Magnet shift repair is easy...

About a year ago my daughter decided to body check one of my Monitor 10s off of it's stand. The magnets on both mid woofers broke loose and seized up against the voice coil.

I spent a lot of time reading about the methods some folk on this forum tried to repair a shifted magnet and the many more opinions about whether or not it was worth the effort.

I decided not to bother and just wait until I found some drivers at a good price down the line. Well, I wish I had just gone ahead and tried the repair a year ago…

Had some spare time this morning and decided to give the repair a half a**ed attempt figuring that the worst I could do was ruin some ruined drivers.

1 3/4" cutoff of 4" PVC pipe
8-2" drywall screws
One tube of Loctite Red
15 min of jig assembly
Hooked iPod up to driver for audible guidance
5 min dry run
5 min of "wet" adjustment per driver

Result= Two fully functional drivers back from the dead.

I wanted to share this to encourage others who feel like this project is over their heads or "not worth it" to go ahead and give it a try. After all I read on the subject here I thought it would be WAY harder than it ended up being. Of course, results may vary but if you're even a bit handy I feel that a repair attempt is well worth the meager effort that I personally put into it.

Looking forward to hearing the 10s back in action tomorrow when the loctite has fully cured. I've missed them so much! Now I can bring the Infinity RS II s that I've been using in their place out to the shop and start that mod project…. Ha! I love this nonsense.

Sounds good to me...
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Comments

  • Here are a couple pics of my lazy-man's jig.

    566b70foqqob.jpg
    2qscpn57hsgx.jpeg
    Sounds good to me...
  • mhardy6647mhardy6647 Posts: 25,394
    I'm sure someday - sooner or later - I'll be looking for threads like this one! :- )
    -
  • MysteryMystery Posts: 2,462
    Ya there are few threads on this.
    Thanks for the parts list.
    I have couple that are frozen... sometime...

    Sonus Faber Concerto Grand Piano, Klipsch Heresy, Epicure 20+,T/E 280, Polk 4,4.5,5A.
    DB Plus 880, AR 48S, Smaller Advents. SUBs: Monitor Audio. Pre: HK AP2500, C1, Tandberg 3002A.
    Amps:
    BB275, Crown XLS1500, QSC, Rotel, Luxman R-114, Nakamichi...
  • boston1450boston1450 Posts: 6,635
    Very nice. I hope they sound great too..... I recently bought 2 drivers off ebay & one had a pushed in dust cap & in past ive used different methods to get them out & usually doesnt look as good. So with the one that had been pushed in i cut 97% of it & gently lifted & gently glided my finger to push it out. I then used a special glue i got online for woofers & it came out super.... Little helpful things like what you have done can save money & down time. I plan on doing my -not yet- froze up one soon & on a few spare drivers i have. Nicely done
    ...
    ...
    Randy / Maine .... SDA-CRS+TL & RTA15TL
  • I see where you have locked in the mag inside the pvc pipe, how do you determine the location of the" locking screws" so the magnet is located on the coil properly??? Or are you just locating to correct location and holding the speaker basket till the glue holds???
    Main Rig:
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  • MysteryMystery Posts: 2,462
    edited September 2014
    I see where you have locked in the mag inside the pvc pipe, how do you determine the location of the" locking screws" so the magnet is located on the coil properly??? Or are you just locating to correct location and holding the speaker basket till the glue holds???

    From what i read in other threads, idea is to have two sets of screws.
    One is solely to adjust magnet from all sides while something is playing to check for vc rub.

    Sonus Faber Concerto Grand Piano, Klipsch Heresy, Epicure 20+,T/E 280, Polk 4,4.5,5A.
    DB Plus 880, AR 48S, Smaller Advents. SUBs: Monitor Audio. Pre: HK AP2500, C1, Tandberg 3002A.
    Amps:
    BB275, Crown XLS1500, QSC, Rotel, Luxman R-114, Nakamichi...
  • SchurkeySchurkey Posts: 1,938
    The magnet isn't the critical-alignment item. The pole-piece is.
    .
    .
    For the good of the Free World, DEMAND COMPENSATION FROM CHINA for their release of an engineered virus from their Wuhan laboratory. Two trillion to start with, increasing as needed from there.
  • I see where you have locked in the mag inside the pvc pipe, how do you determine the location of the" locking screws" so the magnet is located on the coil properly??? Or are you just locating to correct location and holding the speaker basket till the glue holds???


