Thanks for the responses. I have had these for a few years, and obtained them as partial payment for a woodworking job that I did for someone. These ones aren't pot-bellied. They have about a 6" woofer, and abut a 1" tweeter incorporated in them. There is also a bass port at the upper left side, with an adjustable 'High Frequency Level' knob right above it. I don't really know how good these are (my very first pair of reference monitors), and I thought of, maybe, trying out another pair against them (such as the Wharfdales, ofr the KRK Rokits).
The problem that I am having is that one of my monitors have a bad woofer - which rattles with the lower frequencies. I had been told, by some, that putting another, similar sized, woofer into the enclosure may give very unsatisfactory results. Something about marrying the 'proper' woofer to the system's crossover components. The bottom line, given, was that I would have to find the same exact woofer, or just forego the matter altogether. But shouldn't two woofers (I would replace them both, at the same time) of like size, from the same manufacturer, suffice? I doubt, very seriously, if I could locate the same type of woofers that are presently in this old system.