The original KEF datasheet is here https://us.kef.com/pub/media/pdf/Datashe...SP1044.pdf which gives all the details - other than the hole diameter!
But as has been suggested, Falcon Acoustics are a good bet. They have also remanufactured the B139 (and other KEF drive units).
But as has been suggested, Falcon Acoustics are a good bet. They have also remanufactured the B139 (and other KEF drive units).
