There are people out there who re-cone speakers. I would do a 'google' search and try to find the service online. I live in the SE Michigan area, and know of a local person who re-cones speakers...her nick name is JBL Judy. Or, you could call/write Kef and purchase new speakers from them. I have a pair of Kef Ref 3-2. Each speaker has two bass speakers mounted internal, one fires up, the other down. Mounted either in tension or compression and between the pair of internal bass speakers is what Kef calls a 'force canceling rod'. Does your 104/2 speakers have this type of bass speaker arrangement? If yes, the 'rod' is suppose to keep excessive resonence frequency at bay. If you pull the 'rod' yourself, make note how it was installed, and how tight it was from the factory.
Regards,