Resetting a loose magnet (with pictures)

[mech986]

A detached magnet with anything more than the gap of glue material will lose some strength to the voice coil gap, but if properly glued back, should be fine. If there is any worry at all, Great Plains Audio, and a few other speaker repair companies can remagnetize the magnets to full strength. The magnetic strength loss occurs much more with Alnico magnets in high power woofer situations or falls and shocks. Ferrite magnets are relatively impervious to strength loss.

 

[gtmechanic]

I had magnet detached on my SEAS 33F-WKA. I did not risk to do it myself, even after reading great posts here, and instead sent it to Miller Sound in Pennsylvania. These guys are truly great. Not only they repaired issue with magnet, but they found and fixed issue with voice coil. There was damage at the point of connection of voice coil to cone during magnet shift. Anyway, I'm glad to get over it and share my experience. BTW, Miller sound was the only company who took the job and actually did it perfectly, while others backed up




.

 

[mech986]

On your 33F-WKA, how did the magnet get detached, shock, fall, impact of some sort? What application is this being used in - Dahlquist DQ-1W sub, Beovox M100, or Rogers L35B subwoofer (or another like the SEAS 308 kit speaker)?

 

[gtmechanic]

Rogers L3/5B. It fell due to accident. Had to restore cabinet as well.

 

[mech986]

Hi gtmechanic, Welcome to AK! Sorry to hear about the Rogers L35B cabinet and driver damage. Those are some rare subwoofers. Do you have any pics of the cabinets before, during, and after restoration? I have a pair of them as well and I'm trying to collect information on the serial numbers. Could you provide the numbers, here or by PM, as well?

Also, when did you get them and from where? My understanding is there may be less than 20 pairs in existence or built.

 

[RussHuns]

Ray,
Thanks for sharing your method. I've got two MW6600X drivers from my Polk RTA12B speakers that the magnets shifted from old epoxy and other than that surrounds and cones are still supple and tacky like new. I tackled this problem by going to a friends shop and centering the basket and the magnet on a hardinge lathe, "walked" the two together and centered. applied epoxy, walked them the rest of the way on and left it to dry for a few hours.
I realize not everyone has access to a lathe, but I didn't think to look on Audiokarma..
I wanted to share this for those who do.
Regards to all.. newb who still has to fill out profile, Russ

 

[seventy1]

another tool... repeating post #12 to add back lost photos

What a great thread Ray W., thanks for taking the time to document this! I was intent on keeping my thrift store Polk Monitor 10s a thrift buy and these instructions and jig helped immensly. Polk 6503 drivers are notorious for jettisoning magnets. I wanted to share a something that helped me out.

I was paranoid about dropping the backplate post into the jig and damaging the voicecoil. So I cut a piece of broom stick long enough to pass through the voice coil and support the backplate post. I used a piece of old molding for a stand and attached the dowel with a screw and glue.

I also used a paper sleeve to help align the backplate post to the dowel and guide it through the coil. I first placed the paper sleeve through the voice coil then lowered the speaker over the dowel.

Then I put the alignment jig on the speaker (I used a 3" coupler from HD). No photos after this since I didn't pause after putting a thin bead of epoxy near the OD of the backplate. Lowered the backplate, positioning the post through the sleeve and then rested on the end of the dowel. Then just slowly raised the speaker to the backplate - no drama, no damage. I followed this thread's instructions and successfully aligned the magnet using the jig. Now if I can only learn how to repair the voicecoil on the other bad driver.:scratch2:

 

[vsat88]

If you are able to do that then I really do want to know ! I have seen a guy in India wind VC by hand. Now he is an artist.

 

[johnhoef]

I have a pair of Yamaha NS-690II speakers here that arrived from shipping with seized woofers. My guess is they were handled very roughly, or dropped. I decided to simply tap the magnets back in place carefully with a short piece of 2x4 wood and a hammer. That was successful. My first mistake was to tap against the rim of the magnet - NO!!! That caused the magnet to slide. I tapped it back, then tapped the magnet frame....that works fine, and with a little time and care, this worked. Using shims to check centering. So, now the question, and this was mentioned above - how about just slathering a bunch of epoxy all around the magnet and magnet frame edges? I would think this would be good enough since the speakers will now live a gentle life in the customer's home?

 

[johnhoef]

Just thought I would add an update to this forum. As I described above, using a hammer and 2x4 wood, and slathering adhesive. The speakers have been in the customer's possession now since around late September. He has music going every day at quite a decent volume. He contacted me just today to thank and compliment me on the work I did. So, seems my method is sound...at least with these speakers. By the way, I slathered super glue around the magnets after I had them perfectly aligned.

 

[sirpodzol]

Picked up a pair of Yamaha NS-5s for about $15, one of them had a shifted magnet. After looking at various forums online (including this thread) I eventually came up with this method using a 3d printed jig.

Modeled these in Tinkercad. The orange one has a lip inside for the magnet to sit on, the magnet is also a tight fit to prevent it from rotating (since the backplate was not perfectly concentric with it). The red one has 4 holes for meccano screws and nuts that allow you to adjust the position of the whole thing, and they screw into each other so you can slowly bring the magnet onto the back of the driver.

Here's a picture of it partially on the driver, I had not added the large rectangular notches on the orange piece so it was getting hard to turn:

And here is how the screws interface with whatever this part of the driver is called, not the most elegant but it seems to work:


Seating the magnet is a bit of a tedious process, since I could only go 1/6th of a turn or so before it started pinching the voice coil again and I had to readjust all the screws, but it's not too bad. I ended up cutting corners a bit and not even gluing the magnet, but the jig seems to be holding it in place just fine even after a few months and moving the speakers around a bunch. It also saved me when I was reassembling them because I got the surround on slightly wonky and the coil was rubbing; just had to take the driver out and fiddle with the screws a little. And I'm no audiophile, but I think they both sound pretty good now!

Anyway, just thought I'd share since I think this is a new method for fixing this issue. Now I'm looking around for more speakers with shifted magnets, partly to film the process and maybe make a tutorial, but also because it seems like a good way to get nice speakers cheap!

 

[vsat88]

On the Polk drivers, "6.5 inch" Like the MW 6510, 6511, we have been using red lock tight to great effect to set the pole piece and magnet then after it drys on the jig taking the two part epoxy to the areas above and below the actual magnet. Works great.

 

[Copa1934]

I did this years ago.