Magnepan Voice Coil Repair : A Sagaby Peter Gunn

All right, here it is as promised, my trials and tribulations of re-coiling the “beast”. In this case, apair of SMGa loudspeakers. Be warned, it’s long. Hopefully that means all the questions areanswered.

Chapter One - What’s the Buzz?

You hear a buzz; you hear a rattle. Not constantly, but consistantly at the same musicalpassage, and always emanating from the same location on the Maggie. What does it mean? Itmeans the coils on your Maggies are coming unglued. Why? Because the two products used toadhere them went bad. The first being 3M Super 77 spray adhesive, the second a liquid waterbased PVC called Milloxane. The former is just supposed to hold the coils in place while thelatter is applied and cures, and aye, there’s the rub.

I know as a woodworker, if I want to bond 2 surfaces, I PUT THE GLUE BETWEEN THEM. WhatMagnepan does, is use a tacky substrate, and then hopes a liquid blanket is going to hold thecoils down. Oh it does, but not forever, certainly not forever... I think it is fair to say everyMaggie 20 years or older has, had, or soon will have coils coming off. A fair number even startlosing them in 10 years or less. For this I blame the procedure, and the use of a product in a jobit 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 itwas handy because he worked for 3M at the time and they made it. I am sure they continue touse it because Magnepan makes changes like watching catci grow. They both look differentafter 10 years but you never really saw it happen...

However my experiences with this product have caused me to not only think little of it’squalities, I revile it. And I don’t mean the way liberals hate Bush but don’t know why, or howsome right wing nuts blow up abortion clinics because life is so precious; no, I mean the kind ofpure hatred a real man reserves for a thing that lets him down so repeatedly (a car is a goodexample) that all he can do is go out and unload a magazine of rounds into it. That act is theonly thing preserving his sanity.

IMHO, 3M Super 77 is a vaudevillian product. By that I mean it harbours all the qualities of aThree Stooges or WC Fields stage prop. It will NOT glue the things you want, at least not remainglued in the long term, but it WILL glue every thing else in which it comes in contact with atenacity that is unparalleled. I have tried it in countless applications, all acts fully supported bythe label and in a manner of application described on the can, and EVERY time it has eitherimmediately or in the short long term, failed.

And let’s be honest, this is the thing really holding the coils down, because when it stops, theMilloxane can’t 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 abanana. Amazingly too, they’ll make less noise like this than the loose wire mid panel will. The“person” I bought these from was in fact sure that they played just fine. You can check them inperson by feeling the backs lightly with your hand wiping from the inside to the edge of thepanel. If they are raised, you’ll feel it.

To get to the point pictured above, you’ll first need to remove the side wood trim which is easyenough. Then lie the panels down on their faces (which is the magnet side and always thepreferred face to be down) and remove the jillion staples holding the socks on. (this is thehardest part of the whole business actually) You’ll find 2 layers, and about 75 staples on each. IfMagnepan 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 bevery careful because if your lower coils are coming off, taking the fabric off will go against their“lie” and will pull at them, ripping them off further. Pull the fabric up high and away from themuntil you are past them. You can then stand the speaker up and take the sock off the rest of theway easily, but watch out, there may be more staples at the top sides.

Chapter Three - The Fix

Now it’s time to clean the old adhesive off. I cannot be positive, but I have noticed 2 kinds ofaging. It seems in dry hot areas, the adhesive gets amber colored and brittle. In more humidareas, 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 theamber state.

You will need a can of acetone, large cotton puffs or other natural wipe, and Q tips. Years ago inthe shop I used a man made sponge only to find the minute it hit the acetone a reactionoccurred and the sponge got hard as a brick. Whatever wipe you use can’t 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 bluelines) to insure the problem didn’t re-occur in a year. Pour some acetone in a small bowl, anddip your pad into it. Squeeze it out so it does not run, but is generally wet and apply it to thepoint in purple above and stroke with the wire towards the outside of the panel. I go downshort of the blue line because it will spread out that far on it’s own when you press.

Do one coil at a time, turning the wipe as crud builds up on it, and discarding it when fullyloaded. To clean the wires themselves put a finger under them and drag the wipe over thempulling 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 thelose point and lifting them. (if a double loop be careful to get both) You can then dip Q tips inthe acetone to get to the very narrowest undersides and places you couldn’t wipe. Sometimesyou get a ball of crud going but it won’t 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 workingfine, 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 3MSuper 77 spray adhesive to the panels. I allowed it to tack up, and then carefully pressed thecoils back in place. (in place is between the magnets on the other side. You’ll see the spaceline, 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 wideartists brush, not the one in the damn can) That’s when the funny thing happened. Milloxane iswater based like elmers glue, only it sets up rubbery not hard. It’s purpose is to make a rearersatz panel over the coils. Well, the 3M decided not to have any part of this, and let loose. Since the Milloxane can’t 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 itAGAIN and applied less 3M. SAME result. Threw 3M in the trash and swore loudly andvigorously. Same result, but I felt better. At this point I am not interested in hearing fromengineers. YES, I read the can, YES I followed instructions, YES the room was 70 degrees, YESthe can was new. THE PRODUCT JUST SUCKS. It’s that simple.

