Before you spend any money, try unplugging the bad speaker and vacuuming both sides of the diaphragm. A foreign object could be causing this problem.
I repaired a similar problem with an Audiostatic SW-100 (it was delayed action shipping damage in my case, which caused most of the diaphragm's charge to migrate to the problem area).
I repaired a similar problem with an Audiostatic SW-100 (it was delayed action shipping damage in my case, which caused most of the diaphragm's charge to migrate to the problem area).