Alnico VS Ferrite

[speakerlust]

This vote has left out so many speaker magnet types that I would like all votes that are
in favor of anything besides alnico to be in the, "other" category. But Alnicos are my passion.

[Elfasto]

Hmm....Neodynium gets my vote....but alas I cannot......I am sad.

[speakerlust]

Why Neodynium ???

[bowtie427ss]

Gotta be alnico, the best ferrite drivers are the result of lots of innovation and technology applied to make the magnetic field that the voice coil "sees" mimic that of a motor constructed around an alnico slug.

[Zilch]

http://audioheritage.org/vbulletin/showthread.php?t=4031

[Celt]

Each have their virtues, but I'd venture to say if both ferrite and alnico were made in the same manner (slug or other) with the same gauss ratios, voice coils and cones, that they'd both *sound* the same.

[speakerlust]

Thanks for the comments so far, I read the Audioheritage link and here is a statement from it that I believe, "Ferrite is basically a lousy magnet material for speakers but it is cheap and readily available".

Also read this link,

http://www.meta-gizmo.com/tri/aroma.html

[Charivari]

Each have their virtues, but I'd venture to say if both ferrite and alnico were made in the same manner (slug or other) with the same gauss ratios, voice coils and cones, that they'd both *sound* the same.

There is a lot of theory behind dynamic drivers, a heckuva lot more than I used to think, and there are parts of it that would disagree. The term for the day here is "Barkhausen noise".

The idea there is that the major differences in sound between AlNiCo and ceramic or ferrite magnets is that the former is electrically conductive compared to the latter. In the case of electrically non-conductive ceramic magnets, the theory, strongly forwarded by John Wilkinson (look his name up, he's not just another throw away "I know it exists because I can hear it" audio BSer) amongst others, is that eddy currents differentially form between the top and bottom plates that are both formed by the magnetic field created by the voice coil and interact with it again making for non-linearities in the overall magnetic field.

The basic idea is that this interaction causes all the materials involved to experience some jumps in magnetic domains that creates rapid changes in the magnetic field that works with the voice coil to create electromotive motion that in amount to a background noise. This noise is thus named for our Dr. Barkhausen from his first discovery of this effect back in 1919. The theory here is that this lowers the effective signal to noise ratio of the driver and the aforementioned Wilkinson argues that in effect, ceramic drivers are in capable of recreating the dynamic range found in modern digital media and may even have less effective SNR than even quality vinyl.

With drivers that have greater excursion, such as woofers, this has been measured as impedance variations during excursion. The resultant non-linearities result in a great deal of distortion as well. A fix has been implemented with the addition of copper rings to the magnet structure around or inside the voice coil to help break up the worse of these eddy currents and thus improve the linearity quite a bit. Sometimes multiple shorting rings are used such as in the XBL^2 technology that some subwoofer drivers use.

However, there are those who argue that shorting rings are only a bandaid that holds up improved impedance behavior as a quality while ignoring the low SNR due to the Barkhausen noise altogether. Proponents of the idea hold that only electrically conductive magnetic material such as AlNiCo and Neodymium can minimize this issue and allow maximum fidelity.

But hey, don't take my word for it. Let's go back to 1991 with US Patent #5,070,530:

Electroacoustic transducers with increased magnetic stability for distortion reduction

BACKGROUND OF THE INVENTION AND PRIOR ART
The above-referenced copending application discusses observed differences between loudspeaker constructions utilizing non-conductive ceramic magnets and loudspeaker constructions utilizing alnico-type magnets and points out the general inferiority of the ceramic magnet structures. In particular, the effects of distortion due to eddy currents, in the top and bottom plates, which generate local magnetic fields that are coupled back to the voice coil are noted. These eddy currents produce harmonic distortion effects due to the non-linear iron characteristics as well as frequency selective, i.e., frequency dependent, distortion effects because the amplitudes of the eddy currents are proportional to frequency.

