They were built by Slawa of SW1X for his personal use and improved on the Endorphin P17 who's design is on line. When I bought them the drivers were vintage Alnico Grundig tweeter, Saba Greencone vintage alnico, and vintage alnico Altec 416B (VOTT). Everything silver wired and high quality crossovers.
Like all Hi fi its a never ending process to bring about further improvements and I have been trying for about a year to see if I can improve on the Saba Greencones. I persuaded myself that I should be able to improve on midrange drivers costing about £150 and about 60 years old. Surely hi fi had moved on in that time! Its been a long journey but finally I found the Cube Audio FC8s albeit at ten times the cost of the Sabas. They replace the midrange and tweeters with a point source driver.
I just have the job of integrating them perfectly into the baffles. They extend further up and down the frequencies than the Sabas so 'crossovers' will need some tweaking.