
 
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