I suppose, if it is allowed in the digital format, 5 Hz could be there, but I don't know any commercial theaters that would bother paying for subs down to 5 Hz.

The exception may be some specialty theaters, like those of Showscan, that include motion seating and other effects. These theaters may wish to include very low frequencies.

For consumer playback, I would think strong 5Hz signals would be harmful to most equipment and therefore would be something that internal filtering would eliminate in order to protect the equipment.