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Author Topic: Current model JBL SRX boxes induce buzz in mic cables/channels  (Read 3636 times)

Greg_Cameron

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Re: Current model JBL SRX boxes induce buzz in mic cables/channels
« Reply #10 on: September 15, 2018, 04:08:49 pm »

Ok, I had some spare time this morning to do a solid experiment. Behold the power of the demonstration:


https://youtu.be/yojkSrE2yDE




I had mentioned previously that the SRX amp module gives off a similar mechanical buzz to the one that's induced into the mic cables:


https://youtu.be/5hSmih-P0Hs


And yet another annoying issue with the SRX-p boxes - frequency dependent mechanical buzz:


https://www.youtube.com/watch?v=cHzi2_51JL0


Greg







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Art Welter

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Re: Current model JBL SRX boxes induce buzz in mic cables/channels
« Reply #11 on: September 15, 2018, 06:28:18 pm »

Ok, I had some spare time this morning to do a solid experiment. Behold the power of the demonstration:
Greg,

Yeah, that's nasty, can easily hear it over my tinnitus ;^). I can remember that noise from when I placed a direct box too close to a cheap switching PSU amp on stage several years back.

It's almost expected that a crap PSU from a widgit, computer or cheap light dimmer may radiate noise from it's AC cord, but sad when a "pro" audio device does.

As you suggested in your OP, the noise can probably can be eliminated (or attenuated) with snap on ferrite beads on the offending AC cords (sometimes both ends), though you may even want to add them to the vocal mic cords that have to live in the mess. If it were not for warranty issues, putting the ferrite beads inside the speakers would be goood- you might dampen that funky 200 Hz resonant buzz too.

http://audiosystemsgroup.com/SAC0305Ferrites.pdf

RF noise problems radiating from PSUs seems to be common, (disclaimers abound for all sorts of digital devices) fortunately there are a lot of cheap ferrite beads available in various sizes and types to fix problems that should have been taken care of within the offending devices.

Art




« Last Edit: September 15, 2018, 06:46:21 pm by Art Welter »
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Greg_Cameron

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Re: Current model JBL SRX boxes induce buzz in mic cables/channels
« Reply #12 on: September 16, 2018, 12:07:16 am »

Greg,

Yeah, that's nasty, can easily hear it over my tinnitus ;^). I can remember that noise from when I placed a direct box too close to a cheap switching PSU amp on stage several years back.

It's almost expected that a crap PSU from a widgit, computer or cheap light dimmer may radiate noise from it's AC cord, but sad when a "pro" audio device does.

As you suggested in your OP, the noise can probably can be eliminated (or attenuated) with snap on ferrite beads on the offending AC cords (sometimes both ends), though you may even want to add them to the vocal mic cords that have to live in the mess. If it were not for warranty issues, putting the ferrite beads inside the speakers would be goood- you might dampen that funky 200 Hz resonant buzz too.

http://audiosystemsgroup.com/SAC0305Ferrites.pdf

RF noise problems radiating from PSUs seems to be common, (disclaimers abound for all sorts of digital devices) fortunately there are a lot of cheap ferrite beads available in various sizes and types to fix problems that should have been taken care of within the offending devices.


It's pretty disappointing. While these boxes have a lot of output, features, and sound good, they have some real shortcomings. Along with my review where I point out the cabinet buzzes, flimsy grills, and delicate, unprotected controls, I guess I have to add "RF noise generator." While these aren't the most expensive boxes, they're also not cheap. Street is $1100-$1300 new.


I've contacted support today with a full written assessment and a link to the video. Maybe they're aware of the issue(s) and have service bulletins to address them. I'll post back when I get a response. They must have sold a shit-ton of these by now. I can't believe nobody else has complained.


Cheers,
Greg
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Greg_Cameron

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Re: Current model JBL SRX boxes induce buzz in mic cables/channels
« Reply #13 on: September 20, 2018, 02:08:47 pm »

Does anyone by chance have a direct support email address for JBL in Northridge? They're not returning my support inquires via the website.


Thanks,
Greg
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Jean-Pierre Coetzee

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Re: Current model JBL SRX boxes induce buzz in mic cables/channels
« Reply #14 on: September 23, 2018, 02:23:32 am »

Must be quite a lot of buzz to get past CMR on the mic cables...

How are your connectors terminated? Do you have the shell terminated to pin 1 or is the shell floating, have you tried it the other way?

Does your cables have a braided shield?

You say that you encounter this issue with multiple consoles so I doubt that there is any issue there.

I've had similar issues with mics on random stages, cable test as correct with MM and cable tester yet is buzzes, swap out cable with another and it is fine so I just end up retiring the cable.

regarding switch mode power supplies, I know HAM radio guys hate them because of the RF they spew out, very few have correct PF correction and RF shielding and even then the only place for the RF to go when it is shielded is to the ground connector.

