With the right room you could probably take advantage of modes to boost the bass response of smaller speakers at specific frequencies but, ultimately, to achiev

With the right room you could probably take advantage of modes to boost the bass response of smaller speakers at specific frequencies but, ultimately, to achieve a reasonably flat frequency response down to 20-30 Hz you're simply going to need the ability to move some air. There's no getting around that. What you're suggesting is a bit like trying to turn a 4-banger into a V10 by tweaking the spark-plug and fuel injection parameters.