brand new LSR's self destruct?

[sdaniel]

It was Sunday afternoon, listening to XM via DirecTV, when my brand new JBL LSR speakers started to scream and crackle. Before I could turn them off, one was dead, and the other smells burnt. The amplified subwoofer survived. They were playing a signal from a Sony TV’s ‘audio out’ jacks. I had the TV outs run to the subwoofer, and its outputs were sent to the now smoked LSR 6325's. It was a temporary setup, something to listen to while I finished the theater.

How could two brand new speakers, or anything, fail in the same way at the exact same time without ‘outside’ help?

As soon as I heard the sound, it thought we were having a thunderstorm because it sounded just like when the signal is lost due to clouds, only it went on for about three seconds and got real loud, instead of being a quick ‘chirp’.

So, DirecTV was polite and said they would investigate, but also pointed out that a lot of people would have heard it, and there would be more damage. True, but other equipment may have not been as sensitive, and just played on.


So I ask this group if they had any problems or have any ideas as to what happened?


Thanks!

[edgewound]

It was Sunday afternoon, listening to XM via DirecTV, when my brand new JBL LSR speakers started to scream and crackle. Before I could turn them off, one was dead, and the other smells burnt. The amplified subwoofer survived. They were playing a signal from a Sony TV’s ‘audio out’ jacks. I had the TV outs run to the subwoofer, and its outputs were sent to the now smoked LSR 6325's. It was a temporary setup, something to listen to while I finished the theater.

How could two brand new speakers, or anything, fail in the same way at the exact same time without ‘outside’ help?

As soon as I heard the sound, it thought we were having a thunderstorm because it sounded just like when the signal is lost due to clouds, only it went on for about three seconds and got real loud, instead of being a quick ‘chirp’.

So, DirecTV was polite and said they would investigate, but also pointed out that a lot of people would have heard it, and there would be more damage. True, but other equipment may have not been as sensitive, and just played on.


So I ask this group if they had any problems or have any ideas as to what happened?


Thanks!

Sounds like the power amps are defective. Take them back to the selling dealer for replacements.

[sdaniel]

UPS picked them up yesterday. Your thoughts give me hope that I wont have to pay.

And, while on the topic,

While I’m at it, The LSR 6332’s tweeters ‘horn’, (or ‘wave guide’) is made of three parts, the tweeter, a spacer ring, and then baffle board. The fit and finish is not what I would expect, and compared to the other products in the series, it is a rough edge, a bumpy road. I tried to take pictures, but none showed it well. I guess the difference between surfaces to be less than the diameter of a small paper clip. I can easily imagine the ‘bump’ is taller than the amplitude of the frequencies the tweeter reproduces. If I were making it, it would be a lot better, a lot more like this:

http://www.audioheritage.org/vbulletin/image.php? :applaud: (http://www.audioheritage.org/vbulletin/image.php? u=606&dateline=1130200405)
The depth of the ‘horn’ is less than an inch from the diaphragm to the pane of the baffle board.

I have not been able to listen to them, and imagine they will sound just fine until one gets to the extreme of ‘off axis’. However, it still bugs me a bit, and while they are not in service this would be the time to act. Trouble is, I don’t know if I’m being too picky?

I have never seen any others, and understand that mass production has its limits. If they are all built to this tolerance, there is no point to try to remedy the situation. They can not be adjusted, it is not an alignment problem.

So, does anyone have a pair, or live near a store that stocks them? I ordered mine through a custom installer – they do large churches, clubs, stadiums and the like. They have no showroom.

[Titanium Dome]

That's a great image! I love how that looks. ;)

You're right in that all EOS Waveguides should look as good.

[doodlebug]

I was always on the alert when someone brought in 2 speakers with the same problem and reporting that they died at the same time. Now, I'm not a statistics kind of guy but the odds of this happening are pretty far so I'd start suspecting the speaker failure is only a symptom and the root cause is not yet known.

With that in mind, then, here's the question: What kind of Sony TV are we talking about? Is it plugged into the same outlet as the speakers? Do you have cable hooked up to the TV? Can you confirm that its well-grounded? Have you had a bad thunderstorm recently where, perhaps, other people's stuff was damaged or suffered some loss?

In other words, suspect other things around the speakers. You may well have to be Sherlock Holmes and eliminate things from being the culprit until there's only one thing left....

Cheers,

David

[Anthony L100]

UPS picked them up yesterday. Your thoughts give me hope that I wont have to pay.

And, while on the topic,

While I’m at it, The LSR 6332’s tweeters ‘horn’, (or ‘wave guide’) is made of three parts, the tweeter, a spacer ring, and then baffle board. The fit and finish is not what I would expect, and compared to the other products in the series, it is a rough edge, a bumpy road. I tried to take pictures, but none showed it well. I guess the difference between surfaces to be less than the diameter of a small paper clip. I can easily imagine the ‘bump’ is taller than the amplitude of the frequencies the tweeter reproduces. If I were making it, it would be a lot better, a lot more like this:

http://www.audioheritage.org/vbulletin/image.php? :applaud: (http://www.audioheritage.org/vbulletin/image.php? u=606&dateline=1130200405)
The depth of the ‘horn’ is less than an inch from the diaphragm to the pane of the baffle board.

