[jhm731]

For one thing, the bass and midrange drivers in the 20.7 cost a lot more to make, because they use dual magnets, one on either side. Manufacturing them apparently costs more than just the extra cost of a second magnet assembly.

$8K more for a speaker that's 30% larger with non-Neodynium magnets on each side?

How about a dual magnet version of the 3.7s for people with smaller rooms?

And what caps does Magnepan use in the 20.7s?

[medium jim]

Don't like the sound of neodymium magnets, prefer old school Alnico.

Jim

[studiotech]

Don't like the sound of neodymium magnets, prefer old school Alnico.

Jim

Um, how do you know this?  Ever heard the exact same driver with neodymium and then Alnico?  Now that's one I'd like a blind test on!  If you are thinking that Magnepan uses Alnico you are sorely mistaken.  Ferrite all the way baby.

Greg

[medium jim]

Um, how do you know this?  Ever heard the exact same driver with neodymium and then Alnico?  Now that's one I'd like a blind test on!  If you are thinking that Magnepan uses Alnico you are sorely mistaken.  Ferrite all the way baby.

Greg

I know that whatever magnet magnepan uses that it works perfectly for their design.  The big thing in guitar speakers is the Neo magnets.   Jensen makes them with both Neo and Alnico and the Alnico blows away the Neo, but ymmv. 

I suppose Neo might work nicely for box home stereo speakers, but I will likely never know

I have no doubt they have R&D'd their panels with several different types of magnets.  In fact, that would be a good question for Wendell.

Jim

[kevin360]

Ferrite all the way baby.

To quote you, how do you know this?

Their patents state otherwise. I'm not saying they use Alnico. I am saying they don't use simple ferrite all the way. In fact, they use more than one magnet composition on each pole piece. Frankly, I don't see anything wrong with the permanent magnets they use. So what if their speakers are somewhat inefficient?

All of these intellectual debates concerning how Magnepan ought to construct their products ignore one simple fact. Magnepan has been, is, and will continue to be a successful manufacturer precisely because the company is run by some rather intellectual individuals who are wise enough to consider the complete impact of every decision they make. Magnepan employs sound (pardon the unintended pun) engineering in the design of their speakers (and they are experimenters). Maggies are pretty damn reliable and they sound pretty damn fantastic when set up properly.

Regarding the relative inefficiency of Maggies - frankly, I don't give a damn! Okay, so a flea watt SET amp is out of the question. Take the money left in your pocket because Magnepan didn't do all the things some folks wish they did, and put it towards some more power.

[studiotech]

Could you please point me to the patent?  I'd be curious to know what the originals used if something other than ferric magnetics.

For all current models, ferrite is really the only possible choice given the cost associated with each of the other types offered on the market.  Neo, Alnico and Samarium cobalt are all quite a bit more expensive than the common variety ferrite/ceramic.

Well, I have found this romp around the world of planars and their characteristics fascinating.  Sorry Kevin if you do not enjoy the armchair quarterbacking of Magnepans designs.  It's only natural that the discussion of what we love about planar loudspeakers would also make note of their weak points.  Being a DIYer, I find it especially interesting to discuss ways to improve their performance considering they tend to do so many things well.

I totally get it that Magnepan has held course with their founding principles and they have done an admirable job of keeping costs down.  Most of their models really do exceed the performance of similarly price competition on many levels.  I also get it that they only modify a design if they can prove to themselves beyond a doubt that it will increase performance.  Good for them.  However, that does not mean that even further performance is not possible with much higher associated costs. 

Greg

[studiotech]

I know that whatever magnet magnepan uses that it works perfectly for their design.  The big thing in guitar speakers is the Neo magnets.   Jensen makes them with both Neo and Alnico and the Alnico blows away the Neo, but ymmv. 

Ah yes, guitar speakers.  Not necessarily the best comparison for accurate sound reproduction, though I see what you mean.  They certainly seem to sound different.  Although, we still cannot be certain that all other variables of the the drivers are the same.  Guitar speakers are meant to break-up and distort, kinda the opposite of hi-fi reproduction.  So maybe Alnico is "better" at being "worse", ya know?   

Greg

[Davey]

Don't like the sound of neodymium magnets, prefer old school Alnico.

Jim

That's most probably an apples/oranges comparison.

Drivers with neodymium magnets don't have a neodymium "sonic signature."  Those drivers probably have a different sonic signature because it's a different motor design because of the neodymium magnets.

If a transducer could be constructed with easily interchangeable magnet assemblies and the same magnetic field strength or remanence was maintained, then it wouldn't matter what type of magnets were used.

Rejecting a particular type of transducer out of hand just because it uses neodymium magnets is just silly.

Cheers,

Dave.

[kevin360]

Could you please point me to the patent?
Sorry Kevin if you do not enjoy the armchair quarterbacking of Magnepans designs.

