Neodymium magnets in subwoofers - AVS Forum
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post #1 of 20 Old 11-06-2011, 03:39 PM - Thread Starter
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This statement from SVS got my curiosity:

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Exactly. I have a fully functional SB16U - with a legit 1300W amp - sitting 20 feet from me.

Neo prices have gone up 1400% since we designed that motor. Even when neo prices were quasi-rational, that motor alone costs far more to produce than most complete high-end woofers from other brands. Now with neo through the roof and into the next solar system, there is no way that motor is economically feasible. It's too bad, but we can't control neo prices - so don't hold your breath on the SB16U - it's not on the production docket.

This is a good example of what a world-class radial neo woofer is costing these days on a retail level....

http://www.parts-express.com/pe/show...number=293-674
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What’s the advantage by using neodymium magnets in a driver? Paradigm’s marketing claims the stronger magnetic field improves transient and phase response along with power handling and output linearity, yet they use ferrite magnets instead in all of their woofers. Wouldn’t stronger magnets be useful in woofers, especially in subwoofers where they’re huge?
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post #2 of 20 Old 11-06-2011, 04:13 PM
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Well, for one, weight ....

TC Sounds Pro 5100 18" Neo Subwoofer Driver 53.40 lbs.

TC Sounds LMS Ultra 5400 18" DVC Subwoofer 86.20 lbs.

The magnet is probably a big part of that weight difference.

 

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post #3 of 20 Old 11-06-2011, 04:49 PM
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As far as I know, the magnet type doesn't have anything to do with sound quality, as long as you have sufficient magnetic strength in the motor. Neodymium simply has a more powerful magnetic field than other magnet types, which make the speaker much lighter. It also makes the speaker more sensitive and easier to drive for amplifiers. But the same magnetic strength can be achieved by different magnet types, it just takes more ferrite magnet mass to reach the same magnetic strength, so you need more power to push that extra weight. I would imagine that for a similarly performing ferrite version of the SB16, you would need such a large and heavy magnet that the driver would be impractically large and heavy.
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post #4 of 20 Old 11-06-2011, 05:22 PM
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Quote:
Originally Posted by shadyJ View Post

As far as I know, the magnet type doesn't have anything to do with sound quality, as long as you have sufficient magnetic strength in the motor. Neodymium simply has a more powerful magnetic field than other magnet types, which make the speaker much lighter. It also makes the speaker more sensitive and easier to drive for amplifiers. But the same magnetic strength can be achieved by different magnet types, it just takes more ferrite magnet mass to reach the same magnetic strength, so you need more power to push that extra weight. I would imagine that for a similarly performing ferrite version of the SB16, you would need such a large and heavy magnet that the driver would be impractically large and heavy.

...not to mention alot more power than the 1250 watts RMS from the Sledge amp SVS planned to use. I'm guessing this is why subs such as the Paradigm Sub 25 need so much power?
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post #5 of 20 Old 11-06-2011, 05:29 PM
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Neodymium magnets are considered to be a rare earth element. These magnets are being heavily used in green technology for turbine engines. The reason the price has skyrocketed is 98% of all REE's including neodymium is controlled by one country, China. About 2 years ago China cut it's exports and increased the price of all it's REE's thus you see the jump in cost of the magnets and other rare earth elements. As long as China controls 98% of the world market we will see prices go higher.
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post #6 of 20 Old 11-07-2011, 04:40 AM
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What does the sheer mass of the magnet have to do with the drivers efficiency?

Isn't it (driver efficiency) related to the strength of the magnetic field not the size of the magnet creating it. (?)

So (for the sake of argument) if you have a 40lb ferrite magnet and a 20lb neo magnet which create equal magnetic fields, they will equally affect driver efficiency, regardless of their mass. I mean you're not pushing the magnet weight anywhere but rather working against the magnetic field it creates...correct?

Maybe I'm missing something.

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post #7 of 20 Old 11-07-2011, 05:36 AM
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There's nothing like high prices and shortages to spur innovations. Like this: http://www.ibridgenetwork.org/umn/ir...re-earth-and-n
Doesn't help anyone right now but maybe someday.