In the prior art, the effects of energy loss due to eddy currents in the conductive parts of an electroacoustic magnetic transducer motor structure have been misunderstood. For example, extra conductive material, generally in the form of copper, has been added to the motor structure to flatten the loudspeaker impedance characteristic, i.e., make the characteristic more uniform with frequency. The fact that the energy transferred into the conductive material reduces the energy that is transformed into useful loudspeaker diaphragm motion, and that this effect, which is non-uniform with frequency, results in a reduction in the accuracy of reproduction of transients, has either not previously been recognized or has been ignored. This frequency selective loss in prior art transducer constructions results in transducers with reduced ability to track the rapid changes in audio signals. Indeed, a flat impedance characteristic in a loudspeaker driver has been found to be of secondary importance and is even undesirable when it is produced by non-linear or frequency selective losses in any of the parts of the magnet structure.

It has been discovered that in addition to eddy current effects in ferromagnetic structure parts, ceramic magnets in contrast to alnico magnets, introduce another distortion component. Magnetic fields are introduced into the magnet material by the motion of the signal-carrying coil, whether in a loudspeaker or a microphone embodiment. This energy, which is effectively subtracted from the available useful energy, is proportional to coil travel and is thus inversely proportional to frequency. There are undesirable consequences associated with the phenomenon. For example, the signal-related AC magnetic energy that is induced into the magnet causes distortion. While the exact mechanism has not yet been proven, it is believed that the induced AC magnetic field modulates the DC field in the magnet.

I recommend doing your own research and reading on the subject, because I'm really just trying to figure it out. Well, actually, I kind of gave up trying to figure it all out once I kept running across all these little things that add up to the total driver behavior. It's beyond me, simply put. Can we hear the end result? Dunno, but if there's such a bias for the sound of AlNiCo and Neodymium magnets without people having previously read about this effect, then maybe there's something there. Definitely some interesting stuff, though.

Oh, contrary to what the name Barkhausen may imply, the theory does not apply merely to woofers. (Yeah, yeah, lame, I know.)

- JP

[gearhound]

From the perspective of a guitarist since 1967...........

While both Ferrite and Alnico drivers will break-up with high SPL levels.....
A Ferrite speaker's break-up is rather abrupt....it sounds clean....then goes to sh*t rather fast.
An Alnico speaker's break-up is smoother and more gradual.
IMO, it handles (controls?) break-up....while a Ferrite speaker cannot?
Might not be a scientific explanation....but I've had enough beer bottles deposited my way over the years....to hear the difference!!

Steve

[Celt]

From the perspective of a guitarist since 1967...........

While both Ferrite and Alnico drivers will break-up with high SPL levels.....
A Ferrite speaker's break-up is rather abrupt....it sounds clean....then goes to sh*t rather fast.
An Alnico speaker's break-up is smoother and more gradual.
IMO, it handles (controls?) break-up....while a Ferrite speaker cannot?
Might not be a scientific explanation....but I've had enough beer bottles deposited my way over the years....to hear the difference!!

Steve

Well the thing I keep wondering is, especially with MI speakers, is most of the alnicos have slug magnets that reside behind the voice coil, whereas most ferrite/ceramics surround the voice coil. That has to make a difference in the focus of the field. Admittedly, I haven't spent time reading about motor theory and probably should do so. I tend to punch in the T/S numbers and see whether a given driver will fly or not and not worry about whether the motor is alnico, ferrite or neodymium (Neil Diamond?).

[Celt]

There is a lot of theory behind dynamic drivers, a heckuva lot more than I used to think, and there are parts of it that would disagree. The term for the day here is "Barkhausen noise". Oh, contrary to what the name Barkhausen may imply, the theory does not apply merely to woofers. (Yeah, yeah, lame, I know.) - JP

Funny you mention that. My neighbor's dogs woke me up with that around 5am this morning. :gigglemad

[speakerlust]

QUOTE, "Funny you mention that. My neighbor's dogs woke me up with that around 5am this morning".

