John, I did this a few years ago for the purpose of investigating if a sub could provide "tight" bass or could be "musical". All settings were left the same(i.e. the sub was rolled off above 80Hz), but all speakers(set "small") except the sub were disconnected. The result was neither tight nor musical, except in the sense that the material being played was music; relatively low level, dull, loose thuds was a fair description. Tightness of impact and musical qualities of, say, an instrument playing a 50Hz fundamental depend primarily on the overtones which aren't reproduced by the sub.
