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demagger and speaker question

On

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there is a section of demagnetizing a speaker magnet. Is this just a matter of creating a large coil and bursting it with a very large current to create a counter magnetic field to the speakers? (in theory at least)

BTW, I have a speaker that reads lower impedance(or rather DC resistance) than rated. 12ohms vs 16ohms another identical speaker reads 17ohms. These are suppose to be 16 ohm speakers. I'm assuming the coil is shorting out possibly due to chafing? These speakers run in parallel and have a dc resistance of about 7 ohms. What's the electrical and aural issues with using the speaker? This is a tube amp and the amp is designed to run

In the manual it says "You can always have a higher resistance ( 16 ohms, for example ) without damaging results, but too low of a resistance will likely cause problems."

Which suggests I should probably use the 4ohm connector rather than the 8ohm at a cost of output power and whatever aural issues the speaker has?

Reply to
Stretto
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WTF you want to kill the magnet? Want a clear pure incredibly delicate sound of silence out of the speaker? Because you'll get no sound of the signal in the coil has no field to work against.

Why? Because the coil measures 12R at DC? Or because you put a battery on one side of the coil, other side to the frame, and heard it chafing as you moved the coil (gently) through its travel range.

Lost the sentence? No, the plot!

At the cost of lower power transferred to the speaker, but, at higher quality, all other factors being equal, since speaker damping will be improved.

Reply to
Grant

"Grant"

** Speaker repairers sometimes need to do it.

Magnetisation is the LAST step in speaker manufacture and de-magnetisation the first step when repairing the magnet structure - say because the pole piece has come loose and is displaced to one side or the gap has steel particles trapped in it.

The forces on the components of a speaker magnet are very large and the beast must be sedated before operating.

.... Phil

Reply to
Phil Allison
1) it's means IT IS 2) Copper has a high tempco, what the hell do you care that the DC resistance changes? That's what it's gonna do anyways! Speakers are quite inefficient at turning electrical power to audio power, so yeah, the voice coil will get hot. So what's your point?
Reply to
a7yvm109gf5d1

WTF you want to kill the magnet? Want a clear pure incredibly delicate sound of silence out of the speaker? Because you'll get no sound of the signal in the coil has no field to work against.

Why? Because the coil measures 12R at DC? Or because you put a battery on one side of the coil, other side to the frame, and heard it chafing as you moved the coil (gently) through its travel range.

Lost the sentence? No, the plot!

At the cost of lower power transferred to the speaker, but, at higher quality, all other factors being equal, since speaker damping will be improved.

------------

Um, if you cared to follow the link you would realize why you would demag a speaker.

It seems that the dc coil resistance can very quite greatly from it's "impedance" which I guess is the resistance measured at some frequency. I read generally that the DC resistance is about 75% of it's "rated impedance". Not sure why I was reading 16ohms on one speaker and 12 on the other though unless the 16 ohms was bad. They now are both reading 12 ohms though. Strangely enough if I touch the cone the dc resistance drastically changes(not sure why it would). If I move the cone the meter goes crazy.

If parallel the impedance(or rather DC resistance) is 6.8 ohms. If one was broke causing this to drop from 8 to 6.8 this would require the tubes to drive harder and there would be an imbalance in the two speakers that may have some strange aural effect. It also might change the impedance quite drastically causing unbalanced power usage and driving one speaker harder than the other which will create both electrical and aural problems.

Reply to
Stretto

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