I would check impedance to ground on your distros as well, this is a test probably best done by a decent electrician but may actually reveal your problem, could be some corrosion on a connector or something causing a higher than normal impedance to ground.
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Greg_Cameron

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Re: Current model JBL SRX boxes induce buzz in mic cables/channels
« Reply #15 on: September 23, 2018, 03:41:46 am »

Must be quite a lot of buzz to get past CMR on the mic cables...

How are your connectors terminated? Do you have the shell terminated to pin 1 or is the shell floating, have you tried it the other way?

Does your cables have a braided shield?

You say that you encounter this issue with multiple consoles so I doubt that there is any issue there.

I've had similar issues with mics on random stages, cable test as correct with MM and cable tester yet is buzzes, swap out cable with another and it is fine so I just end up retiring the cable.

regarding switch mode power supplies, I know HAM radio guys hate them because of the RF they spew out, very few have correct PF correction and RF shielding and even then the only place for the RF to go when it is shielded is to the ground connector.

I would check impedance to ground on your distros as well, this is a test probably best done by a decent electrician but may actually reveal your problem, could be some corrosion on a connector or something causing a higher than normal impedance to ground.


The shell is floating. As shown in the video, the issue clears when the exact power cable is plugged into an EV powered speaker. There is no signal cable plugged into either speaker, so the noise is self generated and not related to a ground loop. The JBL is the noise source. Mic cables in this test are new Whirlwind MK4 series which are good cables: [size=78%]http://whirlwindusa.com/catalog/pre-wired-cables/microphone/mk-series[/size] . But it also happens with Canare quad mic cables. This issue occurs with my distro as well as non-related power in more than 1 venue. It's not the power. It's not the mic cable. It's not the console. I'm waiting for an order of ferrite beads to arrive to see if that mitigates the issue. I've tried reaching JBL support to discuss the issue several times this past week and have received no response yet. Their customer service so far is disappointing.


Greg
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Robert Lunceford

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Re: Current model JBL SRX boxes induce buzz in mic cables/channels
« Reply #16 on: September 24, 2018, 12:49:32 am »

That is some nasty buzz, electrical and mechanical. Do all of your SRX boxes have this same issue or is it just one?
It is surprising that with the large number of forum members using SRX speakers, that no one else has reported this issue.
I have only heard SRX speakers being used at a local outdoor event. I haven't been impressed with them at all, especially considering their girth. But then again, I haven't been impressed with the people running the system so it may be operator error.
Too bad that JBL service seems to be MIA. You never know what you are going to get once a company changes hands. I wonder if you would get better response if you were calling about one of their "professional" products.
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Debbie Dunkley

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Re: Current model JBL SRX boxes induce buzz in mic cables/channels
« Reply #17 on: September 24, 2018, 09:30:23 am »


I have only heard SRX speakers being used at a local outdoor event. I haven't been impressed with them at all, especially considering their girth. But then again, I haven't been impressed with the people running the system so it may be operator error.


That HAS to be down to the system operators - the SRX speakers are excellent sounding speakers as has been attested to so many times on this forum.
The buzzing?.... well not sure what to say about that. Maybe someone could try to duplicate the condition to check theirs - me included if I get time....
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Debbie Dunkley

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Re: Current model JBL SRX boxes induce buzz in mic cables/channels
« Reply #18 on: September 24, 2018, 12:14:16 pm »

OK... so of course I couldn't resist and I just set up my 2 SRX812's ( a bit easier to get to than my SRX815's), my little analog Peavey mixer and an SM 58  as you describe - same power to all and running the cables together as you show on the video. The only difference is that my little mixer has TRS outputs instead of XLR.
I cannot get either speaker to buzz at all whether the faders are up or not. I hear the usual quiet hiss when I push fader up but no buzz.

To add a few things.... I used an inexpensive XLR cord to the mic, along with an inexpensive XLR >TRS speaker cord and mains cords also - so nothing fancy. I ran the test in my garage which is where I drew power through a 3 tap 16 gauge short extension cord.
« Last Edit: September 24, 2018, 12:30:06 pm by Debbie Dunkley »
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Steve Garris

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Re: Current model JBL SRX boxes induce buzz in mic cables/channels
« Reply #19 on: September 24, 2018, 02:19:55 pm »

That HAS to be down to the system operators - the SRX speakers are excellent sounding speakers as has been attested to so many times on this forum.
The buzzing?.... well not sure what to say about that. Maybe someone could try to duplicate the condition to check theirs - me included if I get time....

I can also attest to the great sound quality of these boxes. This was my second year using them for an outdoor park concert series, for crowds up to 1000.

I think I did hear (once) a rouge rattle when we were pushing the vocals hard, but that was the only time I've heard anything weird from these boxes. I have not experienced the hiss that Greg is describing.
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