Wow. Thanks for the responses everyone. This site must have quite a following! I've included an image. The cone is now making cracking noises at `moderate' levels.
I'm thinking the recone kit is the way.
EpicKlipshFan: thanks for the link.
billybob - thanks for the tip. I'm actually thinking about something a bit bigger. Kp450 or larger.
moray james - yeah, I suspected they were the same. This journey started with me as a 15yr old being amazed by the Chorus 1s. There's something raw about that vented box.
RandyH000 - thanks for the K48 specification and possible source. I'm toying with building something myself with two or three of these woofers per channel - maybe that's the source for my beast.