Why the obsession with the lowest octave

It took me years to achieve it, but now my best recipe or great bass for reasonable cost are newer OHM series 3 or X000 series Walsh speakers driven by a good 500w/ch Icepower AMP. MIT networked ICs seem to work well in this combo.

Set this up well and use decent gear around it and you have some mighty tasty and hard to fault bass that hangs with the best.

And the rest is right up there as well.

The ability to fully and faithfully reproduce the lowest octave adds considerable realism to music reproduction.
However, I do not think it is best accomplished by a "full-range speaker." This is expensive, and leads to compromises in other areas of the speaker's design.

Reproduction of the bottom octave is what good subwoofers are for -- as in my Velodyne DD-18.

There is 40hz bass and then there is 40hz ATC active 100's bass. Real 40hz isn't all that bad.

Elizabeth, LOL and then there was the woman on Jeopardy who was shown a picture of a bird and asked "What is a Booby?" Well if she doesn't know, then who would?

adding on to Dan_ed's post, from what i could figure out the fundamental at 40 Hz has a subharmonic at 20 Hz as well as overtones at 80 /160. it is a combination of all of these which give the flesh/timbre to the tone.
Any graphic equalizer using a digital out (eg i used a DEQ2496) shows a surprising amount of music in the 20-25hz region in many peices. the most surprising revelation has been "GrandMas hands" by Livingston Taylor. supposed to be an Acapella but has a consistent 20-25 hz bass content which is not heard in anything but a fullranger OR with subs and once you hear it that way can never ever listen to it without that bass fabric!

Where are people getting this sub-harmonic talk. Yes, string instruments can produce sub-harmonic sounds, but it is not a commonly used technique and it's virtually never written into compositions. Harmonic overtones are always present in acoustic music, sub-harmonics are not.

"Grandma's Hands" was recorded on a suspended wooden floor which is being excited by the foot tapping of the singers. It's a common effect in recorded gospel music. It's debatable if those sounds are part of the performance or are they in the class of falling mic stands, A/C rush, passing subways, page turning and fret scrapping, in other word noise. Although on tunes like the Supremes "Where Did Our Love Go" the floor effect is prominently featured as part of the rhythm track.