Magnepan Mid/Bass Panel Repair Instructions

by DavePride

The following is one long-time Maggie users guide to repairing planar panels.   I have employed all of the following techniques to maintain a pair of Magnepan Tympani 1D’s whose design features three panels per side—two of which are mid/bass.   The third is a tweeter panel which is not a ribbon tweeter.   I have replaced my own tweeters which I purchased from Magnepan, but have never attempted to pry apart their sealed casings to repair the originals.   I simply drilled out the rivets affixing the old tweeters to the panels and replaced them with the new ones.   The following comments therefore relate to mid/bass panel repairs.   I welcome constructive comments, modifications or improvements on this guide, but please, no flaming.   If you don’t care for the advice, don’t use it but don’t feel obliged to write some condescending screed to me.   As they are all I have, I need to concentrate my two or three remaining brain cells on things constructive, and don’t wish to be bothered.


NOTICE OF LIABILITY: All descriptions of repairs that follow are based upon my personal experiences repairing my own pair of Tympani 1D’s.   They may not apply to newer designs.   Further, there is generally more than one way to skin a cat, and my way may not be the right way for you.   In all instances, you must be the judge, and you must take responsibility for the consequences of any repairs you attempt on your Maggies.   This information is provided as a courtesy.


    Voice Coil Repair

This section is intended to address two issues—a break in the voice coil (usually stemming from impact damage—i.e. you fired your .44 at the TV but missed) or a loose voice coil.   It is not intended to address corroded voice coils which will be covered in the voice coil replacement section.

Symptom: Your mid/bass section on one speaker (or one or more panels of one speaker in the case of multi-panel speakers) does not produce any sound.   You have already checked the fuses in your amp(s).   You have checked the connections on each channel.   You have swapped the left and right channel speaker wires to see if the problem persists or changes sides.   You have removed the covers on the affected panel and actually found the break in the wire.

Testing: You can locate breaks by using performing a continuity test with a meter.   If you wish to perform a test to assure that the break you have located is the only break, you can get a small bottle of rear window defogger repair fluid at any good automotive parts supplier—paint it on the suspected break, let it dry for a few minutes, and fire up the system at low volume.   If it restores sound to the panel, you have isolated the problem.   (Actually this repair will usually work for several days, sometimes even weeks, but I regard it as temporary at best.)

Repair: You will need the following items to perform this repair:

  • Voice coil wire—A thin insulated aluminum wire available from Magnepan or any good electronics store.   Gauge varies, but match the gauge on your speakers.   Note that the gauge is thinner on tweeter repairs if you have been brave enough to pry apart an old pair of tweeters to try to repair them.   For purposes of discussion here, I am only dealing with mid/bass panel repairs.

  • Acetone—Available from any good hardware store

  • Aluminum solder—Available from any good electronics store.

  • Anti-oxidant sealant (for solder joints)—available at most hardware stores and electronics suppliers.

  • 3M #77 spray-on adhesive—Available from any good hardware store

  • UV Sealant—I have only acquired this from Magnepan, but I suspect it can be purchased at a good electronics store.

    Procedure: At the site of the break, take a small rag or sponge with some acetone on it and gently rub it on the affected area.   The acetone is a solvent that will strip off the old glue and UV sealant.   It will not damage the Mylar diaphragm.   You may damage the Mylar, however, by rubbing too hard and grinding the wire into the diaphragm, so be careful.   (If you do tear it, or your pot shot at the TV did more than break the voice coil, see the section on Mylar diaphragm repair.) Now both ends of the broken coil should be relatively easy to lift off of the Mylar.   You will need about 3-4 inches of working room on each end.   Using a very fine sandpaper you will strip off the very thin insulative coating on each end of the wire so that you can get a good connection.   Again, be gentle, as the aluminum wire is pretty frail.   You will now take a piece of new wire, strip both ends of it of insulation and twist the ends of it over either end of your voice coil.   Put a small piece of cardboard or cloth covered with some aluminum foil between the diaphragm and the repaired area as a shield as you will need to solder the new connections.   Note: This is aluminum solder—tricky stuff.   When overheated it pops sending molten beads of solder skittering across your diaphragm—hence the precaution of using a shield beneath the area you are working on.   Now, once the joints are soldered you will need to daub on an anti-oxidizing sealant to keep the joints from corroding.   Then you will reaffix the wire to the Mylar.   You can fold the wire back on itself to take up any slack.   I use 3M #77 spray adhesive, and have not had a wire come loose for over six years now, but others have used a brush on adhesive, with which I am personally unfamiliar.   Try to keep the wire aligned between the bar magnets which you can see through the Mylar.   Once you have glued the wire down, let the glue dry a bit and brush on some UV sealant to protect the Mylar and the wire.   Let this dry, test the speaker, and if it works to your satisfaction reinstall the cloth cover and you are finished.


