Wireless Microphone Coordination

[Chris Rigby]

I am currently sound designing and operating a show for a community theater. We run a portable sound set up, with minimal microphones due to limited resources. Specifically, the set up is 6 Shure SLX reciever/transmitters and two Shure PGX systems. In past shows, some that I have designed and some others have designed, microphone issues are a constant issue. The most common issue is cutting in and out. What should I be doing beforehand to try to avoid these issues?
I have done a large amount of research and attended several classes on wireless microphones, all in hopes of educating myself enough to fix the issue. However, most place I look and people I have talked to suggest extra stuff, whether it be a antenna distribution system or something else in order to help our issues. Due to the limited resources often found in community theater, a distribution system or a different type of mic is just not feasible for us. What sort of actions can I be taking right now, during pre-show set up, as well as during run of show, that will help me avoid problems?
Thanks for all suggestions!

 

[Morte615]

Placement is probably the biggest thing you can do that will help. Make sure the antenna's are line of sight to the actors, make sure the actors keep their antennas out of their pockets as much as possible. The more items you are going through (walls, floors, clothes, ect) the worse the reception.

One cheap thing to possibly do is to add some length of coax between the antenna and the receiver (not easily possible with the PGX but can be done easily with the SLX series.) Even moving the antennas out of the rack and to a support structure that is not surrounded by metal will help a lot. The material is cheap to purchase and can be packed away easily in between uses. You will get better results using Coax that is rated with the correct impedance for the antenna but I have successfully used standard TV coax for short runs (under 5 feet, just to get it out of the case)

Also something I have noticed a lot is that "cutting in and out" may not be a signal issue at all. The connector for the headset to the transmitter is a common place for wires to break and solder joints to come loose. A good test is to take a transmitter and mic, right next to a receiver, and shake the hell out of the wire. If it cuts out at all chances are that the connector needs to be re-soldered. I see this more on older mics, or ones that get a lot of abuse (i.e. temporary or touring setups.) Also check the entire wire for the headset and make sure it's not been pulled or kinked. Feel for anywhere that there may be a broken wire that may lose connection when moving.

 

[JD]

See http://www.controlbooth.com/threads/ac-cable-routing-lesson-learned.37126/#post-322402

Nothing wrong with "Porcupine Mode." Also contains links for picking up extenders and such. Just keep your quills organized!

Two things to check,
1) Scan for what frequencies are already in use. (sometimes LED lighting makes 518mhz to 530mhz tricky due to noise)
2) Chart your frequencies and inter-modulation overlays. (Free software on web)

 

[FMEng]

Here is a good article on RF intermodulation.
http://www.prosoundweb.com/article/whoa_you_cant_do_that/

 

[themuzicman]

One cheap thing to possibly do is to add some length of coax between the antenna and the receiver (not easily possible with the PGX but can be done easily with the SLX series.) Even moving the antennas out of the rack and to a support structure that is not surrounded by metal will help a lot. The material is cheap to purchase and can be packed away easily in between uses. You will get better results using Coax that is rated with the correct impedance for the antenna but I have successfully used standard TV coax for short runs (under 5 feet, just to get it out of the case)

Well the SLX ship with 1/4 wave antennas which require a ground-plane to work. You cannot extend quarter wave with any amount of BNC additions, they need to plug into the receiver or a panel mount connector.

 

[Jay Ashworth]

Put the receivers at the stage end of the snake, not in the booth.

 

[JFutty90]

Here is my favorite link for using Shure Microphones. http://www.shure.com/americas/support/tools/wireless-frequency-finder Even when using other manufactures that will show you the actual frequency. It will show you TV channels that broadcast on frequencies near or in the Wireless Spectrum. Also make sure that the frequencies are far enough apart to not cause issues. Finally, set up the worse case situation. That is typically all of them on in a cluster together. There can be issues of beam forming that can change frequencies and cause connection issues.

 

[themuzicman]

Also make sure that the frequencies are far enough apart to not cause issues. Finally, set up the worse case situation. That is typically all of them on in a cluster together. There can be issues of beam forming that can change frequencies and cause connection issues.

The reason these pieces of software exist is because once you have a handful of frequencies you cannot figure it out manually -- you can't simply space them "far enough apart to not cause issues" because it gets pretty difficult to figure out harmonics.

Also your worst case scenario isn't really a thing...sorry. As long as all of your mics are coordinated properly and the output transmission power is relatively similar per unit, you won't run the risk of everyone together on stage in one group becoming an issue. You'll run into far more issues should you have a poor coordination and you have 2 freqs near overlapping each other or a 3rd order harmonic on top of a freq in use (which is why coordination is a huge deal). There is no "beam forming that can change frequencies and cause connection issues". You'll also run into issues if you have a single crazy high power transmitter too close to your receive antennas (especially true if you have an actor wandering around your RF Rack and you are strictly using 1/4 wave antennas on all of the receivers) -- you'll overload the front end of the receivers and you won't get any frequencies passing!

