Magnepan Voice Coil Repair : A Saga
by Peter Gunn
All right, here it is as promised, my trials and tribulations of re-coiling the ďbeastĒ.  In this case, a pair of SMGa loudspeakers.
Be warned, itís long.  Hopefully that means all the questions are answered.
Chapter One - Whatís the Buzz?
You hear a buzz; you hear a rattle.  Not constantly, but consistantly at the same musical passage, and always emanating from the same location on the Maggie.  What does it mean?  It means the coils on your Maggies are coming unglued.  Why?  Because the two products used to adhere them went bad.  The first being 3M Super 77 spray adhesive, the second a liquid water based PVC called Milloxane.  The former is just supposed to hold the coils in place while the latter is applied and cures, and aye, thereís the rub.
I know as a woodworker, if I want to bond 2 surfaces, I PUT THE GLUE BETWEEN THEM.  What Magnepan does, is use a tacky substrate, and then hopes a liquid blanket is going to hold the coils down.  Oh it does, but not forever, certainly not forever...  I think it is fair to say every Maggie 20 years or older has, had, or soon will have coils coming off.  A fair number even start losing them in 10 years or less.  For this I blame the procedure, and the use of a product in a job it CANNOT do.
Why I HATE 3M Super 77 spray adhesive
I am not a conspiracy sort, and I am sure the reason Jim Winey used 3M Super 77 is because it was handy because he worked for 3M at the time and they made it.  I am sure they continue to use it because Magnepan makes changes like watching catci grow.  They both look different after 10 years but you never really saw it happen...
However my experiences with this product have caused me to not only think little of itís qualities, I revile it.  And I donít mean the way liberals hate Bush but donít know why, or how some right wing nuts blow up abortion clinics because life is so precious; no, I mean the kind of pure hatred a real man reserves for a thing that lets him down so repeatedly (a car is a good example) that all he can do is go out and unload a magazine of rounds into it.  That act is the only thing preserving his sanity.
IMHO, 3M Super 77 is a vaudevillian product.  By that I mean it harbours all the qualities of a Three Stooges or WC Fields stage prop.  It will NOT glue the things you want, at least not remain glued in the long term, but it WILL glue every thing else in which it comes in contact with a tenacity that is unparalleled.  I have tried it in countless applications, all acts fully supported by the label and in a manner of application described on the can, and EVERY time it has either immediately or in the short long term, failed.
And letís be honest, this is the thing really holding the coils down, because when it stops, the Milloxane canít do it, and I have proof.  So let us begin.
Chapter Two - The Problem Revealed
Here is what the culprit usually looks like:
They do let loose in the middle, but this is the more common ailment, the ends peeling up like a banana.  Amazingly too, theyíll make less noise like this than the loose wire mid panel will.  The ďpersonĒ I bought these from was in fact sure that they played just fine.  You can check them in person by feeling the backs lightly with your hand wiping from the inside to the edge of the panel.  If they are raised, youíll feel it.
To get to the point pictured above, youíll first need to remove the side wood trim which is easy enough.  Then lie the panels down on their faces (which is the magnet side and always the preferred face to be down) and remove the jillion staples holding the socks on.  (this is the hardest part of the whole business actually) Youíll find 2 layers, and about 75 staples on each.  If Magnepan was only this anal about the capacitors going into these things...
Then unscrew the back terminal plate.  With the speaker still flat start removing the sock, but be very careful because if your lower coils are coming off, taking the fabric off will go against their ďlieĒ and will pull at them, ripping them off further.  Pull the fabric up high and away from them until you are past them.  You can then stand the speaker up and take the sock off the rest of the way easily, but watch out, there may be more staples at the top sides.
Chapter Three - The Fix
Now itís time to clean the old adhesive off.  I cannot be positive, but I have noticed 2 kinds of aging.  It seems in dry hot areas, the adhesive gets amber colored and brittle.  In more humid areas, or especially near the ocean, it turns green and gets gummy.  Mine came from Brooklyn, so they were green and gummy.  I do not know if the adhesive comes off easier or harder in the amber state.
You will need a can of acetone, large cotton puffs or other natural wipe, and Q tips.  Years ago in the shop I used a man made sponge only to find the minute it hit the acetone a reaction occurred and the sponge got hard as a brick.  Whatever wipe you use canít be man made.
The picture below shows my method of dealing with it.
