The nickel plating on mine continues to flake off. Worse: the remaining 'grit' stuck inside is making them buzz again despite my best efforts. I will try to use a small vacuum cleaner nozzle next time I take the grills off. If that doesn't work, then these may have reached the end of their life...
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Here's a picture I took of one that was too far gone to be salvaged.
You can see it would be difficult to clean fully w/o opening it up, and even if you fixed the buzz how long would it be until: A) you have to do it again, B) a magnet shifts out of place?
I might be able to do a picture-by-picture "how-to" in order to open these, fully clean them out, and (hopefully) prevent further magnet corrosion. Let me know if you're interested. It's a pretty straight forward procedure and shouldn't cost more than $5-$10, but there will most likely be complications when trying to get to the front half of the clam shell due to the diaphragm being glued in place under tension.
Yeah, this one was pretty bad, but I'm guessing it was kept in a moldy old basement, or something. It was cheeaaap and my friend found it at Salvation Army all by itself so he figured he'd check it out and let me tear it apart.I know there are much better examples out there AND if I can maybe spray or paint the magnets with some type of clear coat to keep the Nickel from corroding further (or at all if I can catch one at the right time in its life) that one pair of MM-700's might be happily ever after, you know? Anyway, I'm at least taking a gamble and hopefully I'll have a pair at my door by the end of next week so this thread should hear back form me soon-ish.
Well, forget soonish, but I'm back.
It's hard to open these up to repair/protect the magnets because you need to achieve the same tension on the diaphragm once you put it all back together. That is, if you don't think of a way to keep the diaphragm at stock tension upon disassembly that also enables you to re-adhere the diaphragm post mod without chance of damage... You'll also need to reconnect the two halves of the clam that won't hinder the rest of the construction.
Basically, I've got a "repaired" MM-700 speaker that has lower tension (quite a bit more bass than stock, but it crinkles at max excursion so it can only be played so loud) and can't be put back into its frame and stand.
Best option? Find a pair with good magnets and hope for the best, imo.
Agreed. You can get lucky on craigslist, but more often than not they are right around what you'd pay on eBay. :/
I'd love to find maybe 4 solid pairs of MM-70x satellites to get my feet wet in hi-fi speaker building, but that isn't going to happen soon.
It'd also be fun to experiment with diaphragm tension (and possibly adding very thin spacers if you didn't kill the sensitivity doing so). My "repaired" MM-700 has a surprising amount of bass in a near-field setting. These would really sound spectacular strapped to your face (I'm imagining a Jecklin Float inspired headphone frame) despite the odd looks you'd get.
I'd love to find maybe 4 solid pairs of MM-70x satellites to get my feet wet in hi-fi speaker building, but that isn't going to happen soon.
It'd also be fun to experiment with diaphragm tension (and possibly adding very thin spacers if you didn't kill the sensitivity doing so). My "repaired" MM-700 has a surprising amount of bass in a near-field setting. These would really sound spectacular strapped to your face (I'm imagining a Jecklin Float inspired headphone frame) despite the odd looks you'd get.
The screws probably just hold the front and back grills together. I'm guessing the magnet assembly uses rivets like the others. D: The sad part is even a pop rivet like ericj mentioned would probably require modification to the grills for reassembly. I'm not saying it's impossible, putting it all back together is the least of our worries, I feel, but it'd be nice if reassembly required a little less attention. Unless, of course, you plan to mount the speakers in your own custom baffle, then you're tossing the stock frames out anyway.
Also, I don't know if there's any truth to this at all, but I heard the MM-1000 and MM-700 had problems with magnets, but the MM-702 doesn't. Could have just been a lucky set, Idk. I also heard the MM-702 system has a considerably nicer subwoofer than both other systems which are earlier revisions.
Also, I don't know if there's any truth to this at all, but I heard the MM-1000 and MM-700 had problems with magnets, but the MM-702 doesn't. Could have just been a lucky set, Idk. I also heard the MM-702 system has a considerably nicer subwoofer than both other systems which are earlier revisions.
