Three short comments, if I may …

First, my compliments to all, especially SH, for contributions to an excellent thread. A fully extended range stereo reproduction can help make the playback of acoustic, large space recordings come just a bit closer to ‘real,’ psycho-acoustics coming into play.

Second, I appreciate this bit of knowledge, assuming I interpreted SH correctly: I don’t have to worry about mixing the LFE with either or both of the R and L stereo, because the LFE will not contain the same audio information, either in or out of phase, as either the L or R … correct?

Thirdly, those that think a perfect subwoofer will be ‘fast’ enough to help make the ‘thump’ of a bass drum (or similar source of complex-frequency, sudden and large-amplitude sound) seem like that drum has moved right into the room with them has a conceptual problem. To make that happen, one would need improved capability across more of the sound spectrum than a subwoofer is intended to reproduce. Imagine the perfect loudspeaker that can produce frequencies from 0.1 Hz to a megahertz, flat, without distortion, at amplitudes so low that it actually absorbs any unwanted sound in the room, to levels so high that one could level a city with it. Now simply do one thing to limit its performance: restrict it to frequencies below 80, 60, or 40 Hz. No matter how much amplitude and ‘speed’ the transducer has, so much of the sound of a bass drum thump will be missing. If one needs more realism in sounds such as a bass drum, improvement in the woofer and mid-range may be equally or more important than improvements in the subwoofer.

That said, IMO, you can’t get close to realism without the range of frequencies that are covered by one or more well placed and adjusted subwoofer(s).