Hi, new here so finding my way! I run vintage Cambridge Audio R40/50's and Lentek Monitor speakers all of which use various iterations of Kef B139s. I have spare 'later' ones for my Lenteks when needed so no problem there. The Cambridges have the earlier 'racetrack' versions which require a different opening in the baffle to the later ones. I have acquired a pair of racetracks but they are rough and I want to rebuild them. Those of you who know these speakers will realise that 'normal' rebuild procedures do not apply because the 'cone' is a solid lump of 'styrene. They can be rebuilt, I've had one done in the past but the price is exorbitant, anyway I want to do it myself. So has anyone any hints and tips which may help please.