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You may actually be right, Andersonix. Taking a closer look at things, it appears the damping cloth that they glue to the magnets is just inside the rear grill. Also, the traces don't look the same to me:
MM-???
Very odd looking circuit to me, specifically the bottom. Also, there's no discernable pleating.
MM-700 with horrible buzz, the first MM-700 I took apart.
Notice the pleating and squarish tines to the serpentine (sigma) layout.
MM-???
An externally hosted image should be here but it was not working when we last tested it.
Very odd looking circuit to me, specifically the bottom. Also, there's no discernable pleating.
MM-700 with horrible buzz, the first MM-700 I took apart.
Notice the pleating and squarish tines to the serpentine (sigma) layout.
No pleats, wider and shorter then the MM-700-1000's. Have an excellent response from 200Hz (requires wider baffle to do this well tho) to 10k or so. Diaphragm width dictated a cross at 5k before beaming sets in.
Last time I'll do this til another project requires the need. Want 2 more for an MTM dipole setup with an AMT. When opening the magnets repel and slide to the side so care must be taken. The unbound edge crinkling creeps me out thinking you're tearing it to shreds. They are fine drivers for sure, perhaps build them into my Lazyboy on adjustable arcing poles extending out a meter, with a sub in the base, dunno, it's a thought
The design was licensed from Bruce Thigpen at Eminent Technologies here in Florida (panhandle, I be way south)
Eminent Technology, Incorporated
Have a few response curves found on the net too. Tho don't know how they were measured so cant say how accurate they are and haven't measured them myself yet.
Last time I'll do this til another project requires the need. Want 2 more for an MTM dipole setup with an AMT. When opening the magnets repel and slide to the side so care must be taken. The unbound edge crinkling creeps me out thinking you're tearing it to shreds. They are fine drivers for sure, perhaps build them into my Lazyboy on adjustable arcing poles extending out a meter, with a sub in the base, dunno, it's a thought
The design was licensed from Bruce Thigpen at Eminent Technologies here in Florida (panhandle, I be way south)
Eminent Technology, Incorporated
Have a few response curves found on the net too. Tho don't know how they were measured so cant say how accurate they are and haven't measured them myself yet.
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Nope, not bidding, knee deep in another project atm. Tho was offered to buy a full PM-9 setup by a member back last December, new in box for $150+50 to ship. He had bought his the same time as I when eBay was littered with them for $50. They retailed for $100. Several others here have them, some of the best nearfield computer desktop speakers made IMHO
Today the sub is used in my son's FAST system in his bedroom.
A couple of other critical points about this driver.
1. Be very careful how much low freq energy they receive and cross LR4 above 200Hz.
2. The driver is lacking at 200Hz due to baffle width and if increased with a cut out of it's shape in a ¼" panel => 12" resolves this. I've made one that was curved back from the side steam bending a panel, leaving the center flat for mounting and worked a peach. Sadly they got crunched in our last move, but easy to make quick enough and cheap todo with a nice stained/varnished finish.
3. Limit power to 25 watts and only feed it clean power!!! It is very easy to melt the diaphragm with too much. This is easy todo as they have an efficiency of about 82dB/w/m. Enough for normal listening levels but be very very careful when turning them up to the limit.
They are gems and will last a long time if treated with care.
Cheers
Mike
Today the sub is used in my son's FAST system in his bedroom.
A couple of other critical points about this driver.
1. Be very careful how much low freq energy they receive and cross LR4 above 200Hz.
2. The driver is lacking at 200Hz due to baffle width and if increased with a cut out of it's shape in a ¼" panel => 12" resolves this. I've made one that was curved back from the side steam bending a panel, leaving the center flat for mounting and worked a peach. Sadly they got crunched in our last move, but easy to make quick enough and cheap todo with a nice stained/varnished finish.
3. Limit power to 25 watts and only feed it clean power!!! It is very easy to melt the diaphragm with too much. This is easy todo as they have an efficiency of about 82dB/w/m. Enough for normal listening levels but be very very careful when turning them up to the limit.
They are gems and will last a long time if treated with care.
Cheers
Mike
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