Found another source for a supply of an early FeONIC prototype. Called the Omnivox, as far as I can tell it appears to be the earliest publicly released version of the FeONIC technology. Usefully, it not only uses but also comes with the same (F110) amplifier as the current models – so even if they don’t perform well then the amplifiers will still be useful. I got a very good price for a bulk purchase of their remaining Omnivox kits (amplifiers plus audio drivers) and so it will be a saving whatever the outcome. As these ‘Omnivox’ drivers are built to work horizontally, I will have to construct a supporting device that will convert them for vertical use (for my shop windows).