Magnepan IIIA Rewire
By Derek Atkin firstname.lastname@example.org
I have always wanted a pair of Magnepans. Found a set of MGIIIAs on ebay that happened to be at an audio shop around the corner. They were described as being in good condition - with one bass panel out. I traded an old Marantz receiver for them and the fun began. I tried to repair the broken wire on the bass panel but it kept just falling apart. I knew that I would have to tackle a rewire on these speakers. Below is the chronicle of a Maggie re-wire.
Start by calling Magnepan and getting a repair kit for your speakers. The folks there are really helpful and its pretty specialized stuff, trying to track down the special wire (22ga & 31ga for the MGIIIA) is not worth it. I spent $140 for the bass and mid repair kits, two new black socks and a set of four tone discs.
|Here are is the original untouched speaker as I brought it home and fired it up. You will notice what looks like a water stain at the bottom of the sock. Amazingly, everything under the covers looked ok. It took a while to get all the staples off to finally be able to remove the cover. I never removed the ribbon tweeter, was able to work around it|
|As you can see, these are not always wired from the factory in perfect shape. Wires are sometime crossed. People think that the green is a copper patina. The adhesive magnepan uses is actually green in color. All those wires are aluminum.|
|If you look closely you can see the little white zits on the wires. These are pockets of corrosion that eventually disintegrate the wire, and cause an open circuit.|
|First step is to strip off the old wires. Acetone and patience are the two major ingredients. Make sure before you start that you document the speaker. A wiring diagram and many digital pictures are essential. I counted the wires and noted where the double loops were, also where is one started and ended. You can not over document this step. Do not do both speakers at once, leave one all together for reference.|
|Using acetone and paper towel carefully clean all the old adhesive off the mylar. Use small pieces of scotch tape to fix any tears. Do not try to sterilize the mylar, to much pressure especially near the edges can tear it. If you have the tuning discs installed, very carefully drill out the rivets. I used a Dremel as it was smaller and offered more control|
|Here is the Mylar all ready for its new wires.|
|I choose to tackle my speakers without a jig. I had another person available to help with the rewire and we just did it by hand. The wires may not be 100% symmetrical but it doesn't really matter. As long as the wire runs are similar and in the magnet channels, the speakers will sound fine. I am not a good woodworker and figured it would take more time to make a jig than to just do them by hand.
Lay down a base of 3M #77 spray adhesive and start running the wires. I used an empty X-acto pen knife handle (blades kept at a very safe distance from the panel)for the bass wires and just did the mids by hand.
|I used a small collection of washers to make sure the wire loops stuck down, don't leave them on to long or and extra cement might make them part of the speaker . Make sure that you leave plenty of wire and label them well.|
|First panel wiring runs are complete.|
|The tools of the trade. I found the special 3M Fastbond 30NF adhesive at Grainger. It was $22 a quart. In my attempt to initially repair the speaker, I got some aluminum specific solder and flux from a company call Kapp Alloy. Magnepan gives you solder in the kits they sell, I found this to work really well. It was at this point that I soldered my connections and tested the speaker. The wires are insulated, so you need to strip the insulation off. I used a combination of the soldering iron and a 220 grit sandpaper. For the 31ga wire, i joined them and soldered as a single wire. When done make sure you seal up the connection with the silicone. When testing the speaker make sure to keep the power to a very minimum, I wanted to confirm that they were operational. I also ran a multi meter across the circuit from the speaker terminal and got about 5 ohms for each driver.|
|You need to apply two light coats of the 3M contact adhesive. I waited a minimum of 12 hours between coats, using a 1" brush to apply.|
|After I reattached the discs and put the stands back on. I hooked the speakers up and let them play for a while. The adhesive had dried for a few days. Magnepan said that it might remain tacky for a little while yet. As long as its not "wet" tacky you should be fine. It is true, when these things are complete - they look like some bizarre 8th graders science project went wrong.|
|Back side of the finished right panel. I choose not to cut out the covers for the tweeter. It makes access a whole lot easier. The new socks from Magnepan went on without a hitch. Need 1/4 staples and a staple gun to attach at the bottom. I did a small cutout for the back panel and stretched the material around it.|
|Front of finished right panel|
|Finished left panel. These sounded like crap when I first hooked them up. They require just as much break in as a new pair of speakers.
All in all the process took about three weekends to complete. Nothing really super complicated. I was the most nervous about tearing the mylar, so taking the discs out was probably the biggest pain. This is basically the same thing the Magnepan does when you send them your speakers. I would guess that if these need this process done again, I would probably send then in and the mylar would need to be replaced. Total cost with all the stuff was under $200.