I have not been able to listen to them, and imagine they will sound just fine until one gets to the extreme of ‘off axis’. However, it still bugs me a bit, and while they are not in service this would be the time to act. Trouble is, I don’t know if I’m being too picky?

I have never seen any others, and understand that mass production has its limits. If they are all built to this tolerance, there is no point to try to remedy the situation. They can not be adjusted, it is not an alignment problem.

So, does anyone have a pair, or live near a store that stocks them? I ordered mine through a custom installer – they do large churches, clubs, stadiums and the like. They have no showroom.

Hi SD, yes I agree that the transition from the mouth of the 053TiS to the cast baffle could be a little better engineered, mine has a slight "step" as well. The picture doesn't fully capture it but it can clearly be seen as a small gap. Dunno if it affects the sound tho'.

[boputnam]

I was always on the alert when someone brought in 2 speakers with the same problem and reporting that they died at the same time. Now, I'm not a statistics kind of guy but the odds of this happening are pretty far so I'd start suspecting the speaker failure is only a symptom and the root cause is not yet known.

With that in mind, then, here's the question: What kind of Sony TV are we talking about? Is it plugged into the same outlet as the speakers? Do you have cable hooked up to the TV? Can you confirm that its well-grounded? Have you had a bad thunderstorm recently where, perhaps, other people's stuff was damaged or suffered some loss?

In other words, suspect other things around the speakers. Shame about the damage.

I agree with all of David's post: the speakers were the symptom of the problem; they are not the cause. The only thing David left out was to question the "powerd subwoofer".
What is it (I'm guessing it wasn't the LSR6312SP)?
Have you used it for a while?
How do you know it is not damaged?

I've had a number of neighbors with their goofy HT set-ups (not here implying anything about yours, SD...) who's low-budget powered subwoofers fail frequently.

I suspect there was a grounding issue between the three - DirectTV, sub and the LSR's. I'd not reconnect that signal path until I knew what was going on.

[edgewound]

Shame about the damage.

I agree with all of David's post: the speakers were the symptom of the problem; they are not the cause. The only thing David left out was to question the "powerd subwoofer".
What is it (I'm guessing it wasn't the LSR6312SP)?
Have you used it for a while?
How do you know it is not damaged?

I've had a number of neighbors with their goofy HT set-ups (not here implying anything about yours, SD...) who's low-budget powered subwoofers fail frequently.

I suspect there was a grounding issue between the three - DirectTV, sub and the LSR's. I'd not reconnect that signal path until I knew what was going on.

The only thing goofy about the low-budget HT set-up and associated failing subs, is the low-budget part.

Nothing like being awaken in the middle of the night by a possessed subwoofer rumbling at full volume, shaking the house, because the signal- sensing standby circuit failed.

Very often....Very often...The culprit is a faulty 10 cent part that is responsible for the failure of nearly a whole production run of Chinese sourced, onboard poweramps. Man, this causes alot of headaches for everyone involved...

It inevitably becomes a crapshoot for the manufacturer to trust in the QC level of this mass-market-cheap-stuff-by-the-ship-load.

[sdaniel]

Thank you all. I have been plugging away at the chores, and am glad for your help.

Having installed the projector, (Optoma HD72, standard signal so far, and very nice.) I decided more ‘testing’ should be done while I waited for the last box of ceiling tiles (Discontinued, last box found in Kalamazoo, Ugh.)

I spent a lot of time soldering XLRs, RCA’s, putting resistors in the lines*. I printed neato labels for the cabling. It was all heat shrinked and pretty, so I stacked the boxes and plugged them in. Power on, and Surprise! The sub is ‘goofy’ also. I had its outputs run back to a crown dc300a, and that amp made quite a sound! Both clipping lights came on. Thank goodness it is tough, and I was able to shut it down quickly. I cussed a bit, and installed the other sub as the ‘master’, and voila, no problems. I confirmed that the ‘goofy’ sub was the one from the earlier mishap.

Clearly it could have taken out the other two speakers, but we still need to know if it failed, or was broken by outside forces. The TV is a Sony Trinitron, circa 1990. The connection was pretty clean, I used two good guitar cords, with barrel type ¼ to rca adaptors at the TV, (TV 'audio out' jacks.) and they were all plugged into the same circuit. It is a brand new house, so the wiring should be good.

Now I'm hold with JBL, searching for a local JBL repair place, as I don’t want to ship that fat B. to California.

The good news is that the LSR6332 are great speakers. I ran them a stereo pair for a while, and they do the trick! They will be great with the subs.

