Morein (fils):

Compact designs that use large woofers are usually based on the
acoustic
suspension principle. Although speaker designers generally swear by
acoustic
suspension as providing the highest quality bass, it is a low
efficiency
system. In the past, there was a market for high performance, low
efficiency
speakers, for use in conjunction with powerful basic amplifiers.
However,
with the advent of home theater, the basic amplifier is no longer a
mainstream item. Home theater receivers are not capable of powering
acoustic
suspension designs to expected volume levels.

Consequently, there has been a replacement of large-woofer acoustic
suspension designs with ported designs using lighter cones and smaller
magnet structures that can be driven by typical home theater speakers.
However, these designs tend to exhibit large phase anomalies, as well
as an
inevitably steep rolloff of bass below the design corner frequency.
They
don't produce bass of the same quality, but people don't seem to care
these
days.

It is possible to build ported systems that use large woofers, but
tuning
requirements result in large cabinet volume, larger than is accepted by
most
buyers today.


Generally the active sub has been used in lieu of the
really-full-range speaker in mid-fi and middlefi systems, both 5.1 and
2.1. For aficionados of the "full range driver" this is also helpful.
But the home theater receiver is not really taken that seriously by
anyone, and so, I would posit that the fully active biamped or triamped
speaker is a much better way to go in the solid state era. For any
number of channels. Because no passive crossover is used, you save a
lot of heft and power on lack of insertion loss alone. Genelec and
other brands preferred by mixdown and mastering facilities are perhaps
best.