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View Full Version : JBL L300 dead all of a sudden



colorbars
02-16-2006, 12:05 PM
I have a great pair of JBL L300's I picked up last year. Now, one of the units will not make a sound. I have never driven them hard at all and I have a very nice setup of premium components. So I am wondering what inside the speaker cab would have failed to cause all the drivers to not output sound. If a wire has become disconnected from one driver, can this cause the others to go silent? Or are they somewhat independent of eachother coming out of the crossover network?

Or is is some other known problem, I have yet to learn about?

Thanks for any and all info. :-)

Jim K.

johnaec
02-16-2006, 12:14 PM
Have you tried connecting the other L300 to the "dead" channel to be sure it's not really one channel of the amp that's out? Also check all the interconnecting cable between your components.

If you're sure it's really the speaker and not the amp or external wiring, you need to pull one of the drivers so you can inspect the wiring inside the cabinet. I'd suspect a bad connection somewhere between the input connectors and crossover in this case. I think it highly unlikely that everything went at once...

John

L100t Owner
02-16-2006, 12:33 PM
Have you tried connecting the other L300 to the "dead" channel to be sure it's not really one channel of the amp that's out? Also check all the interconnecting cable between your components.

If you're sure it's really the speaker and not the amp or external wiring, you need to pull one of the drivers so you can inspect the wiring inside the cabinet. I'd suspect a bad connection somewhere between the input connectors and crossover in this case. I think it highly unlikely that everything went at once...

John

Do these have fuses? Can't think of what would cause everything to go dead at once except an "open" (as opposed to a short) in the circuit.

Chris

jim campbell
02-16-2006, 02:25 PM
start with the simple stuff dude;go thru all interconnects isolating every component and testing left right etc,and if you havnt reversed the speaker cables to a side that works ....well you probably did that already. i have seen interconnects need cleaning periodically an every now and then the connectors on the back of one or more of the components can be twisted from repeated cabling de cabling causing the wires inside to separate from the connector.if you have access to a multimeter test for continuity (ohms)in your speaker wires and cables.if not just isolate them and the bad one will eventually appear.if after all that then remove one of the drivers and test it.if athe drivers work and everything else tests out then you may have smoked a xover.unless someone installed a fuse in the line they are probably not fused.i have seen more than a few burned x overs.good luck

remusr
02-16-2006, 02:36 PM
Just my ideas,
Check to see if there is anyone home in there - disconnect the speaker wires from the amp and put an ohm-meter across the L300 input terminals. You should get 6-8 ohms. If much lower or higher than 6-8 but not infinite, check the woofer moves freely on its suspension to confirm VC is not fried and put your schnoz at the port to check for a potential burnt smell from the drivers or network.
If infinite resistance, then check inside to see if the wires from the dividing network to the back of the input terminal plate have come apart.
- lay the speaker on its back on a blanket, unscrew the 8 woofer screws (#2 phillips head), set a small cloth on the side of the cabinet beside the woof, lift the woof up (may have to rock it a bit if its been there a while) and set it on the cloth, disconnect its 2 spring terminal leads, set it on a cloth on a table face-down and handcheck the 2 wires from the L300's floor-mounted dividing network to the male spade clips on the input terminal plate are tight. Work them in and out to confirm. Confirm that the other wires to LPads, LE85 & 077 are made-up and tight. If the dividing network is fried you should be able to see and smell that! Some components are visible under the screen, others are buried under some guck and can't be seen.
If all wiring's ok, test the isolated woofer DC resisistance with an ohm-meter, if 6-8 then OK, must be network. There may be fuse in there that I don't know of but otherwise...roll up your sleeves, lots of work ahead!
- Roy

norealtalent
02-16-2006, 03:03 PM
I know I haven't seen it all but I've never seen a quality crossover from a home environment smoked in a manner that took out everything. I'd guess a bad connection or you took out a channel in your amp. Quality amps have a fuse for each channel. Like a lightbulb, fuses blow. Sometimes it is indicative of a problem and sometimes they're just tired. We can't fix it with all our speculation but you can pm anybody who responded and I'm sure one of us would be willing to walk you through it on the phone. There's really nothing more any of us can do without you checking things first.:bouncy:

jim campbell
02-16-2006, 03:15 PM
its the pots that go.it seemed to happen with an old pre amp that i had.once i got the AR its been smooth sailing.

norealtalent
02-16-2006, 03:20 PM
Good thought. Could be right. Seldom turns out the way it does in the song...:D

57BELAIRE
02-20-2006, 07:41 AM
last month I posted a thread ..."no signal to the 077's"

Well, as it turns out, a few of the N333's solder joints failed...all the components tested fine.

That would be a good place to start.

jim campbell
02-20-2006, 10:41 AM
did you figure it out yet?if you need any help let me know.

hapy._.face
02-20-2006, 10:48 AM
its the pots that go.it seemed to happen with an old pre amp that i had.once i got the AR its been smooth sailing.

I sure hope my new AR acquisitions are smooth sailing! $580 bill just to get the old amp and pre up to par. Fingers crossed...:o:


As far as the "dead L300"- CHECK THE AMP BEFORE GETTING CARRIED AWAY WITH SPEAKER DIAGNOSTICS!!!! Switch Left/Right channel wiring. Does the "dead" speaker play on the other channel? If not- THEN go through the connections and make sure they are tight, etc. Work your way up to the more complicated tests until you get your answer. Just remember- if you can't get it to work- PM me with your price and I'll come collect them. :drive: + :deal: = :)

J/K. Good luck. Keep us posted- we're a nosey bunch.

jim campbell
02-20-2006, 11:00 AM
what acquisitions,im drooling

hapy._.face
02-20-2006, 11:06 AM
Basic stuff, really.
Pre Amp: SP-9 (had a bad phono out)
Amp: the 60 (filthy!)