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Steve74 19th April 2012 02:17 PM

Western Electric 728B
 
I was recently told that a WE 728B that I have has voice coil rub.

I am not that versed in speaker technology and was wondering what that means for the speaker.

Can it be fixed?

Will it still have value?

Thanks.

weltersys 19th April 2012 02:49 PM

Quote:

Originally Posted by Steve74 (Post 2991986)
I was recently told that a WE 728B that I have has voice coil rub.

I am not that versed in speaker technology and was wondering what that means for the speaker.

Can it be fixed?

Will it still have value?

Thanks.

The voice coil is in a thin magnetic gap, rubbing can be caused by the cone sagging causing the voice coil former to rub on the magnetic gap.
Rubbing makes the speaker distort, and can damage the voice coil.

It is possible that the rubbing can be fixed by wetting the cone and spider with a proper solvent and applying pressure in the proper direction to reverse the sag.

Sometimes simply rotating the speaker will correct the problem, but if the speaker rubs when out of the cabinet corrective measures need to be taken.

A speaker as old as the WE 728 would loose value if it were reconed, which may be required if the rub is a result of sloughed off voice coil windings (from being overpowered) rather than cone sag.

Applying finger pressure to one side of the cone can determine which side is dragging, if it rubs in all directions the voice coil/former is messed up, requiring "invasive surgery".

A shifted magnetic assembly or bent frame also can cause rubbing.

Good luck,

Art


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