RB,
Price was a driver, but early formulations of ferrite weren't any cheaper than AlNiCo. But it was more reliable in supply, and as chemists learned the proper blends loudspeaker designers found that they had a LOT more stability (magnetically) in ferrite. No longer would a customer have to send back a driver for remagnetizing. Ferrite was better, easier to use, and had stable supplies.
After the supply of cobalt stabilized (samarium cobalt came about in the mid 70s), ferrite was fully entrenched, not because of price but because of performance. The thing that has driven ferrite's price way down is the fact that it's now made by hundreds of companies, because it is so universally used.
At least, that's what I've been told by a few greybeards from that time... Much like the Kapton Crisis of 2004...
Bill,
Thanks for the backing! The only way you can use AlNiCo is to protect the **** out of it from external magnetic fields.
Most companies just go to Neo and are done with it; JBL, I assume, uses AlNiCo occasionally because of the nostalgia associated with it, and the wrongly-held belief by many that it is a superior magnet for reproduction loudspeakers.
Dan Wiggins
Adire Audio
Price was a driver, but early formulations of ferrite weren't any cheaper than AlNiCo. But it was more reliable in supply, and as chemists learned the proper blends loudspeaker designers found that they had a LOT more stability (magnetically) in ferrite. No longer would a customer have to send back a driver for remagnetizing. Ferrite was better, easier to use, and had stable supplies.
After the supply of cobalt stabilized (samarium cobalt came about in the mid 70s), ferrite was fully entrenched, not because of price but because of performance. The thing that has driven ferrite's price way down is the fact that it's now made by hundreds of companies, because it is so universally used.
At least, that's what I've been told by a few greybeards from that time... Much like the Kapton Crisis of 2004...
Bill,
Thanks for the backing! The only way you can use AlNiCo is to protect the **** out of it from external magnetic fields.
Most companies just go to Neo and are done with it; JBL, I assume, uses AlNiCo occasionally because of the nostalgia associated with it, and the wrongly-held belief by many that it is a superior magnet for reproduction loudspeakers.
Dan Wiggins
Adire Audio
Bill F. said:
But, because Alnico magnets tend to demagnetize at high power levels, they've all but disappeared since the 1970s, when amplifier power outputs increased dramatically.
VERY telling quote from the link posted by Bill F. AlNiCo simply demagnetizes well before Ferrite or Neo. How that translates into superior resistance to flux modulation is beyond me...
Thoriated? Any comments?
Dan Wiggins
Adire Audio
Bill F. said:
Hmm, interesting speaker! I guess TAD/PIONEER has been doing this for a while now - Beryllium diaphragm horns & AlNiCo woofers - and has been somewhat of a professional standard for that. Now, all of this does NOT explain however why a reputable company such as JBL would find that:
"Alnico magnets, [are] prized for their lively, high-energy sound, [and] were once widely used in the magnetic circuits of high-end speaker systems. But, because Alnico magnets tend to demagnetize at high power levels, they've all but disappeared since the 1970s, when amplifier power outputs increased ramatically."
I don't think they would be building AlNiCo woofers for their "flagship" studio monitors solely out of nostalgia, do you Dan?
Cheers
You may be surprised...RussianBlue said:
I don't think they would be building AlNiCo woofers for their "flagship" studio monitors solely out of nostalgia, do you Dan?
