Magnet shift repair is easy...

Rev. Hayes

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.

Rev. Hayes

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

mhardy6647

I'm sure someday - sooner or later - I'll be looking for threads like this one! :- )
-

Mystery

Ya there are few threads on this.
Thanks for the parts list.
I have couple that are frozen... sometime...

boston1450

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

soundfreak1

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???

Mystery

soundfreak1 wrote: »

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.

Schurkey

The magnet isn't the critical-alignment item. The pole-piece is.

Rev. Hayes

soundfreak1 wrote: »

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.)

cnh

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

Mystery

Hehe... may be a DIY video should be done next time when someone does it.

OldSchoolPolk

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.

Toolfan66

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!!

70dimer

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.



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



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.



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



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.


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.


Now I have a like new spare in-ground speaker!

pitdogg2

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.

70dimer

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.

xschop

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...

pitdogg2

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

[Deleted User]

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_M

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.

https://www.youtube.com/watch?v=VN0tmyyC0ak


Sort of like this....@ 1:55 and at 3:45, but instead of an actual shim, a toilet paper roll?

stones89

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.

xschop

If you need to clear extra storage space, I need 2ea of 6510 and 6511...

K_M

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?

FestYboy

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.

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?

lawdogg

Magnet to pole piece.

FestYboy

So like it is right now? (In the picture)

lawdogg

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.

FestYboy

Well p00p. Too late.
Here's what wound up happening between the time I last posted and now: I went shopping and found this.

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.


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...

lawdogg

I hope it works! Will look for the good news.

aprazer402

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.

FestYboy

We'll know for sure tomorrow.