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Author Topic: Issue with JBL PRX Speakers  (Read 1216 times)

Greg Bartusch

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Issue with JBL PRX Speakers
« on: September 22, 2020, 07:41:44 pm »

I've got a pair of PRX525 in a cub I work at. The issue(s) I am having are. When the speakers are turned on and  there  is nothing playing through the speakers , I can hear (and this happens with both speakers) a faint crackling noise. I also explain the sound like crumpling up a paper bag, but 1/4 the volume. The way I eliminate the crackle noise is by hitting the side of the speaker or turning off/turning on the speaker, but usually later the noise may come back.  I've taken the speaker apart in the past and it has the enclosed Crown amplifier inside. I've checked the connections inside and didn't notice anything wrong visually. Anyone have any idea what could cause this?
Also another issue I am having is one  of the speakers has a 8.5k squeal coming out of it, and that's been recent and Ive tried ground lifting the plug, and changing the "D" plug as well with no change. Any suggestions would be great.  Thanks all. -Greg
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Riley Casey

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Re: Issue with JBL PRX Speakers
« Reply #1 on: September 22, 2020, 09:27:14 pm »

Sounds very much like oxidized connectors in the gain stage of the amplifier module. Solution is to open the amp and polish any internal connectors ( if they are large enough, say .156 spacing ) or simply repeatedly unmate and mate  any smaller pin connectors to wipe the mating surfaces. If any of this is unfamiliar it's time to have an electronics tech look at it.

Greg Bartusch

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Re: Issue with JBL PRX Speakers
« Reply #2 on: September 22, 2020, 10:53:17 pm »

Sounds very much like oxidized connectors in the gain stage of the amplifier module. Solution is to open the amp and polish any internal connectors ( if they are large enough, say .156 spacing ) or simply repeatedly unmate and mate  any smaller pin connectors to wipe the mating surfaces. If any of this is unfamiliar it's time to have an electronics tech look at it.
I'll definitely try that out. I've been in the trenches with this speaker before. Is my second issue with the 8.5k the same reason as well, with oxidized connectors? Thank you for the help.
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Steve Litscher

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Re: Issue with JBL PRX Speakers
« Reply #3 on: September 23, 2020, 10:32:42 am »

I'll definitely try that out. I've been in the trenches with this speaker before. Is my second issue with the 8.5k the same reason as well, with oxidized connectors? Thank you for the help.

Do you have any other speaker(s) that you could plug-in to see if it's really the speaker that's causing the noise? It seems odd to me that a speaker would start producing an 8.5kHz tone all by itself, but stranger things have happened, I suppose.

I'd beg/borrow/rent/swap another speaker on that connection and see what happens.

Seth Udoll

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Re: Issue with JBL PRX Speakers
« Reply #4 on: September 23, 2020, 10:46:27 am »

I've got a pair of PRX525 in a cub I work at. The issue(s) I am having are. When the speakers are turned on and  there  is nothing playing through the speakers , I can hear (and this happens with both speakers) a faint crackling noise. I also explain the sound like crumpling up a paper bag, but 1/4 the volume. The way I eliminate the crackle noise is by hitting the side of the speaker or turning off/turning on the speaker, but usually later the noise may come back.  I've taken the speaker apart in the past and it has the enclosed Crown amplifier inside. I've checked the connections inside and didn't notice anything wrong visually. Anyone have any idea what could cause this?
Also another issue I am having is one  of the speakers has a 8.5k squeal coming out of it, and that's been recent and Ive tried ground lifting the plug, and changing the "D" plug as well with no change. Any suggestions would be great.  Thanks all. -Greg
  • Do these issues occur both with and without anything (other than power) hooked up to the speaker?
  • Have you tried plugging the power in to other power outlets on various power circuit breakers at your location?
« Last Edit: September 23, 2020, 10:49:21 am by Seth Udoll »
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Greg Bartusch

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Re: Issue with JBL PRX Speakers
« Reply #5 on: September 23, 2020, 12:17:53 pm »

Do you have any other speaker(s) that you could plug-in to see if it's really the speaker that's causing the noise? It seems odd to me that a speaker would start producing an 8.5kHz tone all by itself, but stranger things have happened, I suppose.

I'd beg/borrow/rent/swap another speaker on that connection and see what happens.
[/q
The speaker has the 8.5k with no xlr plugged into it, so nothing outside is causing it. I've got stage monitors to try, but like I said, it happens w/o xlr connected. Thanks for getting back to me.
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Greg Bartusch

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Re: Issue with JBL PRX Speakers
« Reply #6 on: September 23, 2020, 12:21:10 pm »

  • Do these issues occur both with and without anything (other than power) hooked up to the speaker?
  • Have you tried plugging the power in to other power outlets on various power circuit breakers at your location?
and the 8.5k is still there as well.
Yes, I have plugged the power into other outlets and have also disconnected the xlr and it still crackles
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Bill Meeks

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Re: Issue with JBL PRX Speakers
« Reply #7 on: September 23, 2020, 12:52:30 pm »

You may have a failed or failing electrolytic capacitor in the power amp module. That kind of failure can lead to several weird things, possibly including high frequency parasitic oscillations. A cold solder joint is also a possibility, I guess.
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Seth Udoll

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Re: Issue with JBL PRX Speakers
« Reply #8 on: September 23, 2020, 02:59:19 pm »


Yes, I have plugged the power into other outlets and have also disconnected the xlr and it still crackles and the 8.5k is still there as well.

We're these outlets in the same room and on the same circuit breaker or not?
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Tim McCulloch

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Re: Issue with JBL PRX Speakers
« Reply #9 on: September 23, 2020, 03:12:02 pm »

We're these outlets in the same room and on the same circuit breaker or not?

10:1 it's not an issue with the AC power.  The volts come from the same place, and if the neutral is contaminated by a PSU that dumps harmonics, it's gonna be everywhere, not just in 1 circuit.
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Re: Issue with JBL PRX Speakers
« Reply #9 on: September 23, 2020, 03:12:02 pm »


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