Sure SM58 repair advice needed

[Emil Vagabundo]

My oldest SM58 ( I bought it in 1981!!!) has been in use for an average 40-50 gigs a year and now the time has come to save it. Its foam inside the grill doesn't exist anymore and when I opened the cap, the foam that was standing on the top of the diaphragm vanished under my very gentle touch. Now I have bought a replacement grill with a new foam but since there is no foam on the diaphragm, the sound is not the same anymore. Is it possible to get only that kind of foam ( it looks rather like a very fine sponge on a new SM58) or can I try with some replacement? When compared with the sound of a new SM58, now the old one lacks bass and the proximity effect and the sound has become nasal. I have read on some forums that the foam from headphones can be good. Otherwise, the mic is technically completely working just the sound is not good for vocals anymore. The mic can be used for putting it in front of an accoustic guitar and the sound is interesting. I would like to repair it but don't advise me to send it to somebody because this wouldn't be worth my satisfaction of saving a good instrument.
Thanks for any help!

 

[robertmetal]

it may not just be the foam thats causing the sound difference between the old and new sm58's. ive heard that the old 58's were ment to sound better than newer ones since there seemed to be a difference when shure started having the 58's made in mexico?

 

[TragikRemix]

why don't you just put it to rest? its 25 years old dude, put it in a nice wooden box with a glass cover and hang it on a wall in the studio. give it a proper retirement party.