When I discovered the ominous buzz in my MGIII’s, I searched the MUG for help and found Dave Pride’s description of the wiring frame he made to ease the process. I built his frame and experimented with the idea he mentioned of spraying 3M-77 on the wires instead of on the Mylar.
I added #10 oval head screws as adjustable feet on each corner to let the frame’s weight rest on the Mylar frame rather than the Mylar itself. I adjusted the screws individually to have the wiring pegs just touch the Mylar. I didn’t want to spray the wires past the pegs, imagining that gluing the pegs to the Mylar would produce more of a mess than I wanted. So I cut a mask from thick paper that had a slot in it about 4½' (1.4m) long and as wide as the midrange element of my speaker, about 2¼" (57mm). I got to thinking about that last roughly 2" (51mm) of wire on each run that loops around each peg. If it didn’t have glue on it, when I released the frame’s tension, I would have random loops in the wire. So I cut two more masks with holes just 2" × 2¼" (51mm × 57mm) to spray little patches of 3M-77 on the Mylar at each end.
I sprayed 3M-77 glue on the wires between the pegs, then sprayed the two end patches on the Mylar. I was quite surprised at how thick the sprayed glue looked on the Mylar. Given how little of it actually stayed on the wire, and how it tended to lift until it dried, I think it is meant just to hold the wires in place while the Milloxane (3M-30NF) is applied and dries. The 3M-30NF doesn't tack up nearly well enough to be used alone.
I painted the 3M-30NF with a small brush, spreading it out as much as I could. It comes in quart and gallon containers and is meant to be sprayed in industrial uses, but I don't have a sprayer. Even so, the 3M-30NF was quite thin using a small paint brush. When I was done adhering the wires, the glue profile on the whole midrange panel looked exactly like Magnepan’s original pattern, thick on the ends and thin in the middle. I am fairly certain that what I described must be exactly how they made my speakers in 1983: spray most of the wires on a frame, spray a strip across both ends of the Mylar, 3M-30NF it all down.
I sprayed in about 65°F (18°C) weather. So the 3M-77 set up very slowly. I think I didn’t wait long enough before offering the wires up to the Mylar; spots kept coming up. I spent some time while the 3M-77 set pushing the wires back down in places. But ultimately they stayed in place for the 3M-30NF step.
As far as I can tell, the glue is holding. The speakers seem to have broken in. They sound great. Many thanks to Dave for doing all of the research and posting it. It made my rewiring job much easier.