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Author Topic: Sound issue diagnosis  (Read 952 times)

Josh Givens

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Sound issue diagnosis
« on: December 02, 2013, 01:15:57 pm »

This is my first post here.  We haven't gotten a pro sound tech to our church for this issue yet, but I thought I'd ask here and see if the collective intelligence of this group could help with our problem.

We have several wireless mics.  Mostly Analog Shure SM58 models.  We also have 2 Shure SM58 digital models.  Our digital mics have some sort of interference that causes them to be problematic for singers on our praise team or the song leader or just in general.  I used one of the digital microphones for some time with no issues, then suddenly, the two digital mics we have started making "noise" for lack of a more professional term.  They tick, in almost a rhythmic fashion once they are more than 10-15 ft from the receiver.  It has to be intereference of some sort, but I can't figure out what.  None of the analog mics have this problem.

I literally went though every powered item in the entire auditorium and disconnected power from each component, one at a time, and was unable to eliminate the noise.

We've come to the conclusion that we're likely going to just replace the digitals with analogs, but I thought I might check here for suggestions.

Thanks,

Josh
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dick rees

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Re: Sound issue diagnosis
« Reply #1 on: December 02, 2013, 03:38:07 pm »

This is my first post here.  We haven't gotten a pro sound tech to our church for this issue yet, but I thought I'd ask here and see if the collective intelligence of this group could help with our problem.

We have several wireless mics.  Mostly Analog Shure SM58 models.  We also have 2 Shure SM58 digital models.  Our digital mics have some sort of interference that causes them to be problematic for singers on our praise team or the song leader or just in general.  I used one of the digital microphones for some time with no issues, then suddenly, the two digital mics we have started making "noise" for lack of a more professional term.  They tick, in almost a rhythmic fashion once they are more than 10-15 ft from the receiver.  It has to be intereference of some sort, but I can't figure out what.  None of the analog mics have this problem.

I literally went though every powered item in the entire auditorium and disconnected power from each component, one at a time, and was unable to eliminate the noise.

We've come to the conclusion that we're likely going to just replace the digitals with analogs, but I thought I might check here for suggestions.

Thanks,

Josh

Josh...

Try a Google search for "wireless digital microphone interference" and do some reading.

Sounds like you've taken a good approach to start.  I imagine you've asked yourself "what changed?".

Is there a clear line of sight path between the transmitters and receivers?
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Mac Kerr

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Re: Sound issue diagnosis
« Reply #2 on: December 02, 2013, 03:53:30 pm »

They tick, in almost a rhythmic fashion once they are more than 10-15 ft from the receiver.  It has to be intereference of some sort, but I can't figure out what.  None of the analog mics have this problem.

I literally went though every powered item in the entire auditorium and disconnected power from each component, one at a time, and was unable to eliminate the noise.

We've come to the conclusion that we're likely going to just replace the digitals with analogs, but I thought I might check here for suggestions.

Without knowing the exact make and model of the transmitter and receiver it is very difficult to offer an informed suggestion.

In addition to the make and model, what kind of antennas, antenna cable, how are the antennas positioned, and how far is it from the transmitter to the receiver?

Mac
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Cyrus Masters

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Re: Sound issue diagnosis
« Reply #3 on: December 02, 2013, 09:03:39 pm »

  If they both started cutting up at the same time, I would go for a walk outside to see it there is a new cell tower or something. Who knows, maybe a new microwave in the nursery. One thing to try in trouble shooting is to take them some where else and see if it REALLY is the units. Just my poor 2 cents.
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Jerome Malsack

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Re: Sound issue diagnosis
« Reply #4 on: December 03, 2013, 08:53:01 am »

I concur with a test at another location.  RFI can be from a source outside the building.  What is the Frequency band?  2.4     500    600.   This can help also.

What are you Digital TV stations? is your frequencies in same area?    LED Lighting on DMX??  some Video walls of LED have caused troubles. 
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Josh Givens

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Re: Sound issue diagnosis
« Reply #5 on: December 03, 2013, 11:09:49 am »

I realized, after posting this, that I should have gathered more information first.  I'll get the exact specs tonight and post the info.  We're going to test relocating the receivers to an alternate power source and location to see if the problem continues.

