Don't remember his name, there is a French designer who makes great drivers used in some esoteric speakers. That driver goes down to about 40hz and up as far as you can see or hear. I think, it's 10" driver but not sure. The quality of that driver really impressed many people. I even watched an interview with him. Basically, he is a one man operation. Old world craftsmanship.I'm pretty sure you are referring to PHY...
We had a set of those 10" units in a box, made by an associate of PHY. The boxes were rather large, and built like an acoustic guitar body- designed to resonate as a means of extending the bass of the 10" driver. Overall, the little HEAs we have with the 6" woofers play deeper and more accurate bass.