The NRC is a Canadian measurements lab for speakers with NRC standing National Research Council. It was developed by Dr. Floyd Toole, who even JA would refer to as one of the people who defined loudspeaker measurements for modern speakers and currently is employed with Harman Corporation. Harman has a more advanced development of what he started at the NRC. John Atkinson has referenced Dr. Floyd Toole in his own documents on loudspeaker measurements.
Also, look at the NRC charts that Soundstage has published. In the more than fifty speakers measured with 6.5" drivers, not a single unit was able to produce 30hz cleanly without appreciable rise in distortion. It may be negligible at low levels, but it quickly rises above 80db. Could it be done? Yes, I believe it can be made with some extremely expensive materials. I run an FEA lab used for a certain disciplines of engineering and I can tell you about materials that cost is beyond the budget of most loudspeaker implementations. The other factors would pertain to the motor structure in the former, magnet structure, the coil would have to be very high power handling to have extremely long excursion. The surrounds require some impressive roll as well not to mention the spider.
In fact, Focal themselves have pioneered technology into production that does address a number of issues in their EM series drivers, which replaces the permanent magnet with an EM instead. This would allow the motor to reach the excursion required without extreme power loading. If stanene (very new material that holds huge promise) wire would be used, it could really create an incredible powerful motor/field structure. The cone would still require additional rigidity or more of them to spread the load and the suspension would still be a possible issue, but maybe if you implemented suspension via EM with the ability for the former to have a rest position when off, it might work out. Build the former and cone into single solid piece while reinforcing cone. But this wouldn't be in the budget of the Sopra line unless the driver in question went into volume production. I mean tens of millions per year of the very same driver.
I know, its a great deal of techno babble when all you need to is to use larger cones drivers to get there for much less cost. Old engine line, no replacement for displacement. Well, that isn't true any longer and it could possibly be true in speakers at some point. Just not today.
