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[Preston Smith]

Hello all. I need help. If too long for you, see TL;DR at bottom.
I'm working on building a small sound reinforcement system for my backyard stage. So far we have: Electro Voice BK-2442 mixer>Crown X3000>the JBL's... one of which is proving to be super problematic.

I picked these up for $150 for the pair, not having heard them, or even heard about them as the seller knew nothing about the speakers or even audio in general. The only info I could coax out of him was that he was selling them for a widow who's late husband had them once upon a time. He knew they were last sitting in a shabby barn, he didn't know for how long. Didn't even know how long the guy had been dead for.

So when I got home I plugged em in, got a signal into my board, set to unity, then eased the gain on my amp an ever so modest 3 clicks from all the way down. They warmed up ok, although I noticed a pretty stark tonal difference in the two- the right one was markedly muddier. I started making sure all drivers were working, which they seem to be. As I'm messing around on the board panning left and right and switching the speakers trying to pinpoint the difference in tone, the speaker on the left cuts out and I'm like wtf... the left stereo fader isn't doing anything, but the right is working fine. Then as I'm bringing it up theres a small pop and bam it's running again. Few minutes later the right one does the same thing, only it never cuts back in. Now when I bring the faders up to unity, the left one fires away and right has signal, but VERY weak. If I turn back down the signal to the left speaker all the way I can hear the guitar loop I've got going coming from the right, but it's almost like when you turn off your speakers and can still hear the music coming from the record.

Too Long;Didn't Read:
Speakers worked for about 10 minutes, then right cut out and is only playing a very faint signal.

Like I said, I took the channel that was running into the right speaker and plugged it into the left, and the left worked fine. So I think I've narrowed it down to a speaker problem and now have no idea what to do.

Judging by the looks of the hot glue job on the crossover, complete with melted and scorched brown glue dripping down a couple components I'm guessing it's probably that. At least I'm sure as hell hoping that's just hot glue.

So.. What do I do?

Thanks everybody for any thoughts you may have.

[Ivan Beaver]

So when I got home I plugged em in, got a signal into my board, set to unity, then eased the gain on my amp an ever so modest 3 clicks from all the way down. They warmed up ok, although I noticed a pretty stark tonal difference in the two- the right one was markedly muddier. I started making sure all drivers were working, which they seem to be. As I'm messing around on the board panning left and right and switching the speakers trying to pinpoint the difference in tone, the speaker on the left cuts out and I'm like wtf... the left stereo fader isn't doing anything, but the right is working fine. Then as I'm bringing it up theres a small pop and bam it's running again. Few minutes later the right one does the same thing, only it never cuts back in. Now when I bring the faders up to unity, the left one fires away and right has signal, but VERY weak. If I turn back down the signal to the left speaker all the way I can hear the guitar loop I've got going coming from the right, but it's almost like when you turn off your speakers and can still hear the music coming from the record.

From your description, it sounds like more of a mixer problem, or possibly a cable problem.

Or else I am not understanding what you are meaning.  Specifically the section in RED

[Riley Casey]

how this gets handled in a sound company warehouse:

1- Connect a smart phone with a signal generator app to an amplifier
2-Play a sweep tone from 40 Hz to 5000 hz to each speaker in turn at a loud enough level that you have to yell to talk over it listening for distortion
3-Play a piece of music  that your familiar with thru each speaker in turn listening for the expected tonal balance
4- if a speaker fails the tone test remove the distorted driver and retest outside the cabinet, recone or repair as required
5- if a speaker fails the music test remove all drivers and test individually with tone. Make sure the lowest frequency tone is appropriate for the driver under test.
6- after confirming that all drivers are working and repairing any that aren't remove the crossovers and send them to someone who can fix them.

I could go on for a few more paragraphs about what a sound shop would do to troubleshoot and repair passive crossovers but in your situation just pull them and send them out for repair. Without test equipment and training the best you can do is find gross failures like open components and even that requires a fair amount of skill and knowledge. Passive crossovers also suffer from much more subtle failures like components changing values from being over powered.

If you're not skilled at setting up and using sound systems buying cheap used gear may not be your best course.

[Mike Caldwell]

That era of JBL SR speakers used 1/4 inch switch jacks to automatically do the switching between full range and bi-amp operation. Everyone I have known that used or even still uses that series of the JBL SR speakers had problems with the switching jacks.

I have repaired maybe a dozen various SR speakers with those 1/4 jacks in a few different ways, hard wiring the the speaker to operate in bi-amp and install a speakon, hard wiring passive and using a speakon or install a heavy duty four pole switch.

Try cleaning the jacks and working them with a plug may help.....at least for a while.

   

[Stu McDoniel]

Hello all. I need help. If too long for you, see TL;DR at bottom.
I'm working on building a small sound reinforcement system for my backyard stage. So far we have: Electro Voice BK-2442 mixer>Crown X3000>the JBL's... one of which is proving to be super problematic.

