Ok I get it I guess the surround also can be damaged on a new speaker
Thanks a lot anyway!
I´m so glad that my GK works again!
It´s very neat to have on small gigs when there´s no need for high volume.
I think I´ve solved the problem
I Recorded some low notes and looped them
and listened for any leakage
I found a tiny hole under the cabinet that made a great deal of bad buzz
so I put a screw in the hole and now my old GK sounds fine