The green line shows the point the wires are loose to.  I cleaned a little past that point (the blue lines) to insure the problem didnít re-occur in a year.  Pour some acetone in a small bowl, and dip your pad into it.  Squeeze it out so it does not run, but is generally wet and apply it to the point in purple above and stroke with the wire towards the outside of the panel.  I go down short of the blue line because it will spread out that far on itís own when you press.
Do one coil at a time, turning the wipe as crud builds up on it, and discarding it when fully loaded.  To clean the wires themselves put a finger under them and drag the wipe over them pulling both fingers along.  The glue should come off in very little time.
Then bend back the coils to about the angle shown in the pic below by holding a finger at the lose point and lifting them.  (if a double loop be careful to get both) You can then dip Q tips in the acetone to get to the very narrowest undersides and places you couldnít wipe.  Sometimes you get a ball of crud going but it wonít pick up.  Just flip the Q tip and grab it with the dry side, that usually gets it, then wipe the spot it was at again with the wet side.
When done, it should look like this.  Squeaky clean and no more green.
You may notice the tips of the tweeters are green, but they were really down fast and working fine, so I let well enough alone.
Chapter Four - A New Horror
This is when things started getting ugly.  Once dry, I applied the RECOMMENDED amount of 3M Super 77 spray adhesive to the panels.  I allowed it to tack up, and then carefully pressed the coils back in place.  (in place is between the magnets on the other side.  Youíll see the space line, and the wire should go down the middle between the rows)
I let them go for a good while, and then came back and applied the Milloxane.  (with a wide artists brush, not the one in the damn can) Thatís when the funny thing happened.  Milloxane is water based like elmers glue, only it sets up rubbery not hard.  Itís purpose is to make a rear ersatz panel over the coils.  Well, the 3M decided not to have any part of this, and let loose.  Since the Milloxane canít hold a rising coil alone, they rose, and took the Milloxane with it.
I had to re-strip it all over again.  This time I applied even more 3M.  Same result.  I stripped it AGAIN and applied less 3M.  SAME result.  Threw 3M in the trash and swore loudly and vigorously.  Same result, but I felt better.  At this point I am not interested in hearing from engineers.  YES, I read the can, YES I followed instructions, YES the room was 70 degrees, YES the can was new.  THE PRODUCT JUST SUCKS.  Itís that simple.
Worrying.  That was my next step.  So I then ran to the archives and began to see Iím not the only one apparently.  People were making elaborate jigs out of aluminum or buying heaters to attach to the speaker terminals to heat the coils until they lied flat etc...
Well F*CK that.  I will be damned if I am going to go to an extreme like that to make up for the shortcomings of a product that does not work.  Iíll find a product that does work instead.  So after a little thought only one thing came to mind.
Yes, DAP Weldwood contact cement.  It is also acetone based, but unlike 3M Super 77 , it WORKS.  I have used it in the past to adhere veneer, and it never comes off, EVER.  Wet part A, wet part B, attach parts, you now have part C because you are never getting them apart again.  This little bottle cost $2.65 compared to nearly ten bucks for the 3M.
There is required care in itís use however, which I will explain.
So I returned to a newly stripped panel to try my luck again.  For application purposes I used 2 sizes of artist brushes, NOT again the one that comes in the bottle.  In fact, I cut that one entirely off to facilitate ease of use and recommend you do likewise.
I used the fatter blue brush (1/4 inch wide) to first apply adhesive to the undersides of the wires.  I shortly found the glue was already curing and getting a little stringy out of the bottle.  The trick is to keep dipping the brush in acetone as you work.  From time to time you also have to stop and clean the buildup that happens.  (be careful doing this.  Acetone dissolves the glue holding the bristles in the brush, so be careful not to pull at them or you will pull them right out) I did 2 or 3 wire rows, and then did the corresponding part of the panel.  For the Mylar I got the brush good and soaked in the acteone first, then got a good glob of adhesive and wiped it on with the ďgrainĒ.  When getting to where the coil touches the Mylar, allow the brush to run under as far as it can.
When putting on the DAP, you canít be a slob, but you also canít overly worry.
Even done right, it will look like itís going to be ugly, or dark etc... but if you use care it will turn out OK.
The trick in applying it to the wires is to keep the brush wet by cleaning it after every 2-3 coils with acetone, and to apply a ďniceĒ amount.  A ďniceĒ amount is putting the brush in just up to the ferrule and pulling it straight out of the DAP.  Donít try to ďdigĒ more.  Then apply per the diagram below by not only moving the brush, but slightly turning it as you go to prevent globs.  If you just move the brush it will act like a plow and will glob glue in front of it.  On top of it the DAP will naturally hang from the brush.  Thatís why you must spin it as you go.
