Diagnosing & Fixing Shifted Polk MW Drivers

lawdogg

Have been tied up with work and have been remiss in answering PMs about fixing shifted magnets.

Hoping it isn't gauche or obtuse to bump my guide to the first page to make sure it's visible to those with questions.

May all our drivers stay aligned in 2024!

lawdogg

I've just confirmed that the same general process will work for a shielded MW7015 driver. These were used as the powered bass drivers in for example the CS1000P and ... they can shift. From what I understand they are VERY hard to find, so it may be useful to know they can be re-centered.

They are different than the old MW drivers in that (a) they are shielded with a bucking magnet and (b) the basket flange O.D. is larger than the magnet O.D.

I found that I could squeeze the basket frame in my same re-centering jig, and drill some new screw holes to re-center the magnet & pole piece relative to the frame.

Here you can see what's under the shielding, with my epoxy on the upper & lower magnet edges in the process of curing.



All back together waiting to go back to its owner.

pitdogg2

Very nice @lawdogg 👍

xschop

Good save. What are the physical dimensions of the magnet?

lawdogg

Dang I didn't measure it before I packed it back up. I should have. I don't want to guess - it was probably a hair smaller than the normal MW diameter.

Also, the voice coil former is vented. This led to an unfortunate scrunch upon shifting.



FWIW I did measure the voice coil: ~3.3ohms DCR.