    Schurkey wrote: »
    The magnet isn't the critical-alignment item. The pole-piece is.

    Mystery has it right there, Soundfreak. Shurkey as well.

    The first set of screws is just to hold the jig stationary in relation to the basket. The second set is to adjust the poll-piece so that it is precisely in the center of the voice coil.

    In my case one of the magnets still had the poll-piece firmly attached to the magnet so I was able to adjust the magnet and poll-piece at the same time.

    The other driver had broken into the 3 separate parts. That being the case I had to first adhere the magnet to the plate that is attached to the basket. That positioning doesn't have to be super precise. Once that had set up I added more loctite to the "top" of the magnet then dropped the poll-piece down into place and used the jig to guide it into the sweet spot.

    Using a sound source (iPod) during the initial adjustment made it very easy to hear when I was getting close. Once it sounded like it was floating free I would disconnect the signal and use the "push test" to see if I could hear or feel any scratching of the voice coil against the poll. Pressing on the center on the cone as well as various points closer to the surround let me determine if it the alignment was still a bit off.

    There are many threads on this wonderful forum and elsewhere describing variations on this method of driver repair. Most are long, scattered and show several attempts over the course of days. I just pulled the best bits of info from several different threads and then gave it a go.

    If there is a desire here for a photo accompanied, step by step tutorial of what I did I would be happy to do so but I really started this thread to show that the info is here and that it's not as difficult as it seems once you get started. (No offense to those who had trouble with their drivers. Maybe I just got lucky.)
    Sounds good to me...
  • cnhcnh Posts: 13,310
    edited September 2014
    Maybe I'm being a bit dense. But I still don't get how you can tell where the magnet should be aligned. Sounds like a lot of "guesswork" and a modicum of "luck" to me. But I've always been VERY bad about moving from words to pictures of the actual process. It's always been much easier to "visualize" something FIRST, then fashion "words" to describe it. Probably too much right brain power? lol

    What are you actually doing? Immobilizing the magnet then messing with the four screws and checking voice coil rub/movement and then just locking everything down when there is no rub and freer but not 100 percent free movement--because there is no way of gauging that? That sounds like a pretty "crude" procedure if I have it right?

    As for me, I'm just going to JB weld the heck out of everything very soon so as not to have to worry about this!

    Glad this worked for you. But I wonder how often it would "work" and how "accurate" the movement actually is!

    cnh
    Currently orbiting Bowie's Blackstar.!

    Polk Lsi-7s, Def Tech 8" sub, HK 3490, HK HD 990 (CDP/DAC), AKG Q701s
    [sig. changed on a monthly basis as I rotate in and out of my stash]
  • MysteryMystery Posts: 2,462
    Hehe... may be a DIY video should be done next time when someone does it. :wink:

    Sonus Faber Concerto Grand Piano, Klipsch Heresy, Epicure 20+,T/E 280, Polk 4,4.5,5A.
    DB Plus 880, AR 48S, Smaller Advents. SUBs: Monitor Audio. Pre: HK AP2500, C1, Tandberg 3002A.
    Amps:
    BB275, Crown XLS1500, QSC, Rotel, Luxman R-114, Nakamichi...
  • I 2nd Mystery!

    If Rev Hayes can put a video of the process on YouTube it would clarify a lot of questions for people.

    Not that we all don't appreciate the step by step and revisions Rev Hayes has done. Keep up the good work; I know I would be lost w/o you guys.
    HT: Marantz NR-1603, Oppo 981, Def Tech SM55, SVS PB-1000
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  • Toolfan66Toolfan66 Posts: 14,473
    Glad I have 8 of each 6503's, 6510's, 6511's in my goodie closet. Funny thing is I have never had to use one because of magnet shift.. LOL!!
  • 70dimer70dimer Posts: 2
    Sorry to bring an older thread up from the dead, but I just wanted to point out that this really helped me fix a TIC GS5 burial speaker that was dead on arrival, and while the manufacture sent me a replacement and told me I didn't have to send the bad one back, I took it apart and was able to save it!

