Magnet Shift Repair Solved...for me that is.

txcoastal1

He’s using them as spacers

Gardenstater

I'm glad it's clear to you. The picture seems to show a pole piece and a basket with a ring gauge inserted between the two. That sure can't be a voice coil former! So if the ring gauge weren't in there I guess those wires fit in between the basket and the pole piece, and the magnet which is already glued to the pole piece is moved around (with an aluminum vice clamped to it) to fine tune before the epoxy between the magnet and basket has time to set up. But the question is, if one already has a ring gauge that is the proper size, why not just use that instead of all those wire pieces? PS: I guess I can see the advantage of the wires to be used as initial "feeler gauges" and to find the high spots to know which way you have to move the magnet/pole piece vs the basket to get it exactly center so the ring gauge (must be aluminum) fits in.

dcmeigs

Shirley here. There is no ring gauge there. I don't have one. Obviously the cone and voice coil have been removed. I measured the gap between the pole piece and the basket and discovered I need a set of shims exactly the size of 18 gauge solid core wire. So... Why not?

I purchased a replacement driver in perfect shape and used it in my RT5 and so I'm left with either tossing these driver parts or making an attempt at repair. What you see is a COVID madness project, haha.

Gardenstater

OK thanks. It looks like there is a ring in there. I see now that the 18 gauge *stripped* wire would have a dia. of about 0.040" and that is apparently what you have there for the annular space for the voice coil to get centered up into and then you will do the final centering of the voice coil when you glue the surround to the basket by using some flexible shims between the ID of the voice coil and the pole piece? That's one way to do it I guess.

dcmeigs

You are mostly correct. The 40 thousandth diameter bare wire is the shim, period. Some of the wires are in a bind, pinched by the pole piece which is drawn off center by magnetic forces. Once the epoxy is in place I mounted the assembly in the vice oriented to force the pole piece to the center as the vice is tightened until all the wires are equally loose while the epoxy sets. That part appears to be successful. Tomorrow I'll replace the cone and voice coil. Downinmexico's approach is by far the better, but I dont have the lathe or the skill set to pull that off. Hat's off to him.

BlueBirdMusic

Gardenstater wrote: »

Alright I can't take it any longer.......what are these wire segments I'm looking at? Surely those can't be voice coil to pole piece gap spacers (sorry for calling you Shirley).

@Gardenstater, I'm glad you asked the question. I read it yesterday and I was confused to no end. I did not know what question to ask. I thought a picture or two had been omitted.

Gardenstater

dcmeigs wrote: »

You are mostly correct. The 40 thousandth diameter bare wire is the shim, period. Some of the wires are in a bind, pinched by the pole piece which is drawn off center by magnetic forces. Once the epoxy is in place I mounted the assembly in the vice oriented to force the pole piece to the center as the vice is tightened until all the wires are equally loose while the epoxy sets. That part appears to be successful. Tomorrow I'll replace the cone and voice coil. Downinmexico's approach is by far the better, but I dont have the lathe or the skill set to pull that off. Hat's off to him.

Could you show a picture of the assembly in your vice? Where do you get an aluminum vice and what size is it and orientation relative to basket?

dcmeigs

It’s a zyliss brand. Popular with cruisers and woodworkers. If you think you want one, you might want an older one. The new ones are said to be not as strong. The aluminum vice is obviously handy around magnets but I can’t see why a steel vice wouldn’t work about as well if you’re careful not to get your fingers pinched.

Gardenstater

Question.....Epoxy is probably quite a bit thicker joint than Blue threadlocker or whatever Polk used, does it effect the magnetic field strength? Also, do you need to clamp it to try to squeeze out the excess or does the magnet do all the clamping necessary? The Swiss made Portable Aluminum Vice is very cool. I found some on eBay for about $100 shipped.

lawdogg

Apply the adhesive around the perimeter of the magnet, on the edges where it meets the basket on one side and the pole piece on the other. You will avoid issues of uneven adhesive causing the axis of the voice coil and pole piece to be out of alignment. Epoxy isn't ferrous so it shouldn't have any effect on the magnetic field...

