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Author Topic: Issue with JBL PRX Speakers  (Read 1214 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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Greg Bartusch

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Re: Issue with JBL PRX Speakers
« Reply #10 on: September 23, 2020, 03:18:49 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.
Thanks Bill, I'll look into that.
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Greg Bartusch

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Re: Issue with JBL PRX Speakers
« Reply #11 on: September 23, 2020, 03:20:14 pm »

We're these outlets in the same room and on the same circuit breaker or not?
Everything is on the same 40A circut.
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Seth Udoll

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Re: Issue with JBL PRX Speakers
« Reply #12 on: September 23, 2020, 05:08:05 pm »

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.
Still worth eliminating the simplest possible causes, even at 100:1... IMO  Standard process of elimination.
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Seth Udoll

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Re: Issue with JBL PRX Speakers
« Reply #13 on: September 23, 2020, 05:12:10 pm »

Everything is on the same 40A circut.
You might consider what else is on that 40A circuit and just try one out at another location and see if there is any change in behavior.
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Greg Bartusch

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Re: Issue with JBL PRX Speakers
« Reply #14 on: September 23, 2020, 08:37:08 pm »

You might consider what else is on that 40A circuit and just try one out at another location and see if there is any change in behavior.
It's a dedicated 40A circuit. In my thread I mention that when I hit the speaker on the side with my hand, the crackling sound will go away. It might come back in 5 minutes or 2 hours later. My console is in the back of the club and the crackling sound is very faint and you've got to be next to the speaker to hear it. The 8.5k is only happening to 1 of the speakers. This issue has been going on for a few years now and I just deal with it. I took the speaker apart a year ago, but found visibly no issues.
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Riley Casey

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Re: Issue with JBL PRX Speakers
« Reply #15 on: September 23, 2020, 08:56:06 pm »

Some internal connection in the gain stage is likely causing this. Internal connectors, bad solder joints, something along those lines. It's going to take some component level repair skills and working with live, exposed circuitry. If you've got some background in that have at it but it's definitely one false move and you've destroyed the PC board or even sent yourself to the hospital style repair. Why do I keep stressing this? It's because if you have to ask you're probably going to have trouble.

It's a dedicated 40A circuit. In my thread I mention that when I hit the speaker on the side with my hand, the crackling sound will go away. It might come back in 5 minutes or 2 hours later. My console is in the back of the club and the crackling sound is very faint and you've got to be next to the speaker to hear it. The 8.5k is only happening to 1 of the speakers. This issue has been going on for a few years now and I just deal with it. I took the speaker apart a year ago, but found visibly no issues.
« Last Edit: September 23, 2020, 08:58:21 pm by Riley Casey »
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Scott Holtzman

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Re: Issue with JBL PRX Speakers
« Reply #16 on: September 24, 2020, 02:31:00 am »

Some internal connection in the gain stage is likely causing this. Internal connectors, bad solder joints, something along those lines. It's going to take some component level repair skills and working with live, exposed circuitry. If you've got some background in that have at it but it's definitely one false move and you've destroyed the PC board or even sent yourself to the hospital style repair. Why do I keep stressing this? It's because if you have to ask you're probably going to have trouble.


The modules are really inexpensive from JBL.  A few hours of bench time and you are upside down.  Be careful spending money on low value items. 
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Scott AKA "Skyking" Holtzman

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Bill Meeks

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Re: Issue with JBL PRX Speakers
« Reply #17 on: September 24, 2020, 08:50:26 am »


The modules are really inexpensive from JBL.  A few hours of bench time and you are upside down.  Be careful spending money on low value items.

Scott makes the best point. Most of today's electronics is just not worth the hassle of repairing at the component level on a circuit board. There are aggravations of multilayer boards, surface-mounted devices and chip resistors and capacitors so damn small that a guy my age can't even see them anymore ...  ;D.

I was trained and worked for a large part of my life repairing analog and digital things at the component level, but I saw that need slowly fade away over the years as new technology took hold. Unless it's something really simple like an obvious dangling connector or visible corrosion, it might be easiest to simply replace the amp module.
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Jim Thorn

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Re: Issue with JBL PRX Speakers
« Reply #18 on: September 25, 2020, 02:34:21 am »

In my years as a bench tech, I have run into a few cases where low level random crackles and oscillations have been due to a loose or oxidized mounting screw on a circuit board.  Often, one of the board's mounting screws is used as the only connection between the board's signal ground and the chassis ground.  If that is the case, the screw will usually have a star washer, and it will be on a solder pad of the board.  If the screw or washer's solid connection to the solder pad is compromised, you can get a variety of gremlins.  The fix is simple and safe -- back the screw out a half turn, then re-snug it.  Check each board in the device.  If that was not your problem, you've done no harm.  Certainly worth a try!

Jim Thorn
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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Marc Vangrunderbeek

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Re: Issue with JBL PRX Speakers
« Reply #19 on: September 25, 2020, 06:18:14 am »

I've had the same problem, crackling noise.
After a few months, when I took my wifi over powerline extender out of the wall socket, the noise was gone.
Maybe you have the same problem in the building?
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Dave Guilford

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Re: Issue with JBL PRX Speakers
« Reply #20 on: September 25, 2020, 09:02:13 am »

Prx500 series was known for crummy amp modules
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Greg Bartusch

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Re: Issue with JBL PRX Speakers
« Reply #21 on: September 25, 2020, 10:06:34 pm »

I've had the same problem, crackling noise.
After a few months, when I took my wifi over powerline extender out of the wall socket, the noise was gone.
Maybe you have the same problem in the building?
The WiFi router is in another room about 10' away. It's not on any stage circuit, but I'll definitely put that on my checklist. Thanks.
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Jim Layton

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Re: Issue with JBL PRX Speakers
« Reply #22 on: October 27, 2020, 08:51:36 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

I have the PRX 600 series and the latest 800 series. The 600s were bought after the "amp reliability" problem was corrected-second gen?. I forget what the issue was. My 600s have worked well for many years, BUT the 615s (monitors) started having the crackling issues you describe. I went through all the recommended steps everyone mentioned. Turns out the amps were about to die. The crackling came and went randomly. The cabs never failed during an event. Then one by one they just would not fire up pre-show. I think, if I remember correctly, the power light flickers and the amp shuts down. It won't stay on. I replaced the amp on one cabinet and it has been working fine. I saw on Ebay there was a guy in the Philly area that sold an "amp repair" for this issue at a flat rate but the new amp was only slightly more. He also sold used amp plates. When my other amp went I discovered there were no new amps available from the major distributors. The Ebay guy does not appear to offer the repairs. I bought a number of the new PRX 800 monitors to replace the 600s. That is my crackle experience.
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Re: Issue with JBL PRX Speakers
« Reply #22 on: October 27, 2020, 08:51:36 am »


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