What happened to the alnicos? - Page 2 - diyAudio
Go Back   Home > Forums > Loudspeakers > Full Range

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 19th February 2013, 10:31 AM   #11
diyAudio Member
 
chris661's Avatar
 
Join Date: Feb 2008
Location: Sheffield
Blog Entries: 8
Not sure. We haven't done much on a quantum level yet (1st year Physics at Sheffield).

I'm thinking of eddy currents: when current flows through the voice coil, it creates a magnetic field, which must disturb that of the permanent magnet.
For a perfectly conducting magnet, huge eddy currents would flow in order to oppose these changes, and the magnetic field would hold rigid.
For some material that doesn't conduct perfectly, its magnetic field is dented inwards, as the eddy currents don't fully compensate.
Copper demodulation rings are often used in higher-end speakers to ensure greater eddy current flow, to keep the magnetic field more rigid. These are usually found on Ferrite magnets: I'm told Neodymium doesn't need it, as its a much better conductor.

A "rigid" magnetic field is desirable for HiFi: it reduces distortion. For guitar, its all about which subjectively is better.
I'd infer that AlNiCo is a relatively poor conductor of electricity, giving it the legendary "smooth" sound.

Chris
  Reply With Quote
Old 19th February 2013, 10:57 AM   #12
diyAudio Member
 
Join Date: Feb 2013
So, speaker design is the battle of the eddies?
Indeed, it's entirely subjective. It's just because I'm a guitarist that I'm an alnico buff. And even then many guitarists prefer a harsher sound.

In guitars a mahogany body and a maple top work against each other, causing frequencies to cancel, to which the smoothness (in sound) of this wood combo is attributed.
So I would expect alnico smoothness to be based upon the filtering of frequencies also.

Thanks/regards
- Guitarski
www.rocking.mobi
__________________
(\__/)
(='.'=)
  Reply With Quote
Old 19th February 2013, 04:54 PM   #13
xrk971 is offline xrk971  United States
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Virginia
Quote:
Originally Posted by chris661 View Post
Not so.

Think about the relative conductivities of different magnets, and what happens when current flows through a voice coil.
Are you talking about magnetic conductivity (permeability) or electrical conductivity? Alnico is a metal and conducts well, NIB and ferrite are ceramics - poor conductors. So is the issue the relative susceptibility of each magnet to having eddy currents induced in them, thereby altering their field, hence distortion? If this is the case, alnico being a conductor is most susceptible to induced eddy currents and probably has the most distortion, explaining why electric guitarists like them.
  Reply With Quote
Old 19th February 2013, 05:03 PM   #14
diyAudio Member
 
chris661's Avatar
 
Join Date: Feb 2008
Location: Sheffield
Blog Entries: 8
Quote:
Originally Posted by xrk971 View Post
Are you talking about magnetic conductivity (permeability) or electrical conductivity? Alnico is a metal and conducts well, NIB and ferrite are ceramics - poor conductors. So is the issue the relative susceptibility of each magnet to having eddy currents induced in them, thereby altering their field, hence distortion? If this is the case, alnico being a conductor is most susceptible to induced eddy currents and probably has the most distortion, explaining why electric guitarists like them.
I'd've expected AlNiCo to be a poor (electrical) conductor, thus keeping eddy currents down and distortion up.

Large eddy currents would hold the magnetic field more rigid, which is why manufacturers like Peerless use them in HiFi speakers.

But you're quite right, AlNiCo is a decent conductor, while ceramic magnets aren't.

Anyone care to shed some light over here?
  Reply With Quote
Old 19th February 2013, 05:15 PM   #15
jcx is offline jcx  United States
diyAudio Member
 
Join Date: Feb 2003
Location: ..
High density sintered Neodymium magnets are metallic glasses - conductivity is within a factor of 2-3 of AlNiCo

BH product, coercivity/permeability are the big differentiators, in some applications AlNiCo beats on high operating temperature


both are "poor electrical conductors" compared to Al, Cu, Ag but still quite electrically conductive

lower performance bonded Nb magnets can have electrically isolated particles, high bulk resistivity

Last edited by jcx; 19th February 2013 at 05:19 PM.
  Reply With Quote
Old 19th February 2013, 06:41 PM   #16
xrk971 is offline xrk971  United States
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Virginia
This discussion also makes me wonder if all the "field coils" in uber-high-end drivers is really all hype? There is no room temperature (read non superconducting) electromagnet that can achieve the same field strength of a NIB magnet. Why bother unless you want some sort of active field strength adjustment or something like that? Are there other benefits to field coils that I am unaware of other than having to provide yet another high current regulated DC power supply for the coils?
  Reply With Quote
Old 19th February 2013, 06:58 PM   #17
DrBoar is offline DrBoar  Sweden
diyAudio Member
 
DrBoar's Avatar
 
Join Date: Apr 2003
Location: Stockholm
global cobolt production AlNiCo
Cobalt Production by Country (Metric tons, cobalt content)
And from Wiki
The Second Congo War, beginning in 1998, devastated the country and is sometimes referred to as the "African world war" because it involved nine African nations and some twenty armed groups.[4] Despite the signing of peace accords in 2003, fighting continues in the east of the country. There, the prevalence of rape and other sexual violence is described as the worst in the world.[5] The war is the world's deadliest conflict since World War II, killing 5.4 million people since 1998.[6][7] The vast majority died from conditions of malaria, diarrhea, pneumonia and malnutrition.[8]
  Reply With Quote
Old 19th February 2013, 07:27 PM   #18
diyAudio Member
 
Join Date: Feb 2013
Quote:
Originally Posted by DrBoar View Post
global cobolt production AlNiCo
Cobalt Production by Country (Metric tons, cobalt content)
And from Wiki
The Second Congo War, beginning in 1998, devastated the country and is sometimes referred to as the "African world war" because it involved nine African nations and some twenty armed groups.[4] Despite the signing of peace accords in 2003, fighting continues in the east of the country. There, the prevalence of rape and other sexual violence is described as the worst in the world.[5] The war is the world's deadliest conflict since World War II, killing 5.4 million people since 1998.[6][7] The vast majority died from conditions of malaria, diarrhea, pneumonia and malnutrition.[8]
That's shocking, isn't it? Everyone should write to their president or PM to do something about it, because THEY (the legislators) have the power and responsibility to do something about it, although they deny it.

Thanks/regards
- Guitarski
www.rocking.mobi
__________________
(\__/)
(='.'=)
  Reply With Quote
Old 19th February 2013, 11:16 PM   #19
diyAudio Member
 
Join Date: Feb 2013
Anyway...this thread is quite interesting, thanks to the previous posters. I used to think that speaker distortion was a mechanical thing: the cone and the paper going haywire. As a home recordist I can't put my neighbors through pushing my speakers to distortion anyway. But now I understand that speaker distortion is also in the interaction between magnet and coil. Would it then be possible to control or induce speaker distrortion electrically, that is, vary the susceptibilty of the speaker to distortion, so that it distorts at lower volumes?

Thanks/regards
- Guitarski
www.rocking.mobi
__________________
(\__/)
(='.'=)
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Enclosure for vintage 18inch alnicos GaryKrant Subwoofers 4 21st November 2012 05:03 PM
Audio Nirvana Alnicos? coverto Full Range 20 1st February 2012 09:51 AM
Are the magnets alnicos or ferrites? kkt0516 Multi-Way 3 15th June 2009 02:52 PM
OK... what really happened? MatthewS Car Audio 0 13th November 2008 03:52 AM


New To Site? Need Help?

All times are GMT. The time now is 10:06 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2