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My JL Audio sub is dead. What exactly happened?

So at my wife's request, I hooked up a Roku to my main system. Roku is a device for internet streaming movies and tv. The connection between the Roku and my preamp, a Meridian G68, was a 12 foot optical cable.

The first night, I hook up the Roku and it works perfectly.

The next night, I move some cables around, then I hook up the Roku again, exactly the same way as the previous evening. I get picture but no sound. Weird. I pondering what I might have done wrong when out of the speakers... POP. POP! POP!!!

Uh oh.

I dive for the amps, switch them off. The POPs stop immediately. But...

Now there's a TERRIFYING HIGH PITCHED PULSATING NOISE coming from somewhere in the room. I finally realize it's coming from the sub, a JL Audio Fathom 113. I dart across the room, switch it off.

I stand frozen, savoring the final moments of the fantasy that maybe things aren't that bad.

Here are some questions in no particular order...

1. I suspect the amp in the sub is fried. Does that sound right?

2. Where did those POPs come from? Could a damaged optical cable do it? Or maybe the optical cable wasn't fully seated?

3. Do I really have to ship this 150 pound sub to Florida? Or do you think there's any chance of finding someone local to fix it? (I'm in L.A.) The sub is out of warranty, btw.

4. I tried to take the panel off the rear of the amp (I know, lethal voltages inside) with the thought that maybe I would just bring the amp portion of the sub to someone local to fix. I removed about 12 screws from the rear panel and still it doesn't budge. Why can't I open this thing?

If you have any suggestions, I'm all ears. If not, thanks for reading.

Bryon

P.S. The rest of the system appears to be fine.
bryoncunningham
chadeffect
586 posts
 
Bryon,

Sorry for your loss.

I would say if its the sub that has died, it is most likely to be the amp section. The woofer would be very hard to destroy.

Normally the amp in a sub is sealed with a gasket. So it will take a fair amount of leverage to release the amp section. Especially considering the weight of the amp section.

Give JL a call. They will give you guidance.

As to a cause, without looking myself it would be impossible to say. Unlikely to be the optical cable. If it came lose the clock would stop and you may get a brief bit of white noise.
tesseract86
156 posts
 
I heard a similar story and the individual just changed the fuse in the sub and had it work again, not sure how its done or if that could be your problem but its something to know, I also have a f113.
good luck!
bryoncunningham OP
890 posts
 
Hi Chad and Tesseract - Thanks for your condolences. :-)

Chad - I agree that it's hard to see how the optical cable could do this damage.

I talked with the folks at JL. They agree that the amp is blown. As to the cause, they don't know. They speculated that it could have been a major voltage swing on my power lines. But I don't think that's it. My power is pretty stable here.

I did read in another forum about a guy whose F113 did the same thing (high pitched noise, no obvious cause), except his system was off at the time, which is even stranger.

I'm currently investigating the possibility of getting the sub fixed locally. Getting the back panel off might be tricky, because of the gasket you mentioned. The JL people said that, over time, the gasket fuses with the paint, in effect glueing the rear panel to the cabinet.

I'll let you know how things turn out.

Bryon
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almarg
9,670 posts
 
Hi Bryon,

My sympathies on this also. Hopefully it will just turn out to be a fuse, as Tesseract suggested.

Is there any sign of life from the sub, such as LEDs illuminating? Or is it totally inert, as if an AC line fuse is blown?

Do you use the sub in master or slave mode? If you are using it in slave mode, with the Meridian processor implementing the level and crossover functions, it would presumably have been more sensitive to an input that went berserk for some reason.

Can you test the Roku's optical output, and the optical cable, on something other than your main system, that is inexpensive? I wouldn't rule out the possibility that one of those things was the root cause of the problem, especially given that symptoms were present in the signal path to the main speakers as well as to the sub. Also, can you test the optical input of the processor using some other optical source and cable?

Best,
-- Al
bryoncunningham OP
890 posts
 
Is there any sign of life from the sub, such as LEDs illuminating? Or is it totally inert, as if an AC line fuse is blown?
When you turn the sub on, you get the same high pitched screech that I heard when it blew. This is true even with just the power cable attached (i.e. no signal cable attached). So it's not the fuse. And it's not the signal input.
Do you use the sub in master or slave mode? If you are using it in slave mode, with the Meridian processor implementing the level and crossover functions, it would presumably have been more sensitive to an input that went berserk for some reason.
I use the sub in master mode, but I don't use the crossover. Instead I use the digital crossover in the Meridian. Come to think of it, I don't recall whether there is a way to actually defeat the sub's crossover or if I just turned the sub's low pass to the highest available frequency.
Can you test the Roku's optical output, and the optical cable, on something other than your main system, that is inexpensive? I wouldn't rule out the possibility that one of those things was the root cause of the problem, especially given that symptoms were present in the signal path to the main speakers as well as to the sub. Also, can you test the optical input of the processor using some other optical source and cable?
As you can guess, I'm totally paranoid about plugging ANYTHING into the Meridian's optical input at this point. If that's the source of the problem, I don't want to damage something else. I don't ordinarily use the Meridian's optical input. I use the coaxial inputs. I just used the optical with the Roku because that is the only S/PDIF output the Roku has.

I've abandoned the idea of using the Roku on my main system. Yesterday I ordered the just released Oppo BDP-103 to replace my first generation Pioneer Elite blu ray player. The Oppo has streaming capability, so I'll be able to make the wife happy without taking another chance on that **** Roku.

That is assuming that I decide to keep the Oppo. Everybody raves about the picture quality, but I recently bought and returned a high end Panasonic that everybody raved about also. I returned it because its picture quality wasn't as good as my Pioneer Elite, even though my Pioneer is roughly 5 years old. Everybody says the Oppo is the cat's pajamas. We'll see.

Bryon
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