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post #8 of 20 Old 11-07-2011, 09:02 AM - Thread Starter
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Searching via Google seems to indicate the main advantage is applications where size and weight are important. For tweeters perhaps the compactness allows them to be situated closer to adjacent drivers.

Quote:


http://www.eminence.com/pro-audio/neodymium-series/

Just before the turn of this century, speaker manufacturers started seriously evaluating the potential benefits of using neodymium magnets in loudspeakers. Although neodymium magnets were expensive, they allowed loudspeaker motors to be as little as half the weight of comparable ceramic magnet motors. Prices of neodymium started coming down and interest in lighter weight speakers grew, as did neodymium speaker options.


http://jensentone.com/history.php

The three different types of materials used in speaker magnets are Alnico, Ceramic (Ferrite) and Neodymium. Each material has a different effect on the tonal characteristics of the speaker.

Alnico, the original magnet material used in speakers, produces a classic tone. Alnico magnets tend to be a bit more expensive due to their cobalt content. These speakers sound warmer and sweeter at lower volumes and many musicians feel they react more quickly to the player's touch.

Ceramic magnets were developed as an inexpensive alternative to Alnico. These speakers have a few advantages: they do not cost as much, are more versatile and create a wide range of tones. Both the Vintage and MOD ceramic speakers tend to weigh more, generally handle more power and sound better at high volumes.

Neodymium is the newest material being used for speaker magnets. Price-wise they fall between Alnico and ceramic magnet speakers. These speakers respond to a player's touch much like Alnicos and they have a well balanced frequency response. The major advantages of these magnets are weight and efficiency. A neodymium speaker weighs about 50% less than other speakers without giving up power or tone. Neodymium speakers are especially good in large, heavy amplifiers or amplifiers that have more than two speakers.

http://www.neodymiumloudspeakers.com/

Neodymium Loudspeakers have several advantages over traditional ceramic magnet designs. Typically they are much lighter and more powerful than conventional speakers which use ferrite, Alnico or Samarium Cobalt magnets. Neodymium speakers often have motors that use a small cylindrical slug or ring magnet that is encased in a low carbon steel pot structure. The magnetic flux which is already more than 10 times higher than any other material is concentrated across the "gap" where the voice coil moves back and forth. The strength of the motor (BxL) increases so efficiency goes up and the whole magnetic structure becomes more compact. Typically Neo speakers have the additional benifit of not causing any (EMI) interference from stray magnetic flux so by definition they are video shielded. Neodymium magnets are part of the material science of the future with applications growing everyday. One example is the fast growing earbud market. Neo has made it possible to essentially shrink down headphones to sizes that will fit inside your ears. In addition they are also efficient enough to produce high volume sound from small battery powered devices with low amplifier output such as walkmans, MP3 players , laptops and cell phones.

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post #9 of 20 Old 11-07-2011, 10:49 AM
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Quote:
Originally Posted by mbfleming View Post

Searching via Google seems to indicate the main advantage is applications where size and weight are important. For tweeters perhaps the compactness allows them to be situated closer to adjacent drivers.

Yes, neo magnets make some sense in tweeters but are hardly a necessity for subwoofers.

Very disappointing that SVS has shelved the SB Ultra 16. Perhaps the original claims for this ~$3,000 sub were more difficult to achieve than originally projected.
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post #10 of 20 Old 11-07-2011, 11:09 AM - Thread Starter
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I don't understand why they can't redesign the SB16u to use ferrite magnets. What is it that depended on neodymium?
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post #11 of 20 Old 11-07-2011, 11:29 AM
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Quote:
Originally Posted by mbfleming View Post

I don't understand why they can't redesign the SB16u to use ferrite magnets. What is it that depended on neodymium?

I think that the SB16U would have to be at least a little larger and probably significantly heavier with ferrite magnets.

