DizRotus Posted February 2, 2019 Share Posted February 2, 2019 I have a pair of round magnet Alnico K-77s in a pair of HIPs. They seem to work fine. Is there truth to the folklore that Alnico magnets can get demagnetized? If so, how would one know, and what would one do? The following are alerted to this thread out of respect for their collective demonstrated knowledge. The list was quickly compiled in my head. Please do not take umbrage if I neglected to include you. Yes, I know djk has prematurely gone to his reward, but I included him out of respect for the wealth of knowledge he shared. @djk, @BEC, @ClaudeJ1, @Chris A, @Deang, @jwc, @DrWho, @Marvel, @pzannucci, @Chief bonehead, and all other members of the collective brain trust who might read this. Quote Link to comment Share on other sites More sharing options...
pzannucci Posted February 2, 2019 Share Posted February 2, 2019 4 minutes ago, DizRotus said: I have a pair of round magnet Alnico K-77s in a pair of HIPs. They seem to work fine. Is there truth to the folklore that Alnico magnets can get demagnetized? If so, how would one know, and what would one do? The following are alerted to this thread out of respect for their collective demonstrated knowledge. The list was quickly compiled in my head. Please do not take umbrage if I neglected to include you. Yes, I know djk has prematurely gone to his reward, but I included him out of respect for the wealth of knowledge he shared. @djk, @BEC, @ClaudeJ1, @Chris A, @Deang, @jwc, @DrWho, @Marvel, @pzannucci, @Chief bonehead, and all other members of the collective brain trust who might read this. In theory, https://e-magnetsuk.com/alnico_magnets/characteristics.aspx In practice, it probably matters to how hard you drive them and equipment around them. As far as self demagnetizing from the above site: Unless the magnet has a very good Pc (Permeance coefficient) it is best to avoid pushing Alnico magnets into each other in repulsion. Because Alnico has low Hc (coercive force) and Hci (Intrinsic Coercive force) values, Alnico can demagnetise itself. This is why many Alnico magnet have “keeper plates” of mild steel – they short-circuit the magnetic circuit to increase the Pc making it harder o demagnetise the magnet whilst in storage. Indicating not the most stable material. 1 Quote Link to comment Share on other sites More sharing options...
DizRotus Posted February 2, 2019 Author Share Posted February 2, 2019 10 minutes ago, pzannucci said: In theory, https://e-magnetsuk.com/alnico_magnets/characteristics.aspx In practice, it probably matters to how hard you drive them and equipment around them. As far as self demagnetizing from the above site: Unless the magnet has a very good Pc (Permeance coefficient) it is best to avoid pushing Alnico magnets into each other in repulsion. Because Alnico has low Hc (coercive force) and Hci (Intrinsic Coercive force) values, Alnico can demagnetise itself. This is why many Alnico magnet have “keeper plates” of mild steel – they short-circuit the magnetic circuit to increase the Pc making it harder o demagnetise the magnet whilst in storage. Indicating not the most stable material. Whew . . . wait while I sit down. You are obviously knowledgeable, but that went flying straight over my head. Quote Link to comment Share on other sites More sharing options...
JohnA Posted February 2, 2019 Share Posted February 2, 2019 Yes, AlNiCo will demagnetize from high power (strong field strength from the voice coil), shock (dropping, bumping too hard) or old age. Some labs can test them. Measuring output vs. voltage can tell. And loss of high frequencies is an indication. Great Plains Audio can magnetize /remagnetize some drivers, perhaps K-77, too. 1 1 Quote Link to comment Share on other sites More sharing options...
pzannucci Posted February 2, 2019 Share Posted February 2, 2019 9 minutes ago, JohnA said: Yes, AlNiCo will democratize from high power (strong field strength from the voice coil), shock (dropping, bumping too hard) or old age. Some labs can test them. Measuring output vs. voltage can tell. And loss of high frequencies is an indication. Great Plains Audio can magnetize /remagnetize some drivers, perhaps K-77, too. The better answer. Little more grounded 1 Quote Link to comment Share on other sites More sharing options...
Chris A Posted February 2, 2019 Share Posted February 2, 2019 All magnets can be demagnetized, especially when you heat them to their Curie temperature. For Alnico, that temperature is ~700 degrees C (1292 degrees F). The other factors mentioned: shock, opposing fields, time are also factors. All you need is someone with a driver magnetizer that can handle the shape/size/form factor of the K-77. There should be folks local to your area that can do it. You can use something as simple as a hand-held SPL meter and use a program or test CD to step up in frequency above 1000 Hz. If you see lower SPL above ~6-7 kHz, you'll know that you've got some issue. Chris 1 Quote Link to comment Share on other sites More sharing options...