One such example is US Patent 4210786 which states:

“ ...a magnetic structure confronting the diaphragm in spaced relation and having means connected with the diaphragm and preventing relative movement between the magnetic structure and diaphragm in a direction generally along the diaphragm, the magnetic structure having a plurality of elongate and spaced magnetic strips extending along each other and defining elongate magnetic gaps there between and extending along the conductor runs of the diaphragm, the magnetic strips being permanent magnets establishing magnetic flux in and adjacent the gaps, the magnetic strips being disposed at one side of the diaphragm, the magnetic structure including an acoustically transparent panel of iron against which the magnetic strips lie, said magnetic strips adjacent to each other being formed of different magnetic materials with significantly different magnetic properties, certain of the magnetic strips containing samarium cobalt, and other of the magnetic strips containing barium ferrite, the samarium cobalt-containing strips producing a coercive force significantly greater than the coercive force produced by the barium ferrite-containing material.”

To date, I have not read about anyone dissecting one and taking a Gaussmeter or Hall probe to the removed section of each strip. I have plenty of Hall effect sensors, but I haven't either of the aforementioned at hand. It would be interesting to read the results of such an inquiry.

Don't mistake my intent. I have no problem with the armchair quarterbacking – it's all very fine and interesting. I'm sure some of the ideas that have been postulated in the many threads of this nature that have played out over the years would contribute a measurable improvement to Magnepan's speakers, but at what cost? I'm equally sure the engineers at Magnepan (and what about the engineers at 3M?) have inquired into the same ideas – testing for effect and viability. Wendell categorizes them as 'cut and try' – they have experimented. Of that, I am dead certain.

I understand the concept of imagining what could be done if fiduciary concerns did not exist. My only point is that they do and Magnepan has championed the cause, but I sincerely do not believe that they have done so to the detriment of their products. I am not, however, so blind a 'fanboy' as to suggest that Maggies are absolutely perfect.

Let the posits flow freely (I have no objection).   

(Addendum: It's funny how we miss things when we proofread (I made an incorrect correction, which I had to correct - returning things to their original wording (until I decided to add this bit of superfluous text)). I should now add something of value. I think there's a bit of 'black art' to their designs - but that art is the result of extensive 'cutting and trying', hence, not so black, after all.)

[medium jim]

That's most probably an apples/oranges comparison.

Drivers with neodymium magnets don't have a neodymium "sonic signature."  Those drivers probably have a different sonic signature because it's a different motor design because of the neodymium magnets.

If a transducer could be constructed with easily interchangeable magnet assemblies and the same magnetic field strength or remanence was maintained, then it wouldn't matter what type of magnets were used.

Rejecting a particular type of transducer out of hand just because it uses neodymium magnets is just silly.

Cheers,

Dave.

Never said anything about rejecting them out of hand.  Alnico is warmer sounding than Neo, it has nothing to do with how they break up as one opined.  Some of the best sounding speakers for hi fi have Alnico magnets, Tannoy concentric's, JBL, Altec, and too many others to name come to mind.

Hey, it's all good.

Jim

[*Scotty*]

Does anybody here remember the humble magnetic refrigerator door seal material. That's what they were using or a material very much like it, when I toured the factory almost thirty years ago. Unlike the wholly ceramic ferrite magnet which is brittle and has to be cast in its final shape, the "rubber" is flexible and can be extruded in strips which lends itself to Magnepans construction techniques. If I am not mistaken the ribbon tweeter used cast bar magnets in the steel structure supporting the ribbon. When I toured the factory, the ribbon construction area was not part of the tour for security reasons.
The next time someone talks to Wendell you might try to see if he has anything thing to say about Halbach arrays.
 Remember, you can patent an idea or design, but you don't have to use it in your product.
Scotty

[kevin360]

Does anybody here remember the humble magnetic refrigerator door seal material. That's what they were using or a material very much like it, when I toured the factory almost thirty years ago. Unlike the wholly ceramic ferrite magnet which is brittle and has to be cast in its final shape, the "rubber" is flexible and can be extruded in strips which lends itself to Magnepans construction techniques. If I am not mistaken the ribbon tweeter used cast bar magnets in the steel structure supporting the ribbon. When I toured the factory, the ribbon construction area was not part of the tour for security reasons.
The next time someone talks to Wendell you might try to see if he has anything thing to say about Halbach arrays.
 Remember, you can patent an idea or design, but you don't have to use it in your product.
Scotty

Isn't that 3M's Plastiform? The thing is that it would look the same no matter what type of magnetic material was bonded to the rubber.

[kevin360]

Never said anything about rejecting them out of hand.  Alnico is warmer sounding than Neo, it has nothing to do with how they break up as one opined.  Some of the best sounding speakers for hi fi have Alnico magnets, Tannoy concentric's, JBL, Altec, and too many others to name come to mind.

Hey, it's all good.

Jim

I have some monster JBL drivers in a closet with Alnico magnets. Trust me when I say that the old Olympus speakers could rock the house!

[*Scotty*]

Does anyone remember why Alinco magnets stopped being used in loudspeakers? It was because over time the Alinco material lost field strength and the speaker lost efficiency. The more power was fed into the speaker the faster the magnet died. This meant that the speaker had to be made with a high precision structure that could be disassembled in the field and allowed the magnet to be removed so that it could be re-magnetized and restored to it's original strength.
 I am not sorry that Alinco magnets are no longer commonly used in drivers found in home stereo loudspeakers. Them that's wants them can have 'em.
Scotty

[medium jim]

I have some monster JBL drivers in a closet with Alnico magnets. Trust me when I say that the old Olympus speakers could rock the house!

