What happened to the alnicos?

Could be like Gasoline the price fluctuates with speculation?
Although the Jump was last month and it has receeded :)
London Metal Exchange: Cobalt
Sad part is that Alnico performs far better than Neo in speaker motors. Neo is Very temp sensitive.. at 100C most all Neo variants demagnetises.. Not good. But then it's beyond normal for speaker motors to get to even that level of overheat.. or not?
Besides Neo self oxidizes into toxic powder as soon as the encasing plating fails.. typically far Sooner rather than later. Even I have few examples of that self destruction. Safely, in sealed containers.
Whereas the Cobalt alloy Alnico has a 2000 year Utterly stable Gauss with a 2000 year projected Half Life . Also has ~600+ Celcius Currie point and NEVER actually needs a remag.
(Unless owned by someone who has no clue and the 'servicing' is by some inept disreputable )

Interesting material indeed.. even beyond strategic (Nuclear warhead) uses.

Alniico is one of the time proven better motor components of any worth owning speaker.
Likely some makers are starting to charge even more than their costs :).
Profit is where they can squeeze / find it.. increasingly the way of the world.
Too much? don't Buy :)
 

Guitarski

Member
2013-02-08 11:54 am
@Bare
I read somewhere that alnico magnets costs $44 / Kg, so the price may be in the production, but why the overnight hike? If it has a military angle, as too many things do nowadays, then what happened in 2010, just curious.
I didn't even know that neodynium was so unstable, that's not the bang for buck I'm looking for.
@xrk
Alnico smooths out the sound of a distorted guitar and gives it a quick attack. Many people like the "British" sound, which is spikey by definition, as opposed to smooth. Therefore alnicos with a British voicing, like the above-mentioned, are actually a contradiction.

Thanks/regards
- Guitarski
Http://rocking.mobi
 
many forms of NdFeB mags exist, some of which withstand temperature far better, such as those used in permanent magnet wind generators (Which i was involved in testing some 5 years ago). As with many things, you get what you pay for, although you can pay too much (poor neo can be found, just as poor alnico and ferrite can also be found, Whatever material quality costs. Samarium cobalt seems to have fallen from favour, i have no idea why.
 
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There are old threads on this topic of alnico vs neodymium vs ferrite.

http://www.diyaudio.com/forums/full-range/106945-does-neodymium-sound-like-alnico.html

I am of the belief that it all comes down to field strength. If you design motors to have same B field in magnetic gap, the voice coil knows no different. Different magnet materials call for different physical dimensions. Good design technique should be used to provide adequate cooling to stabilize temperatures but the fundamental physics of Lorentz's law doesn't care about what material is in the equation: Force = q (v X B), where q is fundamental charge of electron, v is the velocity of electron in wire loop, and B is magnetic field. The magnetic field B is all that shows up, not any other 'intrinsic' property of the material. When arguments for the sound quality of any component in a system refer to subjective descriptions, it needs to have physical basis otherwise it becomes similar to arguments of why audiophile grade speaker wires are better than cheap lamp cord, or why Teflon insulation is better than PVC insulation on audio (not RF) signals, etc. I am not saying that there is no difference in the sound, of course there is, but is the difference really due to the magnet material? As an earlier post in the referenced thread, it may come down to manufacturers giving better build quality and fit/finish and tolerance in their high end premium 'alnico' systems rather than any difference in the actual material if the B value was held fixed. A design that provides identical B field strengths, there should be no difference as far as the physics are concerned.
 
Not sure. We haven't done much on a quantum level yet (1st year Physics at Sheffield).

I'm thinking of eddy currents: when current flows through the voice coil, it creates a magnetic field, which must disturb that of the permanent magnet.
For a perfectly conducting magnet, huge eddy currents would flow in order to oppose these changes, and the magnetic field would hold rigid.
For some material that doesn't conduct perfectly, its magnetic field is dented inwards, as the eddy currents don't fully compensate.
Copper demodulation rings are often used in higher-end speakers to ensure greater eddy current flow, to keep the magnetic field more rigid. These are usually found on Ferrite magnets: I'm told Neodymium doesn't need it, as its a much better conductor.

A "rigid" magnetic field is desirable for HiFi: it reduces distortion. For guitar, its all about which subjectively is better.
I'd infer that AlNiCo is a relatively poor conductor of electricity, giving it the legendary "smooth" sound.

Chris
 

Guitarski

Member
2013-02-08 11:54 am
So, speaker design is the battle of the eddies?
Indeed, it's entirely subjective. It's just because I'm a guitarist that I'm an alnico buff. And even then many guitarists prefer a harsher sound.

