I just discovered this manufacturing problem in the main panels: There is a plating on the bar magnets which partially peels loose and causes a buzz.
A couple of days ago, I persuaded a friend to sell me his MM-1000, and while dusting and running a 200-300Hz tone through them heard an annoying buzz from both. (I had heard the buzz earlier while playing music: Israel Kamakawiwo'ole's 'It's a Beautiful World' is perfect for exciting this buzz.) Wondering if it was a track that had come loose from the diaphragm or something, I began poking through the rear slots (with the rounded end of a small plastic tie wrap so that I didn't damage the diaphragm) and discovered that the magnets have a plating which had begun to peel and separate from the magnets, and this partially loose piece of plating was now vibrating in the gap. Each unit oddly had only one area which was separating, and it was actually visible through the slots in the rear once I realized what I was looking at. (You can't see anything from the front as there's a sheet of black felt between the diaphragm and stators.) With a lot of patience and some bent wire ties of different sizes (I bent the end of the wire ties into an L, so that I could actually scrape the far side of the magnet facing the diaphragm.) and a pair of tweezers I was able to push, scrape, drag, and pull out the offending pieces of plating, and now the speakers sound good again.
A couple of days ago, I persuaded a friend to sell me his MM-1000, and while dusting and running a 200-300Hz tone through them heard an annoying buzz from both. (I had heard the buzz earlier while playing music: Israel Kamakawiwo'ole's 'It's a Beautiful World' is perfect for exciting this buzz.) Wondering if it was a track that had come loose from the diaphragm or something, I began poking through the rear slots (with the rounded end of a small plastic tie wrap so that I didn't damage the diaphragm) and discovered that the magnets have a plating which had begun to peel and separate from the magnets, and this partially loose piece of plating was now vibrating in the gap. Each unit oddly had only one area which was separating, and it was actually visible through the slots in the rear once I realized what I was looking at. (You can't see anything from the front as there's a sheet of black felt between the diaphragm and stators.) With a lot of patience and some bent wire ties of different sizes (I bent the end of the wire ties into an L, so that I could actually scrape the far side of the magnet facing the diaphragm.) and a pair of tweezers I was able to push, scrape, drag, and pull out the offending pieces of plating, and now the speakers sound good again.
peeling plating
Hmnn.. are those Ne-Fe-B magnets in these units? I recall working on plating technology for coating Neo's for computer drives 20 years or so ago when the technology was new. It's a difficult alloy to plate without advanced knowledge and tight process control, as are many of the magnet materials. If it is the Ne-Fe-B material, it needs plating though, as the alloy is active as hell and corrodes (rusts) if you look at it wrong.
So, if they are neos they may be self-destructing even as you type. The peeled plating iactually accelerates the corrosion once it starts.
FYI: What looks to be "just plain" magnet material may actually be plated with a nickel alloy to protect against corrosion.
John L.
Hmnn.. are those Ne-Fe-B magnets in these units? I recall working on plating technology for coating Neo's for computer drives 20 years or so ago when the technology was new. It's a difficult alloy to plate without advanced knowledge and tight process control, as are many of the magnet materials. If it is the Ne-Fe-B material, it needs plating though, as the alloy is active as hell and corrodes (rusts) if you look at it wrong.
So, if they are neos they may be self-destructing even as you type. The peeled plating iactually accelerates the corrosion once it starts.
FYI: What looks to be "just plain" magnet material may actually be plated with a nickel alloy to protect against corrosion.
John L.
Dave, the magnets in my MM-1000 are thinner (I estimate 5 mm) and shinier (from the plating) than in your 'poor picture.'
I saved the pieces of plating that I pulled out so that we can have them analyzed by an expert. Interested, John?
At the time I had them apart, I should have taken some pictures to fully document my repair:
It involved first making a hook from some sheet steel to pull apart the barbed clips holding the front and rear grills together. Then covering the panels in a bag to keep out the steel chips while I drilled out the rivets holding on the base. To make them more easy to disassemble in the future, I made a small triangular plate with threaded holes for screws to replace the three rivets. (I think it becomes obvious what I did if you examine an MM-1000.)
PS. Israel K's song is of course 'Over the Rainbow.' And believe me, I'm pretty sick of hearing it.
I saved the pieces of plating that I pulled out so that we can have them analyzed by an expert. Interested, John?
At the time I had them apart, I should have taken some pictures to fully document my repair:
It involved first making a hook from some sheet steel to pull apart the barbed clips holding the front and rear grills together. Then covering the panels in a bag to keep out the steel chips while I drilled out the rivets holding on the base. To make them more easy to disassemble in the future, I made a small triangular plate with threaded holes for screws to replace the three rivets. (I think it becomes obvious what I did if you examine an MM-1000.)
PS. Israel K's song is of course 'Over the Rainbow.' And believe me, I'm pretty sick of hearing it.
many. from the some 200+ panels i had, i have saved 2 pair of MM1000 panels, and 2 pair of MH502 tweeter panels.
I'm going to mount them on an OB jst a bit wider than 4xMM1000 would be (removed the need for EQ to get them flat to 225 Hz) 1000 panels vertically mounted with tweeter panels right next. Just have to decide what bass units to use. I have 4s, 7s, & 9s left over. Probably triamp then using multiple MM500 amplifiers (which just happen to have XOs built-in at the right place (and using only 2 of the 5 amps onboard, with a separate PS on each module, should be a serious upgrade from stock without changing anything else.
dave
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:
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.
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
I've since painted over the bare neodymium with black nail polish but i have no pictures of that yet.
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:
An externally hosted image should be here but it was not working when we last tested it.
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.
An externally hosted image should be here but it was not working when we last tested it.
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
An externally hosted image should be here but it was not working when we last tested it.
I've since painted over the bare neodymium with black nail polish but i have no pictures of that yet.
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.
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.
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???
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???
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.
dave
Thanks
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.
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.
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_vol20/1369S.pdf?PHPSESSID=6c84b0ced12c5c2de864470415be0210
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_vol20/1369S.pdf?PHPSESSID=6c84b0ced12c5c2de864470415be0210
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.
Thanks for all the good info though.
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