    Here is the magnet that was shifted and locking up the VC.
    395qh8t0ye7z.jpg


    I took the baseplate apart and cleaned off all the surfaces of the old glue with a dremel sanding drum.
    4a1glgvvgrtt.jpg


    A $3 piece of 4" PVC coupler was just the right diameter for me to hold the speaker using the original speaker mounting holes (pre-drilled the coupler)
    Using my iphone, I was able to verify the VC was freely moving up/down and the speaker worked.
    gb8p634t0hit.jpg


    After verifying the alignment I used JB weld on the magnet/baseplate.
    1hb9i9ylqnq4.jpg


    I used some alignment numbers on the baseplate as well as tape wrapped around the outer aligning screws (same numbers as alignment on magnet) when it was all in place and working, so I could get a better idea of where the magnet alignment should be to save some time.
    73a09mtp6meq.jpg

    You can see the tape I wrapped around the outer alignment screws used to give me a marker for how far I had to adjust them to get back to the same position.
    is517fo44tld.jpg

    Now I have a like new spare in-ground speaker!
    pga68qgqygxv.jpg
  • pitdogg2pitdogg2 Posts: 16,327
    There is a good reason Loctite Red is the better adhesive for this work. It is a very thing anaerobic super glue and works much better in these situations.
  • 70dimer70dimer Posts: 2
    I would agree with that^, but basically I used whatever I had on hand in my garage.
    Truth be told, when I set it up to dry (using the JB Weld), the speaker was moving freely...but come the next day, the VC was locked up again!

    Darn epoxy wicked it's way to the center and bonded with part of the VC.
    I was ready to toss in the towel, but a quick hit with the hammer on the baseplate knocked it loose and I sanded the epoxy off and started over, this time using 5 minute epoxy. I was able to align everything in 2 minutes, then I added more around the outer edges to be sure it wouldn't give so easily.
  • xschopxschop Posts: 1,407
    What's ironic is whatever the factory used (Loctite or similar) is high-heat inactivated. Someone posted a vid last year and the factory sends high current thru the ceramic material to magnetize it....along with a high exothermic reaction...
  • pitdogg2pitdogg2 Posts: 16,327
    xschop wrote: »
    What's ironic is whatever the factory used (Loctite or similar) is high-heat inactivated. Someone posted a vid last year and the factory sends high current thru the ceramic material to magnetize it....along with a high exothermic reaction...

    Correct because it would darn impossible to glue and fight the magnetism at the same time. Yes all are built THEN magnetized in i believe the term is inductive coil. Basically they same way you can magnetize a screwdriver with wire and a 12v battery by wrapping the wire around the shaft and touching each end of the wire to + and -- post
  • I worked for Petra's loudspeakers for a while in the 80's and we used the cardboard tube inside toilet paper cut down to the size of the voice coil to center it while glues dried.
  • K_MK_M Posts: 1,617
    edited May 2017
    Slapaho wrote: »
    I worked for Petra's loudspeakers for a while in the 80's and we used the cardboard tube inside toilet paper cut down to the size of the voice coil to center it while glues dried.




    Sort of like [email protected] 1:55 and at 3:45, but instead of an actual shim, a toilet paper roll?
    Lsi15, Lsi9, LsiC,Rta11t,M5jr+,M4, SDA SRS 2.3TL, Rti6....Still listing stuff, a work in progress.
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  • stones89stones89 Posts: 231
    Toolfan66 wrote: »
    Glad I have 8 of each 6503's, 6510's, 6511's in my goodie closet. Funny thing is I have never had to use one because of magnet shift.. LOL!!

    You know how it goes, if you didn’t have those spares all your magnets would have shifted. B)
    Basis 2200 Signature, Vector 4, Transfiguration Proteus, Allnic H3000, Meridian 200/563, CJ ET5, McIntosh 501's, Thiel CS6, 3.6, Polk SDA SRS 2.3tl, MIT EVO, KS/Wywires PC's
  • xschopxschop Posts: 1,407
    If you need to clear extra storage space, I need 2ea of 6510 and 6511...
  • K_MK_M Posts: 1,617
    nbrowser wrote: »
    Toolfan66 wrote: »
    Glad I have 8 of each 6503's, 6510's, 6511's in my goodie closet. Funny thing is I have never had to use one because of magnet shift.. LOL!!

    Knock on wood...fast!

