What's the deal on Alnico?

[Coytee]

Is it a brand?

Is it a material?

Why has it seemed to vanish? (gone out of business?)

What is so special about Alnico drivers that can't otherwise be designed into a current production driver?

Why doesn't someone make more drivers with Alnico magnets?

[itsmyforte]

alnico is a type of magnet. made up of aluminum, nickel, and cobalt. though it wasn't a consideration back then, those types of magnets are great for shielding.

[Coytee]

What makes it great for sheilding?

Can't all magnets be sheilded?

By the makeup of the magnet, that infers to me that it might be a man made magnet?

I'm not trying to ask to annoy anyone. I'm just trying to understand the historical/current reality of this magnet called Alnico.

[Marvel]

http://www.magnetsales.com/Alnico/Al1.htm#general

Alnico costs more than ceramic. They are both hard materials to work (grind, polish, etc.)

[boom3]

Alnico was developed in the 30s and 40s because the permanent magnet motors of the time tended to be heavy for their power. Permanent magnet DC motors were needed for aircraft and the existing iron-based magnets were simply too heavy and inefficient. Alnico, until the developmenmt of so-called rare-earth magnets (samarium and neodyium)had the greatest magnetic power for a given size.

In the early 1960s, civil strife in what was then called the Belgian Congo (later Zaire, now the Congo again) disrupted the Western supply of cobalt, which is also used to make steel alloys vital for many products. The price of cobalt steadily climbed until the mid-70s when many speaker manufacturers switched to ceramic ('mud') magnets, and then the rare-earth magnets evolved in the late 70s and early 80s.

Shielding of a magnetic circuit can either be accomplished by a counter (bucking) magnet, or by an iron enclosure. Since ceramic magnets are literally dirt cheap, it is more economical to glue a bucking magnet on the back, and voila, it is "shielded"-not totally, but good enough for home theater.

Many people believe that speakers using alnico magnets exhibit lower distortion than those using ceramic magnets. That may have been true of the early designs, but with better computer visulaization of the magnetic circuit and use of rare-earth magnets, I believe the alnico "advantage' has disappeared. In any case, the choice of a loudspeaker/driver is a disciplined, balanced one and today, the type of magnet material is really not one of the more important factors to consider.

[Spkrdctr]

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On 4/6/2005 7:47:05 AM boom3 wrote:

Alnico, until the developmenmt of so-called rare-earth magnets (samarium and neodyium)had the greatest magnetic power for a given size.

Many people believe that speakers using alnico magnets exhibit lower distortion than those using ceramic magnets. ----------------

The current magnets are superior to Alnico in pretty much every way for manufacturing anything. I would stay away from any Alnico magnet design unless you are rehabbing a vintage piece of gear that requires it. Basically it is outdated in todays world.......

[Deang]

The current production Atlas PD-5VH, as well as the K-55-X which Altas supplies to Klipsch -- is Alnico.

[JohnA]

I'm having trouble remembering the exact details, but AlNiCo driver magnets are said to react differently (less?) to the magnetic field created by the voice coil and thus have better linearity and less distortion.

[KT66]

ALNICO is a conductor whereas a ferrite (a ceramic) is an excellent insulator, hence they exibit low eddy-current effets (or losses)which is why they are used at RF, however ALNICO conduction fosters better transient cone damping (precisely because of these eddies i.e. faraday induction - EM brake effect and all that)aiding amplifier damping.

Use of conductive magnets appears to be considered a good thing by those that know about these things. I'm yet to be convinced but have an open view at present. It would be nice to A/B these claims

Neodymium is also a conductor and I presume 'anachronistic audiophiles' like it for same reasons as ALNICO in addition to its excellent B-H advantage.

It has been said that the best place for a lowly ferrite magnet is your fridge door

[ZAKO]

The magnet (alnico or ferris ceramic) is connected to the top plate & pole piece. The voice coil passes through these two (Gap flux) The voice coil never passes through the magnet. Any type of magnet can be used. Alnico, ceramic. neodymium. The voicecoil dont care. Alnico is easier to demagnetize. (heat, a transient blow, etc).

