Neodymium magnets vs Ferrite magnets

[Pano]

The ferrite drivers that replaced alnico versions were generally heavier due to the greater magnet mass required to give the same gap flux.

Quite true. Thanks for mentioning that. The Alnico magnets were mostly rod shaped. I.E. the magnet is the pole piece. So magnet geometry is different.
Don't know how the neo magnets are done.

Anyone?

 

[blueae1405]

So it's all about looks when higher end speakers use Neo magnets? There is really nothin better that Neo has then Ferrite?


Do Neo magnets last longer and are they usualy durable? Since if that's the case maybe that's the biggest reason why they use Neo on higher end speakers.

 

[tinitus]

Hmm, you get higher magnet power on alnicos by increasing the length

On ceramics its the opposite, its more effective to increase diameter
Greater thickness gives less

Optimal size of ceramic magnet could easily end up being as big as driver mounting hole, or bigger, which isnt practical

In the old days with alnicos it sort of worked on its own
When forced to use ceramic instead problems began
Concerns flux variations caused by the moving voice coil

Oh, I actually forgot the only thing I wanted to say
One reason some use high power neos is because it really is the only way to get close to alnicos, and its cheaper

 

[thunk303]

Neo is often the only choice when building something like a tweeter where a compact body allows placement much closer to the mid range driver.

Is that foam between the neo magnets on the Tangband?

 

[ted4412wilt]

I think the small size of Neo magnets gives less restriction to the backside air flow. The lowest distortion midwoofer I have ever seen used Neo.
Ted

 

[Iain McNeill]

The target application is important too. Is this a high power, high reliability application (e.g. 18" driver 200' up in a stadium scoreboard) or is it a portable music player (minimum weight, maximum efficiency)? Different strokes, YMMV, etcetc.

As I said, there's no best, just least bad - and its different for everyone.

 

[mp9]

a shielding cup is a mickey mouse way of doing it unless it's also enclosing a bucking magnet. they do helps in other ways too, think spendor.

 

[Iain McNeill]

Does anyone have any data on the 'resilience' of the different magnets. What I mean is, when you put a big signal through the voicecoil it generates a significant magnetic field of it's own. How does neo respond to that counter field with respect to flux saturation in the core and dynamic range compared to ferrite & alnico?

 

[planet10]

http://www.diyaudio.com/forums/multi-way/5857-barkhausen-noise-drivers-inductors.html
http://www.diyaudio.com/forums/multi-way/12565-neodymium-now-mainstream.html
http://www.diyaudio.com/forums/multi-way/35936-best-sounding-magnet.html
http://www.diyaudio.com/forums/full-range/106945-does-neodymium-sound-like-alnico.html

dave

 

[Iain McNeill]

..without leaving the site

Thanks Dave!

 

[Brian Kingsbury]

Ill hazard a guess...Neodymium magnets' smaller size and lighter weight allow for a smaller/thinner basket structure on woofers. The benefit of a smaller basket is two-fold - you get more airflow around the driver and also allows the speakers backwave to radiate into the cabinet instead of being reflected off the magnet/basket structure. This theory follows the same reasoning why most DIY speaker builders use a chamfer around woofer cutouts to allow the speaker to 'breathe' properly. Scan-speak's descriptions of their woofers using neodymium magnets emphasizes their airflow characteristics and lack of compression as being a benefit of the open frame and small magnet structure.

 

[thoriated]

thoriated, good explanation, how about the lanthanum-colbalt magnet of my fostex 166esr?

I hear good things about the special features of this driver in general, compared to the standard ferrite magnet 166e. Not having listened to it myself, I shouldn't comment on the magnet's qualities compared to alnico, etc.

 

[blueae1405]

So it seems like alnico magents are the best but since they are too expensive they use Neo magnets that are very close to Alnico magnets on speakers like the Sonys I have right? Meaning if they used Alnico Magnets for my Sony speakers it would have costed more but then it would of been the best magents.

 

[InclinedPlane]

I notice the Precision Devices 10" and 12" Neodymium drivers boast a flux of 1.67T. For a large speaker that's the highest I've seen - close to that of JBL's $1k compression drivers or even some of the Lowther drivers. I'm not saying this kind of flux can't be achieved with ferrite, but I just haven't seen it.

Oh, and please buy me some, kthnx.

 

[blueae1405]

What makes me really wonder is how can a small speaker like the Sony SRS-ZX1 that is only 57mm driver can make soo much deep bass and can go pretty loud? Does the speakers have a big Neo magent or something?

 

[Scottmoose]

Ignore what the large companies claim in their advertising. It's advertising.

Re those loathsome little Sony's, basic physics. There's only one way to get any LF out of a tiny box, and that's a long throw driver with miserable sensitivity. We look at the spec. page and what do we find? A 4Ohm impedance with a shockingly low 78dB efficiency rating. Even electrostatics usually have a higher figure than that. Note too the convenient lack of anything resembling measurements (FR & impedance graphs, polar response, displacement, vent velocity...)

There is no one answer as to why a specific type of magnet material is used, could be any one of a few dozen. Cost is a major factor, and advertising in the commercial market dominates. Neodium can be, and is, often presented as some form of 'high-tech' solution, and because of the nature of the magnets, can usually be arranged to give a driver a fancy appearance. I'm amazed. It's much better than my usual washing powder. New & Improved (just think, I've been working with Old and Inferior all my life).

Back down on planet Earth, this is seen as the bollocks it really is. In reality, it's as much about how you use the materials as the materials themselves, once you reach a certain level of quality. Neodium is not a panacea; no more is AlNiCo, or ferrite (of whatever type).

 

[Geek]

Ignore what the large companies claim in their advertising. It's advertising.

Not to mention their specs are taken under (for reputable companies anyhoo) perfect conditions in an anechoic chamber.

Our rooms are rarely anechoic.

I'm lucky in that my listening room has nearly +20dB boost at 40Hz and I don't need any woofer to speak of.

I'm unllucky in that my listening room has nearly +20dB boost at 40Hz, so when I take my "perfect" speakers to friend's houses, they sound like @#$%^

Cheers!

 

[Brian Kingsbury]

My speakers are a 2-way with 6.5in woofers, I'd take +20db @ 40hz anyday..... Make your friends come over if they want a listen

Back to magnets.. It's not about which magnet material is best, it's about wether the material used is implemented properly. Maybe a good analogy is to re-use an age-old saying refering to something else altogether:

"It's not the size that matters, it's how you use it that counts"

 

[blueae1405]

Is this really true? "There's only one way to get any LF out of a tiny box, and that's a long throw driver with miserable sensitivity" Since I would think that you need great sensitivity to make the speakers have alot of bass but you made it sound like all it needs is a long throw driver and not good sensitivity to make good low bass.

 

[Geek]

Is this really true? "There's only one way to get any LF out of a tiny box, and that's a long throw driver with miserable sensitivity"

Pretty much, but I'd hate to think 88dB is "miserable" for good bass.

Since I would think that you need great sensitivity to make the speakers have alot of bass...

You got that backwards...

...but you made it sound like all it needs is a long throw driver and not good sensitivity to make good low bass.

Speakers are all about tradeoffs.

Grossly simplified as I understand it:

Good bass + high sensitivity = LARGE diameter and low Xmax.
Good bass + reasonable diameter = lower sensitivity + longer Xmax.

Bass = moving lots of air. So if you want small diameter + high sensitivity, you need a big horn to move air.


Cheers!