Robert Morein wrote:

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.

Few people were bigger fans of AR than I was during its
heyday. I cut my teeth on the philosophies of Ed Villchur,
Henry Kloss, and Roy Allison. (Allison remains a good friend
of mine, and the speakers in the largest of my three AV
systems are all Allison models.) However, I will have to
defend the ported-woofer contingent at this time.

I have reviewed some superb ported subwoofer designs by Hsu
and SVS and must say that although with special test tones
they were very slightly outpointed by some of the
servo-controlled acoustic-suspension subwoofers I have also
reviewed (by Velodyne and Paradigm, mainly), with music all
bets were off. The big Hsu and SVS subs I have reviewed have
been able to hold their own with the very best
acoustic-suspension subwoofers, even fine servo jobs.

Admittedly, with full-range systems I have had better luck
with acoustic-suspension woofer systems than I have with
ported versions, but with ultimate-design woofer systems
(subwoofers) the ported jobs were often able to hold their
own with the best right down into the bass-range cellar.

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.

I agree, although compared to the larger Velodyne and
Paradigm subs, the woofers drivers in the better ported subs
are not all that large. The enclosures are often large,
however, although subs like the Hsu VTF-2 or the SVS 25-31
are not all that huge and they can match the low-bass
performance of just about any full-range system that employs
the acoustic-suspension design. They can also match the
performance of usually much more expensive
acoustic-suspension subs of similar size, at least down to
about 25 Hz. Above that frequency they can often play louder
than the AS units, which gives them an edge with most music
and movies in larger rooms.

Howard Ferstler