B&w 'dm/4'

[Brainticket]

Hi Folks
New here.I have an old pair of 'DM/4's i want to get up & running.I have a saggy bass unit on one side that's causing the Coil to rub on the magnet hence distortion..This is actually the third unit to do this...Any ideas?...

I'm also intrested in a pair of theose 'DM/2'S that came out around the same time, transmission type design, any specs or help with those would be mouch appreciated.

[v-bro]

It's commonly caused by rust/oxidation of the pole(plate) or basket, a bent magnet assembly or even a loose magnet, often caused by dropping the speaker. It can also be caused by dust, ironpowder or just a flake of iron, loose coil windings, damaged coil carrier, loose spider and maybe even more pssibilities....

When it is a bent magnet assembly/bent basket you can most of the times determine by pushing on the cone all around, you'll find a spot or area where you can push it to run free...with a bit of luck you can bend it straight again...

I once had repaired a Seas W111 with an oxidation problem from the magnesium basket. The white oxidated magnesium powder had flooded the magnet gap causing terrible scratching ditortion. I carefully 'pulled' the rubber surround loose and did the same with the spider using a sharp flat screwdriver. After cleaning and coating the area behind the spider I glued back the cone and it played wonderfull again...