Home » Audio » Speaker » Is Neo really the One? Oracle Cleo wouldn't tell me...
Is Neo really the One? Oracle Cleo wouldn't tell me... [message #17480] Mon, 24 January 2005 18:41 Go to next message
Duke is currently offline  Duke
Messages: 297
Registered: May 2009
Grand Master
I've been reading good things about Neodymium as a magnet material, namely that it has some of the desirable properties of Alnico (such as low flux modulation) at a much lower cost.

Now from what I gather reading some of the dialogue between Earl Geddes and Wayne Parham, one of the nice things about Alnico is that it's conductive, so that in effect it is its own "shorting ring".

Does Neodymium have this self-shorting properly like Alnico? Or, in order to approach the low distortion performance of say a JBL driver, would a Neo driver need its own shorting ring?

Thanks!

Duke

Re: Is Neo really the One? Oracle Cleo wouldn't tell me... [message #17482 is a reply to message #17480] Mon, 24 January 2005 21:54 Go to previous messageGo to next message
Bill Martinelli is currently offline  Bill Martinelli
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Registered: May 2009
Illuminati (1st Degree)

There are more neo driver I like over any other type. Scientifically It would seem flux in the gap is flux in the gap. The flux measurments of neo drivers is more often higher than ceramic counterparts. Subjectively, I like the sounds of neo drivers over the ceramic counterpart. Cant say the ame about alnico. I havnt fooled with the sheilding properties in a while but alnico definately sheilds itself and I think the neo drivers are the same. I'll have to make a test.

Bill

Re: Is Neo really the One? Oracle Cleo wouldn't tell me... [message #17483 is a reply to message #17480] Mon, 24 January 2005 22:13 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
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Registered: January 2001
Illuminati (33rd Degree)
Here's a link to a discussion about neodymium magnets in the Speaker forum:

Re: Is Neo really the One? Oracle Cleo wouldn't tell me... [message #17484 is a reply to message #17482] Mon, 24 January 2005 23:23 Go to previous messageGo to next message
Duke is currently offline  Duke
Messages: 297
Registered: May 2009
Grand Master
I appreciate your taking the time to reply, Bill.

When you say you like the sound of Neos over their ceramic counterparts, are you referring to compression drivers, or cone drivers, or both?

Thanks,

Duke

Re: Is Neo really the One? Oracle Cleo wouldn't tell me... [message #17485 is a reply to message #17483] Mon, 24 January 2005 23:24 Go to previous messageGo to next message
Duke is currently offline  Duke
Messages: 297
Registered: May 2009
Grand Master
Thanks for posting the link, Wayne. Interesting discussion.

Duke

Re: Is Neo really the One? Oracle Cleo wouldn't tell me... [message #17493 is a reply to message #17484] Tue, 25 January 2005 18:27 Go to previous messageGo to next message
Bill Martinelli is currently offline  Bill Martinelli
Messages: 677
Registered: May 2009
Illuminati (1st Degree)

Hi Duke,

Both compression drivers and cone drivers with neo magnets have become my drivers of choice. For compression drivers I have only heard BMS with neo magnets I like to listen to the sound better and they measure smoother/flatter and more bandwidth. For cone drivers The Eminence Deltalight series, BMS, 18 sound and BC drivers all offer neo and there are many others too. Another great feature is weight savings. Both in moving/handling and shipping.

Bill

Re: Is Neo really the One? Oracle Cleo wouldn't tell me... [message #17504 is a reply to message #17480] Thu, 27 January 2005 06:58 Go to previous messageGo to next message
Earl Geddes is currently offline  Earl Geddes
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Master
Duke

Most of the important points have been covered but one very important one was not even mentioned.

First ALNICO does have the lowest flux modulation, followed by Neo and ceramic is pretty bad. But this problem can be fixed with a "good" shorting ring.

BUT what was never mentioned is the thermal changes. ALNICO, owing to the fact that it is a hot cast material, has no change of flux with temperature thus it has the lowest possible thermal compression. Neo is pretty bad in this regard, but ceramic is really bad. A ceramic magnet can loss as much as 40% of its flux when heated to a typical temperature in higher output situations.

We discovered this when making a speaker for an active exhaust system that got to about 150 c°. We found that at operating temperature the ceramic magnet had almost no B left. ALNICO was the only choice in this application.

Of course the very best magnet, Symarium Cobalt, is just too expensive to even consider.




Thanks, Earl! [message #17518 is a reply to message #17504] Fri, 28 January 2005 09:33 Go to previous messageGo to next message
Duke is currently offline  Duke
Messages: 297
Registered: May 2009
Grand Master
I appreciate your taking the time to describe what's happening to the flux as the temperature goes up.

Now from what I gather, with a ceramic magnet motor a good shorting ring effectively minimizes flux modulation, while as long as the temperature doesn't go up too much the flux remains high. If indeed pro-sound drivers barely even "break a sweat" in a home audio application, in your opinion is the real-world performance difference between ceramic (with shorting ring), neodymium, and alnico fairly insignificant, at least in an application like your home theater room?

Thanks!

Duke

What about field coil drivers? [message #17519 is a reply to message #17480] Sat, 29 January 2005 04:07 Go to previous messageGo to next message
Arturo is currently offline  Arturo
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Registered: May 2009
Esquire
http://www.audioasylum.com/forums/hug/messages/83429.html

Re: What about field coil drivers? [message #17520 is a reply to message #17519] Sat, 29 January 2005 05:22 Go to previous messageGo to previous message
Wayne Parham is currently offline  Wayne Parham
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Registered: January 2001
Illuminati (33rd Degree)
That's an excellent mention. One certainly has some flexibility when using field coil speakers that isn't there with fixed magnet speakers. You can energize the field coil enough to saturate the magnetic circuit and maximize flux in the gap. Or you can reduce field coil strength to change electro-mechanical parameters of the speaker. You can even modulate the field coil, perhaps making it opposite to the voice coil drive. Then again, since the field coil is an inductor, the ability to modulate its magnetic strength diminishes as frequency rises. It will tend to filter the signal and average the flux.

There are two things I'd like to point out. First, a constant-current supply has high source impedance, so it isn't what those guys are thinking about. Constant-current supplies limit current so that even when the load fluxuates, the current flowing is the same. But this means that as the load impedance fluxuates, the voltage across it does too. Constant-voltage supplies maintain a constant voltage regardless of the load. Automobile batteries are a good example, pretty much constant voltage even at high current levels. I think that's what those guys meant when they said they wanted constant-current supplies. They probably really wanted a constant-voltage supply capable of unwavering high current levels. They wanted consistent flux.

The second thing I wanted to point out is that the speaker's magnetic circuit can be put into saturation. The pole pieces and the magnet form a circuit, and when the circuit is saturated, it doesn't matter if you add magnetic energy, very little additional magnetic flux is added to the gap. So you can increase magnetic strength from zero to saturation, but if the circuit is already saturated, you cannot add more. What that means, is that if you want to modulate the field coil, it must be done at levels under saturation.

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