My parents own.ed a major number of mono recordings from their times living in the states in the 50's. A part is musically so-so, but there are treasures like eg. the Mozart sonata recordings with Walter Gieseking. I always liked the magical sound of these recordings "even" played with my stereo cartridges like Koetsu Black, Monster Genesis 2000 and others. (Turntable were at some time Merrill Heirloom, then WTT Signature and lately a modified Technics SL1210, I used the ET2 arm, where possible). I BTW used these mono recordings to tweak lateral azimuth by minimizimng the"null" mono signal via electrically mono-ed- out-of-phase channels.
After reading several enthusiastic UK reviews of the Miyajima Mono cartridges I started to get intrigued and asked friends, and finally bought a Miyajima Zero and mounted it on a friends Lenco "monster" with Adanalog air bearing arm, where we could "directly" compare a modded (and very good sounding) Denon DL103 vs. the Miyajima on mono recordings.
I was quite smashed by the difference. "Stereo illusions" excepted, I rarely heard as lifelike true timbres and dynamics, and as much colours, and the bass was in a class by itself - in a never heard of way. The "virtual mono" coming from the stereo cartridge somehow simply sounded broken and fluttering, somehow instable.
I truly recommend trying to hear - no, experience this difference for yourself, if you are interested in mono recordings.After listening, some observations and thinking trickled in: Stereo cartridges have to track and electromechanically decode vertical information, mono cartridges do not. For stereo cartridges there is a certain design freedom regarding lateral and vertical compliance, eg. resonance frequency, but in the end vertical resonance will practically never be above 20Hz. The stiffer the suspension, the less the cantilever moves vertically - and that's where almost all extra-musical LF "rubbish" lays.The Miyajimas suspension is much stiffer vertically than laterally, and stiffer than any cartridge I ever saw. And IMO / IME this reduces flutter / Doppler distortion from excess cantilever movement by (almost) an order of magnitude.It reduces this on both a mechanical level and by not decoding it electromagnetically. Which means the coils. cores, and magnetic circuits are much less modulated / saturated by LF, where saturation is at its worst.Internally or externally mono-ing will simply not do the same distortion elimination trick. (It might simply be a marketing decision to sit on a me-mono-too-bandwaggon :-).
Yes, probably cartridge tips will make a difference too...