nola Posted July 5, 2009 Share Posted July 5, 2009 Is Demagnetization in Alnico Drivers Ever a Real Problem? Older Heritage gear (Klipschorns, LaScalas, Heresy's) all use Alnico drivers. Most of mine are 20-35 yrs old now. I think older Altec-Lansing drivers were also alnicos. An old article found via a search for the Altec 511 horn and Voice of the Theatre speakers (VOTT) mentioned that demagnetization could be a reason for some speakers to sound bad. Has anyone here on the forums, or at the Mother Ship (Professor Thump, Trey, etc) ever noted, or even looked for this? How would you know if you had a demag'd driver? A wiki search for alnico confirms this: "This means alnico can produce a strong magnetic flux in closed magnetic circuit, but has relatively small resistance against demagnetization." Has anyone ever tested the old alnicos? I am not even sure how to test them. If they were out of spec, how would you re magnetize them to factory spec or are they just killed? Hope I posted this to the correct forum here. I also posted this at Audiokarma. (Man, the crazy things that come up in LA). Thx NOLA Quote Link to comment Share on other sites More sharing options...
twistedcrankcammer Posted July 5, 2009 Share Posted July 5, 2009 Is Demagnetization in Alnico Drivers Ever a Real Problem?Older Heritage gear (Klipschorns, LaScalas, Heresy's) all use Alnico drivers. Most of mine are 20-35 yrs old now. I think older Altec-Lansing drivers were also alnicos. An old article found via a search for the Altec 511 horn and Voice of the Theatre speakers (VOTT) mentioned that demagnetization could be a reason for some speakers to sound bad. Has anyone here on the forums, or at the Mother Ship (Professor Thump, Trey, etc) ever noted, or even looked for this? How would you know if you had a demag'd driver? A wiki search for alnico confirms this: "This means alnico can produce a strong magnetic flux in closed magnetic circuit, but has relatively small resistance against demagnetization."Has anyone ever tested the old alnicos? I am not even sure how to test them. If they were out of spec, how would you re magnetize them to factory spec or are they just killed? Hope I posted this to the correct forum here. I also posted this at Audiokarma. (Man, the crazy things that come up in LA). Thx NOLA Nola, Alnico magnets biggest enemy is heat. Since you say your Klipsch Speakers are only 20 to 35 years old, I have to assume you are talking about K-55V drivers and K-77 Tweeters. The smaller Alnico magnets in the Tweeters have gotten a reputation for going weak. I have some completely redone Electro Voice 15W-K Alnico Drivers that I absolutely love. Cholter and Indy Roger have seen one of these in person. Back on subject, Alnico can be zapped to give a recharge to the magnet, but if you do a search for Speaker Workshop in Ft Wayne Indianna, and talk to the owner (He does all of Electro Voices outdated model recone work and is the only one authorized to do the EV 30W recones). He has had Alnico rezapped before and the results he has seen were worse then prior to being zapped. I was looking heavily into putting Neodymium Magnets in my EV 15W-Ks, but at present, 6 inch diameter is the maximum diameter that most custom Neodymium Magnet manufacturers can produce. Neodymium has ten times the field strength of Mud Magnets and none of Alnicos short comings. Research Neodymium Magnets and you will find many different grade ratings, with different magnetic strengths, but you can order custom made magnets more reasonable then you might think. This would make for even more efficient drivers then the Alnico ones. If Bob Crites ever gets arround to making his Titanium diaphrams for the K-77, I will be replacing alot of them and upgrading magnets as well. Hope this helps.... Roger Quote Link to comment Share on other sites More sharing options...
Daddy Dee Posted July 5, 2009 Share Posted July 5, 2009 I've had trouble with alinco k77s'. Some of them play so softly, it's almost like not having a tweeter. Also, think they roll off at 14 or 15khz. Some folks REALLY prefer the sound, but I've never had square magnet K77 let me down. Supposedly one can have them remagnitized at EV in Russellville, AR. Quote Link to comment Share on other sites More sharing options...
PrestonTom Posted July 5, 2009 Share Posted July 5, 2009 I was always told that the problem is primarily when the unit is knocked around and secondarily if the unit is driven hard. That first issue is going to be a real problem in pro sound where cabinets and drivers are frequently transported and sometimes dropped. As others have mentioned, they can be re-magnetized. However if the magnet has been knocked out of alignment, the re-magnetizing will not be as effective or as long-lasting. Quote Link to comment Share on other sites More sharing options...
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