I've heard this topic come up in Steve's writings.  When I ran the idea of using bass guitar loudspeakers in place of subwoofers, I got negative impressions from users of a facebook audio group.  I wasn't really surprised because a lot of them are lunk-heads, anyway but I felt I should become a bit more knowledgeable about their practical usage as substitutes for subwoofers.  I'm much more interested in fact, accurate bass, and have no interest in pissing off my neighbors... all the time.  XD  Since I listen predominantly, to metal (especially, classic metal like Dio and Sabbath, Saxon, etc.) I would rather the low-end stuff is accurate.

But am I amiss in my supposing that instrument loudspeakers are better for this feat than many other varieties of paper-coned subwoofers?  It seems that professional loudspeakers, even some labeled as such that are often used in automobiles, have half-roll paper surrounds rather than foam.