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Old speakers.........an observation

goldtop0

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I've seen a handful of old speakers over the years as in my original '65 Super Reverb and old alnico Celestions that I've bought. My SR has had the original 10" speakers replaced long ago.
Further to that my amp guru here in Auckland has had many vintage Vox(and to a lesser degree) Fender and Marshall amps through his workshop over the years that I've seen and talked with him about.
The outcome of that has been that I see the predominance of alnico speakers(Celestion and Fender/Eminence) being more reliable and 'fit for purpose' than their ceramic counterparts.
Now I'm not a technical guy in any sense of the word and have only my observations to rely on.......but are alnicos more long lasting than ceramic......
 

PaulD

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are alnicos more long lasting than ceramic

No, if anything the reverse is true as an alnico magnet is much more susceptible to losing its magnetic strength over time or due to environmental conditions. The reason you see more alnico speakers in vintage amps is simply that they were what was readily available at the time. Ceramic magnet speakers were not widely available until well into the 60's / early 70's.
 

goldtop0

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No, if anything the reverse is true as an alnico magnet is much more susceptible to losing its magnetic strength over time or due to environmental conditions. The reason you see more alnico speakers in vintage amps is simply that they were what was readily available at the time. Ceramic magnet speakers were not widely available until well into the 60's / early 70's.

Interesting comment Paul, so yes the celestion ceramics didn't appear until late '65/66 in Marshall amps/cabs when they switched over to the higher rated 20, 25 and the 30 watt G12s but Vox carried on with alnicos well into the '70s with the pulsonic cone alnicos.
Fender in the US at the time(and much earlier in the '50s) were using both alnico(Jensens) and ceramics, but predominantly the ceramic CTS, Utah etc from the '60s onwards.
Why do you say 'an alnico speaker is much more susceptible to losing its magnetic strength', what's the science behind that.
My example of alnico longevity is a Celestion 74 1772 from '54 that I now have in my PR 1x12.... for a 12w speaker it's an amazing sounding thing.
 

PaulD

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Why do you say 'an alnico speaker is much more susceptible to losing its magnetic strength', what's the science behind that.

Alnico has a low coercive force which means that it can easily be demagnetised by being exposed to external magnetic fields. Ferrite (ceramic) however has a high coercive force which makes it much less likely to be demagnetised in the presence of external magnetic fields.

https://e-magnetsuk.com/alnico_magnets/characteristics.aspx

https://e-magnetsuk.com/ferrite_magnets/
 

maxwedge

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The loss of magnetism in Alnico is caused by being over powered and heavy use. Alnico speakers that are not used, say NOS, loose little magnetism and ones that are not pushed hard loose little too. It's a property of the metal and nothing else. Man made ceramic does not have this problem and probably (I'm 95% sure) that the main reason for the switch over in the late sixty's and into the seventy's was cost. At the time Alnico was becoming hard to get (I think, with out looking it up, because it was mined in South Africa) and very expensive hence the switch over. The only disadvantage of the ceramic is the weight and with big high power magnets they can get really heavy!
Go over to the JBL forums and they can really clue you in, much better than me. Edit: I was just looking up Alnico and it is an alloy meaning that it is made from several different metals. There was something coming from south Africa that made it very expensive to make at the time but I don't remember what it was.
http://www.audioheritage.org/vbulletin/forum.php


 
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maxwedge

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Let me add. The weak link in any of the speakers from the 50's and into the 60's was the low power paper constructed voice coils and not magnet type. IMO
 

PaulD

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Edit: I was just looking up Alnico and it is an alloy meaning that it is made from several different metals. There was something coming from south Africa that made it very expensive to make at the time but I don't remember what it was.

Alnico is an alloy of aluminium, nickel and cobalt. Cobalt is quite scarce and around two thirds of the worlds supply comes from the Congo (not South Africa) which is a politically unstable area adding to the problems obtaining it. In addition the demand for cobalt has increased dramatically in recent years as it is used in the manufacture of lithium-ion batteries so be prepared for the price of alnico speakers to go up!
 

goldtop0

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Thanks for the info fellas.
Yes the voice coil thing I've discussed with Brian at Bygone Tones re Celestion upgrading this part during the '60s(on their alnicos specifically).
 

maxwedge

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Alnico is an alloy of aluminium, nickel and cobalt. Cobalt is quite scarce and around two thirds of the worlds supply comes from the Congo (not South Africa) which is a politically unstable area adding to the problems obtaining it. In addition the demand for cobalt has increased dramatically in recent years as it is used in the manufacture of lithium-ion batteries so be prepared for the price of alnico speakers to go up!
Thanks for the clarification, I didn't know that.
 
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