seized subwoofer?

[Rich4349]

I have a pair of very vintage 87ish Rockford Fosgate's "The Punch" 15" subs that I've had since...87ish! I've meant to refoam them over the years, but yadda yadda yadda, life, etc. So I finally picked up a set of surrounds that FIT them (they have an oddly large, 11 7/8", compared to most that are smaller) cone and was checking them out with a 9v battery, and found that one pops in and out as expected, the other is rock solid. The rock solid one measures 7.2 ohms. I REALLY would like to keep these subs operational, even though they have no use in a horn. (Sentimental type and all.) I found these pages:
http://www.audiokarma.org/forums/showth ... p?t=202963
and
http://www.audiokarma.org/forums/showth ... p?t=130808

Any (better) advise beyond the info contained herein?

[Bill Fitzmaurice]

A frozen voice coil usually indicates that the magnet structure is broken. There's no fix for that.

[Rich4349]

How hard is it to / what's the process to visualize the windings? I've seen pictures guys have posted of little bits of cooked copper but as is, the windings aren't visible on mine.

Also, has anyone *intentionally* removed the magnet from a driver? I'm reading about prying them off with screwdrivers, after time has made the glue brittle enough.

[Bill Fitzmaurice]

How hard is it to / what's the process to visualize the windings?

You must remove the entire cone/spider/voice coil assembly. Since the coil is frozen you can't do that. Besides, you have to cut the spider, so this is not a process you use to make a repair, it's what you do in preparation for a re-cone.

Also, has anyone *intentionally* removed the magnet from a driver?

You won't be able to fix this, trust me. A seized coil is usually caused by the magnet having separated from the rest of the motor or the polepiece having separated from the backplate. Even if you manage to get the magnet off you'll destroy the voice coil in the process. Reassembling the motor structure requires specialized jigs.