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Author Topic: Curious CL pan/polarity weirdness  (Read 4677 times)

Mac Kerr

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Re: Polarity check
« Reply #10 on: May 28, 2015, 11:59:46 PM »


Unfortunately I can't. They are dead hung ~26 feet over the stage, cabled from above and the NL8 cables are run only long enough to make it to the speakers when they are in the air. We have to go up on top of our lighting bridge to disconnect them when we bring them in.


I guess I could make a bunch of NL8 extensions....  :o

No man lift you can get close with? Attach the mic to a long stick so you can get it in front of each driver and at least check them. You can deal with any issues whenever you can get to them.

A basic polarity checker will let you work through the whole signal chain to discover where it might go wrong. From this thread it sounds like you haven't been able check anything yet. So far the only test is that the road guy thought it didn't sound right. He might not be right.

Mac
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Justice C. Bigler

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Re: Polarity check
« Reply #11 on: May 29, 2015, 12:04:59 AM »

From this thread it sounds like you haven't been able check anything yet. So far the only test is that the road guy thought it didn't sound right. He might not be right.


That is correct. I will have to wait until next week to go through the system thoroughly. I might be able to get a lift close, but the array is right over the edge of the stage at the downstage edge of the pit. I don't know that I can get the outriggers positioned safely to get it up that high.
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Merlijn van Veen

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Re: Curious CL pan/polarity weirdness
« Reply #12 on: May 29, 2015, 01:36:26 AM »

A polarity inversion will light up like a Christmas tree on a dual-channel analyzer e.g. Smaart. Even individually mis wired drivers are fairly easy to spot.   

Geri O'Neil

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Re: Curious CL pan/polarity weirdness
« Reply #13 on: May 29, 2015, 06:59:55 AM »

Several years ago, I was tasked with checking the polarity of the components of the house system installed in a local auditorium. This was as a result of a theater road show engineer that complained of "major phase issues" in the system (red flag #1).

As the system couldn't be brought in, I had figure out how to get my Cricket in front of the speaker (JBL custom shop AM series, I think). The first idea was to affix the receiver end of the cricket to a long pole, lower it down from the light bridge to the front of the cabinet, and observe the results (red or green LED) from the ground wth binoculars. However, that idea failed because the white screen material in front of the boxes turned out to be too thick to see the Cricket through it.

We finally lowered a stagehand down in front of the cabinets in a harness with the cricket receiver. This was a left/center/right system, each cluster utilizing a 2-way down-fill, a 2-way main box, and a 2-way long-throw box for the balcony, in addition to some 15" low boxes and a double-18 box on each side (I'm not 100% sure of all of this, the original installer is a friend of mine and might this and correct me).  Point being, there was a lot of components to check and the guy in the harness had to be brought up every 20 minutes or so because of the harness (we learned about the proper harness to use for such work that day!), so this all made for a long day for everyone involved.

And no problems were found. We checked the rig with the Cricket connected to the console and powering up and down the individual amp channels. No problems. At the end of the day, it finally occurred to me to ask if they observed the road guy as he was checking the rig and with what. They said he walked the room, then used something like my Cricket. Okay, but how was he checking things? Oh, he checked left, then center, then right. The entire rig popping at once? Yes. And he went to the local show buyer later that night and reported "all kinds of phase issues with the house system". Now I'm wishing I asked this question before we spent all day checking things.

So this can and does happen, Justice. It's certainly worth checking out, but don't be surprised if you don't find any problems with your system. Especially after reading about your observations during the show.

The local union guys in this situation told me that the show sounded very good, but it doesn't mean that he was good at diagnosing system problems.
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Riley Casey

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Re: Polarity check
« Reply #14 on: May 29, 2015, 10:33:16 AM »

Transfer function test each subset of boxes that you can conviniently whittle down to by muting amp channels.  Use a fishpole ( window washer extension pole comes to mind ) to get the mic as close as possible.  Phase trace should at least tell you which boxes or pairs of boxes ( depending on how things are wired )  are different from other others on polarity if indeed there are simple polarity issues.


Unfortunately I can't. They are dead hung ~26 feet over the stage, cabled from above and the NL8 cables are run only long enough to make it to the speakers when they are in the air. We have to go up on top of our lighting bridge to disconnect them when we bring them in.


I guess I could make a bunch of NL8 extensions....  :o

Josh Millward

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Re: Curious CL pan/polarity weirdness
« Reply #15 on: May 29, 2015, 01:21:26 PM »

The push / pull rods from Music Supply Company would be perfect for use in this situation. They are 2 feet long by around 1/2" to 5/8" diameter each and thread together quickly and easily. If you had some of these, it would be easy to make a long pole that you could stick down in front of the loudspeakers from above and monitor the LED read out.

Otherwise, I would suggest getting a golf ball retriever (for fishing golf balls out of the water or other places) from a golf store. They are generally not as robust as the Music Supply Company sticks, but they also cost less and are probably more readily available. Only problem is that they only get about so long whereas with the Music Supply Company poles, you can make it as long as you want, if you have enough poles.
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Josh Millward
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Helge A Bentsen

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Re: Curious CL pan/polarity weirdness
« Reply #16 on: May 29, 2015, 02:39:06 PM »

Depending on the array layout, lowering a measurement mic from above down the array with a mic cable is good enough for spotting major issues.
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ProSoundWeb Community

Re: Curious CL pan/polarity weirdness
« Reply #16 on: May 29, 2015, 02:39:06 PM »


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