Cheers
There's a lot of stuff done in the name of nostalgia and marketing! Certainly seems like they went to a lot of trouble to make sure that AlNiCo would work properly...Dan Wiggins
Adire Audio
hi - russian blue
this is i think straight out of - martin colloms book , or the lodspeaker & headphone handbook - ive read it cant place it
about - alnico and jbl i am with Dan i have had to recharge quite a few jbl s (alnico) - speacially the 10 / 12 inch cement doped woofers they used in their studio monitors
and neither an easy job - had to take it apart the entire motor structure to give it a good re-coat of high quality primer - as the plates - inside surface of the - u - shaped back plate war in a bad state
all i like of that time - is the high quality machining and the soft steel used in the magnet plates
as for the original thread
ceramic 0r neo - most important factors in a designers head now a days is
bh - curve
fr plot to spl verses distortion - including 2 nd & 3 rd harmonics
and the correct propotion of - vc inductance you may say - to your choice of given parts for a driver
& also all the points mentioned by ZAPH in the first page
take care
suranjan das gupta
this is i think straight out of - martin colloms book , or the lodspeaker & headphone handbook - ive read it cant place it
about - alnico and jbl i am with Dan i have had to recharge quite a few jbl s (alnico) - speacially the 10 / 12 inch cement doped woofers they used in their studio monitors
and neither an easy job - had to take it apart the entire motor structure to give it a good re-coat of high quality primer - as the plates - inside surface of the - u - shaped back plate war in a bad state
all i like of that time - is the high quality machining and the soft steel used in the magnet plates
as for the original thread
ceramic 0r neo - most important factors in a designers head now a days is
bh - curve
fr plot to spl verses distortion - including 2 nd & 3 rd harmonics
and the correct propotion of - vc inductance you may say - to your choice of given parts for a driver
& also all the points mentioned by ZAPH in the first page
take care
suranjan das gupta
Resolution
hunter audio said:hi - russian blue
this is i think straight out of - martin colloms book , or the lodspeaker & headphone handbook - ive read it cant place itHmm, I assume Phillip Newell must have read it elsewhere. I think he quotes Martin Colloms "High Performance Loudspeakers" and G. Bank's "Loudspeaker and Headphone Handbook" in the references, so you are correct.
Would anyone like to comment on the idea put forth by several people that the resolution rate ("bit rate" to speak in John Watkinson's words) is inherently limited in Ferrite materials, AND that this is NOT so in either Neodymium or Alnico materials? I would contend from this that it is material that may be used successfully for high-power low frequency applications. Dan, don't you make woofers primarily?
Wow, this thread has taken a very interesting turn, Dan your comments and links are very appreciated.
I also second RussianBlue's comments, this seems to be the root of the issue: do certain types of magnets have better 'resolution' or 'sensitivity'? I am not sure how one would measure this character, but it is an interesting concept.
I also second RussianBlue's comments, this seems to be the root of the issue: do certain types of magnets have better 'resolution' or 'sensitivity'? I am not sure how one would measure this character, but it is an interesting concept.
Suranjan,
I remember talking with one old engineer from the early days who talked about having drivers regularly returned every few years. Installed in movie theaters, the AlNiCo magnets would be demagnetized a bit from power, which meant the film operator would turn the volume up, which would demagnetize it some more, and so on, until the amps ran out of headroom. Then they'd remove the drivers, send them back to WE, get them recharged, and start over again...
As for the steel of that time, it was great! Of course, I've got a nice source of first cast 1006 and 1008 I use now. Love that low carbon, first cast metal!
RB/Sbolin,
Most Ferrites are ground down to the 7-10 micron range prior to sintering, so that would be the size of the domain. But I think the whole "domain" concept is irrelevant! Why? Because the flux seen by the voice coil isn't directly from the magnet to the pole - it goes from the magnet to the top plate to the pole. The flux is channeled by the top plate.
This would be analogous to having a stream diverted to a channel via thousands of hoses. Yes, the flow is "quantized" by the hoses (flux quantized by domains). But you don't use the flux at that point - you use it at the end of the channel when it's "merged" again (at the gap).
I guess that, theoretically, this could be an issue for radially oriented magnets (where the magnets line the gaps). And IIRC both AlNiCo and Neo also have the 7-10 micron grain size. So a motor built with radial Neo would be the only one you could really say has discrete domains; any motor that uses steel to create the gap would not have this problem.
Dan Wiggins
Adire Audio
PS: RB, we do everything from 1" tweeters to 18" woofers. In fact, by numbers we ship many more drivers smaller than 8" than we do 8" or larger.
And we do a LOT of design of drivers for other companies, too. We build stuff, but we are also guns-for-hire who contract out for driver design and development.
I remember talking with one old engineer from the early days who talked about having drivers regularly returned every few years. Installed in movie theaters, the AlNiCo magnets would be demagnetized a bit from power, which meant the film operator would turn the volume up, which would demagnetize it some more, and so on, until the amps ran out of headroom. Then they'd remove the drivers, send them back to WE, get them recharged, and start over again...
As for the steel of that time, it was great! Of course, I've got a nice source of first cast 1006 and 1008 I use now. Love that low carbon, first cast metal!
RB/Sbolin,
Most Ferrites are ground down to the 7-10 micron range prior to sintering, so that would be the size of the domain. But I think the whole "domain" concept is irrelevant! Why? Because the flux seen by the voice coil isn't directly from the magnet to the pole - it goes from the magnet to the top plate to the pole. The flux is channeled by the top plate.
