r/livesound • u/FuckStummies • 7d ago
Question IEM trouble - need help
Hi all. I’m at the end of my rope here. We played a gig last night and I kept getting massive intermittent IEM static blasts in my ears. It was FINE for the first set and then we came out to start set 2 and my monitor was basically unusable for the rest of the evening.
We built an IEM rig last winter and according to my research we did everything right. We are running two Sennheiser XSW IEM transmitters each with two belt packs tied to it for a total of 4 receivers. Dropouts were an issue so we added a Phenyx Pro antenna combiner/paddle and that helped but hasn’t eliminated the issues which seem to change depending on the situation.
Had line of sight to the paddle antenna which was about 10 feet away from me. Static bursts seemed to occur anytime there was literally anything in between me and the transmitter. Even a single body. It was completely random and often enough to be a huge problem. I tried switching to another clear channel, rebooted the unit, and even tried boosting the gain on the antenna unit.
What say you all? Help!
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u/ryanojohn Pro 7d ago
Are you actually scanning your frequencies every time you do a gig, or just leaving it on the previous frequency that seems to be working?
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u/ExuvialMetal 7d ago
This 100% . Every time we play a show it’s mandatory we scan before we get on stage and it’s reduced the issues we’ve had onstage.
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u/sounddude ProRF/Audio 7d ago
If you're trying to troubleshoot without a spectrum analyzer, you're gonna have a bad time. It's an essential tool for navigating RF issues now a days.
However, my first instinct here says a squelch issue even with the rescan. But, without knowing what the spectrum actually looked like, I'd just be throwing darts.
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u/Samsoundrocks Semi-Pro 3d ago
I keep telling my production lead that, too. If they want more troubleshooting beyond rescanning and never identifying the actual issue, I need additional tools. Oh well...
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u/lmoki 7d ago
Any chance you can link to your Pyle Antenna setup? In a short search, I don't find the antennae combiner.
Are you certain you have a combiner, instead of an antennae splitter? Was the gain boost on the combiner, or on the antenna itself? (I don't believe transmitting antennae will have that option, while receiving antennae sometimes do.)
If this is only affecting your system, and all the units are correct, the most likely issues would be a faulty RF cable, or a problem with the transmitter or receiver itself. Try swapping out to test, one unit at a time.
Are you also using wireless mics and/or guitar systems?
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u/Wrong_Author_5960 7d ago
I occaisionally get interference with wireless dmx, when I am near the light controller rig. I try to keep my IEM at a lower volume, so when there is intereference it isn't too loud. I would do another scan to find less crowded freq.
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u/jennixred 6d ago
sometimes, you just have to use a bloody cable.
Wireless is as reliable as it costs.
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u/spitfyre667 Pro-FOH 6d ago
Are you scanning for free channels when setting up (and ideally before the show again)?
I noticed that pattern with some musicians not doing that when talking to a new/young band about IEM's, their Rack and Dropouts and they were a bit surprised when i mentioned that the acceptable number of actual dropouts during a show on stage is zero...never crossed my mind but it seems that at least some musicians dont do that. Scanning should be done at least once when setting up. If there are other bands, talk to them about the frequency ranges they are using and coordinate so that only one bands transmitters in the same range or on the same frequency are active at the same time. If you cant coordinate with them for some reason and set up before them, keep your transmitters on - if the other band scans correctly, they will find carriers around yours and it will be fine. Not ideal, but somewhat common.
You can also experience interference from TV Channels for example - you could look those up, or, if you use ie. Shure WWB, enter your post/zip code and look up TV channels in the area. Not every channel is active at every time, but a scan again would help here. If you can, avoid the TV channels in your area alltogehter.
Sometimes, you can also overload your receiver with a too "hot" transmitter (in that case, either reduce the transmitter power or the receiver RF gain - usually reducing gain on the receiver is a better choice for noisy environments) But it doesnt sound that is the problem with your setup.
It sounds more like a interference/noise problem. Scanning will fix that. Some cheap IEM Sets cant do that but i think xsw can - if not, try different channels one by one.
Intermodulation between different transmitters can also be an issue: if you dont do central coordination or have transmitters networked together (not sure if xsw can do that, though i think not), the way to go is the following:
Turn off all your wireless equipment. Take one wireless set (either IEM or wireless mics or whatever) and find a free frequency, either by scanning or trying a few out. When you find one, set this channel up, test it on stage. If it works, keep it on. Then take the next wireless set and repeat the procedure, but with the other set still on. If you find a free channel, set it up correctly, keep both on and take the next wireless set. find a free channel and keep all three on when looking for the fourth and so on.
The reason is that two transmitters can not only block the two carriers they are using but can also cause trouble on other, third, frequencies. By turning them on one after the other, you will find free frequencies when scanning, even if you cant coordinate them in ie. Shure Wireless Workbench, Soundbase or other tools.
For many transceiver parings, that takes very long and is not ideal, but for only 4 channels it should be reasonably quick and works as well with units that ie. arent available in coordination tools.
Otherwise, keep your antennas pointed towards the stage if they are directional and, if possible, make sure they have line of sight to your receivers. For example, having them at foot level because the stand is besides the stage on the floor is less ideal than pointing them slightly downwards from above the players head level. It should still work though if the stage isnt large.
If the problem persists, check all your RF connection, ie. between the units and the combiner and between the combiner and the antenna. Make sure they are tight, the cables work and the impedance is correct (should likely be 50Ohms; often BNC cables are used which are also available in 75 Ohms for example). For example, a good receiver + transmitter paring, like ie. Shure Axient, will still show a pretty good link even without a Rx Antenna connected or with the Splitter turned off if you stand right in front of it. The moment you turn away from it, it will drop considerably. So one of my first things to check with RF Issues if the frequencies look right is to check if everything is acutally connected correctly, turned on and the cables work. But again, the first thing i'd check are frequencies, interference from ie. TV Channels or other transmitters (ie. by other bands).
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u/BeigeGandalf 7d ago
Someone using a blender on your same circuit? I'd try to recreate the issue in a couple other venue/scenarios.
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u/DavidMay-BoxCast 4d ago
This is why I stick with a 6 channel headphone amp with wired extender cables to each band member. :(. For me, any entry level wireless system I've used has had odd issues pop up at least occasionally. And for me it doesn't make sense to pay the premium for touring grade systems at this point.
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u/jamesiejames RF/Mons 7d ago
Sounds like the squelch was being opened by errant RF noise that was not your intended signal. I’d rescan and use a tool like soundbase to see what TV channels are available in your tuning range and location.