* As my receiver only has speaker level outputs, I contacted a tech at JBL, and he directed me to a schematic from one of their products that had a ‘speaker in’ input. It was basically one resistor on each the positive and neutral leads. So the signal leaves the speaker connections of the receiver, with a resistor on each. The neutral and shield are combined for the run, and the shield is floated at the XLR input to the LSR Sub speaker. Positive to pin 2, neutral to pin 3. All will be re-checked this weekend, when my fresh-eyed daughter is available. (What a joy she is, 18 years old, smart, well mannered, and can talk about all this stuff with interest, and helps out. But, does anybody know how to get Mom to stop telling her to go to law school, so she can do something worthwhile, like engineering?!!! Ha Ha, I hope she does both.)



POSITIVE NOTE: JBL got the little ones monday, and today, friday, they let me know they have been shipped back, repaired under warrantee. Cool.

[boputnam]

* As my receiver only has speaker level outputs, I contacted a tech at JBL, and he directed me to a schematic from one of their products that had a ‘speaker in’ input. It was basically one resistor on each the positive and neutral leads. So the signal leaves the speaker connections of the receiver, with a resistor on each. The neutral and shield are combined for the run, and the shield is floated at the XLR input to the LSR Sub speaker. Positive to pin 2, neutral to pin 3. Now THERE's an interesting little tid-bit. This is a very unconventional connection and almost surely a source for a grounding problem between the three power supplies (TV, Receiver and speakers).

Does your receiver have a Tape out? I would use that to drive the LSR's. Should be a pretty close impedance match, and will avoid the grounding question. If the impedance do not match, you could get a line-drive amp or something. Aphex has that 124A (http://www.aphex.com/124A.htm) - a very handy little unit...

[Bill H.]

I don't know about plugging audio into my tv as I would not try it. My wife threatens to throw our Sony FD Trinitron VEGA XBR {bought 7 years ago} in the river. Been in shop twice for a total of 800.00 repair,and is down again. Paid 2200.00 and using a 25 yr. old Zenith now. Must have got the lemon!
Bill

[doodlebug]

with that Sony TV. You need to *make* sure that the connections you're making to it are isolated. Many TVs without power transformers - to make them cheaper - have floating grounds. Since all the other stuff - with the exception of that receiver connection arrangement you were directed to - has a better ground reference in the chassis.

I'd suggest you check further into that TV arrangement and be suspecious of the receiver connections, too. With the power output of a DC-300 - large enough to do short-duty welding - a ground loop, which is pretty much what you originally described in your first post, would cause the problems you've had.

Cheers,

David

[boputnam]

Many TVs without power transformers - to make them cheaper - have floating grounds. Yea, man.

A possible solution here is to put an isolation transformer between the TV's RCA outs and the receiver. I've used the Radio Shack model (270-054 http://www.radioshack.com/product/index.jsp?productId=2062214&cp) quite successfully in consumer situations like this...

[Titanium Dome]

Yep, that's a staple in a lot of problematic situations. It's better to solve the problem, but sometimes it's very elusive or maybe it just can't be solved without removing something that you don't want to get rid of.

[edgewound]

Sounds to me like they were defective...

It even happens to JBL's...particularly electronics....that's why the warranty period is shorter.

But you guys make some great points and precautions.:) :applaud:

[Ducatista47]

It inevitably becomes a crapshoot for the manufacturer to trust in the QC level of this mass-market-cheap-stuff-by-the-ship-load.
I know I'm ignorant, but I thought the LSR line consisted of JBL PRO studio monitors, the nearfield legacy of the 43xx and 44xx lines. What's going on here?

Clark in Peoria

[Thom]

If you're not real sure what you're doing (I don't mean to imply that you don't) You might put something you value a little less than those speakers (JBL may be a little less understanding a second time) like say 100 watt light bulbs or something, across the output of the amp first, and put some resistance in series with your speakers. Then, if the lights light up real bright, and a little time on an abacuss tells you that its enough to burn up the speakers you get a second chance to try to figure out what's wrong without ruining your day and annoying some poor guy at jbl. And even if the guy at jbl doesn't matter you'll be in a better mood. It may have taken burning up a thing or two for me to come up with that.

[sdaniel]

Now THERE's an interesting little tid-bit. This is a very unconventional connection and almost surely a source for a grounding problem between the three power supplies (TV, Receiver and speakers).

Does your receiver have a Tape out? I would use that to drive the LSR's. Should be a pretty close impedance match, and will avoid the grounding question. If the impedance do not match, you could get a line-drive amp or something. Aphex has that 124A (http://www.aphex.com/124A.htm) - a very handy little unit...

The speakers broke while hooked up to the Sony Trintron while I was working on the theater room. The receiver/resistor rig is the 'permanent' setup. It is working well with the surviving speakers. I use the receiver because it has the 5:1 processor.


And thanks to all, there were some good tips presented. I think Ill get an isolation transformer just to have handy!

Thanks.
SD