This would be analogous to having a stream diverted to a channel via thousands of hoses. Yes, the flow is "quantized" by the hoses (flux quantized by domains). But you don't use the flux at that point - you use it at the end of the channel when it's "merged" again (at the gap).
I guess that, theoretically, this could be an issue for radially oriented magnets (where the magnets line the gaps). And IIRC both AlNiCo and Neo also have the 7-10 micron grain size. So a motor built with radial Neo would be the only one you could really say has discrete domains; any motor that uses steel to create the gap would not have this problem.
Dan Wiggins
Adire Audio
PS: RB, we do everything from 1" tweeters to 18" woofers. In fact, by numbers we ship many more drivers smaller than 8" than we do 8" or larger.
And we do a LOT of design of drivers for other companies, too. We build stuff, but we are also guns-for-hire who contract out for driver design and development.
As a Fly on the wall
I've enjoyed reading the disscussion above. The comments from Dan, R.B. and Bill are particularly salient. It's refreshing to see an authority, and well informed gentlemen disscuss something in this forum.
It's also refreshing to see the personal opinions and pseudoscience put out to pasture and replaced with wisdom and fact.
Hats off to you gentlemen!!
Mark
I've enjoyed reading the disscussion above. The comments from Dan, R.B. and Bill are particularly salient. It's refreshing to see an authority, and well informed gentlemen disscuss something in this forum.
It's also refreshing to see the personal opinions and pseudoscience put out to pasture and replaced with wisdom and fact.
Hats off to you gentlemen!!
Mark
Very little of what we actually do is listed for the DIYer... A typical month will see 12-18 drivers developed, 3-5 amps, 10-12 crossovers, and 4-5 systems. Most of what we do is strictly for the OEM world. And a lot of our products are for sale to DIYers, just under different brands/names.
Dan Wiggins
Adire Audio
Dan Wiggins
Adire Audio
Dan,
I agree with almost everything you have been saying in this thread, apart from the magnet not reaching high temperature without the voice coil falling apart. In standard power testing, even in vented boxes, I have reached 70-80 deg magnet temperature and the voice coil has survived. If the box is well thermally insulated, after a sufficient time period the magnet will start to approach the voice coil temperature.
These power tests are based on running IEC noise at power levels of 50-75W average power for 96hrs, then increasing by 50% for a further 24 hrs. After the 96 hour test, (and a cooling down time!) the speaker is still supposed to meet all the standard specifications.
RussionBlue, you brought up the subject of TAD drivers. I don't know if these fall into Dan's definition of "modern" pro drivers, since most of them were designed a long time ago, but they are still in production, and most of them use Alnico.
In part this is because of tradition, they have been in use for a long time and are considered as a reference in many studios. As such, TAD has to maintain production of them for replacement and spares.
Although not a "musical instrument" speaker, they still have their own sound character, as do all drivers, and the alnico may well contribute to this. Therefore TAD cannot just replace the magnet structure with a ferrite based or neo based one. However, TAD pro has released some drivers with ferrite and neo based motors, and all the drivers for the TAD Home Audio Model 1 speaker are based on neo.
Rather than speculate, as many do in these type threads, it would be better to ask the engineers directly why they use Alnico in such drivers.
Andrew
I agree with almost everything you have been saying in this thread, apart from the magnet not reaching high temperature without the voice coil falling apart. In standard power testing, even in vented boxes, I have reached 70-80 deg magnet temperature and the voice coil has survived. If the box is well thermally insulated, after a sufficient time period the magnet will start to approach the voice coil temperature.
These power tests are based on running IEC noise at power levels of 50-75W average power for 96hrs, then increasing by 50% for a further 24 hrs. After the 96 hour test, (and a cooling down time!) the speaker is still supposed to meet all the standard specifications.
RussionBlue, you brought up the subject of TAD drivers. I don't know if these fall into Dan's definition of "modern" pro drivers, since most of them were designed a long time ago, but they are still in production, and most of them use Alnico.
In part this is because of tradition, they have been in use for a long time and are considered as a reference in many studios. As such, TAD has to maintain production of them for replacement and spares.
Although not a "musical instrument" speaker, they still have their own sound character, as do all drivers, and the alnico may well contribute to this. Therefore TAD cannot just replace the magnet structure with a ferrite based or neo based one. However, TAD pro has released some drivers with ferrite and neo based motors, and all the drivers for the TAD Home Audio Model 1 speaker are based on neo.