DizRotus Posted February 2, 2019 Author Share Posted February 2, 2019 16 minutes ago, JohnA said: Yes, AlNiCo will democratize from high power No politics. Are you trying to get this thread locked? Quote Link to comment Share on other sites More sharing options...
DizRotus Posted February 2, 2019 Author Share Posted February 2, 2019 Are you following this Tim @teaman? 1 Quote Link to comment Share on other sites More sharing options...
pzannucci Posted February 2, 2019 Share Posted February 2, 2019 12 minutes ago, DizRotus said: No politics. Are you trying to get this thread locked? We're all divided between Neo, ceramic, and Alnico... Yes let's try to not get this one locked. Not sure how the newbee thread is still alive. 1 Quote Link to comment Share on other sites More sharing options...
DizRotus Posted February 2, 2019 Author Share Posted February 2, 2019 3 minutes ago, pzannucci said: Not sure how the newbee thread is still alive. To which "newbee" thread do you refer? BTW, with a join date of June 11, 1999, you are one of the most senior memebrs still active. You make me look like a newbee with March 1, 2002 as a join date. Maybe this is the "newbee: thread you referenced. Quote Link to comment Share on other sites More sharing options...
pzannucci Posted February 3, 2019 Share Posted February 3, 2019 21 hours ago, DizRotus said: To which "newbee" thread do you refer? BTW, with a join date of June 11, 1999, you are one of the most senior memebrs still active. You make me look like a newbee with March 1, 2002 as a join date. Maybe this is the "newbee: thread you referenced. Ya been around for a long time, since the old forum. Only follow a few forums, that's why I have such a huge post count :-) The thread was really more of a referencing for beginners - Quote Link to comment Share on other sites More sharing options...
Deang Posted February 3, 2019 Share Posted February 3, 2019 Most helpful thread for newbies ever. Just buy cheap shit and call it a day - but make sure you have a mono switch. Quote Link to comment Share on other sites More sharing options...
JohnA Posted February 3, 2019 Share Posted February 3, 2019 On 2/2/2019 at 2:28 PM, DizRotus said: No politics. Are you trying to get this thread locked? D$%^&ed autocorrect! Quote Link to comment Share on other sites More sharing options...
DizRotus Posted February 3, 2019 Author Share Posted February 3, 2019 19 hours ago, pzannucci said: Ya been around for a long time, since the old forum. Only follow a few forums, that's why I have such a huge post count 🙂 The thread was really more of a referencing for beginners - Now I'm totally confused. Does everyone else see the photo of a mini-Karlsonator? Quote Link to comment Share on other sites More sharing options...
garyrc Posted February 4, 2019 Share Posted February 4, 2019 I believe round magnet K77s are Alinco, and, some newer ones are not. The K77F is ferrite which I think is the same as ceramic. Quote Link to comment Share on other sites More sharing options...
pzannucci Posted February 4, 2019 Share Posted February 4, 2019 13 hours ago, DizRotus said: Now I'm totally confused. Does everyone else see the photo of a mini-karlsonator? No clue where the picture came from. That was the thread on beginners when you click on it. Quote Link to comment Share on other sites More sharing options...
DizRotus Posted February 4, 2019 Author Share Posted February 4, 2019 37 minutes ago, pzannucci said: No clue where the picture came from. That was the thread on beginners when you click on it. So you too can see the partial photo in your post? I’m familiar with the thread you reference. That photo is attached to a post of mine in that thread. I’m curious as to how and why that partial photo of a foam core mini-Karlsonator I built appears here, especially if you didn’t intend for it to appear. Quote Link to comment Share on other sites More sharing options...
pzannucci Posted February 4, 2019 Share Posted February 4, 2019 1 minute ago, DizRotus said: So you too can see the partial photo in your post? I’m familiar with thread you reference. That photo is attached to a post of mine in that thread. I’m curious as to how and why that partial photo of a foam core mini-Karlsonator I built appears here, especially if you didn’t intend for it to appear. Forum oddness. I just posted the link and the forum resolves the address. Odd. 1 Quote Link to comment Share on other sites More sharing options...
DizRotus Posted February 4, 2019 Author Share Posted February 4, 2019 FYI, this thread is now academic, as I sold and shipped the subject K77s to Tim @teaman. It’s now up to him to assess their state of magnetism, demagnetism, or “democratization.” 1 Quote Link to comment Share on other sites More sharing options...
Dave A Posted February 4, 2019 Share Posted February 4, 2019 20 hours ago, Deang said: Most helpful thread for newbies ever. Just buy cheap shit and call it a day - but make sure you have a mono switch. And pretty knobs you can caress. Quote Link to comment Share on other sites More sharing options...
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