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Old 1st February 2013, 05:17 PM   #31
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To Dave Zhan, Here is a good JBL reference showing the distortion reduction (fig 22 and 23).

http://www.aes.org/tmpFiles/elib/20130201/3936.pdf

For Mr Fahey, its a reference to those who "studied chemistry" in the late 60s, primarily in the San Francisco flower power areas.

David S.
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Old 1st February 2013, 05:39 PM   #32
JMFahey is offline JMFahey  Argentina
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Quote:
For Mr Fahey, its a reference to those who "studied chemistry" in the late 60s, primarily in the San Francisco flower power areas.

David S.
Oh, we had many of those too.

Unfortunately, *many* braindead or full body dead by now
No kidding.

Thanks for the addendum to the "Urban Dictionary".
Always interesting

EDIT: almost forgot; just yesterday, by sheer chance, I was reading pages at a JBL Forum.
I'm researching everywhere to build a larger Magnetizer and wanted to see theirs.
Very interesting:
http://audioheritage.org/html/history/history.htm

Last edited by JMFahey; 1st February 2013 at 05:54 PM. Reason: Slow mind.
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Old 1st February 2013, 06:51 PM   #33
Giarsun is offline Giarsun  France
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Sorry to derail this topic a bit more, I just remembered this from John Watkinson's "Putting the Science Back into Loudspeakers":

"Traditional loudspeakers use ferrite magnets for economy. However, ferrite is an insulator and so there is nothing to stop the magnetic field moving within the magnet due to the Newtonian reaction to the coil drive force. In magnetic materials the magnetic field can only move by the motion of domain walls and this is a non-linear process. The result in a conductive magnet is flux modulation and Barkhausen noise. The flux modulation and noise make the transfer function of the transducer non-linear and result in intermodulation.
The author did not initially believe the results of mathematical estimates of the magnitude of the problem, which showed that ferrite magnets cannot reach the 16-bit resolution of CD.
Consequently two designs of tweeter were built, identical except for the magnet. The one with the neodymium magnet has higher resolution, approaching that of an electrostatic transducer"
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Old 1st February 2013, 09:10 PM   #34
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Quote:
Originally Posted by tinitus View Post

For JBL and other companies that added Faraday loops then the ferrite drivers are comparable with the Alnico.

question...did they continue with this 'practice'
JBL have published a bit about variations on where to place the Faraday turn.
The newer Dual Coil structures are clever, eliminate the cause of the problem entirely and therefore have no turn.
What is odd is that the JBL tech. note about the DC structures totally misses the point.
Was it written by a trainee? seems unlikely to be deliberate disinformation.

Best wishes
David

Last edited by Dave Zan; 1st February 2013 at 09:17 PM.
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Old 1st February 2013, 09:15 PM   #35
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Quote:
Originally Posted by Giarsun View Post
Sorry to derail this topic a bit more, I just remembered this from John Watkinson's "Putting the Science Back into Loudspeakers":

"Traditional loudspeakers use ferrite magnets for economy. However, ferrite is an insulator and so there is nothing to stop the magnetic field moving within the magnet due to the Newtonian reaction to the coil drive force. In magnetic materials the magnetic field can only move by the motion of domain walls and this is a non-linear process. The result in a conductive magnet is flux modulation and Barkhausen noise. The flux modulation and noise make the transfer function of the transducer non-linear and result in intermodulation.
The author did not initially believe the results of mathematical estimates of the magnitude of the problem, which showed that ferrite magnets cannot reach the 16-bit resolution of CD.
Consequently two designs of tweeter were built, identical except for the magnet. The one with the neodymium magnet has higher resolution, approaching that of an electrostatic transducer"
This was one of the pieces of misinformation I had in mind in my first post.
In particular the comment on Barkhausen noise seems incorrect. I can find no support for this at all despite enquiries.
I would appreciate any professional's comment on this too.


Best wishes
David

Last edited by Dave Zan; 1st February 2013 at 09:20 PM.
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Old 2nd February 2013, 03:21 AM   #36
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Quote:
Originally Posted by speaker dave View Post
To Dave Zhan, Here is a good JBL reference showing the distortion reduction (fig 22 and 23).

http://www.aes.org/tmpFiles/elib/20130201/3936.pdf
Thank you for the reference. I will save any comments until I have studied it.

Best wishes
David Zan
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Old 2nd February 2013, 10:24 AM   #37
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For tweeters some use amorphous. I have these in the Raal Lazy ribbons.
I have Alnico in my JBL2482's (Phenolic diaphragm).
For bass I use 2 x Eminence Kappa PRO LFII's and 2x Kappa 15A's for mid bass. Nothing wrong with the Kappa use of Ferrite IMHO. I only use the LFII's to 100Hz and the 15A's to 330Hz though

Quote:
Originally Posted by Giarsun View Post
Sorry to derail this topic a bit more, I just remembered this from John Watkinson's "Putting the Science Back into Loudspeakers":

"Traditional loudspeakers use ferrite magnets for economy. However, ferrite is an insulator and so there is nothing to stop the magnetic field moving within the magnet due to the Newtonian reaction to the coil drive force. In magnetic materials the magnetic field can only move by the motion of domain walls and this is a non-linear process. The result in a conductive magnet is flux modulation and Barkhausen noise. The flux modulation and noise make the transfer function of the transducer non-linear and result in intermodulation.
The author did not initially believe the results of mathematical estimates of the magnitude of the problem, which showed that ferrite magnets cannot reach the 16-bit resolution of CD.
Consequently two designs of tweeter were built, identical except for the magnet. The one with the neodymium magnet has higher resolution, approaching that of an electrostatic transducer"
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