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

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

• Alnico verses ferrite verses neodymium

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

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

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.

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

• http://www.audioasylum.com/forums/hug/messages/83429.html

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.