[dragonfyr]

I am going to do the rare thing and duck on this one!

Personally, I tend to stick with the physics and then look at the business ROI relative to various design options regarding applications. After all, like it or not, every product is not designed to be the ulimate 'ideal' device addressing and resolving every issue. Maybe that is why I have given up looking for the DC to gamma rays, linear phase, point source device with infinite sensitivity (Although I am sure that Bose & too many others are probably advertising one! Sorry, I couldn't resist!)

But if you want to benefit from another group's mutual abuse, you can refer to their discussion regarding the Alnico vs nedymium, etc. Yes, each substance has different characterisitcs and advantages, but unfortunately the object is not necessarily to create an ideal transducer regardless of cost, so you have to deal with both internally and externally determined construction and business constraints. Therefore I fear, the debate over which material makes the best driver is moot, as a properly designed driver using either material should perform within the accepted constraints!

I cannot recall ever being presented with a real world engineering challenge to produce the ideal design regardless of (a myriad of other physical restraints and) cost! (We only did that when in academia and doing funded research for the military or Dept. of Energy!!;-) Usually it is "try to do 'this' (or only occassionally 'the most') within these constraints". And those constraints more often determined the resultant materials and topology.

I fear we may be confusing optimal transducer design with practical market driven design.

But ignore me and enjoy their wrestling match which also has some pretty good references scattered amongst the posts!

http://www.diyaudio.com/forums/showthread/t-54110.html

[TBrennan]

There have been extensive discussions of Alnico over at the Lansing site forum, a search there will bring them up.

For what it's worth I've used high quality Altec and JBL compression drivers with both Alnico and ferrite magnets. I never heard a difference in sound I'd attribute to magnet material. In fact the finest compression driver I ever heard is the ferrite Altec 288K.

Now according to the ever astute and well connected Don McRitchie at the Lansing site the first generation of JBL and Altec ferrite woofers (not compression drivers) had problems with nonlinearities caused by stronger drive force in one direction than the other. Interesting that other companies making and using ferrite woofers evidently found this problem acceptable but JBL and Altec had higher standards.

Those problems are long since solved.

[ZAKO]

At JBL...Symmetrical field geometry magnetic structure greatly reduced speaker distortion. Magnetic flux being equal on both sides of top plate/pole piece. increasing efficiency & power capacity. Later differential drive dual voice coil increased better linearity & greater dynamic accuracy. All new thinking in magnetic geometry.

[Spkrdctr]

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On 4/6/2005 9:01:15 AM DeanG wrote:

The current production Atlas PD-5VH, as well as the K-55-X which Altas supplies to Klipsch -- is Alnico.

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Dean,

I am amazed. I didn't think anyone had any in production anymore for modern gear. Oh well.... Klipsch of all people!

[TBrennan]

TAD, ALE, Goto, Onken, Lowther, Fostex and JBL make Alnico drivers.

[KT66]

As do Celestion and Jensen .. though they are guitar speakers ..

'ALNICO' just sounds right doesn't it ? Just say it and see.

[Spkrdctr]

TBrennan, I wonder if the Alnico is cheaper to manufacture now? There is a reason they are using it and "usually" cost in manufacturing is the #1 reason.......Gee, I have been out of touch with magnets for awhile! The things that happen when your back is turned.....

[BEC]

In my experience, alnico magnets are available in about any size you want to specify. Just that the cost is about 3 times as much as ceramic of similar strength.

Bob Crites

[KT66]

well lets put it this way :

Given the chance to buy two otherwise identical speakers but one with AlNiCo the other a Ceramic magnet. Which would you buy if offered at the same price?

Why?

What if the AlNiCo one cost 3 x as much ?

IMHO, many would go for ANiCo as a phicological reasurance.. just in case - may be even for snob value.

Some companies realise the yerning some have for AlNiCo and are blameless in trying to capitalise on that part of the market?

[ZAKO]

I,m happy with my neodymium magnet drivers. They are mutch lighter in weight. The magnet being smaller than alnico. But having the same magnetic strength & less prone to demagnetization. Remember the voicecoil does not pass through the magnet. The flux density is at the gap between top plate & pole piece.