And, if I am not mistaken the LMS 5400 driver, a favorite among DIY does not have a neo magnet and it is ~$350 less than the TC Sounds Pro 5100 which has the neo magnet.
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post #12 of 20 Old 11-07-2011, 11:35 AM
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I'm assuming SVS was hoping to keep weight down. If the 13 Ultra is any indication, I would imagine the Ferrite 16 ultra driver would be massive and heavy.

Or...Perhaps SVS is redesigning the SB16 Ultra right now as we speak.
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post #13 of 20 Old 11-07-2011, 12:16 PM
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Quote:
Originally Posted by kesando View Post

I'm assuming SVS was hoping to keep weight down. If the 13 Ultra is any indication, I would imagine the Ferrite 16 ultra driver would be massive and heavy.

Or...Perhaps SVS is redesigning the SB16 Ultra right now as we speak.

Given that SVS was sold, I wouldn't take anything for granted. Seems like Ed Mullen said the SB-16 Ultra project has been shelved.
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post #14 of 20 Old 11-08-2011, 10:11 PM
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If the design called for a radial motor, then its pretty much got to be neo. Ceramic mags get way too thick to work in a radial design because that design has no focusing via top / gap plate, so you can't just make the magnet wider to increase the B. In fact making the magnets longer or "wider" can in fact reduce B density in a radial design once saturation occurs.

Radial designs have a really low flux loss % so they are very efficient with the magnets they use -- downside is you can't focus the gap so you need neo. But if we were to convert a radial motor to an outside neodymium ring, we would almost double the amount of neo required. Converting that to ceramic would be even more massive, more than double the weight of the original radial motor in many cases.

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post #15 of 20 Old 11-09-2011, 05:14 AM
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Quote:
Originally Posted by mbfleming View Post

I don't understand why they can't redesign the SB16u to use ferrite magnets. What is it that depended on neodymium?


In other words, unfortunately it's not as simple as swapping the neo magnet for a ferrite magnet.

 

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post #16 of 20 Old 11-09-2011, 06:54 AM
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Theory aside, the REAL problem is that China (The SOLE provider for the raw materials to produce neodymium) is holding the rest of the world hostage by raising the price (1400% increase) and limiting it's export.


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post #17 of 20 Old 11-09-2011, 01:27 PM
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Found an enlightening article regarding China's rare earth element production and artificial supply constraints:

http://www.independent.co.uk/news/wo...s-1855387.html

Note this article is nearly two years old, so we're *slightly* closer to having alternative sources (mines) come online. Interesting stuff.

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post #18 of 20 Old 11-09-2011, 01:40 PM
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Quote:
Originally Posted by BillCinLR View Post

Theory aside, the REAL problem is that China (The SOLE provider for the raw materials to produce neodymium) is holding the rest of the world hostage by raising the price (1400% increase) and limiting it's export.


Bill C

Well, rare earth elements aren't really that rare, but they are particularly toxic and hazardous to mine. The US (and most other countries) have tons of these "rare" elements, but no one wants to mine them due to hazards.

http://www.foreignpolicy.com/article..._actually_rare
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post #19 of 20 Old 11-09-2011, 02:13 PM
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The US had a mining facility in Mountain Pass California. But it shut down in 2002 due to the fact they could not mine the REE's as cheaply as China. It's due to reopen in 2012 or 2013 under Molycorp Corperation. Just remember this is an open pit operation w/alot of pollution and low level radiation involved. Mining companies here in the US must deal w/EPA regulations. Something that China doesn't have to worry about. So It has the advantage of keeping the minig costs lower. Also there is a great deal of intrest in Afghanistan for a huge amount of REE's. It's no coincadence that China is building a new Silk Road to Northen Afghanistan. As soon as we're out of there watch China, India and Pakistan make mining deals. Open pit mining in this country. Forget it. We can't even get off shore drilling for oil.
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post #20 of 20 Old 11-09-2011, 07:18 PM
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Quote:
Originally Posted by mfer View Post

Well, rare earth elements aren't really that rare, but they are particularly toxic and hazardous to mine. The US (and most other countries) have tons of these "rare" elements, but no one wants to mine them due to hazards.

http://www.foreignpolicy.com/article..._actually_rare

Thanks for the link man, I didn't know that.
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