Anybody ever regauss magnets on their speakers?

warnerwh · « **on:** 27 Jan 2004, 12:25 am »

Wonder if anybody has tried this. Seems like the stronger the magnet the better coherence(speed) and sensitivity. I'm sure this could change other parameters such as Q but not enough to worry about. Have noticed that neodymium has become much more popular for speakers as the price has come down. IF someone knows how to regauss I'd appreciate learning how. Or is it possible to mount magnets to existing magnets to make them stronger? I suspect this may be a worthwhile tweak. Also how much strength do magnets lose from use and/or over time. I suspect it's different for ferrite, alnico and neodymium. Thanks for any info.

gonefishin · « **Reply #1 on:** 27 Jan 2004, 02:49 am »

I've got some Alnico drivers and have often wondered the same thing. If you find anything out...I'd appreciate it if you could post the info you find here.

thanks!

warnerwh · « **Reply #2 on:** 27 Jan 2004, 03:03 am »

I found where Brian of VMPS stated he'd recharged magnets and said it had a significant improvement in performance and that the sensitivity would be higher with a recharged magnet. This over at AA I believe in the speaker asylum. I did find a magnetizer at Edmonds scientific but they aren't easy to find. Also magnets near electricity and heat can lose their magnetism, know of any magnets in that environment? Been googling around but haven't been able to come up with much relevant. Any physicists should be able to help us out. So Kevin if you're out there...

_scotty_ · « **Reply #3 on:** 27 Jan 2004, 05:57 pm »

Alinco magnets used in speaker applications do loose their strength over time. When guitar amps had speakers with Alinco magnets they were designed to be able to remove the magnet so that it could be remagnetized when necessary. When the magnet gets weak the speakers efficiency falls off. When ferrite type magnets were introduced this problem was considered to reduced to the point that it was nolonger an issue. As the magnets in our loudspeakers are epoxied in place correctly remagnetizing them insitu would not be easy. Also if they get weak enough
it is usually easy enough to just replace the driver in most cases. Warnerwh
could you post a link to Brians comments on this subject . I would be interested in reading them. I have been concerned about the long term stability of the new neodymium magnets now found in use on some tweeters.

warnerwh · « **Reply #4 on:** 27 Jan 2004, 09:50 pm »

Scotty the post I found of Brian's was regarding Alnico magnets. Do a search on Neodymium and you'll find your concerns are warranted. It appears that neodymium can lose it's strength and it won't come back. It's temperature for operating is pretty low before it becomes damaged too, which of course could be a problem with a tweeter. I don't want to state specifics as I'm somewhat confused at this point after reading so many different sites. Brian stated it's amazing how field strength affects performance. That's why I thought it may be a good idea. Here's Brian's post:
http://java.audioasylum.com/cgi/m.pl?forum=speakers&n=99326&highlight=do+magnets+wear+out&r=&session=

_scotty_ · « **Reply #5 on:** 27 Jan 2004, 10:45 pm »

warnerwh, here is a link I found on Neodymium temp vs field strength
and maximum operating temp. 100degrees C is the limit. http://sura.dcs.net/support_guidemtrl_3compari.php . Car stereo applications are where reports of tweeter failure have been reported.
High summer temps coupled with high volume levels could easily send the temp over 100degrees C. In home use at less than rock concert levels
this shouldn't be that big a problem. The tweeters in my Reimer Teton GS-HT are all aluminum in their construction and the faceplate acts as a heat sink. Samarium cobalt magnets are as high as 300degrees C. This sounds like the preferred material for high temp apps. It would take more of it to do the same job but that wouldn't matter. The Infinity EMIT tweeter used
samarium cobalt and worked very well.

warnerwh · « **Reply #6 on:** 27 Jan 2004, 11:07 pm »

Thanks for the link scotty. The temp problem with neodymium would have me concerned as well as it's inclination to oxidation if it's not coated. The strength though is super good. I'd still like to find out about regaussing and if you run into anything please let me know. I searched all over.