Freestanding basshorns are huge. To have a real basshorn requires a cabinet the size of a refrigerator. Anything smaller is very peaky - I've seen some popular designs with as much as 15dB peaks within a single octave. I personally would do without. Go large or don't go at all where basshorns are concerned. An example is the 12π basshorn.12π basshorn
On the other hand, a good compromise is a midbass or even low midrange horn. You can horn load down to say 100Hz in a reasonably sized cabinet. You might like something like the eight π loudspeaker, which is a two-way design with both drivers horn-loaded.
eight π loudspeaker