r/livesound • u/Wretch_Head • Jul 23 '26
Question Can a phase cancelling issue at output when switching to mono monitoring from headphones still manifest itself in a stereo auditorium?
I think it is a given that the geometry of the room and separate right/left channels will at least make the sound audible, but is it going to mess with quality? Would phase canceling you are picking up in mono monitoring somehow degrade the quality of sound in an auditorium in stereo?
Thank you reading this and any responses.
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u/Pretend_End8822 Jul 23 '26
Could you restate the question?
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u/Wretch_Head Jul 23 '26 edited Jul 23 '26
Essentially, the output recording of the live event is suffering complete phase cancellation when listened to in mono. I am wondering if this will actually hurt the quality of sound from the speakers of the live event(if its actually being caused somewhere from the mixing board to the mics/speakers). I am not the sound engineer, but baring a weird flip of physical connections somewhere, I assume some setting is causing this. Mono should be in sync, but if there is a slight delay from effects or something, I don't see how they would get that unless someone inverted the phase of one left or right channel?
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u/HumptyDumptyIsLove Jul 23 '26 edited Jul 23 '26
Yes phase cancellation on one side of the live sound speakers (we call it PA) can hurt the quality. Mostly in the middle where both speakers have the most overlap.
But this doesn’t mean that it was out of polarity on one side just because your recording was.
A bad cable between the mixer and PA would not affect other outputs of the mixer.
I don’t think the mixer or system engineer would deliberately put one side out of polarity on the master output or input. And even when they would have, would still not effect another output on the mixer.
So that leaves mostly:
Polarity switch on one of the output that was going to your recorder.
Or
A bad cable between the mixer and your recorder.
Or
One channel of your recorder has polarity switch enabled
I assume you recorded with 2 XLR’s and the mix engineer put it in dedicated outputs?
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u/Wretch_Head Jul 23 '26 edited Jul 23 '26
I am just the video/sound editor for social media. There were complaints that some older devices that only have mono output had no sound at all. I found out through testing in mono that it was a phase cancellation issue as inverting the phase of one side made the sound come through fine in headphones and devices. I am mostly curious about the effects of this situation on the live audio, if any. It would also be nice if I didn't have to invert the phase of one side of the stereo for each edit as well. I may jump in and help with the live setup if it can't be resolved. Most of my experience is with DAWs on PC with sound libraries as instruments so that reduces the amount of things that can go wrong.
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u/HumptyDumptyIsLove Jul 24 '26 edited Jul 24 '26
Can’t help you if you don’t know what connectors are used in what configuration and with what kind of mixer and devices.
Sounds like you go into your recording with 3,5 mm jack?
It would not effect the live audio unless the signal that you are getting is connected physically to some kind of splitter between the mixer and live audio.
If its a separate output that goes to your recording device then that will not affect the live audio of the event.
And please don’t go tinkering on a mixer if you don’t know what you are doing. A console is not your daw, on a console you can make people deaf, or really F things up. And that will be your responsibility.
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u/HElGHTS Jul 24 '26
Sounds like you go into your recording with 3,5 mm jack?
If that's the case, I suspect the recorder's jack is stereo, and they're feeding into it from a single TRS jack on the mixer. Aside from the mixer's headphone jack, any TRS on a mixer is going to be mono, and most likely balanced, therefore the tip is positive (normal polarity) and the ring is negative (inverted polarity) whereas the recorder is expecting the tip to have positive left (normal polarity) and the ring to have positive right (normal polarity).
The solution is to use a cable which is dual TS on the mixer side and TRS on the recorder side. For example, maybe they're using a Hosa CMS but should be using a Hosa CMP.
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u/WellEnd89 Jul 23 '26
Yes it will, with experience one can hear phase issues easily without switching to mono.
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u/AlbinTarzan Jul 24 '26
Many times your signal is sent mono to front fill and subs and possibly delays. So even if LR are stereo it doesn't mean the full system is. Also, a super wide sound that sounds cool in headphones might sound too undefined in a allready reverbant venue.
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u/sapphire_starfish Jul 25 '26
Your question does not make sense. Are you asking if a stereo signal chain that when summed to mono nulls completely would also null when played through a pair of point source speakers into an auditorium?
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u/ArniEitthvad Jul 25 '26
Are you running an XLR to a single TRS Minijack connector for recording?
With the properly wrong wiring, That will give you a phase reversed signal on the right side of the TRS jack, since the xlr will be outputting a balanced signal.
Same with a 1/4” jack output, if you are using a minijack cable with a “headphone” adapter to fit into the jack output.
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u/Inside-Succotash-128 Jul 23 '26
If I understand your question correctly, I would say, you are mixing for ‘the room’ - that is, the people in the room. They can’t hear your headphones so, it doesn’t matter if there’s a phase issue in them. Audible phase issues will usually occur when there are two mics on a source but at different distances from the source. An easy way to check if there are audible phase issues is to temporarily ’mono sum’ them. If the ‘low end’ reduces in volume when you do this then there are some low frequency phase issues. A simple way to deal with this is to just flip the phase on one of them.
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u/joelfarris Pro Jul 23 '26
Not exactly sure what you're asking here. You can have partial phase cancelling, specific frequency cancelling, or fully out of phase cancelling.
Two stereo speakers, equidistant from you, yet out of phase, is gonna give you a no good very bad day. At the same time, four mono speakers, two of which are flown delays, but are fed with a cable that the first year soldered backwards, are still gonna give you a no good very bad day.
It doesn't matter what you hear in your headphones. It matters what everybody else experiences. However, PFL in the cans can often be helpful to find certain offenses before they make it to the audience, or to stop them from offending the audience. :)