You need to exchange the front piece of the piece of the speaker to be able to attach the Alu Frets.
That does sound difficult & expensive but in fact its not. I did it for mine and was worth the effort.
Took 10 minutes to do, you need to be quick and some point I think I heard they stopped selling spares for the BL2500 and the fornts were considered that. Baffle Kit is called what you need.
Cheers
JK
BS9000, BS2300, BC2, BL2500, BL3, Bl2, BS1, BV8, BC4, A8