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EMIM Magnet Nickel Plating - Anyone Re-Done it?

Here are two pictures of the diaphragms from one of my Nd EMIMs, and one of a magnet assembly that has been treated with Polyurethane (5 coats of Wipe-on Poly and one coat of Urethane Conformal Coating).

In the diaphragm pictures, notice how the center section is clear plastic, while the outer sections are translucent and appear to be made from parallel strips of a different type of plastic.


In the magnet assembly picture, the darker areas of the magnets are where the old nickel coating has peeled off. Not the prettiest look, but rest assured it is well-sealed from the elements, and who looks inside your EMIMs, anyway.
 

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I have finished treating all my neo EMIMs with polyurethane, group photo below. Each has 5 coats of Minwax Wipe-on Poly and one coat of MG Industries Urethane Conformal Coating, brushed on. They now have a nice shiny, smooth, and tough coating, which should protect them very nicely from the elements. The high dielectric of the coating (1800V/mil) also eliminates the need for the strips of clear plastic tape that were on each magnet to prevent it from shorting against the diaphragm. The coating does not seem to have affected the magnetic properties, since the coated EMIMs have about the same repulsive force as the uncoated did - I measured this by placing the top plate down over the bottom one while they were on my "EMIM jig" (four nails through a piece of MDF); both the coated and uncoated suspend at a distance of 3/4" apart.

As you can see, I only have 4 diaphragms for them at the present time, but I'm eagerly awaiting word from Graz as to the status of the new ones. All of my diaphragms were in various stages of delamination, but I managed to flatten the bumps with a wooden roller, then secure them with a drop or two of clear nail polish, so now they are pretty much flat. All measure 2.9 - 3.0 ohms resistance.
 

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EMIM peeling update?

I hope it's OK to dig up this old thread...
Since my IRS Gamma woofers are gonna be down for repair, I thought I might see if there are any updates to the peeling EMIM magnet conundrum. I need to do something for mine, as one rattles a bit. I have put this off because I'm scared to take the EMIM apart. I have read about and understand the "jig" is required for this process. If the magnets come loose, break, or shift, I'm screwed!

Max:
How is the coating holding up?

Dave
 
It has been 11 months since I coated them and the coating is still perfect. No bubbling, peeling, visible rusting or any other such defect. I am in the process of reassembling the EMIMs right now so they have been lying out on the counter top in the basement for 11 months and I have been able to check them out continually over that time period, so I can unequivocally say that the coating is holding up just fine.
 
Thanks for the update, Max. Mine need to be done, but I'm gonna try to hold off until the Graz Diaphragms are ready, and do the whole deal at the same time. Good idea?
Dave
 
Just an update. I have one of the speakers completely re-assembled, using the stock EMIM diaphragms, and it sounds excellent! So if there were any fears about the coating impacting the sound quality of the EMIMs, please lay them to rest. They sound great!
 
I got brave and took one of my EMIMs apart, although with some difficulty. It seems to have been glued together. Mine have a thin fabric screen on the back surface of the driver, attached to the magnets. To clean the magnets, I have to remove this. I'm pretty confident that I'll have to replace it with new, or leave it off. Any thoughts on just not replacing it? Anyone know what the fabric is or how to get more, and what kind of glue to use when re-attaching it?
Always something, you know?
 
Mine had the same thing. I carefully peeled it off and saved it. After the magnets were done I glued it back on with a thin film of Amazing Goop, making sure to pull it tight on the magnets. It did not seem to have decayed at all.
 
Thanks for the replies. It may be a challenge to recycle the original, as the nickel plating came off on the fabric. I haven't tried to clean the fabric yet. If my magnets weren't so deteriorated, I could have gotten away with just re-coating the front set. I may try running them without the fabric first, as the crossover in the Gamma is pretty high (700Hz) compared to other models.
 
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Mine had nickel plating on the fabric, too. I peeled it off as best I could, and used the residue left on the fabric as a guide to where to line up the fabric on the magnets when I put it back on. Always making lemonade out of lemons!

I think the fabric also plays a role to reduce the intensity of sound coming out of the back of the EMIMs - without it the balance between front and back-radiated sound might be a bit different, but wall treatments behind the speaker could help to fix that if it is too much.
 
I have windows with heavy drapes behind my Gammas. Running without the fabric may give me a better balance than I had before. Ya never know until you try..
D
 
The fabric is completely transparent at frequencies 300hz and up. I tested both emims from the back with tones and a db meter and they measure the same.
 
A little late to the party - probably a good thing you didn't have them plated. Electric current is used in the plating process, which could have affected the magnets. I know when plating automotive suspension springs, the plater has to know what he's doing or the springs become brittle and break from extreme bumps or potholes.
 
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