There is more than one way to look at it, with one being that a subwoofer deals with some particular set of frequencies (probably conjoined with the idea that it does
not do certain other frequencies, perhaps, say, above 200 Hz), and another being that a subwoofer deals with whatever is below a "regular" speaker. With the first of these, my computer "subwoofer" may not qualify as a subwoofer (its low end, if memory serves, is about 50Hz), but with the latter idea, it probably does, if we mean regular computer speakers.
If we went with the former idea, we might be tempted to call the woofers in
these speakers "subwoofers," because they only handle sound from 150Hz down. The manufacturer called them "woofers." (And also interesting is the fact that they called the ribbon driver "full range" in a brochure I have.) The woofers in those speakers don't deal with any frequencies that some "subwoofers" may be set to do.
Or we might think about the Music Goddess speakers one can see in the brochure
here, where the 10" driver deals with frequencies below 150Hz and is called there a "woofer", though rather curiously, the driver that is in the Music Goddess called a "midrange" is the same driver that is called a "woofer" in the Moon Goddess speaker, and a very slightly modified version of that driver is called a "mid-woofer" in the Leisure 2 SE.
The Music Goddess case is particularly interesting because if I took a pair of those 10" drivers and put them in their own boxes (like typical subwoofer boxes) and used a separate amplifier to drive them, with a crossover of 150 Hz and used them with my Leisure 2 SE speakers, most people would call them "subwoofers."
I personally tend to think of the term "subwoofer" differently in different contexts (which is not entirely unlike the way
Wikipedia handles the term).
But in any case, you are right that many people are calling ordinary woofers "subwoofers," which can be seen from reading ads on eBay and Craigslist, where sometimes people call a little woofer in a small bookshelf speaker a "subwoofer." And, like you, I wish they would stop, as they are wrong in what they are stating.
