I have long known that this is theoretically true. After all, what sound quality advantage could there be in listening to a mono signal divided into L+R speakers, then folded back together to produce a center image? Surely it's a lot simpler just to listen on one speaker, without dividing and then recombining the center image. Logically, one would expect better fidelity from the simpler process. Also, there is a midrange frequency anomaly caused by dividing and then recombining the signal. I have a graph of it, and will try to post it here if I can find it. But knowing all this, I never, until now, tried the simple experiment of deliberately listening on one speaker versus two. Like most two-channel audiophiles, I always listened to mono "in stereo," so that the center image "floated" between the two speakers. I'm embarrassed that it took me so long to do it, but I finally tried the experiment. And the results are as I expected. (If you reproduce this experiment at home, don't forget to double the volume when listening on one speaker. Otherwise the two-speaker state will always win.) I found the center image clearer on one speaker than on two. The music really pulled me in to a greater extent than with "mono-in-stereo." I listened to a variety of music recorded in mono: classical, rock, pop, and jazz. I always found listening on one speaker to be more involving than listening on two. I could hear further into the music. The image had greater depth. This is the best way I can describe it: as an improvement in imaging and coherence. I am converted. From now on I'll listen to mono in mono, not in stereo. It's just better. Readers, please try this at home. It's an experiment that's easy to do and costs nothing, and could really improve your listening experience. And if you try it, please report back!