DIY Magnepan SMGa repair

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Hi folks,

Here is a brief progress report on rebuilding my SMGa speakers. As mentioned elsewhere, I tried localised re-gluing of the original wires. This lasted for a while, but eventually they started to detach and rattle against the diaphragm.

The problem was not being able to remove the old, soft adhesive sufficiently to get good clean surfaces for the glue to do it's job. In my opinion the only way to tackle this problem is to strip the panel and replace the wiring (salvage of the original is not really an option). To help with this I purchased the repair kits available from Magnepan, one for Bass and one for treble wiring. This seems to be the only (easy) way to get hold of insulated aluminium "magnet" wire. I spent nearly a day on the 'net seeking alternatives....

Progress:

Yesterday the left speaker was dismantled and a careful note of the "voice coil" wire patterns made, along with photographs to complete the record. These have proven essential to get the details correct during reassembly.

The old wires were removed by softening the adhesive with acetone. The remaining residue was cleaned up with more acetone. Luckily I have a covered outdoor workspace, as quite a lot of solvent is required and breathing the vapur is not recommended.

Today I set things out for rewiring. At first I planned to build a jig so that I could string the wires, then offer them up to the panel (pre coated in contact adhesive) in one go. Thinking about this further, I decided instead to run the wires by hand. The diaphragm was sprayed with 3M super 77 contact adhesive - as recommended by Magnepan's instructions.

It was possible to place each 4' run of wire, shape it around a suitably sized dowel, tack down the "loop" then run back to the bottom of the panel. In this way the pattern for the bass wires was completed in about 10 minutes. Care is needed to ensure the loop ends do not lift (I weighted them down as recommended elsewhere).

After this the wires receive 2 coats of a water based adhesive to complete the bond to the panel. There is some risk of this upsetting the tack layer of "Super 77" but I had little problem in this regard. (I did some experiments with a length of old wire and a grocery bag to gauge handling & drying times)

The bond between wires and panel appears to be very secure.

The treble wires were set in a similar manner, though being of finer gauge, this was easier to apply. There is also a much smaller, simpler pattern, so it was very easy in comparison to the Bass section.

Next I need to solder the wires to the terminals at the panel edge (aluminium compatible solder included in the repair kit) and test the speaker.

If that works out, I'll pull the other speaker apart and repeat the experience.

Cheers,

Ed

References:

http://www.opus45.com/magnepan/

http://www.integracoustics.com/MUG/MUG/tweaks/peter_gunn/repair.html


http://www.integracoustics.com/MUG/MUG/
 
Good Idea. I'll upload some pictures when I have a chance. Certainly it might be useful to others if there's a record of the wire pattern. The bass section is a mixture of single and double passes between the magnet rows, and the layout needs careful attention to detail.

No chance to hook up the panel to an amp yet, but it did get a signal form the radio in the work area. Both sections played music, so we're well on the way.

Ed
 
This is rear of the left speaker (in my setup) before repairs were started. The tweeter panel is normally on the extreme left, when one is in the "listening position" in front of the speakers. Here it is just visible on the right of the panel, comprising the fine red wire.

The bass section makes one full circuit, beginning on the left and completing 12 upward and 12 downward runs between the magnet poles. The wire then runs along the base of the diaphragm to begin another partial run, with 4 upward and downward passes on the extreme left side. The centre is bypassed, then a further 3 passes are made on the right. The wire is then returned to the terminals.

The ends of the first and second passes are offset by 3/8", and I used the end of a 5/16" drill to form the end of each loop.
 

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Second panel is underway. Though I hadn't noticed whilst listening, the bass wires were in a poorer condition than the first speaker. Many were loose and overall, very poorly stuck at this stage. Production notes on a label inside the speaker indicate that this pair was made in 1987. If I get this repair right, I can hope for another 20 years!

New bass wires are in place, with their first application of overcoating adhesive applied.