Feed em a bunch of cow magnets .... :yes:

[Celt]

QUOTE, "Funny you mention that. My neighbor's dogs woke me up with that around 5am this morning".

Feed em a bunch of cow magnets .... :yes:

Then they'd probably start mooing...

[speakerlust]

:lmao::lmao::lmao::lmao::lmao::lmao:

"Ferrite is basically a lousy magnet material for speakers but it is cheap and readily available".

[JimJ[VT]]

Ferrite's a bitch to move but it's relatively forgiving...Neo has that nasty habit of not regaining back lost magnetic strength after heating. Oops!

[speakerlust]

So what a about a new simple but reliable technology ???
An Alnico Magnet that is wound over with an electro-magnet like from one
of the old field coild speakers and re-energizes the Alnico after it cools ???

[Tom Brennan]

I've owned scads of Altec, JBL and EV compression drivers, both ferrite and Alnicos, and never heard a difference I'd attribute to magnet material.

[ARRAY]

http://www.audiokarma.org/forums/showthread.php?t=72076&highlight=alnico

[speakerlust]

I really, really, like this quote from this link Zilch Posted,

LINK, http://audioheritage.org/vbulletin/s...ead.php?t=4031

QUOTE, "Ferrite is basically a lousy magnet material for speakers but it is cheap and readily available".

[goraman]

What speaker magnet sticks best to the refridgerator? just kiddin a bit.

[speakerlust]

Those damned Roto-Rooter plumbing ones never come off.
Maybe they should make speakers out of fridge magnets ???
:lmao::lmao::lmao::lmao::lmao::lmao:

[Tom Brennan]

Maggies use refrigerator magnets. Really.

[speakerlust]

Do They Taste Like Chicken Too ???

[Charivari]

Maggies use refrigerator magnets. Really.
True, but so does every speaker that uses ceramic magnets. Magnepan magnets are regular ol' ceramic magnet strips attached to a perforated metal sheet with a squashed voice coil over it as opposed to shaping the material into a donut and sticking the VC inside. However, once you get into the ribbon elements for like planars, the magnetic material switches to samarium cobalt or neodymium.

- JP

[speakerlust]

REALLY ??? --- NO JOKE ??? --- I want my fridge door to be a Magnapan !!!
Well, it is looking like everyone pretty much likes alnico ???

[Tom Brennan]

My Maggies had those rubberish strip magnets, just like refrigerator ones, they probably came off a roll. Between that and the saran-wrap diaphragms......

[jblmar]

JBL, for one, over came the flux issue with Ferrite buy way of SFG (Symetrical Field Geometry, IIRC) which focused the magnetic flux in the gap. That's the good news.
Ferrite, for the same flux level as Alnico uses a much heavier magnet. This became an issue with touring groups that had to lug their gear after every gig.

One of the downsides of Alnico is that it will lose it's magnetic strength if droped or played at very high levels over time. Most if not all Alnico JBL drivers bought used will need their magnets 'recharged'.
As for sound, from what I've heard on JBL systems using both types of magnets, I've found the Alnico to have a 'darker' sound compared to Ferrite. Not saying that one is better than the other, just different. The L300 I heard sounded very nice with Alnico. The 4435 and my own 4671 which are Ferrite based, had, IMO, a much more open sound. Similar jazz played on both systems.

Ron

[speakerlust]

What is a darker sound :) ???

[Charivari]

Between that and the saran-wrap diaphragms......
Magnepan diaphragms are made of biaxially-oriented polyethylene terephthalate film, such as most often sold under the trademarked names of Mylar, Hostaphan, Dacron, etc. This material is known for its superior mechanical and chemical properties and finds a great deal of use in the high tech sector. The standard NASA "space suit" employs five separate layers of this material to protect the astronaut within from the extremely low pressures of the outer limits of the atmosphere, stellar and interstellar radiation, providing strength to the contained breathable atmosphere, as well as providing abrasion resistance and some protection against micrometeroids. All in all, a superior material.