    Knock on Metal?
    Lsi15, Lsi9, LsiC,Rta11t,M5jr+,M4, SDA SRS 2.3TL, Rti6....Still listing stuff, a work in progress.
    B+W-Sold
    Electro Voice EV-SIX
    Infinity-Sold
    Advent-Now gone
    Yamaha A-S801
    Yamaha RX-V377
    Yamaha RX-A860
    Yamaha RX-A3060
    Harman Kardon Hk-350i
    Harman Kardon Hk-........
    Harman Kardon PM-665
    Harman Kardon HK-775
    Pioneer.......Stereo Receiver

  • FestYboyFestYboy Posts: 3,852
    Woot!! Now I get to try this... :/

    Picked up a pair of 10s with the sl2000 for really cheap and in my documentation of the drivers, I noticed the first driver I pulled looked like the magnet had shifted. Me being the OCD dipschitt that I am, thought I'd try to get it shifted back to center... Yeah... I locked it right up!!! Go me. So now I'm in the 3 piece club.
    tid47jhkxmwd.jpg
    The pole, magnet, and of course base plate are all loose. I've got the red Loctite and PVC. But I'm debating in my head what should be locked down first... Magnet to base plate or magnet to pole?

    Thoughts?
  • lawdogglawdogg Posts: 375
    Magnet to pole piece.
    <3 my 3.1TLs

    I will fix your shifted magnets for free. :)
  • FestYboyFestYboy Posts: 3,852
    So like it is right now? (In the picture)
  • lawdogglawdogg Posts: 375
    edited August 2017
    Yep - that'll keep the pole piece stable as you adjust the frame relative to the magnet in your jig. The "magnet shift" phrase is a misnomer, since it's the shifted pole piece that sandwiches the voice coil against the frame and causes a seized driver.

    Edit, I'm looking at the above images now, I don't advise following the same process.

    First, use a razor blade followed by isopropyl alcohol on a soft cloth to remove the old glue residue. If you use a grinder or dremel you not only will generate metal shards that risk getting into your voice coil gap, but you will also potentially compromise the true flat surfaces of your pole piece, magnet, and frame.

    Second, do not put any adhesive on those flat faces. In other words, once you scrape and wipe the old glue off, do not apply new glue to the same spot. If you apply the glue unevenly, this may cause imparallel surfaces between your frame and pole piece, which may cause non-centered voice coil articulation causing potential voice coil interference and even uneven flux density as a function of cone extension. Instead, after cleaning the old adhesive off, put the magnet on the pole piece and center it, and then apply the adhesive in a bead around the shoulder where they come together. Let it try with the pole piece centered. Then, apply the same bead between the magnet and frame before going into your re-centering tool. Center it and leave in the tool overnight so that it doesn't re-shift when you take it out.
    <3 my 3.1TLs

    I will fix your shifted magnets for free. :)
  • FestYboyFestYboy Posts: 3,852
    edited August 2017
    Well p00p. Too late.
    Here's what wound up happening between the time I last posted and now: I went shopping and found this.
    23w2o4jqaah1.jpg
    The inner most ID (there's a shoulder lip at the mid point) is an exact fit to the pole plate And as it turns out, if you take the basket and mark the PVC at the hight of the base plate, and then remove that marked off section it's a perfect fit for hight to the pole plate as well. The ID of the PVC is very close to the OD of the magnet so I shimmed it with a few wraps if tape. The rest of the job was very similar to the top explanation except I now have the pole and magnet secured and only have to adjust the motor to basket relationship. Red Loctite was applied to both cleaned plate pieces.
    7e6qtvrtb70g.jpg
    ij0qqviq4gjr.jpg
    Now it's drying and I'll retest it in the morning before pulling off the jig.

    I used my tone generator app and garage amp for fine tuning once the cone moved freely. I used 10Hz as a base and then swept up and down to make sure things were clear. At around 9.6Hz I noted an issue that would disappear above and below it so I concentrated there till it went away and called it good. We'll see...
  • lawdogglawdogg Posts: 375
    I hope it works! Will look for the good news.
    <3 my 3.1TLs

    I will fix your shifted magnets for free. :)
  • aprazer402aprazer402 Posts: 1,857
    If anyone can effectively and reasonable repair vintage Polk MW drivers (many have tried, most have failed) let me know, I can send you a case of them to repair. :)
  • FestYboyFestYboy Posts: 3,852
    We'll know for sure tomorrow.
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