In guitars a mahogany body and a maple top work against each other, causing frequencies to cancel, to which the smoothness (in sound) of this wood combo is attributed.
So I would expect alnico smoothness to be based upon the filtering of frequencies also.

Thanks/regards
- Guitarski
www.rocking.mobi
 
Not so.

Think about the relative conductivities of different magnets, and what happens when current flows through a voice coil.

Are you talking about magnetic conductivity (permeability) or electrical conductivity? Alnico is a metal and conducts well, NIB and ferrite are ceramics - poor conductors. So is the issue the relative susceptibility of each magnet to having eddy currents induced in them, thereby altering their field, hence distortion? If this is the case, alnico being a conductor is most susceptible to induced eddy currents and probably has the most distortion, explaining why electric guitarists like them.
 
Are you talking about magnetic conductivity (permeability) or electrical conductivity? Alnico is a metal and conducts well, NIB and ferrite are ceramics - poor conductors. So is the issue the relative susceptibility of each magnet to having eddy currents induced in them, thereby altering their field, hence distortion? If this is the case, alnico being a conductor is most susceptible to induced eddy currents and probably has the most distortion, explaining why electric guitarists like them.

I'd've expected AlNiCo to be a poor (electrical) conductor, thus keeping eddy currents down and distortion up.

Large eddy currents would hold the magnetic field more rigid, which is why manufacturers like Peerless use them in HiFi speakers.

But you're quite right, AlNiCo is a decent conductor, while ceramic magnets aren't.

Anyone care to shed some light over here?
 

jcx

Member
2003-02-17 7:38 pm
..
High density sintered Neodymium magnets are metallic glasses - conductivity is within a factor of 2-3 of AlNiCo

BH product, coercivity/permeability are the big differentiators, in some applications AlNiCo beats on high operating temperature


both are "poor electrical conductors" compared to Al, Cu, Ag but still quite electrically conductive

lower performance bonded Nb magnets can have electrically isolated particles, high bulk resistivity
 
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This discussion also makes me wonder if all the "field coils" in uber-high-end drivers is really all hype? There is no room temperature (read non superconducting) electromagnet that can achieve the same field strength of a NIB magnet. Why bother unless you want some sort of active field strength adjustment or something like that? Are there other benefits to field coils that I am unaware of other than having to provide yet another high current regulated DC power supply for the coils?
 
global cobolt production AlNiCo
Cobalt Production by Country (Metric tons, cobalt content)
And from Wiki
The Second Congo War, beginning in 1998, devastated the country and is sometimes referred to as the "African world war" because it involved nine African nations and some twenty armed groups.[4] Despite the signing of peace accords in 2003, fighting continues in the east of the country. There, the prevalence of rape and other sexual violence is described as the worst in the world.[5] The war is the world's deadliest conflict since World War II, killing 5.4 million people since 1998.[6][7] The vast majority died from conditions of malaria, diarrhea, pneumonia and malnutrition.[8]
 

Guitarski

Member
2013-02-08 11:54 am
global cobolt production AlNiCo
Cobalt Production by Country (Metric tons, cobalt content)
And from Wiki
The Second Congo War, beginning in 1998, devastated the country and is sometimes referred to as the "African world war" because it involved nine African nations and some twenty armed groups.[4] Despite the signing of peace accords in 2003, fighting continues in the east of the country. There, the prevalence of rape and other sexual violence is described as the worst in the world.[5] The war is the world's deadliest conflict since World War II, killing 5.4 million people since 1998.[6][7] The vast majority died from conditions of malaria, diarrhea, pneumonia and malnutrition.[8]

That's shocking, isn't it? Everyone should write to their president or PM to do something about it, because THEY (the legislators) have the power and responsibility to do something about it, although they deny it.

Thanks/regards
- Guitarski
www.rocking.mobi
 

Guitarski

Member
2013-02-08 11:54 am
Anyway...this thread is quite interesting, thanks to the previous posters. I used to think that speaker distortion was a mechanical thing: the cone and the paper going haywire. As a home recordist I can't put my neighbors through pushing my speakers to distortion anyway. But now I understand that speaker distortion is also in the interaction between magnet and coil. Would it then be possible to control or induce speaker distrortion electrically, that is, vary the susceptibilty of the speaker to distortion, so that it distorts at lower volumes?

Thanks/regards
- Guitarski
www.rocking.mobi