Ed
 
WOW...Great thread! I was actually getting ready to start repairing my SMGa's this weekend.

I was not sure if I was going to try just regluing...or complete wire replacement. Ed, what would you say is the level of difficulty on this project? I am fairly new to the Magneplanar speaker line (owned mine for about 4-5 months so far)....so I don't wanna destroy them...just make them sound the way that they should.

So any advice from you, Ed, or any other Magneplanar guru's would be much appreciated.

Thanks,

Wayne Boyd
 
Thanks Wayne,

Firstly, check out the links in my first post for a bit more info about the speakers, and some other folks accounts of repair - Happily, I'm not the first person to try this :)

I had tried regluing, but it seems this was not satisfactory. The original adhesive was so degraded -soft and gooey- that it was no longer up to the job. Moreover, it was hard to clean any residues completely, with the wires still in place. This meant that my repairs did not hold... For that reason the choice to do a complete refurb with new wire was made. Your situation may be different, but have a careful, critical look before you decide what to do.

The repair is fiddly, but "doable". It would be worth practicing the method with some cheap copper magnet wire so that you get used to handling & setting out 4' lengths from a reel - stretch out a dummy panel e.g a garbage bag and try patterning on to that before you attack the real thing.

The most important thing: take pictures, make notes and record as much detail as you can before you strip the panel. I also marked the positions of the top and bottom "loops" in the wire onto the panel frame, so they were there for easy reference as I worked.

Cheers,

Ed
 
tmblack ,

On the side oak wood pieces , there should be 4 to 5 screws that hold those trim pieces on. Remove those screws . There might be
a screw or two on the top of the top oak piece , remove it (them) also .

The bases will have screws that need to be removed also . Once all the screws have been removed , the wood pieces will come off the speaker with ease , if not , there are still some screws holding the wood trim to the speaker frame .

Once all the wood is off the speaker frame , locate the bottom end of the speaker , there , You will find numerous staples that need to be removed , to be able to remove the sock .

Don't forget to remove the screws from the plate on the back of the speaker , that the speaker wires connect to . . . once all this done , You'll be able to roll the sock up and off the speaker .

Good Luck , it's not hard , just time consuming , removing all the staples . :)

Cheers , Stephen
 
Up from the depths... And I was hoping not to have to revisit this thread on my own account., but here I am.

Enjoying the music this evening, and it dawned on me that things were not quite as they should be.... no treble on the right. I tested the Maggie's tweeter fuse, but it was fine... Digging deeper, I found the tweeter was open circuit, with a tiny break, barely visible, in the wire on the panel. Unlikely that I burned it out - nor was there any sign of surrounding damage, more likely there was a nick in the insulation and it corroded. Nonetheless it needs to be repaired. I still have the kit with plenty of wire, but had to order the over coating adhesive, which was rather expensive.

This will be project for one or two evenings next week. At least I only need to rework that part of the panel, and the wire layout is simple.

Cheers,

Ed
 
Materials are all present and correct. Time to get started later on today.

I also broke down and ordered some new "socks" from Magnepan. What a great company - one of the few that provides a phone number. When you call it, you need make only one selection and are then instantly connected with a real person :). On top of that, they are able to help you with parts or whole repairs for things the company stopped producing years ago.

Ed
 
Ah well, a bit slower than hoped, but I did get started today. The tweeter section of the panel is stripped and ready for the process of applying fresh wire.

Removing the old wire did give some insight into the possible failure mechanism. Once the adhesive was largely removed, and softened up, it was possible to peel the wire gently from the diaphragm. Except that in a couple of places close to the break I found before disassembly, it broke very easily. The rest of the wire pulled away without trouble, all requiring a similar force. I suspect that the wire was damaged, possibly by me when it was fitted 5+ years ago, or that it was defective as supplied. We'll never know...

Anyway, looking forward to finishing the job and getting my the speakers back tomorrow.

Ed
 
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