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Old 10th September 2010, 06:49 PM   #11
suntechnik is offline suntechnik  Russian Federation
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imho light weight and hi efficiency that both come from rear earth magnets are not so critical for nice sound. Let say Magneplanars are heavy and do need some real juice from amplifiers.

Computer hard drives might be another story where small form factor and low power consumption all together makes rear earth magnets mandatory.
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Old 10th September 2010, 07:24 PM   #12
Andrew Eckhardt is offline Andrew Eckhardt  United States
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I've long suspected that the raw mass of large ceramic magnet assemblies can have positive effects on sound especially in the midrange, but haven't been able to afford to proove it for myself. For high power woofers the weight savings can be a big deal. Neodymium flat out makes some tweeters possible.
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Old 10th September 2010, 08:31 PM   #13
Andrew Eckhardt is offline Andrew Eckhardt  United States
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Another thing to consider is neodymium based motor assemblies routinely have shorter iron path lengths and volumes, which could possibly have as much effect on sound as the response of the magnet material itself. I've been hoping to investigate the use of underhung coils with a high grade NdFeBr material as the pole faces. I'm sure that's been done already but I'm not aware of any affordable units to shop that are built that way.
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Old 11th September 2010, 02:05 AM   #14
pjp is offline pjp  India
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and neodymium is electrically conductive - which might have result in different eddy current damping of the voice coil as compared to a ferrite magnet.
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Old 12th September 2010, 04:23 AM   #15
a.wayne is offline a.wayne  United States
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Ok, this is all good, now where can i get my hands on some cheap neo's
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Old 12th September 2010, 04:28 AM   #16
Variac is online now Variac  Costa Rica
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And neo magnets being smaller tend to not block the rear wave of the driver. Seas has done some cool stuff with this idea..

Fostex sells very expensive brass rings to mount their drivers in the front of a baffle, to increase the mass. Nice insight that ferrite, because of its mass, might have one advantage over neo.
"The geek shall inherit the earth"
2017 Burning Amp is November 12 in S.F. Thread here on diyAudio:

Last edited by Variac; 12th September 2010 at 04:30 AM.
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Old 12th September 2010, 04:38 AM   #17
Andrew Eckhardt is offline Andrew Eckhardt  United States
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nobody liked my Halbach sketch
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Old 12th September 2010, 05:57 AM   #18
hunter audio is offline hunter audio  India
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From a geological survey of India report in early 2000 there are proven (large) deposits of all the material components that go towards making of neo mags in India

we are yet to make neo mags here on our own , and import heavily , our 4 cos making ferrite mags for speakers have closed down about 4 years back due to traders dumping cheap lower quality imports (no guess where those are coming from)

in analogy we also have large titanium deposits , we make no finished titanium yet and are buying billions of dollars worth of submarines that too only 6 of them

we have one of the worlds largest deposits of thorium , indian scientists are about months away from making their own thorium power plants when our politicians have dumped a largely controversial uranium power generation policy , all uranium being controversial imports with equally controversial disposal

calcutta is the nearest port to our mining areas , all ships coming here have legitimate cargo for india , on the way out they overstay and load illegally mined rare earth materials and proceed for processing else where

the illegal mines have been set up removing peaceful tribals , to us they may be un-educated but they live off natural materials and give to nature more than take from it , whereas the illegal mines are not conforming any environmental , forest , labor health dept regs and are felling trees and destroying at will

our most educated prime minister till date has set up our uranium hungry power plants

most of our politicians are involved in kickbacks from illegal mining

we do not develop materials here as it will stop the bureaucrats from enjoying all types of pleasure when they visit other places to secure material import tie ups

we bought long range guns , howitzer type from europe , very good ones , but banned the very own supplier on whom our army depends on .
We then ran out of shells at the heat of a battle and since our politicos had banned the gun manufacturer did not have shells for the soldiers fighting terrorists

it goes on , & it sometimes gets funny

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Old 12th September 2010, 03:39 PM   #19
Edmond Stuart is offline Edmond Stuart  Netherlands
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Default Halbach array

Originally Posted by Andrew Eckhardt View Post
nobody liked my Halbach sketch
Where? I haven't seen it yet.
Een volk dat voor tirannen zwicht, zal meer dan lijf en
goed verliezen dan dooft het licht…(H.M. van Randwijk)
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