I picked these up for $150 for the pair, not having heard them, or even heard about them as the seller knew nothing about the speakers or even audio in general. The only info I could coax out of him was that he was selling them for a widow who's late husband had them once upon a time. He knew they were last sitting in a shabby barn, he didn't know for how long. Didn't even know how long the guy had been dead for.

So when I got home I plugged em in, got a signal into my board, set to unity, then eased the gain on my amp an ever so modest 3 clicks from all the way down. They warmed up ok, although I noticed a pretty stark tonal difference in the two- the right one was markedly muddier. I started making sure all drivers were working, which they seem to be. As I'm messing around on the board panning left and right and switching the speakers trying to pinpoint the difference in tone, the speaker on the left cuts out and I'm like wtf... the left stereo fader isn't doing anything, but the right is working fine. Then as I'm bringing it up theres a small pop and bam it's running again. Few minutes later the right one does the same thing, only it never cuts back in. Now when I bring the faders up to unity, the left one fires away and right has signal, but VERY weak. If I turn back down the signal to the left speaker all the way I can hear the guitar loop I've got going coming from the right, but it's almost like when you turn off your speakers and can still hear the music coming from the record.

Too Long;Didn't Read:
Speakers worked for about 10 minutes, then right cut out and is only playing a very faint signal.

Like I said, I took the channel that was running into the right speaker and plugged it into the left, and the left worked fine. So I think I've narrowed it down to a speaker problem and now have no idea what to do.

Judging by the looks of the hot glue job on the crossover, complete with melted and scorched brown glue dripping down a couple components I'm guessing it's probably that. At least I'm sure as hell hoping that's just hot glue.

So.. What do I do?

Thanks everybody for any thoughts you may have.

Yep oxidized female 1/4 jacks.  Remove the screws holding the xover/jack plate and clean up the jacks.

[Mike Caldwell]

You may indeed have some other problems but the 1/4 switching jacks need to be checked if not replaced all together.

[Preston Smith]

Damn. I picked up some contact cleaner today and got all the contact points squeaky clean and noticed no difference. A new problem is occurring as well. Remember that tonal difference I referred to? Well now the box that actually works will switch between two tones at random!

Frustrated. All signs point to the networks? Is there a more thorough cleaning on the jacks I can do? I pulled out the crossover network but the jacks are pretty buried and I couldn't access them from the inside, or manage to see any obvious problem.

Grrr. Thanks for the thoughts everybody, and especially the patience with somewhat of a newbie.

[Mike Caldwell]

Damn. I picked up some contact cleaner today and got all the contact points squeaky clean and noticed no difference. A new problem is occurring as well. Remember that tonal difference I referred to? Well now the box that actually works will switch between two tones at random!

Frustrated. All signs point to the networks? Is there a more thorough cleaning on the jacks I can do? I pulled out the crossover network but the jacks are pretty buried and I couldn't access them from the inside, or manage to see any obvious problem.

Grrr. Thanks for the thoughts everybody, and especially the patience with somewhat of a newbie.

Look for broken solder connections on the crossover circuit boards.
Hook up the speaker with the crossover out of the cabinet, run some pink noise through it while you poke, move and wiggle the components on the crossover, see if you find one that make sections of the speaker cut in and out.

[Preston Smith]

Look for broken solder connections on the crossover circuit boards.
Hook up the speaker with the crossover out of the cabinet, run some pink noise through it while you poke, move and wiggle the components on the crossover, see if you find one that make sections of the speaker cut in and out.

Well I did this to the malfunctioning bin, and poking and wiggling didn't do anything, but what DID was turning the thing horizontal and upside down (jacks/plate facing down). When held in this position the signal comes through loud and clear, when turned vertically it cuts back out.

Also theres this coil of exposed wires that if I touch with my finger when the signal is coming through, it deadens the signal down to the stylus-on-record volume that it plays at when not held upside down.
And even also-er, the coil object is half covered in hot glue, but maybe 50 percent of the copper is completely exposed. Might this be my weak link?

[Preston Smith]

Well I did this to the malfunctioning bin, and poking and wiggling didn't do anything, but what DID was turning the thing horizontal and upside down (jacks/plate facing down). When held in this position the signal comes through loud and clear, when turned vertically it cuts back out. I didn't see any obvious connections broken.

Also theres this coil of exposed wires that if I touch with my finger when the signal is coming through, it deadens the signal down to the stylus-on-record volume that it plays at when not held upside down.
And even also-er, the coil object is half covered in hot glue, but maybe 50 percent of the copper is completely exposed. Might this be my weak link?

Oops, didn't mean to double post, just wanted to edit and add that I saw no obvious solder or connection issues.

I'll also add that the tonal difference is still there but at least the cabs are both running at the same volume. I just put the crossover back in inverted from it's original position and it's ok for now. Tomorrow I'm going to crack open the one that is being weird on tone and see if a little wiggling doesn't expose an issue.

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