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Alnico magnet heat?
Alnico magnet heat?
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Old 22nd October 2014, 08:07 PM   #1
Destroyer OS is offline Destroyer OS  United States
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Alnico magnet heat?
Default Alnico magnet heat?

A friend was playing through a cabinet I made.

The magnets got a little warm, and I don't know if it's normal for alnicos, if it was just more power than they were designed for (no specs, old), or if his clipping (shitty) solid state was doing it.

Either way I'm just trying to not demagnetize them, but would like to know if it's normal.
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Old 22nd October 2014, 09:21 PM   #2
bear is offline bear
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Too much heat is not good.

You said "playing through..." are we talking guitar??

How long was "it" playing before it got hot?
How hot, to the touch?

If the magnet is warm, the VC is MUCH warmer...

How much power, what driver, rated at what, for what?

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Old 22nd October 2014, 10:06 PM   #3
okcrum is offline okcrum  United States
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Alnico has to reach its Curie Point (~1470 degrees F) before it will demagnetize. Alnico is spec'ed to operate at ~1000 degrees F. You need not worry. about the magnet. The voice coil, though...

Last edited by okcrum; 22nd October 2014 at 10:09 PM.
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Old 22nd October 2014, 10:17 PM   #4
Destroyer OS is offline Destroyer OS  United States
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Alnico magnet heat?
Guitar.

Warm to touch, above ambient.

His amp is probably no more than 30w, and no more than 15w into the 8ohm load of alnicos. They're 16ohm, 10in. That's all the information there is.
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Old 22nd October 2014, 11:11 PM   #5
JMFahey is online now JMFahey  Argentina
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Normal.

Voice coils heat and transfer heat to polepiece and plate VERY well, there's a Fane study about that and "thermal conductivity from VC to metal parts is better than silver".

That's why high power speakers put finned heatsinks on the magnet backplate.

Specially necessary in Neo magnets because they are tiny.
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Old 22nd October 2014, 11:34 PM   #6
Destroyer OS is offline Destroyer OS  United States
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Alnico magnet heat?
Thanks.

It sounds good, didn't want to trash it from rockin just yet!
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Old 23rd October 2014, 01:34 AM   #7
okcrum is offline okcrum  United States
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Quote:
Originally Posted by JMFahey View Post
Normal.

Voice coils heat and transfer heat to polepiece and plate VERY well, there's a Fane study about that and "thermal conductivity from VC to metal parts is better than silver".

That's why high power speakers put finned heatsinks on the magnet backplate.

Specially necessary in Neo magnets because they are tiny.
Also, the Curie Point on neo magnets is a lot lower than alnico, as low as 590 F, so good heat conduction is essential to avoid hot spots.
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