This scenario also resulted in horns with large throats and hypex tapers, as the mechanical limitations of the drivers would not allow them to operate into very high throat impedances. With the high Bl/long excursion/high Mms drivers available today I'm able to design bass horns with tapers that give throat impedances far higher than it was possible to employ 60 years ago, which allows a drastic reduction in overall cabinet size. But those drivers would have never been developed if there weren't 300 watt and better amps available to take advantage of them.

The 747 analogy wasn't a joke; Howard Hughes 1946 Spruce Goose was larger than a 747; it 'flew' only once, though in fact it didn't actually fly. Ground effect allowed it to achieve the spectacular altitude of some ten feet. Nothing wrong with the design, but the engines available weren't up to the job. Same thing with the A7, which originally used drivers rated at only 25 watts, not because they couldn't build 100 watt drivers, but because they didn't need to.