Why the obsession with the lowest octave

I cared more about a clear high end when I started and when I was younger with younger ears.

My first good speakers used Heil Air Motion Transformers to that end for better or for worse.

I realized the importance of a quality and complete low end to me as well only within say the last 5-10 years or so.

Why the obsession? Everything discussed in this forum is about obsession.

I like deep, but not too deep bass. In fact I like to have a upward tilt in frequency response below 40Hz. It sounds good to me. But what I have discovered from looking at countless spectrograms of popular music recordings is that there really isn't that much information below about 40-60Hz. As long as the harmonics are present, the ear/brain fills in the "missing" fundamental. However, if the recording actually has true low frequency content, then I like to hear it.

My system goes down to 25Hz and then steeply drops off. Are some people saying that there's musical info below 20Hz?

One last point, humans had not evolved when dinosaurs existed. Human hearing is not at all sensitive to low frequencies, witness the Fletcher-Munson curves. Humans are most sensitive to upper midrange sounds. Think about it.

In my glance, I noticed that nobody mention SPL levels. Just because a speaker can go down to 30hz, does not mean it can do so with any authority or cleanly at listening levels. I can build a 5 1/4" subwoofer that will go down to 20hz, but it will only do it at 60dbs or so. To get 100 dbs at 40hz takes at least a single 12" subwoofer with pretty good excursion.

Many high end speakers at decent volume levels will play the 2nd order harmonic nearly as loud as the first. So often what people mistake as hearing as 30hz bass is the 60hz harmonic. In most acoustic music there isn't a lot of bass below 40hz,but you do get ambience from the sub bass of the room when you have speaker that reproduce it.

As far as obsessed, you haven't seen anything. Go over to the AVS forums and see what those nutballs are doing. Most want to be able to produce 115dbs at 20hz and some are getting 120dbs at 10hz. They are now pushing below the 10hz level, some as low as 5-6hz. Whatever you do over there, don't mention anything about amps sounding different or cables, you will get piled on.

I see the value in having clean bass down to 20hz, and I
agree that much of the value comes from the sense of venue
that those very low frequencies can provide, and if could
have it without tradeoffs that would be great, but there are
tradeoffs indeed and Larryi articulated them very well. It
took me a long time to break away from the obsession and
accept that in many ways the Merlin VSMs with a brick wall
at 28hz and a sharp drop off at 32hz were more musically
satisfying that my previous speakers that were +/-3db at
20Hz. I would take that extra bass if I would not loose that
Merlin midrange and resolution and the ability to run with a
relatively low-power OTL, but I have not found a speaker
like that. The benefits of deep bass are real, but so are
the liabilities that come along with speakers that can do
the deep bass thing. Perhaps with some price-no-object gear
you can have it all, but at relatively real world prices I
would seek to compromise some of that deep bass for other
values. The fact that I listen to acoustic jazz 90% of the
time I'm sure has something to do with that perspective.

The reason most hifi home audio gear has almost always been spec'ed from 20hz-20000khz is because that covers the useful range in the audio spectrum that people can generally hear.

Individual hearing ability varies though. Many cannot hear this full range and some may be able to hear even more, but these are fairly rare and extreme outlier cases.

Many recordings have little or no content towards the extremes. Some good ones do though.

Put the common limits of human ears and the recordings played together and the cases where a low end of consequence exists, can be heard and the listener actually cares are relatively few.

If you care, in general you will pay a premium of some sort generally to enable it in a home system in a quality manner that does not negatively impact all the other good stuff.