Alnico versus ferrite Neodymium

[Helmuth]

Hi,

I see exotic brands produce alnico drivers also seas and Fostex make these. I ask my self do they sound different to a modern low distortion ferrite or neodymium design.

Because the alnico magnet does distort less because it is less effected by the voice coil magnetism this means ferrite seems to change its flux although one would think it is a constant value. As far I know by reading some topics.

So is it a fairytale or are these drivers always better performing due better motor.

[pieter t]

Don't forget the age factor.
Vintage alnico drivers often need remagnetization to reach original specifications (alnico's are no permanent magnets).

[Helmuth]

I believe I did explain it the other way around. Here a topic of "Flashman"

I wondered why an alnico magnet might have an edge on a ferrite magnet and found this on the Internet (Weber Speakers - Making the world a bit louder each day.). Pretty interesting stuff and confirms some of the comments we have heard about the alnico advantages (better high and low frequencies, and can play louder without distortion). There's an interesting comparison to a given magnet's circuit, with the alnico being compared to a tube amp and a ferrite to a solid state amp. Here 'tis:

The whole 'Alnico mojo' is about smooth compression at high average levels, such as what you would have running the amp flat out. AlNiCo (Aluminum-Nickel-Cobalt) is an alloy magnet and all alloy magnets are easier to demagnetize than comparable Ceramic (Strontium Ferrite) magnets. What this means is that as the voice coil starts moving in response to the input signal, it generates a magnetic field of its own that tries to demagnetize the magnet. As its effect lowers the available magnetic field of the AlNiCo magnet, the speaker becomes less efficient, the voice coil moves less, etc. The physics of it is that the small magnets near the surface of the magnet poles (called 'domains') begin to change state, or flip directions. The result is smooth compression, the same kind of operating curve compression that occurs in a tube amplifier. The ceramic magnet, on the other hand, doesn't compress or demagnetize as easily, so the voice coil moves to its mechanical limit and won't go any farther. This is why some players say ceramics sound a little edgy at high average levels as opposed to AlNiCo. However, by properly designing the entire magnetic circuit, ceramics can be made to behave quite well for desireable guitar amp tone and dynamics. You might compare the two magnetic circuits to solid state amps versus tube amps, where the solid state amp gives it all its got then clips hard, while a tube amp compresses nice and smooth. The extension of this idea, then, is that with the AlNiCo, like the tube amp, you can seem to have a louder average volume since it gets compressed smoothly. By the way, the compressing or demagnetization that occurs with the AlNiCo is not permanent. It springs right back to its design operating point.

A voice coil is like an electric motor. The bigger the voice coil, the more wire used, the more torque or pulling power you have to move the cone. With the proper match of components, you can get more sensitivity, wider frequency response, and more power handling ability.

[woody]

It's not just a mater of how strong the magnet is there is another
effect that may explain why alnico and field coil drivers sound better.
Barkhausen effect - Wikipedia, the free encyclopedia I will leave the reading up to you and leave the conclusion up to you also.

[sreten]

Originally Posted by Helmuth

Hi,
So is it a fairytale or are these drivers always better performing due better motor.

Hi,

Its not a fairytale in the sense Alnico structures are like ceramic structures
with included Faraday rings by default, but there is a lot more to it than that.

rgds, sreten.

[Helmuth]

Originally Posted by woody

It's not just a mater of how strong the magnet is there is another
effect that may explain why alnico and field coil drivers sound better.
Barkhausen effect - Wikipedia, the free encyclopedia I will leave the reading up to you and leave the conclusion up to you also.

The barkhausen-effect topic doesn't tell if alnico is better in this area.

http://en.wikipedia.org/wiki/Alnico

[suntechnik]

Originally Posted by Helmuth

Hi,

I see exotic brands produce alnico drivers also seas and Fostex make these.

Regrading Fostex currently I am using T500AmkII which is alnico and was manufactured in Japan + FE206ES which is ferrite and was manufactured in China. Both are nice.

Prior I was owning full size Magneplanar that was ferrite AFAIK. These "doors" were in absolutely another league of music reproduction. Unfortunately had to downgrade due to WAF and class A amplification electricity waste.

The point is magnet type could not prevent solid manufacture come up with a decent product.

I believe modern neodymium magnet is the right way to go if designing speaker motor from scratch. Howevera as I recall there was some kind of discussion on the forum that Japan is experiencing shortage supply with Nd from China that is another aspect to consider for a real manufacture. The article was called something like "Japan under the thumb of China".