Why the obsession with the lowest octave

How much bass comes from the concert hall reinforcing bass from the instruments? When the instruments are measured, they are probably done individually in a room that may have no influence on the sound. No room reinforced bass may be the case. Anyway, something to think about. Resonance of the hall and surroundings. That may be some of the reason for bass being there, good or bad. We here it live, and can miss it at home. Here is a link to look at.[http://www.akutek.info/Posters/KG_Basses_on_Floor_Poster.pdf]

Pardon the grammar. That Akutek link has interesting info. Same link.[http://www.akutek.info/Posters/KG_Basses_on_Floor_Poster.pdf]

Good point that even instruments do not have a single sound. It is a function of the environment played in (ie the venue) and the sensors used to detect the sound (ie your ears, microphones, etc) that create the variations.

Facts like these are the reason why while can appreciate the value of a good venue, I always have to chuckle when it is suggested the room you listen in has to be effectively neutralized completely to get the correct sound.

The fact is the room in which the music is recorded and the room in which the music is played are both factors in the resulting sound in a home system, as much so and often even more so than the system played on.

Practically, the goal should be to optimize the resulting sound to sound good to you, not to achieve some perceived standard of perfection that does not even exist and cannot practically be achieved at any cost.

That thinking is good for the vendor though! It keeps everybody chasing the carrot and draining their funds indefinitely to achieve an impossible goal.

I've found it interesting that while the OP ask about the "lowest octave", which would commonly be defined as 20-40 Hz, so many replies have commented on bass in general or if specific, reproduction above 40 Hz.

But for the general value of a decent subwoofer (or bass extension), I had a learning experience similar to Ecruz. Many years ago I visited a well-respected dealer for a sub-woofer demo. The main speakers he chose were Spendor BC-1s (that may hint how long ago this happened) with an excellent mid-range reputation but known for low frequency limitations. But to my surprise, for the music demo he used a solo violin. Even with such a limited low frequency range of the instrument, it was very obvious when he switched the sub system in and out. That forever sold me on the value of extended bass (again in general, I'm not identifying a specific frequency) for a fuller musical experience.

Why the bottom octave?

Because it sounds so right, when done right.