oh, it's very much possible. just difficult and in most cases expensive. You can get them to extend even higher than that, too. A lot of designs use a rearloaded horn to help produce the bass, meaning that even if a driver starts to roll off at 150hz you can get it flat down WAY deeper. But you can also stick some drivers in bass-reflex cabinets with good results. I've even found a driver (the damn thing is really expensive, close to $150) that would go from 60hz to 20khz in a closed
cabinet. Now that's a speaker that i'd like to have! the same driver would have an F3 of 30hz in a ported enclosure as well.
A Hedlund rearloaded horn setup:
Crowley Acoustics Diatone Speakers:
Wyckoff Super-12's; 12" wideband speakers with a supertweeter:
Bass reflex using fostex FE164:
The inside of one rearloaded horn: