It's pretty simple - it's much, much, much easier to cut, master, and press a single waveform (mono) onto a physical surface without losing or altering the ultra-subtle information that creates "presence" and timbral accuracy, than it is to cut 2 channels into a compound waveform and then retrieve them simultaneously with a single stylus (stereo). On top of that, even if a stereo pressing was 100%, it's virtually impossible to align a cartridge so precisely that information is not constantly lost or distorted. Not the case with mono. (Tape is very different, of course, since the two stereo tracks are recorded and retrieved independently.)
From the Classic Records (reissues) website:
"We cut a reference disc using the Mono cutting system and then switched over to the Stereo cutting system and repeated the cut holding everything else the same. We could finally compare the cutting systems and were surprised at what we heard. First, they were definitely different. The stereo cut seemed a little more "stereo like" in a spatial sense. The mono cut was more focused by comparison and the bass definition was superior. The real test was to play each against the tape that they were cut from to see which was more authentic. The mono cut was definitely more like the tape than the stereo cut... In the end, it was a unanimous decision to use the Mono cutting system exclusively for mono titles because the sound is more authentic than using a stereo cutting system. It would appear that collectors who go to the ends of the earth to find original mono pressings cut on mono systems do so with good reason...
- Michael Hobson, President - Classic Records Inc."
From the Mono Maven at enjoythemusic.com:
"One of my guilty pleasures is the occasional visit by some audiophile friends, where I drop one of these mono gems on the turntable amidst a program of otherwise big-ass stereos. Observing the enthusiasm of my unsuspecting audience, I turn the knife a little and ask if they observe anything unusual in the recording. Only about one in four or five catches on that they are listening to mono... and this even with orchestral music!
By every audiophiliac measure of performance, save one, mono recordings surprise us: frequency response extension; authority of bass; lack of treble clatter; size and depth of stage; correctness of timbres; and presence (where a good mono is often better than stereo): the palpable illusion of a musician playing right there before you. The harmonic structure from a mono LP is likely to be more coherently presented, resulting in a timbral purity and convincing focus and power that stereo rarely achieves without painstaking setup (which of course you should have anyhow.) Vocals have the opportunity to bloom without strain or electronic resonance. In part, as in early stereo, this is because everything in the recording chain from microphone to tape recorder to disc cutter is tube amplified: the overload and distortion characteristics are more consistent with the dynamic expansiveness of live music. The sense of weight together with micro-dynamic resolution catches your average audiophile completely off guard; it's so unexpected.
The one area where stereo can be counted to improve on mono is instrumental placement, for obvious reasons. Locational cues, however, are not the only means to sort out what's going on; neither are they the best means to understand the musical argument on its own terms. My audiophile visitors puzzle about how it can be easier to follow the inner voices in mono than in the corresponding stereo version.
Full article at: http://www.enjoythemusic.com/Magazine/music/1104/classical/mono.htm
Not only all this, but the Thrift store and garage sale crowd completely pass these over, leaving them for the more astute of us!
