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Old 7th January 2007, 05:31 PM   #11
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"if they stick to a magnet, they're nickel.. "

Then it's nickel.
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Old 30th October 2010, 05:40 AM   #12
ericj is online now ericj  United States
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Old thread, I know, but yesterday i went to a university surplus sale and picked up an MM1000 set for $15 - each component on a different shelf, naturally - and a sticky note on one of the panels that said "This speaker has a slight rattle".

The note was a damn lie, because it had a pronounced buzz.

While attempting a noninvasive removal of bad magnet plating, I managed to slip with the tool i was using and tear a trace on the membrane.

So, here are my pictures. I'm sure i can fix the membrane. I'm not sure i can retension it properly.

I'll add more pics over the weekend, as i take some new ones.

Pic from the outisde, back of the panel:

Click the image to open in full size.

Inside, rear magnet structure, membrane peeled back (sorry, didn't take a picture before peeling it back)

The blue you see is the tape i used to mask off the driver faces before drilling out the rivets.

Click the image to open in full size.

Same, after cleaning off the rest of the loose plating and using several feet of tape to pick up the powdery oxide covering the bare neodymium

Click the image to open in full size.

I've since painted over the bare neodymium with black nail polish but i have no pictures of that yet.
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Old 2nd November 2010, 08:40 PM   #13
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"Nearly brand new" pair on ebay starting at $75....
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Old 2nd November 2010, 08:50 PM   #14
ericj is online now ericj  United States
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I'm actually making progress on my rebuild. Sorry i haven't taken more pics.

After some careful testing on the membrane down near the solder points, I've attempted to fix the tear i put in the membrane with a product marketed to seal up holes in air mattresses - Ozark Trail AirStop Vinyl Repair, available cheaply at any walmart. Sporting goods department.

The little brass rivets can be replaced with #4/40 1/4" screws (and associated nuts and washers). This does not appear to require any reshaping of the grilles.

For the larger rivets, I have access to a pop rivet tool and rivets, so I'll just use that.

I plan to use Permatex Quick Grid to fix the trace i broke. I hear this has been successfully used to repair Heil drivers.

I'm pretty sure i can use blue tape to tension the membrane and i hope i get it right. I will be using a thin, slow-curing silicone sealant to reattach the membrane to the frame.
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Old 6th November 2010, 02:44 PM   #15
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I just picked up a pair of these with a load of junk computers the other day. I was very disappointed with the sound when i first hooked them up. very thin sounding. but then i set one into a cardboard box to contain the back wave and they came alive! the mids improved and they actually had a tiny bit of bass. but they seemed quite directional.

So now i am curious about these things? I was thinking they would make nice mid/hi drivers. has anyone experimented with these in a box? these might make nice dash speakers for a car or something too???
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Old 6th November 2010, 07:42 PM   #16
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Seen this thread? Are you using them with the woofers, Zero Cool?
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Old 6th November 2010, 07:50 PM   #17
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Quote:
Originally Posted by Zero Cool View Post
I just picked up a pair of these with a load of junk computers the other day. I was very disappointed with the sound when i first hooked them up. very thin sounding. but then i set one into a cardboard box to contain the back wave and they came alive! the mids improved and they actually had a tiny bit of bass. but they seemed quite directional.
The panels by themselves have a dipole roll-off starting at ~1 kHz. The matching amp/woofers have a 1st order boost to keep them flat to the XO at 225 Hz.

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Old 1st January 2011, 10:09 PM   #18
fonetik is offline fonetik  United States
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Thanks for this thread and information. I have a set of MM-700 2.1 speakers that I've been using on my PC forever and the left satellite just recently started buzzing. I've found the plating that peeled off and now I can work on removing it. I don't really want to drill the rivets so I'm working with improvised tools through the rear panel slots. I've taken the worst pieces out already but there is still some buzzing so I'll have to try and scrape more out.
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Old 2nd January 2011, 04:15 PM   #19
Magz is offline Magz  United States
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Yes, those neo magnets are prone to rusting to the point of disintegration after the nickel peels. I had the same issue on my Infinity EMIM drivers - I've seen some that were reduced to nothing but powder. If you don't re-coat them they will slowly fall to pieces. I ended up cleaning the peeling nickel off the salvagable ones and coating them with polyurethane conformal coating from MG Industries. It's been 2 years since and they are still fine. Here is a thread on Audiokarma wherein I detailed the process for the EMIMs:

EMIM Magnet Nickel Plating - Anyone Re-Done it? - AudioKarma.org Home Audio Stereo Discussion Forums

I also found a nice reference on the corrosion stability of different coatings on neo magnets, it turns out nickle was the WORST of all the coatings tested. Polyurethane was better and electrostatically deposited epoxy and polyester were the best.

http://www.journalamme.org/papers_vo...64470415be0210
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Old 2nd January 2011, 07:03 PM   #20
fonetik is offline fonetik  United States
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It looked like my magnets were already rusting under the peeled plating. There was a lot of dust that scraped off easily. I can say I got a lot of life out of these speakers. I'm pretty sure I've had them for about 10 years. If they go a little bit longer before the magnets totally crumble then I won't be disappointed. If someone else wants to refurbish them then that's cool, but I'll probably just spring for replacements.

Thanks for all the good info though.
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