I had infos that some (a few ? almost all ?) recordings have their bass (below 80 Hz) recorded/encoded in mono. Is it true ? If yes, is it only for a few recordings, or almost all ? Is it true with CD, SACD, DVD-A, vinyl, or only the case with sound in DVD-video ? If it is true, is it mon below 80 Hz ? below 60 Hz ? Below 40 Hz ? P.S.: I do not talk about the non-capacity of the ears to locate bass below 80 Hz. I am really talking about the mono versus stereo recording of bass in records. Thanks.