Saran wrap, on the other hand, at least that of which you speak, is composed of low density polyvinylidene chloride. It is a material not the least bit related to PET and would be difficult for the educated eye to confuse the two.

Now, how exactly is boPET inferior to the pressed toilet paper scrap cones of your avatar speakers? Or how about the compression driver diaphragms made of phenol formaldehyde resin -- a chemical reactant of embalming fluid?

Hmm, NASA space suit and scientific equipment approved film as opposed to compressed toilet paper and embalming fluid diaphragm. No wonder you draw the conclusions you do.

:D
- JP

[Tom Brennan]

Cherry----A long winded reply to a joke you evidently missed. My fault.

[jblmar]

What is a darker sound :) ???

To me the difference is a more open sound with ferrite v a 'darker', more colored sound with Alnico. I heard the al and ferrite based systems on different systems at different times, but judging from my own L 100s and 4671, I can hear a difference. A neighbor has the L 101 speakers which are Alnico. Still not as clear as the ferrite based system.
I may be wrong and by no means are my findings scientific, but I did hear a difference. I used my L 100s and 4671 with the same amp so at least that was consistant.

Ron

[speakerlust]

Yeah, I have three pairs of alnico speakers and two of the pairs I have out
of the cabinets to ad some metal to the cabs. They are 15's and 12's both
pairs with horns. They did sound a little dark but I believe that is a function of me needing to replace the caps for the horns which are over 30 years old.
I say try turning up the treble and repeat the test that you performed and see if the alnicos don't come to life ???

[tomt]

Each have their virtues, but I'd venture to say if both ferrite and alnico were made in the same manner (slug or other) with the same gauss ratios, voice coils and cones, that they'd both *sound* the same.

Ragnar Lian, co-founder of Scan-Speak,
said that speakers with alnico magnets had 10x less distortion than ferrite,
and neodymium had about 20x less.
If a copper ring is added to a ferrite magnet,
it can approach neodymium specs but only above a certain frequency,
below which the ring becomes ineffective.


http://www.audioroundtable.com/Speaker/messages/243.html

http://growabrain.typepad.com/photos/uncategorized/wild_kid.gif

[Celt]

Ragnar Lian, co-founder of Scan-Speak,
said that speakers with alnico magnets had 10x less distortion than ferrite,
and neodymium had about 20x less.
If a copper ring is added to a ferrite magnet,
it can approach neodymium specs but only above a certain frequency,
below which the ring becomes ineffective.


http://www.audioroundtable.com/Speaker/messages/243.html

http://growabrain.typepad.com/photos/uncategorized/wild_kid.gif

Ah...that explains the copper ring I saw inside my FF165K Fostex drivers!

http://www.audiokarma.org/forums/attachment.php?attachmentid=52055&d=1182194900

[tomt]

Ah...that explains the copper ring ...




some Philips drivers have copper on the pole piece ...

[speakerlust]

Ah...that explains the copper ring I saw inside my FF165K Fostex drivers!

http://www.audiokarma.org/forums/attachment.php?attachmentid=52055&d=1182194900

FOSTEX DRIVERS ??? -----I'll take tw of em :banana:

[Celt]

Madisound has plenty of 'em in stock I am sure... :yes:

[speakerlust]

What did your's cost you Celt ???

[Celt]

Those sell for around $60 each.

[speakerlust]

How do you like the sound quality ??? would you buy them again, or choose
a different model same brand ???

[speakerlust]

Someone who is still producing Alnico Speakers http://www.lowtherspeakers.com/lowther.html

[bluesky]

Very Interesting. I have only a few questions:
1. How do you know when your alnico magnets need to be "recharged"?
2. Who "recharges" these magnets?
3. Does anyone know how the sound would change? I take it that it would be for the better.

I have 3 pair of speakers made in 1970 and they have alnico magnet drivers. For me...I have always loved the alnico sound. Maybe that's because it is just the sound that I grew up with and am used to. But...I really do like an alnico sound. To me, it just sounds fullfilling.

Thanks guys!! :thmbsp: