Refurbishing a pair of 2440

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Using scotch tape as shims. Tolerance is 0.1 mm to allow gluing the throat.


Throat and magnet in place.


Phase plug added


Pole piece added


Using paper as shims in magnetic gap. There is a small play (0.1 mm?)

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The gaussing machine


About to magnetize. Lars is operating the machine, which he actually build himself. According to him this is the most powerful machine in Sweden.


Using a piece of wood to prevent the driver from escaping from the coil box.

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I have tested the drivers with 2445 diaphragms, and whey both work as expected. Now I need to glue the throats, and add new gaskets. And of course new diaphragms.

[hjames]

Wow - very cool break down/build up!
Thanks for sharing all those pictures - makes more sense now!

[Earl K]

Beautiful Work !

Thanks for the pictorial !

- Was Lars machine also used to demag the magnet before disassembly of the 2440 ?

- Was there any residual magnetism left in the magnet after demagging ?

<>

[more10]

Beautiful Work !

Thanks :-)

- Was Lars machine also used to demag the magnet before disassembly of the 2440 ?

I don't really know which machine he used. I believe he used the same machine. I think that he magetized with lower and lower energy, turning the driver each time.

- Was there any residual magnetism left in the magnet after demagging ?
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After first demagging the pole piece could be removed. The magnetism was too strong to allow removal of magnet from case. After removal of the throat the magnet could be moved sideways. Then the maget could be removed using a piece of wood and a club. Lars believe that he needed 100 kg force to remove the magnet from the case. When removed from the case the magent could be completely demagnetized.

[Earl K]

Thanks :-)

I don't really know which machine he used. I believe he used the same machine. I think that he magetized with lower and lower energy, turning the driver each time.

After first demagging the pole piece could be removed. The magnetism was too strong to allow removal of magnet from case. After removal of the throat the magnet could be moved sideways. Then the maget could be removed using a piece of wood and a club. Lars believe that he needed 100 kg force to remove the magnet from the case. When removed from the case the magent could be completely demagnetized.

Thank-you for your answers

<> EarlK

[spkrman57]

Best one yet that shows all the inner works of the compression driver.

Thanks for sharimg with us!

Regards, Ron

[Eaulive]

Best one yet that shows all the inner works of the compression driver.

Thanks for sharimg with us!

Regards, Ron

Yup, I really would like to know more about the procedure of magnetizing/demagnetizing, pictures, explanations, etc.

[richluvsound]

Hi Morten ,

absolutely brilliant Sir . Thanks for insight . All your need now is the Be dia and you have a world class component that will out live us all .

You have done the research and deserve every reward .

Rich

[Steve Schell]

Fascinating thread and pictures, more10! You have created and installed the throat inserts that should have been there in the first place had cost not been a consideration. These things have always been a problem, as early D175 drivers had throat inserts cast of pot metal that sometimes deteriorate and increase in size, forcing the top plate up off the pot.

The gap flux density of your drivers should measure 20 kilogauss or more. I have measured this amount on a number of old 2440s and 2441s, some of them in very rough condition.

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Thanks Steve

The aluminium alloy used was 6082-T6. Excellent for machining.

I didn't see the measurement myself, but according to Lars it is over 20000 gauss.

Next test will be to compare sound level with my 2445 drivers.

[tomee]

Thanks Steve

The aluminium alloy used was 6082-T6. Excellent for machining.

I didn't see the measurement myself, but according to Lars it is over 20000 gauss.

Next test will be to compare sound level with my 2445 drivers.

Excellent description - thanks for sharing that!

You should tool up to make as many of those throats as you can and sell them because I think there is a demand for them!

Big question - does the 2445 have these plastic throats?

[Eaulive]

Yup, I really would like to know more about the procedure of magnetizing/demagnetizing, pictures, explanations, etc.

Now that I see this, I realize that there's no need for the machine to have a direct physical contact with the magnet, am I wrong?

So would it be possible to remagnetize a woofer without reconing it ? (removing the cone)

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You need to remove the coil (with the cone) when demagnetizing or magnetizing because the applied magentic force is so huge it would destroy the coil.

Removing the cone is not that difficult I have heard since they use hot melts. Just put the driver in your oven for some time and remove the cone. I have not done this myself, but there should be someone on the forum who knows how to do this.

When putting the cone back you need to shim the coil in order to center it in the magnetic gap.

Something else I have learned is to use the kind of tape you use for painting to remove dust from the magnetic gap.

I have a pair of 2118 which needs new coils, I will take some pictures of them in the oven in the future.