Forum member MW magnet repair tool set

Gardenstater

Wow. Yep that one is an assembly snafu par excellence. The voice coil should be overhung by 1/8" on the top and bottom of the front plate (baseplate).

It is no wonder this driver puts out a lower dB amount.

It is possible that it got slammed with so much overcurrent that the VC former got mashed into the pole piece plate. I think I see that the cone is distorted (can see in the reflection), besides what you pointed out with the folded up feature at the joint between the cone and VC.

xschop

I surmise a Wu-coil will sound much better

From your pics it looks as if the coil was forced forward somehow. Never seen that severity before. Crinkled cone center near former I've seen a few times on mag shifts

MrGeology

Finally wrapping up the M5B driver. Seller said "tested and it works" but figured we had differing definitions of "works". Here is what it looked like (note the permanent state of extreme excursion).

Have a feeling it was stuck this way for a VERY long period of time, as once it was finally freed up it returned to this position in resting state.
Here is what the driver looked like apart.



As you can see not only was the baseplate ID small to begin with, it also had pretty serious corrosion. The VC would not even move through the baseplate in the above pictures.
Dremmeled the baseplate ID until it finally would move freely and re-assembled. Noticed it was resting at nearly the same excursion as before the work.
Decided to let it sit with a weight on the cone (just enough to bring the resting position a touch below where it should be) for 24 hours. Ran through DATS at that point and it looked good. After dinner returned and could see that the cone was once again resting in a high excursion position. Frustrating.
So did another over-night of cone weighting and re-ran DATS. Looked good again so went ahead and glued it last night.
Returned this afternoon and can see it returning to high excursion resting (but not quite as pronounced). Ran through DATS and here is what it measured this afternoon.


So it is under the weight again.
The other M5B came with no driver (knew this going in) so it got a donor MW6502 that I already had. Crossovers look like this.

At any rate my work with the jig is finished (can't get to the 6500 driver #2 Wu-coil overhaul until next month at the earliest).
So looking into who is next on the jig waitlist. Was it @plastic_avatar ?

xschop

This is prime example why you also shouldn't store the MW's laying flat on their cones/surrounds. Over long periods, the spiders develope a "memory".

In your case here, you could help the driver by doing just that, and laying it on a 6.25" diameter by 1/4" thick cardboard circle and let it set for a long time.
Heating with an air dryer does speed up the process some.

plastic_avatar

The jig is w/ @Kryten.

If he posts here that he'll send it, you can step ahead of me in line. I'll take it after you're done.

C'mon, Kryten. Help us out. Send it to MrGeology tomorrow. He needs it, stat.

bcwsrt

xschop wrote: »

Loaner jig #2 being sent out Monday to @MrGeology

pitdogg2

plastic_avatar wrote: »

The jig is w/ @Kryten.
C'mon, Kryten. Help us out. Send it to MrGeology tomorrow. He needs it, stat.

Mar 27, 2023
Last Active

This is why we tend to draw the line at 100 post. This member had less than 100.

MrGeology

pitdogg2 wrote: »

plastic_avatar wrote: »

The jig is w/ @Kryten.
C'mon, Kryten. Help us out. Send it to MrGeology tomorrow. He needs it, stat.

Mar 27, 2023
Last Active

This is why we tend to draw the line at 100 post. This member had less than 100.

After @xschop confirms he has received the required $60 deposit I will send the jig out.
Already sent a pm to @plastic_avatar explaining this.

plastic_avatar

Sorry for the confusion. I know the setup for the jig that's still in circulation

I've got an approximation of the real jig, in PVC [laughs]. No, it is not the same... xschop's work is amazing.

Whoever is next for jig #2, I wasn't jumping the line

xschop

I can vouch for @plastic_avatar if he needs it. Stand up guy right there.

msg

MrGeology wrote: »

...
Returned this afternoon and can see it returning to high excursion resting (but not quite as pronounced).
So it is under the weight again.

Would repeated, gentle heat treatments possibly help with the surround recovery? Is the thought here that the rubber has simply deformed to new memory. At a micro level, I imagine we're talking about overstretching and thinning around a particular area?

I don't suppose there's a way to warm bathe it? Just the surround?

Since it's trashed, how about the oiling process, maybe combined with heat? (is the rubber still supple or hardened to an extent?)

I'm sure this has been discussed somewhere, but is there not a surround kit available? That'd be my last resort, as I don't like the mods with unknowns, and I can't imaging you'd get any sort of compliance or performance spec on an original driver surround, and especially not from a generic replacement.

From what I've seen you guys post about suspension evaluation, this seems to be an important factor.

As a complete troglodyte, is it the spider that controls the cone suspension, or the surround? Trying to understand what's drawing or pushing this cone outward.

I don't know anything about what you guys are doing, but pop in periodically to watch.

MrGeology

The surround feels and looks as it should. Pretty sure the spider is the culprit here.
It is responding well to the weight treatment, but will probably take some time. Heating it might speed up the process but I would rather be patient for the sake of longevity.

Gardenstater

I plan on trying the hair dryer method on the spiders of my OEM drivers, along with these alignment jigs I fabricated, in the future when I'm hopefully not dealing with other crises that always seem to take precedence over audio lately (lol). Rob has his alternative method that he came up with that would work well also. My jigs maintain perpendicularity, concentricity (with small shims), and overhang so it should work like braces on your kids teeth over time and in fact that is how I have been storing my drivers (on my steam radiator) and I check them periodically and one is in perfect alignment except for the overhang and the other one is still close to rubbing but not rubbing. They need spider re-settling or whatever you could call it.

msg

I just had to go check my spare 6510. It's stored on its back.
With a buncha books on top.

MrGeology

M5B 6502 progress update.
Did a manual time-lapse photo set of the drivers resting excursion after weight removal. Took more than a dozen pics over a 48 hr interval, then compared them to better understand what is happening.
The excursion slowly rebounds over time, and by 16 hrs it reaches its final resting state. The excursion is the same at 48 hrs as it is at 16 hrs.
Here are a few pics of the setup and some close-up crops with mark-ups.

The weight was just kicking around in my electrical parts drawer and works great for concentric distribution.



The time lapse setup:






Crops with mark-ups:





This pretty much covers the rebound process. It looks the same at 48 hrs as it does at 16 hrs.

It also looks good enough in DATS that it will now go back into the M5B to await crossover upgrades etc...

xschop

Bump for @JayMX

"The 6500's are just as bad as 6510'2 and 6511's for suspension sag and the fact that there is a smaller VC clearance at the base plate than all other MW's

When I fix one, I remove a few thousandths from the base plate ID and re-center.

I sent another billet jig out and you can use it. I'll find the thread and bump.

What I have done a couple times is put the MW flange in a jig, heat the T-yolk while having a 1/2" wooded flat between the magnet/t-yolk and the steel frame. after a minute or so of heating the t-yoke, it'll pop right off with the phase plug still attached."

I performed this method on all four of my extra phase-plugged 6516's to add focus rings.