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Old 18th April 2013, 02:57 AM   #1
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Default Shipping Magnets by Air

Just came across this, wonder how legal your average speaker shipment is...???
"For air shipment purposes, magnets are considered "dangerous goods" and the International Air Transport Association's (IATA) Dangerous Goods Regulations (DGR) must be followed.
In order for magnets to be shipped by air:
Flux measurements of all packages containing magnets must measure less than 0.00525 gauss 15 feet from the package. (If flux measurements are less than 0.002 gauss measured 7 feet from the package, the package is not considered to contain magnetic material, and hence is not classified as a Dangerous Good.
Packages containing magnetic materials must be clearly identified according to Packing Instructions 902. This calls for a "Magnetized Material" label to be affixed, and for a Shipper's Declaration of Dangerous Goods to be provided to the carrier.
Personnel responsible for shipping magnets by air are required by the Federal Aviation Authority (FAA) to be trained for that purpose and for those training records to be maintained."
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Impedance varies with frequency, use impedance plots of your drivers and make crossover calculations using the actual impedance of the driver at the crossover frequency
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Old 18th April 2013, 03:11 AM   #2
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Magnetic flux falls off very quickly with distance. I doubt most speakers would have a problem with this test, but you'd have to measure to be sure. Remember, they're designed to focus the field in the gap through metal plates, not waste it elsewhere through the air.
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Old 18th April 2013, 04:56 AM   #3
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must be possible to calculate the field at 7' from the BL???? or conversely, a BL factor which is not 'Dangerous Goods" from .00525 Gauss @ 15'
(Weber's site says the range of modern drivers is 10K - 18K Gauss in the gap)
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Old 18th April 2013, 05:09 AM   #4
jcx is online now jcx  United States
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the gap field isn't the problem

it would be the leakage from the outer edge of the ferrite donut, not captured/steered to the gap by the pole pieces that would reach out into space farther

Last edited by jcx; 18th April 2013 at 05:15 AM.
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Old 18th April 2013, 05:13 AM   #5
Enzo is offline Enzo  United States
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I once asked the EMinence factory if all that concentrated magnetic energy had any effect on the environment. No, not like disorienting the squirrels, but whether it made local compasses deviate, or required any special notation on air navigational charts, or similar. They found that mildly amusing and assured me there was nothing of the sort. They told me what Conrad just said, that the magnetic fields are designed to be contained in the gap for the most part. And they don;t spray all over.

If you get a strong speaker magnet near your CRT computer monitor or TV set, you can see the color distortion from it. But you will also see how quickly it diminishes if you move them a foot or two away.
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Old 18th April 2013, 07:11 AM   #6
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there are magnetic field calculators on the web, but I suppose I'd have to make assumptions about how 'leaky' the average driver is...
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Old 18th April 2013, 07:57 AM   #7
Enzo is offline Enzo  United States
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You have a compass handy?

I have to think the speaker makers have already considered this and come out clean. Otherwise we'd find all the speaker air shipments trying to land a hundred miles off course.
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Old 18th April 2013, 12:40 PM   #8
DF96 is offline DF96  England
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Exactly how many modern aircraft use a magnetic compass, even as a backup?
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Old 18th April 2013, 03:06 PM   #9
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Quote:
Originally Posted by DF96 View Post
Exactly how many modern aircraft use a magnetic compass, even as a backup?
Probably all of them.

Remember that every laptop has speakers in it and for that matter, so do the pilots headphones
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Old 18th April 2013, 11:53 PM   #10
Enzo is offline Enzo  United States
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Besides, it was a joke.
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