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Old 23rd September 2006, 01:05 AM   #1
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Default neodymium speakers ?

Greetings,

Anybody know anything about neodymium speakers?

So far I've understood that a neodymium speaker is a speaker that uses
Neodymium Iron Boron (NIB) as the material for the magnet. NIB is a very
strong permanent magnet.

My question is, whats the benefit? efficiency? cost? weight?

I'm taking a guess and thinking it's about power/weight, ie more power for
less magnet volume...but this would have to balance with quality of the coils.
Could also have to do with longer life span, neodymium holding the imprinted
field longer then normal magnetic materials?
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Old 23rd September 2006, 01:23 AM   #2
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Look, I'm not an expert on this, but I read recently that while being powerful for their weight they can lose their strength when heated too much. Which may be a problem when used in cars where they hold some appeal to car-audio designers simply because of their low mass. There'll be others with more magnetic 'knowhow' than me that may clarify/expand on this.
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Old 23rd September 2006, 01:38 AM   #3
poobah is offline poobah  United States
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All other things being equal; a voice coil can develop more force in the presence of a stronger magnetic field.

There are million ways you could comprimise things; probably the best outcome is reduced thermal stress in the voice coil when compared to a non NIB speaker at equal volume.

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Old 23rd September 2006, 02:04 AM   #4
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I've just built my first set of neodymium speakers, all I can say is that they are extremely light and powerful. the 12" PA (SPL 97db) 200w RMS driver is much lighter than say a 8" (89 db) 80 w Hi Fi Driver.

I do not hear a compromise due to the weight loss ect, It is simply much easier to carry! I am overall very impressed by the results!
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Old 23rd September 2006, 04:41 PM   #5
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Quote:
Originally posted by poobah
All other things being equal; a voice coil can develop more force in the presence of a stronger magnetic field.

There are million ways you could comprimise things; probably the best outcome is reduced thermal stress in the voice coil when compared to a non NIB speaker at equal volume.

Does this mean that NIB speakers have thinner gauge voice coil windings to keep the impedance correct?
I suppose if you used the same length of wire in a Neodymium speaker as in a conventional one then ...... hmmm they'd just be very sensitive ...... which they are.

I guess what I'm trying to ask here is: are the voice coils in a Neodymium speaker the same as one with a regular strength magnet?
and
Is a very powerful magnet infinitely more desirable or is best to find a balance of magnet and voice coil?
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Old 23rd September 2006, 04:54 PM   #6
poobah is offline poobah  United States
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Well I guess that you could reduce the number of turns and use thicker wire... this too would improve efficiency.

There are so many ways to "spread things around", that any quantitative remarks have to invoke the "all other things being equal" clause before any A vs. B comparisons are drawn I guess.

My point being is that one could design a NIB speaker, equivalent in every way with norm and realize no benefit other than perhaps weight reduction. Some of these NIB speakers do indeed have the small diameter voice coils... like the old alnicos had.

I'm guessing that unless the magnetic increases are used to boost effifciency, than there may be no sonic advantage. Consider the reverse; the lack of alnico hasn't hurt things has it?

I have done some PM motor design using NIB... the way we "spread things around" was to achieve higher torque with less diameter (smaller) and higher efficiency because of fewer windings. The point remains... we could have opted to make the motor smaller still and foregone the increases in efficiency.


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Old 23rd September 2006, 05:03 PM   #7
AndrewT is offline AndrewT  Scotland
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Hi,
neodymium like ferrite is susceptable to magnetic loss at elevated temperatures.
The VC is unlikely to be any different whether neo or ferrite.
The magnetic flux across the gap could be either stronger of weaker and depends on how much magnetic material the designer builds into the circuit.

Since the spec rarely includes magnetic flux you can guess it has not increased, else they would be shouting about it.

The benefit is reduced weight, this being particularly important for portable speakers.
The extra cost comes from the re-engineered magnetic circuit and the extra magnetic material cost.
There are few if any other benefits unless the designer needs to improve the speaker in some particular regard, but that could be achieved with ferrite or alnico if he so desired.
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Old 23rd September 2006, 05:04 PM   #8
sreten is offline sreten  United Kingdom
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Hi,

There is nothing special about NIB magnet speakers particularly.

Huge chunks of Ferrite magnets are still cheaper, if and when they
are not NIB magnets will become the norm for bigger magnets.

Even if NIB remains remains expensive, it offers serious weight reduction.

As it is there is some redesign in the magnetic pole details but
you end up with the same flux density etc in the magnetic gap.

The magnetic design details have more in common with AlNiCo than Ferrite.

/sreten.
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Old 23rd September 2006, 05:09 PM   #9
poobah is offline poobah  United States
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Geeze... all of us on the same page? Again?

Crusty ole' cynics...


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Old 23rd September 2006, 05:23 PM   #10
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mumble flux modulation mumble mumble

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