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In Reply to: RE: Rare Earth Magnets posted by pictureguy on April 05, 2012 at 15:55:41
In addition, India, Australia, Sri Lanka, and Brazil are also major producers of neodymium. Neodymium is the 26th most abundant element on earth, about the same as Copper. Cost is incurred primarily because refining costs are high: as you noted, the rare earths all mimic each other with the two outer shell electrons.
The other rare elements are critical in the products of flat screen video sets, and thus critical for ipads, Kindles, phones and such: That's how China was able to hold Japan hostage in their recent trade bargaining talks. Neodymium was in great part responsible for the leap in computer memory and motor speed.
Neodymium is already being used for speakers. One of the earliest was Lowther and their DX series of speakers, although sensitivity is not that much increased over their more conventional offerings. There are quite a few tweeters which also use the neodymium type magnets.
There's an excellent book entitled "Nature's Building Blocks" by John Emsley which goes through all the elements one by one and explains them.
Stu
Follow Ups:
If I remember correctly, the Lowther has a field strength of 1.2 Tesla. That is way strong,
Again, if you want a more sensitive driver, increase in magnet strength is maybe the easy way?
I don't know. But the OTHER way is to decrease the gap to as small as you can maintain in production.
For planar drivers, increase in magnet strenth and increase the 'gap' may increase power handling capacity, since you won't get mylar slap quite so easily. This would be with no net increase in sensitivity.
Thinking about panels....and possible improvements is what got me going down this path.
Too much is never enough
Lowther DX drivers have the ferric coating and the VC gap is quite small. Just goes to show that that there are many ways to skin a cat.Stu
PS can you imagine the issues you would have with a planar speaker full of neodymium magnets? I suspect your vacuum cleaner hose, among many other objects would be stuck to it.
Edits: 04/09/12
Fortunately, the polarity reverse with each magnet srip. There are some planars that do use neodynium magnets -- Graz's super Apogees, the big Wisdom in-walls, the smaller BG "Neo" and Eminent Tech drivers. Also some true ribbons.
The reason they aren't usually used in big planars is that they're so expensive. The more efficient speaker would cost the customer more than a larger amp would.
I hadn't thought of that. I guess if you were within 10 yards of a CRT TV you'd mess it up, too.
Not to mention your fillings.
The vac? That's a disaster waiting to happen.
how about on a push/pull panel? would that 'short out' the magnets?
Too much is never enough
My Lowther DX-4 when I moved it to within 2 feet of my computer CRT turned the whole screen into a prismatic array. My greatest fear would be that the magnets could attract something sharp and tear into the diaphragm.
Stu
If I ever come over, I guess I'll have to keep my distance. That steel plate in my head, you know!
Too much is never enough
Graebener planars ( still available at Parts Express I believe) use a mess of BIG neo magnets, arranged so the mag field is kept within the speaker. I have some discards that David Graebener gave to a friend.. Scary strong, foot-long by 1/2 inch square monsters!
cheers
Adam in Ashland Oregon
That is an expensive $$$$$ magnet if made os neo. Also, strong enough to be dangerous while ALSO being somewhat brittle.
How do they sound? Sensitivity?
Too much is never enough
Those are the BG's that Satie uses (Neo 8, these are the bigger brother Neo 10). They apparently sound excellent.
The ones I heard were in an amazing home theatre demo, coupled with attic-mounted tapped horns. Very dynamic, great imaging.
According to the spec sheet below, 93dB sensitivity.
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