[morzh]

I have 3 G speaker, all with open Field coils.

Today I pull one of the shelf and decided to try to remove the FC (spoiler: so far I have not succeeded).

Now, this speaker is very clean and has excellent cone (yeah, yeah, with the solid spider).
I bought it fr om a lady on eBay, and when I found out the FC (she said the speaker worked) was open, I told her and she was willing  to refund everything, but I told her that I would pay part of it as the transformer was good. I used it for something else.
The speaker has been on a shelf for more or less 8 to 10 years.

I remembered what a screwdriver can do to the spider when it slips. I was looking to buy a screwdriver with a spring-loaded guard shrowd, but have not found any. So today I did  this: I took the 7/16 socket from my Kraftsman kit, and used the heaviest screwdriver that could go through it.
   

I helped the socket to stay around the split washer; it did not require any effort: just so it did not slide. This kept the flat screwdriver from sliding sideways. Surprisingly, the screw did not resist too strongly, and I removed it without any damage to the cone or the spider.

Then came the turn of the big nut in the back, that holds the pole.
Luckily I bought 1" socket a year ago. I tried it with the standard Kraftsman driver, and it would not budge, plus my hand was hurting.
Then I remembered I bought a piece of steel pipe as a lever, when 3 years ago I was trying to rebuild my pool pump, and the bolts did not move. With this as a lever, they moved very soon. They were really calcified (I think I put the photos here then; it was, I think, May of 2022).
This is what the pipe is and how it is paired with anything (wrench or socket driver).
   
   

I used a thick large square-crossection screwdriver (same one I used on that capacitors can) to counter the effort. This is good steel and thick enough to not bend.
The screwdriver is inserted in the screw slot in the speaker base, and then pushed clock-wise when the nut is driven counter-clock-wise.
   
It was a good idea but it did not wor either. The nut wouldn't budge.

Then I decided to secure the speaker in my large vise.
   

I would have to be gentle with squeezing as the base looks to be something like cast iron, and could be brittle.
I had to adjust the vise 3 or 4 times as the speaker would get loosened up.
Eventually, I realized this was not working either, and decided it was time for PB Blaster.
Which is what I applied, and the liquid happily got absorbed, both in between teh screw and the nut, and between the nut and the base.
I am soaking it for now and will attempt the nut removal again later.