Phase issue between monitors and FOH when running stereo ?

[bjosko]

A tech once told me I should be careful when running stereo monitors and to FOH in stereo at the same time.

I could get phase issues.

Did he had a point?

We are not talking polarity, but simply mixing up Left and Right speaker, and that way fighting each other.

At rehearsal and at a gig, I am using my Key Largo mixer for my own two monitors and to the PA, but the long cables to PA might very often be crossed between left and right. But then, I’m only the keyboard player and am used to get lost in the mix ….. 🤔

[Baldwin Funster]

Maybe you misunderstood. I've had phase issues when handing a stereo line to the FOH and having them send that to the mono stage monitors. 

If not a misunderstanding then I've not really have or heard of the issue of phase interference between the stereo FOH and a guy's stereo stage monitors. Technically speaking you could get phase problems like that in mono as well. Maybe at a super big venue that happens. I don't play in that league so IDK. 

[stoken6]

I read that it's common for some (budget?) mixers to phase-invert the monitor sends (I don't know the reason). Perhaps your tech is telling you that you could get e.g. phase issues between the mains and the (phase inverted) monitors?

 

I get this (in mono) with my Rolls PM351 - if I get a monitor mix from the desk which contains keys, and I dial in a bit of my own keys as well, they cancel. (Less with a digital desk, which adds a smidgeon of latency)

 

Cheers, Mike.

[Baldwin Funster]

8 hours ago, stoken6 said:

I read that it's common for some (budget?) mixers to phase-invert the monitor sends (I don't know the reason). Perhaps your tech is telling you that you could get e.g. phase issues between the mains and the (phase inverted) monitors?

 

I get this (in mono) with my Rolls PM351 - if I get a monitor mix from the desk which contains keys, and I dial in a bit of my own keys as well, they cancel. (Less with a digital desk, which adds a smidgeon of latency)

 

Cheers, Mike.

You could make yourself a pair of phase inverted adapters and run inline from your monitor sends.

[Reezekeys]

16 hours ago, bjosko said:

We are not talking polarity, but simply mixing up Left and Right speaker, and that way fighting each other.

 

This constitutes a phase issue? Not to me, but I'm happy to be corrected and educated. I'm just the piano player! 🙂 

 

40 minutes ago, Jr. Deluxe said:

You could make yourself a pair of phase inverted adapters and run inline from your monitor sends.

 

If there was an issue with inverted phase between FOH and stage monitors, wouldn't it be easier to ask FOH to flip the phase on their board?

 

I encountered a different but related issue one time, at a festival where our monitor engineer was not allowed to work our set. I told the festival monitor engineer not to put my keys in my mix from him because I use my Rolls mixer to mix my own keys. Of course he did, and of course it was phase flipped from my Rolls mixer. You guessed it, we start our set and I hear the faintest wisp of keyboards in my ears! I knew immediately what he did, but as he was on the opposite end of a large stage, I just turned my Rolls's level off and slogged through the set in mono.

 

Anyway, as far as left & right, I only need the "correct" orientation for myself - it feels very weird to play a stereo acoustic piano and have the bass end move towards my right ear as I play lower on the keyboard! As far as the audience goes, I honestly don't think it matters. Of course if I see DI boxes labeled "L" and "R", I make sure to plug in correctly, but once it leaves those DIs, whatever happens happens and I don't worry about it. I don't think the "polarity" here will matter as far as the mains mixing with monitors either.

[mate stubb]

I don't see stereo monitors causing phasing issues with a stereo FOH. They are pointing in different directions.

 

Stereo keys into mono monitors, sure.

[timwat]

This sounds a bit like very technical advice which may not really apply in a live setting.

 

In a recording studio situation, of course, if you have multiple sets of stereo monitors in relatively close proximity, and aren't careful about phase you could have pretty pronounced issues.

 

But in a FOH / monitor setting, aren't we introducing pretty significant distance (and thus, time offset) with regards to phase, not to mention we really aren't talking about the same listener experience (in other words, the folks listening to one set (FOH) aren't listening to the other?

 

If on the other hand, what engineer is experiencing is an increase in monitor volume leads to noticeable bass reduction in the overall FOH listening experience, it would seem to imply that monitors are too damn loud.

 

My dime store contribution, probably worth just about that much.

[Docbop]

If dealing with UNpowered speakers check polarity of the connection with power amp can even be in speaker cab is wired wrong.  Even a cable wired wrong.  Those are less likely in today's gear, but it happens. 

[bjosko]

30 minutes ago, Docbop said:

If dealing with UNpowered speakers check polarity of the connection with power amp can even be in speaker cab is wired wrong.  Even a cable wired wrong.  Those are less likely in today's gear, but it happens. 

Yep, but that again is an issue between the + and - on the speaker, not Left and Right.

But I have seen this in some HiFi equipment, where there is a common ground.

Typical in Car audio, and when folks use the original wiring, it might happen the phases have been switched so it miss the umph and the speakers are fighting each other.

 

I was struggling with this yesterday with a guitar where I had put a Humbucker in the bridge, and a P90 in the neck. 
Each was playing fine separately, but when I engaged them both, the volume was cut in half. 
Even both was connected correctly per diagram an colors, one of them had to be reversed on polarity. But that was a pair of cheap knockoffs.

But that started me speculating about what that old tech told me once about the Left / Right and that it also could cause similare issues.

If someone have two pair of speakers in their home studio and am able to play both at the same time, it should be easy to test out by reversing the left and right speaker on one of the pair.

My guess is that it would only destroy the stereo image.

[Delaware Dave]

The FOH is facing you and you are facing him; his left could be your right.  Is it an issue? I don't know.  When I'm on the stage I can't hear the main FOH speakers as they are in front of me and there is a wall of guitar/bass amps and drums on the stage.  I couldn't even tell you if I was coming through the mains.  The only way I know is when my wife comes up and tells me I'm being drowned out of the mains.  At that point does it really matter if there is phase cancellation, left/right issues or any other issues if I'm buried in the main mix?

[timwat]

I think the bigger phase issue we run into on stage as keyboard players is the problem of guitar players never outgrowing their middle school phase.

[Al Coda]

16 hours ago, Jr. Deluxe said:

You could make yourself a pair of phase inverted adapters and run inline from your monitor sends.

 

 

I guess that idiot of FOH guy just only needs some phase inverted ears (and brain) !

 

 

A.C.