Rather than speculate, as many do in these type threads, it would be better to ask the engineers directly why they use Alnico in such drivers.
Andrew
I know for a fact that magnets can reach high temperatures if you have a large coil with high thermal handling in a tight B field with not enough venting or cooling this will affect almost any magnet and N42 even more so over time and nobody wants to re charging magnets once there sold but i can.
N42 is very brittle, hard to machine, and sensitive to corrosion, its also expensive, plus we cant forget NdFeB rusts, so it has to be nickel plated or powered coated or painted even, I have been told that the fumes from NdFeB are toxic! and NdFeB burns very quickly and with great heat, so you can see why most manufacturers still use ferrite, its cheap and cheerful, on the plus side, if you want the highest BL then NedFeB has the highest BHmax of any earth magnet, its the might mouse of magnets.
One way to get around this high heat problem is to have a high quality ceramic coating or even Xylan, Kynar or Teflon coating which gives amazing thermal properties to the coil but its very had to spool, chemistry is not my thing by I have a cousin that is has test tubes for fingers. I have found a way around it all but it still requires some hard testing and a lawyer, everything good takes time.
N42 is very brittle, hard to machine, and sensitive to corrosion, its also expensive, plus we cant forget NdFeB rusts, so it has to be nickel plated or powered coated or painted even, I have been told that the fumes from NdFeB are toxic! and NdFeB burns very quickly and with great heat, so you can see why most manufacturers still use ferrite, its cheap and cheerful, on the plus side, if you want the highest BL then NedFeB has the highest BHmax of any earth magnet, its the might mouse of magnets.
One way to get around this high heat problem is to have a high quality ceramic coating or even Xylan, Kynar or Teflon coating which gives amazing thermal properties to the coil but its very had to spool, chemistry is not my thing by I have a cousin that is has test tubes for fingers. I have found a way around it all but it still requires some hard testing and a lawyer, everything good takes time.
I've enjoyed reading this thread so far but have noticed one thing that I don't * think * has been disscussed. Obviously material properties have disscussed fairly well and in depth, benifits due to weight, cost and size in relation to shipping etc, but what about size in relation to reflections?
If it's been disscussed tell me to shut up now. If not, how much of a factor do you folk think reflections from the cone, off of the magnet and then back out through the cone is an issue here. Obviously if it is a considerable issue then Neo has extra points here over standard ferrite magnets, no? Surely it is an issue with more and more driver manufacturers making more aerodynamic basket structures?
If it's been disscussed tell me to shut up now. If not, how much of a factor do you folk think reflections from the cone, off of the magnet and then back out through the cone is an issue here. Obviously if it is a considerable issue then Neo has extra points here over standard ferrite magnets, no? Surely it is an issue with more and more driver manufacturers making more aerodynamic basket structures?
DepthCharge,
I think you are correct w.r.t. the reflection issue:
http://www.seas.no/excel_line/excel/e0015.pdf
http://www.seas.no/excel_line/excel/E0037.pdf
The Neodym driver looks like it has a smaller reflection hump in its FR.
W.r.t. the JBL 1500AL:
Alnico has a cult following in Japan. It is difficult to buy the 1500AL anywhere except in Japan. Also, the KS9800 is freely available in Japan, but not to the same extent elsewhere. Is it even marketed in the US? That might explain the material choice.
Maybe Neodym can be used to make higher efficiency high XMAX drivers? Can underhung motors be a niche for Neodym, apart from the weight saving in prosound cabs? Dan's comment please...
http://bhivemotor.com/index.html
I think you are correct w.r.t. the reflection issue:
http://www.seas.no/excel_line/excel/e0015.pdf
http://www.seas.no/excel_line/excel/E0037.pdf
The Neodym driver looks like it has a smaller reflection hump in its FR.
W.r.t. the JBL 1500AL:
Alnico has a cult following in Japan. It is difficult to buy the 1500AL anywhere except in Japan. Also, the KS9800 is freely available in Japan, but not to the same extent elsewhere. Is it even marketed in the US? That might explain the material choice.
Maybe Neodym can be used to make higher efficiency high XMAX drivers? Can underhung motors be a niche for Neodym, apart from the weight saving in prosound cabs? Dan's comment please...
http://bhivemotor.com/index.html
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