Hi Richard, and welcome to Beoworld. What you have is a very common condition known as foam rot. You will need a repair kit like this.
Beovox S55's foam rings & glue
You will find plenty of threds on here showing you how to fix them. Also worth changing the caps in the crossover too. One of our members (Dillen). can supply these.
Craig
For millions of years, mankind lived just like the animals. Then
something happened which unleashed the power of our imagination. We
learned to talk and we learned to listen..