Chapter Five - 10 Novenas & Call Me in the MorningWorrying. That was my next step. So I then ran to the archives and began to see I’m not theonly one apparently. People were making elaborate jigs out of aluminum or buying heaters toattach 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 theshortcomings of a product that does not work. I’ll find a product that does work instead. Soafter a little thought only one thing came to mind.

Yes, DAP Weldwood contact cement. It is also acetone based, but unlike 3M Super 77 , itWORKS. 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 it’s use however, which I will explain.

So I returned to a newly stripped panel to try my luck again. For application purposes I used 2sizes of artist brushes, NOT again the one that comes in the bottle. In fact, I cut that oneentirely 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 thewires. 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 haveto stop and clean the buildup that happens. (be careful doing this. Acetone dissolves the glueholding 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 thebrush good and soaked in the acteone first, then got a good glob of adhesive and wiped it onwith the “grain”. When getting to where the coil touches the Mylar, allow the brush to rununder as far as it can.

When putting on the DAP, you can’t be a slob, but you also can’t overly worry.

Even done right, it will look like it’s going to be ugly, or dark etc... but if you use care it will turnout OK.

The trick in applying it to the wires is to keep the brush wet by cleaning it after every 2-3 coilswith acetone, and to apply a “nice” amount. A “nice” amount is putting the brush in just up tothe ferrule and pulling it straight out of the DAP. Don’t try to “dig” more. Then apply per thediagram 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 theDAP will naturally hang from the brush. That’s why you must spin it as you go.

You also don’t want to start where the coil and Mylar are in contact because it will glob thereand you can’t get under to make sure it is coated. Starting a bit below halfway, and going to thetip first seemed to work best for me.

Now, of course you don’t have to follow my pattern, but you should keep in mind to turn thebrush, make sure the tip gets done well, and get as far under the wires where they join theMylar 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 withquick, long strokes.

In all cases, even if it looks bad, DON’T RE-DO IT! This product does not want to re-apply overitself. 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. It’s only marginally anal retentive, andit’s over very quickly actually.

I would then go and do the next 2 coils, allowing the adhesive I’d applied to set. Then, I pressedthe coils back to the Mylar in line with the magnets as explained before. To do this I took aclothespin apart and used the flat bottom edge as a pressing guide. Repeat until the panel isdone.

I let it dry a few hours then put the Milloxane on. To my surprise it again lifted, but only at like 2places and only very slightly at the very tips. Water based items don’t dissolve acetone basedones, but perhaps even more time curing might help. I only needed use the fine brush above tore-wet the tips with the DAP and press them back down. They have since held fine and theresult 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 ofmusic. You’ll notice top left in the pic, the ceiling wallpaper came off. That’s right, the 3MSuper 77 adhesive I put them up with ISN’T HOLDING. I have to redo the ENTIRE ceiling. That’sno surprise, it didn’t hold the blue tiles on either. I had already redone them with liquid nails. Itdidn’t hold the grey ones on the side wall either, ditto. Well, we know it won’t hold Maggievoice coils on as well, so what’s the shock?

In a short while it was clear the repair job was a complete success, but I did have rattles amidpanel. Play the selection that makes them rattle and go stand behind them and listen. You’ll beable to hear and “see” exactly where it is coming from, but be careful and DO NOT touch thewires while they are playing. Remember or write down the locations, unhook them, and back tothe work table.

While flat, lightly brush your hand across the wires where you heard the buzz like you’re playinga harp. You’ll soon find the loose ones. My solution was to take the fine brush again, dip it inthe DAP and carefully ride it under the wire, being careful to get both the wire and the Mylarcovered. 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. I’ve put about 10 hours in and not a buzz,and they sound great. Be careful you don’t use Ivy’s “Hideaway”. My wife wanted to hear itand there is an odd buzz sound in it that when your ears are perked for Maggie buzzing makesyou think it’s 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 orgod knows what. If the gushes or acteone don’t harm the Mylar, the DAP sure as hell won’t. Plus it is designed to be used on wood which moves (seasonal expansion and contraction) andnot 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 noMilloxane is afterwards needed. I used the Milloxane afterwards because I had it, but I knowmany people realize they need to redo Maggies in October only to find Magnepan is no longershipping it. (because it freezes in the mail being water based and that ruins it) So, who wants towait 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 theworrying type, order the Milloxane next year and put it on as well, but I think the DAP does thejob. It actually bound the wire to the Mylar, so it doesn’t need the plastic Milloxane coat to holdit there. Of course time and further experimentation will tell. So far my results have been verygood.

Thank you for getting thru it all, and I hope this will be of some help to the loyal sufferingMaggie owners out there. Set yourself free from 3M and Milloxane, and enjoy your musicagain.

And now the next step, the parts upgrade...