      Loose Voice Coil

    Symptoms: Similar to split in Mylar diaphragm—you hear a buzzing or rasping that often appears to be frequency specific.   You have already checked the connections all along each channel (speaker cables, interconnects) and made certain all are clean and tight.   You have already turned the knobs repeatedly on balance, fade and source switches on your preamp and none of these have produced the annoying sound you are trying to duplicate.   You have swapped the right and left channel speaker cables and the problem did not disappear or switch sides.   You have removed the speaker cover and did not find a tear in the Mylar, and you have run your fingers up and down the voice coil while the speaker was making that wretched sound and found a place where, when you pressed the coil against the Mylar while the speaker was playing the annoying sound ceased and desisted.

    Items Needed for Repair:

  • 3M #77 Spray Adhesive

    Procedure: Spray some glue on the loose coil, press it into place, let it dry and test the speaker before you put the cover back on.

    kendo employed more of a rebuilding technique


      Mylar Diaphragm Repair

    Symptom: The speaker makes a rasping or crackling sound that is often frequency specific.   You have already checked the connections all along each channel (speaker cables, interconnects) and made certain all are clean and tight.   You have already turned the knobs repeatedly on balance, fade and source switches on your preamp and none of these have produced the annoying sound you are trying to duplicate.   You have swapped the right and left channel speaker cables and the problem did not disappear or switch sides.   You have removed the speaker cover and found a tear or split in the Mylar.

    Items needed for repair:

  • Good quality clear vinyl tape (perhaps 2” wide)

  • Acetone

  • 3M #77 spray adhesive

  • UV Sealant

    Procedure: Take a sponge or cloth and apply acetone to the area around the tear to clean off the old adhesive and UV sealant.   Then you cut a piece of tape to an appropriate size and insert it through the tear sticky side up and press the Mylar down on it firmly.   Now you take a similar size piece of tape and slip it beneath the loose wires of the voice coil (loose because they came off the Mylar when you cleaned the area with acetone) and you press this piece of tape sticky side down on the outside of the Mylar thus sandwiching the tear between two pieces of tape.   Now you spray on some 3M #77 and press the wires back into place, let the glue dry and recoat the area with UV sealant.   This should complete the repair.

    Note: if you are working with a small hole—too small for example to insert tape through—you simply cut the second piece of tape slightly larger than the hole, center it on the first piece sticky side to sticky side and then apply the larger piece to the outside of the diaphragm.   The small piece serves as a facing over the hole to keep the outer piece from sticking to the magnets through the hole, which of course would impede the response of the diaphragm.


      Voice Coil Replacement

    Oh God, you knew it was going to come to this.   Your whole damn voice coil is shot.

    Symptom: the voice coil is covered with little granular bumps which are corrosion points and some of them have actually corroded all the way through the wire and the panel(s) no longer function or are quite intermittent.   Well, damn.

    Repair: You will need the following items to perform this repair:

  • Voice coil wire—A thin insulated aluminum wire available from Magnepan or any good electronics store.   Gauge varies, but match the gauge on your speakers.   Note that the gauge is thinner on tweeter repairs if you have been brave enough to pry apart an old pair of tweeters to try to repair them.   For purposes of discussion here, I am only dealing with mid/bass panel repairs.

  • Acetone—Available from any good hardware store

  • Aluminum solder—Available from any good electronics store.

  • Anti-oxidant sealant (for solder joints)—available at most hardware stores and electronics suppliers.

  • 3M #77 spray-on adhesive—Available from any good hardware store

  • UV Sealant—I have only acquired this from Magnepan, but I suspect it can be purchased at a good electronics store.

    Procedure: This process is rather involved, but I regard it to be well within the scope of skills possessed by the average home do-it-yourselfer.   First, you will perform this procedure on one panel at a time so that you have an in tact panel to refer to while you work on the other.

    Cover the area around the posts to which the ends of the voice coil are attached (near the bottom of the panel) and use a soldering iron to release the connections—the covering to shield the Mylar against molten solder popping off, as the aluminum solder is tricky stuff to deal with).   Now you will use numerous pieces of clean terry cloth, sponge or other such applicator and lots of acetone to gently clean off all the old glue and sealant from your Mylar diaphragms.   As you do so, all of the old wire of the voice coil will come off too.   Don’t pull at it too hard or you will tear the Mylar.   If you do tear it, see the repair procedure above for repairing the damage.

    Now, you are going to need to build a frame on which you are going to weave your new voice coil.   There are lots of ways to do this I am sure, but I have one that I tried with great success, so I will describe that here.   I constructed this frame out of 2 x 1 inch oak because it was rigid, but if you prefer working with it, I am sure pine, poplar or some other wood would be adequate.   The frame must be sized so that it is large enough to overlap all the edges of the Mylar with perhaps four to five inches to spare on the top to bottom dimension.   This extra room in the vertical dimension is because you are going to need room for a series of tensioning devices to move to draw up slack in the coil.

