That's a Frazier, and while it has some relationship to a horn, and it's definitely a folded air column, it is also clear that the mouthsize is far too small to act as an effective horn as we know it. More like a short (but expanding?) labyrinthic (capacitive) column with diffraction slot or a wide(r) bandpass port.

It will go low; how low, who knows? My GUESS is that:
(1) due to the VERY SHORT pathway, but which still affords some expansion, it has a wider bandpass than a simple reflex port, and it will (due to capacitance), decrease the upper frequency bandpass.
(2) it is also apparently front-loaded, and it will display somewhat higher efficiency due to the air column increasing acoustic impedance.
(3) the "slot" exit effect is another acoustic filter subject also to difractive dispersion characteristics.

So it should do lows, sort of a precursor to slot-loaded subwoofers. Now as to the driver employed, probably NOT a modern subwoofer type. My guess is effective down to approx. 50 Hz, probably with some good punchiness.

I've never heard one, I'm just guessing. Take all of this with a grain of salt!

DM