I fixed buzz in Sonigistix Monsoon planar magnetic drivers

[Andersonix]

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.

[Cal Weldon]

Interesting to know. I wonder if planet10 has had this happen? He has a bunch of Monsoon stuff. Not sure of the exact models though.

[planet10]

I'll have to have a look at my MM1000 panels. On the tweeter panels & the newer mid-tweeter panels the magnets are just plain.

dave

[auplater]

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.

[planet10]

poor picture of a tweeter magnet.

dave

[auplater]

That sorta looks like a ferrite, but I can't tell because it's so blue. Doesn't look like it's rusting tho..here's a shot of a rusted neo vs. a clean neo

[Andersonix]

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.

[Spasticteapot]

I have a pair of MM1000 panels. I'm thinking of adding a woofer and making some nice bookshelf speakers.

Thoughts?

[planet10]

Thoughts?

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

[auplater]

Originally posted by Tosh
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?

<snip>

No real need to analyze.. if they stick to a magnet, they're nickel.. if not they may be a non-magnetic nickel alloy with phosphorus, or something really cheap like tin or zinc...not many other possibilities here.

John L.