Gardenstater

I just thought that the intimacy of contact (for want of a better word lol) between the magnet and the frame pole piece and the inner pole piece might be somewhat decreased by a more viscous and thicker adhesive layer, and that might affect the strength of the N and S poles nearest the voice coil. There might be a reason why they used such a thin *adhesive* as threadlocker. I know that epoxy is not ferrous but the pole pieces certainly are and maybe they need physical contact with the magnet.

PS: I guess what I should've said is what is the best adhesive for this, a relatively thick epoxy, or the thin threadlocker?

dcmeigs

Epoxy is not very viscous until it starts to go off. If you want you could use slower 30 minute or West Systems that takes hours. The clamping force of the magnet will certainly create a thin film. I second Law Dogs comment about biasing the application to the outside away from the pole piece. No clamps required.

Tony M

I just looked through this thread again. But briefly.

I think I have to remove the magnet completely from the speaker frame.

xschop

NO, follow the instructions I posted in the loaner thread, your pole-piece and magnet look concentric. Your magnet looks shifted at base plate....


Step 1.
Set the woofer cone down on a smooth, perfectly flat surface and take a picture of it directly above.

Step 2.
If the pole-piece plate perimeter and magnet perimeter look evenly concentric to each other, then you are in luck as the culprit is the magnet-to-baseplate has shifted and you don't have to pull the magnet/pole-piece apart from baseplate nor use the dowel to recenter them.

Step 3.
Make sure magnet perimeter is perfectly clean near pole-piece perimeter. This is where the inner jig step/lip rests and automatically aligns all set screws.

Step 4.
Retract all Set screws until the ID of the jig has none protruding on the inside.

Step 5
Set the inner step/lip on the magnet top perimeter, then evenly lock the baseplate down with the baseplate set screws. Tighten only hand tight .

Step 6

Position pole-piece set screws on the pole-piece perimeter loosely.

Step 7

Flip the jig and woofer over. Adjust pole-piece perimeter set screws, using a pen-light to see into dust cap, viewing the pole piece/voice coil ID gap. Then adjust incrementally 1/8 -1/4 turns until the woofer if free by lightly pushing on the cone. You can also play audio through woofer AT LOW VOLUME until you hear it free up.

Step 8

Once reset, gently unscrew all base plate setcrews fully, without any showing in the jig ID. Then carefully, ONLY loosen the pole-piece set screws and carefully lift the woofer out of jig. Flip it back over and start your glue process on the magnet perimeters.

Note*

I've had very good results with Superglue Gel as it is quick and easy and holds mega strong. You only need a thin line of it and it wicks into crevices.

Gardenstater

It sure looks like the bond between the ferrite and the frame pole piece (outside the voice coil) slipped.

xschop

The Base Plate attaches directly to the basket by rivets. It does not move.

Tony M

I kind-of thought that. I had one woofer apart a year ago or so and saw the design well enough.

The dust cap is too thick to see the spacing very clearly. It's just a blur to me. And I have a very powerful little flashlight too.

I've been messing with this process for about an hour and I got the woofer to move freely pretty easily and fast each time. NICE JIG DESIGN.

But a couple to 3 times, the magnet slipped and locked the woofer as I tried to get more voice-coil "free space" freedom . I guess the tolerance is small.

I'm at the no friction position again and I now see your instructions above.

I don't have the glue now.

Should I wait to remove the gig until tomorrow?
Or can I remove it now and see if the magnet stays in position.

How fragile is the magnetic position when I remove the jig and try to flip the woofer to "facing the ceiling" so I can apply the glue to that joint closest to the basket plate?

I like this.

I wish I knew where the other 3 woofers were now.

Tony M

I thought the voice-coil tolerance was wider, so I went out and checked my SDA-SRS2's since this woofer was supposed to be for them.

The SRS2's woofers have a wide space for flexibility at any angles.

The unfrozen driver can only flex at angles a little bit before scraping. BUT pushing on one quarter of the cone, it has a good bit of freedom.

That was my thought for trying to get more space from aligning it more the previous times. going for more freedom.
Maybe the spider was oblong for so long, it still has that shape.

I can try putting low volume music to it later maybe.

xschop

Yes, there is only .010" gap all the way around between voice coil and pole-piece. So only firm 1/8 turns are needed for final adjustments.
You can remove woofer from jig once centered because the magnetic force keeps it centered unless you bump it at all.

Once you know it's nice and free, play loud music through it to help relax the spider again from it's contorted position.

Tony M

Thank you.