A better way of testing a "worst case scenario" is to either a. have absolutely zero walls in your theater so there is no bounce from the architecture (wireless outdoors is pretty difficult) or b. put each transmitter in an enclosed metal dish so there is an insane amount of reflections. When I really want to war game that way I go buy a bunch of disposable aluminum foil baking pans that hold mini loaves of bread and put each transmitter in them.

Option B. is a lot more attainable for most people, however I don't even do that most of the time. I usually just power up everything all at once and throw them onstage together and take a listen, and then move them all over just to make sure my antenna placements are fine.

 

[KBToys82]

I am taking over the sound duties for my schools musical and the issue they always had was wireless mics always cutting in and out. They typically used about 6 wireless mics. We are doing 12 this year for Beauty and the Beast. The sound board was always in the very back of the auditorium in a corner underneath the balcony. My plan is to put up a table with the receivers in the from of the house and run a snake to the mixer. We also can't afford an antenna distribution system.

I was told that when the audience shut their phones off it improved, but I doubt that was too much of a factor.

 

[BobHealey]

I am taking over the sound duties for my schools musical and the issue they always had was wireless mics always cutting in and out. They typically used about 6 wireless mics. We are doing 12 this year for Beauty and the Beast. The sound board was always in the very back of the auditorium in a corner underneath the balcony. My plan is to put up a table with the receivers in the from of the house and run a snake to the mixer. We also can't afford an antenna distribution system.

I was told that when the audience shut their phones off it improved, but I doubt that was too much of a factor.

Check your frequencies, especially if your mics are more than 6 years old. If its between 692 and ~800 MHz, those frequencies are both assigned to other users including cell companies; and illegal to operate wireless mics in.

 

[BobHealey]

I am currently sound designing and operating a show for a community theater. We run a portable sound set up, with minimal microphones due to limited resources. Specifically, the set up is 6 Shure SLX reciever/transmitters and two Shure PGX systems. In past shows, some that I have designed and some others have designed, microphone issues are a constant issue. The most common issue is cutting in and out. What should I be doing beforehand to try to avoid these issues?
I have done a large amount of research and attended several classes on wireless microphones, all in hopes of educating myself enough to fix the issue. However, most place I look and people I have talked to suggest extra stuff, whether it be a antenna distribution system or something else in order to help our issues. Due to the limited resources often found in community theater, a distribution system or a different type of mic is just not feasible for us. What sort of actions can I be taking right now, during pre-show set up, as well as during run of show, that will help me avoid problems?
Thanks for all suggestions!

Since you're running all Shure, grab a copy of Wireless workbench from their site and input the models and bands they are in. After that, tell it your zip code and let it figure out what to set your system to. You might get more milage putting the SLX units into master list mode, as it gives the software more frequencies in the existing band to work with. I just used it to get 19 SLX, 2 UHF-R, and 2 ew500g3 units to all play nice with each other for a community production. Only RF issues I had were when an actress severed the antenna on the SLX pack she was wearing, resulting in needing a complete replacement pack.

 

[Max Warasila]

If the audience's phones mess with your wireless microphones, you have the wrong kind of wireless microphones.

Even so, tell them to turn them off anyway, and use the microphones or anything else you want as an excuse.

I also highly suggest WWB6 as a tool for doing most of the heavy lifting as far as intermod and coordination. It's quick and easy and doesn't really require a scan, even though you if you can you should.

Here's a good list of articles over at SoundForums.net, where I live more of the time:
https://soundforums.net/content/290-Optimizing-Wireless-Microphone-Systems-for-the-Real-World-Part-1
https://soundforums.net/content/397-Optimizing-Wireless-Microphone-Systems-for-the-Real-World-Pt-2
https://soundforums.net/content/453-Optimizing-Wireless-Microphone-Systems-for-the-Real-World-Pt-3
https://soundforums.net/content/115...tion-for-Live-Sound-Part-1-The-RF-Environment
https://soundforums.net/content/1957-Fundamentals-of-RF-Coordination-for-Live-Sound-Part-2-Antennas

There's also a good FAQ linked at the top of the Audio Forum here at Control Booth. If you'd like, PM me and I can walk you through some things in WWB6 or otherwise.

And oh my God, Bob, how the hell did she do that?!

 

[BobHealey]

And oh my God, Bob, how the hell did she do that?!

I don't know. Something happened, that caused both the MKE2 to pull out of the TA4 connector, and the antenna to only work when held in a specific position. The show was South Pacific, and the actress was one of the nurses. Some of the antenna damage may have been done in previous show, Shrek, where the actor with that pack had to take a stage fall. At least once he landed badly on a different pack (cut antenna in 2, broke plastic cover off from LCD screen area), but it worked until the second to last performance. And no, this was not the actress playing Nellie. Nellie's pack survived 11 showers with no issues.