In 1964 there was the Atomic Energy Act (and was an amendment to an earlier act of the same name) or something like that, that made it difficult to source all of the elements to make Alnico Magnets and this spurned the making of Ceramic or Ferrous magnets and it was also that they were less expensive.   We now walk in the age of Neodymium which is lighter that both ceramic and alnico and costs in between the two.  Ceramic tends to have better bass, alnico is sweeter and I haven't experienced enough of the Neodymium to really have a dyed in wool feeling other than it is a bit brighter and edgy. 

Again, these are my opinions and ymmv.

Jim

[kevin360]

Does anyone remember why Alinco magnets stopped being used in loudspeakers? It was because over time the Alinco material lost field strength and the speaker lost efficiency. The more power was fed into the speaker the faster the magnet died. This meant that the speaker had to be made with a high precision structure that could be disassembled in the field and allowed the magnet to be removed so that it could be re-magnetized and restored to it's original strength.
 I am not sorry that Alinco magnets are no longer commonly used in drivers found in home stereo loudspeakers. Them that's wants them can have 'em.
Scotty

It costs some cash to have that done. Having those woofers completely restored was an expensive affair. That's why I feel a bit of a dumbass that they are just boxed away in a closet. 

[jk@home]

Does anybody here remember the humble magnetic refrigerator door seal material. That's what they were using or a material very much like it, when I toured the factory almost thirty years ago. Unlike the wholly ceramic ferrite magnet which is brittle and has to be cast in its final shape, the "rubber" is flexible and can be extruded in strips which lends itself to Magnepans construction techniques. If I am not mistaken the ribbon tweeter used cast bar magnets in the steel structure supporting the ribbon. When I toured the factory, the ribbon construction area was not part of the tour for security reasons.
The next time someone talks to Wendell you might try to see if he has anything thing to say about Halbach arrays.
 Remember, you can patent an idea or design, but you don't have to use it in your product.
Scotty

I used to be in the HVAC/R trade, know actually what you are talking about.  When I modded my 2005 MMGs a few years ago, I replaced the panels that had been damaged from a previous mod gone bad, and ordered replacements from Magnepan. So for giggly and kicks, I dissected the old panels to see how they ticked. The magnets used in those MMGs looked very similar to what I used to pulled out of old reefer door gaskets (I would save them and give them to my crafty mother-in-law, who would make refrigerator magnet knick knacks out of them.  Anything to keep in the good graces of the in-laws  ).

What really struck me was the apparent simplicity of the design of the panel, even though I know it took Manepan lots of R&D hours to get there.

[Emsquare]

Admittedly I am really curious as to the way the pole piece magnets are magnetized. I've seen some internet videos for some bar magnet machines being magnetized. No big deal. But since the edges of the Magnepan pole piece magnets are the N/S poles does that mean they have their own specific jig? Do they have to do it all at once can it be done a section at a time?

Here goes a whole wasted morning trying to Google that ...

[studiotech]

Thanks for posting that Kevin.  It seems counter-intuitive to me to use magnetic material of differing strength when I think the ideal is to drive the diaphragm evenly over it's entire surface.  Hmmmm, I'd like to know more.  I'd still have to imagine that maybe that was the design for the original patent, but not how they are created for mass production.

I was also under the impression that both the 3.7 AND the 20.7 were push-pull magnet designs.  I guess I was incorrect and it is only the 20.7?  In either case, I think this proves that even in Magnepans minds, dual sided are the superior performer, but not for all cost points.

I think a little love is due to be shown to Eminent Technologies as well.  They ARE push-pull planar designs and are also VERY affordable.  They don't get nearly as much press or hype as the Maggies, but are consistently revised through the years to stay current.

Greg

[kevin360]

I'm curious about the magnets as well, but I'd like to read more than speculation. Even the comments based upon the outward appearance are nothing more than speculation. Although measuring excised fragments of the strips is the only way to put a number on the field strength of the things, one could address the question of whether Magnepan actually employs differing materials on a single pole piece by measuring the interaction distance of various samples and a piece of iron (we all have rulers). If the piece of iron reacts to the presence of some strip samples at a greater distance than others, I'd say the patent I referenced describes their products accurately. If they all interact at (approximately) the same distance, then I'd accept that all of the strips are comprised of the same material – at least, for that particular model. I'd still warn against extrapolating from the sacrificed model to all others.

Only the folks at Magnepan know for sure, and I see no reason why they should give us an honest answer to such an inquiry. Aren't manufacturers entitled to protect trade secrets? Still, the simple, if inelegant, experiment outlined above would be a great start. So far, I'd categorize everything I've read (and written ) on this matter as pure speculation.

---

By the way, the patent I referenced was from the 80s. I'll have to do some digging again - thought I saved copies of those things, but I've changed computers since I looked into this last time. Anyway, I recall three separate patents awarded to Magnepan which referenced the magnet strips. In the later patents, increased field strength (over the original strips) was a key point.