You also donít want to start where the coil and Mylar are in contact because it will glob there and you canít get under to make sure it is coated.  Starting a bit below halfway, and going to the tip first seemed to work best for me.
Now, of course you donít have to follow my pattern, but you should keep in mind to turn the brush, make sure the tip gets done well, and get as far under the wires where they join the Mylar without clumping it.  And keep cleaning the brush as you go.
When you do the Mylar have the brush much wetter, but also grab more glue, and apply it with quick, long strokes.
In all cases, even if it looks bad, DONíT RE-DO IT!  This product does not want to re-apply over itself.  Trust me, what you did will work, and it will also look better once it dries and cures.
Doing one side of a panel only took about 15 minutes.  Itís only marginally anal retentive, and itís over very quickly actually.
I would then go and do the next 2 coils, allowing the adhesive Iíd applied to set.  Then, I pressed the coils back to the Mylar in line with the magnets as explained before.  To do this I took a clothespin apart and used the flat bottom edge as a pressing guide.  Repeat until the panel is done.
I let it dry a few hours then put the Milloxane on.  To my surprise it again lifted, but only at like 2 places and only very slightly at the very tips.  Water based items donít dissolve acetone based ones, but perhaps even more time curing might help.  I only needed use the fine brush above to re-wet the tips with the DAP and press them back down.  They have since held fine and the result is much cleaner looking and less grungy than the 3M job was.
Chapter Six - Bench Test
The next step is to hook them up and listen, a good long while to various buzz causing pieces of music.  Youíll notice top left in the pic, the ceiling wallpaper came off.  Thatís right, the 3M Super 77 adhesive I put them up with ISNíT HOLDING.  I have to redo the ENTIRE ceiling.  Thatís no surprise, it didnít hold the blue tiles on either.  I had already redone them with liquid nails.  It didnít hold the grey ones on the side wall either, ditto.  Well, we know it wonít hold Maggie voice coils on as well, so whatís the shock?
In a short while it was clear the repair job was a complete success, but I did have rattles amid panel.  Play the selection that makes them rattle and go stand behind them and listen.  Youíll be able to hear and ďseeĒ exactly where it is coming from, but be careful and DO NOT touch the wires while they are playing.  Remember or write down the locations, unhook them, and back to the work table.
While flat, lightly brush your hand across the wires where you heard the buzz like youíre playing a harp.  Youíll soon find the loose ones.  My solution was to take the fine brush again, dip it in the DAP and carefully ride it under the wire, being careful to get both the wire and the Mylar covered.  No, I did not strip on this step, I was just slightly heavier with the DAP.  Let it set up, and press back down.
After curing again I hooked them up for more testing.  Iíve put about 10 hours in and not a buzz, and they sound great.  Be careful you donít use Ivyís ďHideawayĒ.  My wife wanted to hear it and there is an odd buzz sound in it that when your ears are perked for Maggie buzzing makes you think itís them.  I swapped the Alons in and heard the same thing so it was just the song.
Chapter Seven - Moral & Conclusion
I do not doubt some chemist will reply and say I could have ruined the Mylar using the DAP or god knows what.  If the gushes or acteone donít harm the Mylar, the DAP sure as hell wonít.  Plus it is designed to be used on wood which moves (seasonal expansion and contraction) and not come apart, so clearly it does not dry hard and is not effected by, nor does it effect, movement.
Used judiciously it can be applied very lightly yet it holds so strongly I honestly believe no Milloxane is afterwards needed.  I used the Milloxane afterwards because I had it, but I know many people realize they need to redo Maggies in October only to find Magnepan is no longer shipping it.  (because it freezes in the mail being water based and that ruins it) So, who wants to wait till May with buzzing Maggies?  Not me.
I believe you can use the DAP and solve your problem right here and now.  If you are the worrying type, order the Milloxane next year and put it on as well, but I think the DAP does the job.  It actually bound the wire to the Mylar, so it doesnít need the plastic Milloxane coat to hold it there.  Of course time and further experimentation will tell.  So far my results have been very good.
Thank you for getting thru it all, and I hope this will be of some help to the loyal suffering Maggie owners out there.  Set yourself free from 3M and Milloxane, and enjoy your music again.
And now the next step, the parts upgrade...
Itís all about the music...