In the late 80's, my parents got a hi-fi setup at home. For aesthetic reasons, they got smallish bookshelf speakers mounted near the ceiling (next to air ducts -- not the best sounding idea ever) and went with a massive powered sub (on which they've turned down the volume to the point that it might as well not be on at all). Back then, there were no DVDs, no Dolby Pro-Logic, and so forth. Instead, we had a standard two-channel stereo receiver that had pre-amp outputs. The "professional" installer used a y-cable to merge left and right and feed that output to the sub.

So far as I can tell, Dignan's setup in question follows the same "hey, whatever, seems to work" ethos that reigned prior to Dolby Digital and the modern era of surround sound.