  • At the top of the frame you will drill holes and evenly space quarter inch (or whatever diameter provides proper spacing between your rows of magnets) dowel rod pegs over which you will eventually be looping your voice coil on one end.   The spacing of the pegs is determined by the distances between the magnets, as you will note that on your speaker the coil loops up and down the Mylar between the magnets (doubled along some of the runs to achieve 4 ohms of resistance total).   The tensioners will also have pegs on them and I recommend three or four pegs per tensioner rather than individually tensioned pegs—partly for reasons of ease of fabrication and partly for spacing as a large number of individual tensioners will provide too much slop in the alignment of the individual runs of the wire.   I also recommend using two bridges made of wood that slide along the top of the frame to aid the alignment process (though the attached drawing shows only one for purposes of clarity).   These should be made of a softer wood (i.e. pine or poplar) and v-notched (I used an exacto knife) at the appropriate intervals for the wires to be properly aligned.   Rather than try to describe the frame further, I have a sketch of the frame which I can send to those interested as a JPEG--simply call or email me.
    Now, using the frame you loom the wire voice coil up and down the pegs until you have mimicked the pattern on the panel you have not disassembled—placing double runs wherever Magnepan did.   Don’t worry if for reasons that escape you that you end up with one more run than Magnepan did as that will not be enough of a difference to have much effect on the total resistance of the load.   Use the tensioners and your hands to work out the slack all along the coil, but never draw it so tight that you break the coil or you will be starting all over.   Although more substantial, it is not unlike taking out the loose slack in the middle of a shoe lace in which you work the slack slowly toward the end.   Also, leave yourself about 20 inches of slack at each end of the coil as a whole so that you have room to make your soldering connections to the posts at the bottom.   And remember, since the posts are at the bottom (at least on my panels they are) that when you are finished weaving the coil both ends need to end on the bottom of the frame.

    Once you have completed the weaving of the coil, spray the fixative on your Mylar (3M #77), let it get tacky, and then press the frame, coil side down onto the Mylar taking some care to align the runs of the coil between the magnets.   Now with regard to top to bottom placement, the frame should have been built to such a length that , inclusive of the distance the wire runs to and around the pegs, there will be a slight overlap on the top and the bottom of Mylar when you release the coil from the frame and each loop will extend past the end of the diaphragm (refer to your undisturbed panel for comparison).

    Now once the coil is in place, release the tension on each of your tensioners to give yourself enough slack to move the ends of the loops off of the pegs and press them down with your fingers.   Remove the frame and go over the whole panel carefully to correct any alignment problems by hand.   Then strip the ends of the coil of insulation with a fine sandpaper and make your soldering connections to the posts where they were originally attached.   Put an anti-oxidant coating on the solder joints.

    Once the glue has thoroughly dried (I allowed 3-4 hours) you can use a large artist’s paint brush to cover all of your work with UV sealant.   Let that dry and then you can test the panel.   Do not put the cover back on, as you will now be using this panel for reference purposes when you rewire the other(s).


      Postscript

    I hope you find this helpful.   I should mention that there is another alternative to the gluing process that involves spraying the wire, not the Mylar, with fixative—the benefit being less weight on the diaphragm.   However, while I considered this, it did not seem to me that in light of the substantial amount of weight added by the UV sealant that a little extra fixative would make much difference.   Moreover, I hear a good many horror stories on the MUG board about loose voice coils, which I think is partly a consequence of sparing use of glue in manufacture.   Nevertheless, when I was preparing to rewire my panels I discussed both options with Magnepan’s technicians and was told that either way could be used, but that at the time at least they sprayed the wire, not the whole panel.   I did not do it that way, and am quite satisfied with the sound quality I have achieved with the approach I used, and have not had a wire come loose in the six or more years since I completed the project.   Still, I wanted to relate the alternative approach.

    There are some other alternatives as well.   I have heard some people prefer to use a brush on fixative, and apparently Magnepan has offered others some recommendations in that regard.   I do not discuss it here because it is not something with which I have any experience, but I am aware that it has been used.   I used 3M #77 spray adhesive because that was what Magnepan advised at the time, and I am satisfied with the result.   Indeed, all of the procedures I describe above are procedures I have used, and made use of after extensive calls pestering Magnepan for advice.   On a side note I should mention that Magnepan’s technical staff was very helpful to me when I decided to undertake this and graciously fielded a significant number of questions—some of which I am sure they found quite inane.   I excused myself with the assertion that I am historian by trade, not a speaker designer, but I am to this day most grateful for their patience and good counsel.

    If you have questions regarding any of this, I can be reached via email either at anonymourati@msn.com or at 59Mercedes@msn.com.   My telephone numbers are (202) 543-0400 (Supreme Court Historical Society) or (301) 593-4156 (home).