When you do the measurements it is often very surprising, as too what turns out ot be magnetic, and what is ok.
Remember for far field measurements a magnetic field drops of at an inverse cube rate (approx.). So being very crude with the equations (as the physics often hurts my head), if you have a large powerful magnet of say, a 20 cm diameter. At 2.1m the field strength is already reduced to 1/9000th and at 4.6m to nearly 1/100000th of the max field strength measured at the magnets face. Ted Rook wrote: > JBL Professional Audio makes heavy duty loudspeaker drivers which feature the > traditional big magnet at the back. These items are airfreighted all over the > world daily. I recall seeing an airfreight label on the cartons which > declared the contents to be 'magnetic'. The figure given in a recent post for > maximum allowance, mG at meters distance, would be exceeded by these devices, > I think. You could try the JBL website, their US headquarters is in Los > Angeles CA, they are part of the Harman Audio group. > > Best Regards > > Ted Rook, Console Engineering, ext 4659 > > Please note our new location and phone numbers: > > Crest Audio Inc, 16-00 Pollitt Drive > Fair Lawn, NJ 07410 USA > > 201 475 4600 telephone receptionist, 8.30 - 5 pm EST. > 201 475 4659 direct line w/voice mail, 24 hrs. > 201 475 4677 fax, 24 hrs. > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Michael Garretson: pstc_ad...@garretson.org > Dave Heald davehe...@mediaone.net > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > All emc-pstc postings are archived and searchable on the web at: > No longer online until our new server is brought online and the old > messages are imported into the new server. -- Andrew Carson - Product Safety Engineer, Xyratex, UK Phone: +44 (0)23 9249 6855 Fax: +44 (0)23 9249 6014 ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: pstc_ad...@garretson.org Dave Heald davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
