2-way speaker with best bass

These discussions of how low a frequency can be reproduced always lack one important detail...How loud? Earphones, with tiny "cones" can reproduce the lowest frequency, but at a volume so low that they need to be on the ear to be heard. Small loudspeakers can likewise deliver excellent LF performance, but not at a reasonable volume, particularly in view of the human ear's roll-off at low frequency. Large cone drivers can deliver LF at a volume which is realistic, and without the extreme distortion-producing cone excursion typical of small-driver systems trying for the lowest octave.

Eldartford - good point - reasonable SPLs in the bass means large woofers -
large woofers are ill suited to producing midrange - this is why a two way
system ends up as a near-field or life style type trade off. They are the most
common speaker on the planet because they are the "minimum"
necessary to get 60 to 12 Khz in a flat response. Since the 80's two ways
have been delivering ever more prodigious bass but this is at the expense of
quality bass and a quality midrange - it has all become boom boom tizz,
IMHO. And, as a consequence, no wonder some people are enamored by the
midrange magic of single driver speakers!

If one is to ignore home lifestyle and other domestic considerations and go all
out for just quality sound then one is forced to consider three way or four
way (three way + sub) designs, IMHO. However, there is no doubt that a two-
way seems likely to remain the most popular speaker on the planet - so the
question on this thread is an interesting one!

Those who suggest that simply adding a sub will fix the bass issues of a two
way are forgetting that this is NOT true for the majority of ported bass
extended two way designs - if you go this route then you ideally want a
sealed box two way speaker that rolls off at 80 HZ and has its design goal on
the midrange quality rather than shock and awe ( a design that is NOT bass
extended with all the inherent phase & distortion issues and the typical mid
bass bump up to give "impression" of deep bass).

I bought the Acapella LaCampanellas for just this reason. Their plasma tweeter is outstanding but using it in speaker above the LaCampanellas makes for a complex crossover. They go deep and can play loud.

If you want to get bass below 60Hz from a two-way, you can get it. You have to choose your speaker carefully -- the Merlin VSM mentioned above and the orphaned Meadowlark Shearwater are examples -- then place it well. Realistic, tuneful, articulate bass, yes sir, and low enough that the wavelength is too long for the room and them low lows wind up in the kitchen. Punch you in the spleen and flutter your shoelaces, no.

Not forgetting to give your speaker good electronics, a good source, good cables... all things that affect bass from any speaker, just like placement. I would mention room treatment but a poor room also will keep a more-than-2-way from giving decent low end output. But the OP knows about all these, and the crossover tradeoff factor, and bla bla bla.

So to answer his question : Merlin VSM and Meadowlark Shearwater Hot Rod IMO, and I'm sure there are others.

Another approach would be speakers with self-powered LF drivers that can be tuned to optimize bass according to placement such as the Zu Definition 2s or the Rhethm Saadhana. Not sure if these would qualify as 2-way, but they are crossoverless.