I'm fairly certain that the 2 digital systems we are having problems with are Shure PGXD4/PGXD2 with SM58 heads.

I'm not the "sound guy" at our church.  I'm the deacon over worship ministries and the song leader.  However, the tech stuff is directly related to my involvement and I'm just trying to assist.

Thank you for the suggestions thus far with the limited info I've provided.  To address some suggestions, we aren't using any LED lighting.  The receiver is up in the sound booth, around 100 ft from the stage, maybe a little less.  We have a balcony with a 6" glass "wall" on top of the 3-4' wall that makes the ledge on the edge of the balcony.  The receivers sit on this ledge in the sound booth, in direct view of the stage, other than the piece of glass.  I've tested the issue while in the sound booth and I only need to travel around 15 feet from the receiver to get the interference I described.  I was the only person in the building at the time of the testing.  However, I'm becoming highly suspicious of the new wireless router that was added in our office.  That idea just popped in my mind as I was typing.  I'll test that tonight.

Speaking to the frequencies mentioned earler.  We are going to go ahead and order two more wireless systems since we will eventually need them anyway.  I need to do some more reading on what the differences are good/bad/indifferent on these options.

Shure PGX4/PGX2 combo with SM58 head (L5 644-662MHz)

or

Shure PGX4/PGX2 combo with SM58 head (H6 524542 MHz)

These are the same combos (non-digital) as we have currently.  I'm not certain as to the frequencies of our current equipment.
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Jerome Malsack

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Re: Sound issue diagnosis
« Reply #6 on: December 03, 2013, 11:49:15 am »

The wifi should not have any impact on your receivers. 

Is there any other digital gear near the receivers. 

each receiver should be separated from each other by 6 inchs

other digital gear in the mixer room can cause trouble.   AD/DA conversions.
digital effects,  Feedback suppressor,  Digital mixer.   move the receivers away from these. 

http://www.shure.com/americas/support/training/materials

They also have a tool to ensure wireless usage and problems

 Frequency Coordination for Wireless Systems Webinar
August 23, 2012
Presenter: Gino Sigismondi
Watch Presentation


 Troubleshooting Wireless Microphone Systems
March 18, 2013 / March 20, 2013
Presenter: Tim Vear
Watch Presentation

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Josh Givens

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Re: Sound issue diagnosis
« Reply #7 on: December 04, 2013, 08:48:30 am »

Last night I moved one of the receivers down to a port on the stage and tried it from there.  Still got the same ticking/clipping sound that I was getting with the receiver in the booth once I was more than 10-15 feet from the receiver.  I tried adjusting the gain in the mic, that didn't help.  It was late, so I didn't mess with trying an alternate channel.  I may try that from up in the booth tonight since I know it's not happening based on the location of the receiver.

I will try taking the receiver home or to another location to completely rule out interference in the building or outside.

For more info, we're using a Mackie CFX 16 MK2 Channel Mixer

The only other new equipment I can think of is a wireless HDMI system we put in for a screen down in front of the stage.  I disconnected the power to this when I was testing before.

I'll look at the tools suggested above and see if I can find a solution there.
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Cailen Waddell

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Re: Sound issue diagnosis
« Reply #8 on: December 04, 2013, 12:38:55 pm »

Pgxd is 900 MHz I think. It's an iffy band sometimes, some wisps use it for last mile service, I know our traffic department in my town uses 900 MHz wireless transmitters for communication with traffic control systems where they can't get fiber (for one reason or another).

In short - this problem may be out of your control

Otoh - maybe one of the office people got a new cordless phone?
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Jerome Malsack

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Re: Sound issue diagnosis
« Reply #9 on: December 04, 2013, 03:48:39 pm »

Garage door openers are also in the 900.  but this would be a one time transmit to open and close not one hour constant with pops and clicks.  The phone would make sense as it is always talking back and forth from the base to the phone. 

Are there any fluorescent lights in the room next to your hall?  You turned off everything in the room.  Might look at the two or three rooms adjacent. 

Along with proximity to street and street lights or systems.   I worked with one church right on the street and as the truckers went by their CB's would get in on a bad wire running from the organ to the amps for the speakers.   
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