Blown speakers

[Bill, KD0HG]

This is insane...Don't let it happen to you!

The music director for one of our FM stations told me that it appeared that the speakers on his higher-end office stereo system were blown out. I checked, and sure enough, his $450 pair of B+W bookshelf speakers were smoked over the weekend.

He's not the type of person to abuse equipment and I was puzzled how it happened.

I found out this morning.

As the sun hit a certain angle at ~ 10 AM, it blazed through his office windows. And it started operating the infrared remote control sensor on his component amp, slowly ramping up the volume level until it was turned all the way up.

A piece of black electric tape placed over the sensor was the fix.

Now I've seen everything.

[AF9J]

Oops! That IS weird!

73,
Ellen - AF9J

[Todd, KA1KAQ]

Thanks for posting this Bill, and yes - that's a new one on me too! Up until now, I'd only worried about the sun yellowing dials on old radio gear.

IR receivers...something you wouldn't give much thought to, but certainly worthy of consideration in placement of your equipment.

[WD8BIL]

Global warming is destroying our toys for revenge !!!!

[KF1Z]

Hopefully it was a name brand speaker....

Generally, any decent speaker has fuses on the crossover board.

May be one of those resistor looking deals.....

[Steve - WB3HUZ]

Shucks! I was hoping to see a speaker with a supercharger on top.

[WBear2GCR]

In theory, that is impossible! 

Why?
Because the IR light that is used for remote controls is pulsed and coded specifically to avoid this advent!

Something is wrong with this picture.
Either the receiver side of the thing is defective, or else the transmitter side is defective or starts to shoot signals when the battery dies, or there is sabotage!!

          _-_-bear     

[Steve - WB3HUZ]

That's what I was thinking too. Sounds like an urban legend. But, maybe it was a case of overload at the input, due to the intensity of the sun.

In theory, that is impossible! 

Why?
Because the IR light that is used for remote controls is pulsed and coded specifically to avoid this advent!

Something is wrong with this picture.
Either the receiver side of the thing is defective, or else the transmitter side is defective or starts to shoot signals when the battery dies, or there is sabotage!!

          _-_-bear    

[Bill, KD0HG]

Yeah, I thought the IR stuff was coded, too, but the fact is, it happened.
I dunno- The sun shining through the blinds somehow modulating it?

The amp was a 100WPC Denon, and the speakers were a pair of B+W 600 series.
http://www.bowers-wilkins.com/display.aspx?infid=2311&sc=hf
http://www.hometheaterstore.com/ProductDetails.asp?ProductCode=685

$250 a pop for the things, and they sound absolutely killer. Tiny, but they'll fill a room with sound and deep bass. I put fuses in the line of the new speakers.

[KF1Z]

Are you telling us you actually witnessed this happening ??


Depending on the remote/sensor.... I can see this happening...
As mentioned... could have "overloaded" the IR sensor..... could have just as easy tuned through the channels endlessly (or until 10:05am).

Sure, it's either that .....

OR a dis-gruntled employee, with a  universal remote!

[W1RKW]

Way back when I was in the audio repair business I had a customer who had a remote controlled audio system.  He complained that it would work OK in the morning before going to work and not work at all or intermittenly when he got home from work.  I thought that it was odd and thought the customer was a little nutty.  He brought the equipment in for me to look at and I ran it for days without a problem.  Called him to tell him all seemed OK and he could pick it up.  Next day, same complaint.  So I went out to his house when he got home from work.  He demonstrated that his remote wouldn't work and stated it worked fine in the morning.  Come to find out the sun was beaming in on the IR sensor.  The sunlight was strong enough or the system didn't filter out a spectrum of light causing the  system to not respond to the remote. When it worked intermittently it was because he was blocking the sun.  Told him to put a shade on the  window or move the system.  All was well.

[k4kyv]

An old farmer who had started out as a kid with mule and plough, and had grown up to see the first tractors, used to say that a farmer should be careful when using a cultivating disc to till up a field, and always pay attention to the angle the tractor makes with the sun if he leaves the tractor in the field unattended for any length of time, particularly for the noontime meal.

The steel cultivating discs are quickly polished to a bright mirror-like finish by the soil while tilling, and the concave surface of the disc is a very close approximation to a parabolic dish.  If the reflection off the shiny disc happens to focus the sun's rays onto the rubber tractor tire at just the wrong distance away to form a focal point, not only can it ruin an expensive tractor tire, but could cause the rubber to burst into flames and burn up the whole tractor.

[KF1Z]

Sort of like buying a crystal ball as a decoration, and leaving it on a windowsill, or side table near a window....

[WA1HZK]

I must report this to Mr. Gore.....

[WBear2GCR]

Yeah, I thought the IR stuff was coded, too, but the fact is, it happened.
I dunno- The sun shining through the blinds somehow modulating it?

The amp was a 100WPC Denon, and the speakers were a pair of B+W 600 series.
http://www.bowers-wilkins.com/display.aspx?infid=2311&sc=hf
http://www.hometheaterstore.com/ProductDetails.asp?ProductCode=685

$250 a pop for the things, and they sound absolutely killer. Tiny, but they'll fill a room with sound and deep bass. I put fuses in the line of the new speakers.

Fuses are not likely to save the tweeters. 

If you put fuses in line with the entire speaker system, they won't really be able to protect the tweets, since the tweets are padded down to meet the sensitivity of the woofers anyhow - so you'd have to fuse the thing to match the woofer's power hungry requirements.

It might work if you went inside and set up A) a fuse in the tweeter line and/or B) the famous "lightbulb in series" with the tweeter. The latter is a bit standard on some pro sound "stage monitors" as well as in many professional theater speakers.

A little testing will permit you to figure out which auto backuplight bulb or dome light/side light bulb is optimal.  That will probably protect the tweeter against long term overloads.

They also sell some Tranzorb type (PTC, iirc) devices that fire off and protect.

           _-_-bear