Risk of phase issues with IEM monitoring?

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Risk of phase issues with IEM monitoring?

Post by Murray B »

Hi all,

I'd appreciate some guidance from you lovely people in the forum.

I'm in the process of working up to doing some shows with a new band and I'm looking at getting and IEM system for the first time. I'm looking at simple solutions to getting an okay mix and I thought maybe an easy way is to have the FOH mix and then mix in an additional guitar input from my modelling on stage - just adding a little 'more me'.

My concern is that some FOH systems, especially the new fangled digital ones, might have a bit of latency that could be enough to introduce a phase difference between my 'local' guitar signal and the guitar in the FOH mix. So I might get a flanging effect?

Does anyone have any real world experience of trying to do things this way - am I over thinking it.

I know that the best plan would be to have a splitter and our own mixer to do the IEM's with and this is probably the best way to go, I'm just wondering if this rather simpler solution is fatally flawed from the onset :D
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Re: Risk of phase issues with IEM monitoring?

Post by shufflebeat »

Depending on your desk, it would probably be just as simple to set up a mix without guitar to add your local signal to.

I think your worry is technically real but the extent to which it would disrupt your flow could only be assessed by doing it and see.
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Re: Risk of phase issues with IEM monitoring?

Post by Murray B »

That indeed would be a sensible approach, I'm looking at situations where monitoring is more out of my own hands - to offer a solution to a venue sound engineer of sending me a FOH mix and then adding a bit of myself in will hopefully mean I'm getting the best I can out of the situation whilst giving the venue engineer the least amount to do. But it could all go horribly wrong :headbang:
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Re: Risk of phase issues with IEM monitoring?

Post by Aled Hughes »

You're probably right that it potentially could create some issues if you're adding your own local signal which is already appearing in your feed from FOH.

Depending on the desk, it might be just as easy to ask for copy of the FOH mix without your guitar, or to build you a mix from scratch.

I've done a similar thing on a few gigs, where I have local control over my bass signal, and ask for a copy of the FOH mix, but the FOH engineer usually just gives me a new mix anyway.
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Re: Risk of phase issues with IEM monitoring?

Post by Hugh Robjohns »

A round trip through a digital desk is typically 1.5ms or so (at base sample rates) and that will certainly cause some 'colouratio' if you add in a similar level of direct sound. Whether that colouration is off-putting or not varies with different individuals.

However, one thing digital desks usually have in plentiful supply is lots of aux sends, and it's often easy to copy the FOH mix to an Aux as a starting point for a personal foldback mix.
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Re: Risk of phase issues with IEM monitoring?

Post by Murray B »

Thanks all for your advice, hopefully the idea of out front but without me might work out as the best quick solution. Hurrah for technology! I'm a bit of a late adopter when it comes to stage work, so there's a learning curve in store.
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Re: Risk of phase issues with IEM monitoring?

Post by Sam Spoons »

How were you planning to mix your IEM feed? If you end up getting a separate mix from the FOH guy you might as well just ask for a copy of the FOH with the guitar boosted by, say, 3dB which would remove the need for a guitar feed and some kind of mixer at your end? Not quite as controllable by you but simpler to set up.
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Re: Risk of phase issues with IEM monitoring?

Post by RichardT »

I use high-attenuation custom ear protectors and it’s still possible to hear the rest of the band reasonably well (though obviously the sound is largely lacking in HF!). They are solid plastic and don’t have any filters, so their attenuation is quite similar in effect to IEMs.

As an experiment, you could try a simple solution - just send your own guitar sound to the IEMs and rely on the ambient sound to hear the rest of the band. It might not work for you, but if it does it gives you control of the guitar level and you have no dependence on the sound engineer. It would also work for rehearsals and give you protection then too.
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Re: Risk of phase issues with IEM monitoring?

Post by Murray B »

I'm looking at worse case / best case scenarios and what spec I want for the IEM system - there is a whole question about wired / wireless but there are some wireless systems with a headphone output too so I could have a wired option and or one of those little wired belt packs as a fall back . I'm planning to use wireless mainly - a radio based system as the wifi signal range looks too risky from my research so far.

I'm imagining that the base unit is going to go on my pedal board it seems most will fit, as it will be next to the pod go I figured that feeding a direct monitor output would be easy to do, then wondered if this gives me an extra option to mix myself in to taste, then realised that phase issues might make this sound a bit odd.

I think I know what the real answer is - which is either to just accept a mix from front of house or have a splitter and a remote digital mixer - this seems like the best option. But I do lots of different kinds of music with various bands and not every band is going to have that equipment or even enough aux outs to give me a separate mono mix.

I hope on the simple systems I might get away with the more me option as there in theory will be very little latency with analogue mixers. I could then just take a parallel output from the mains - even a tape out and make it work for me. I could also do the thing Richard suggests which is not a bad idea for some shows but some stuff is with acoustic instruments so I don't think it will suit every situation..
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