Folks:
All good points being made. If the TP *requires* that there was NO digital processing in the mastering chain, then this would clearly restrict the available multi-channel sources.
Are any of the newer "purist" recording efforts using any of the modern multi-mic surround arrays (Schoeps, Holophone, etc.)? Are there any masters available that used Decca-tree or even three spaced omnis? How about the Bell Labs 5-mic Sennheiser array?
This was why I was asking (earlier in this split thread) about the mic'ing techniques used for TP sources. Multi-channel mic'ing is 50+ years old, of course. I was guessing that the TP sessions were not simply coming from two coincident microphones.
Even in those cases where two-channels is all that's available, the center and ambience could be "matrixed." The Trifield matrix (Gerzon etal) is perhaps the best for the center and has long been available both as an outboard box for mastering and in Meridian amps for playback. The rear ambience could be as simple as a L+R sum, attenuated (say 6dB) and phase reversed to simulate a rea-wall reflection, as Mark Wilder did for the Sony SACD multi-channel releases of Miles Davis, Brubeck, etc. The rear can always be turned off, as Wilder suggested in an email to me.
IMHO, the center channel is the key improvment. Asking a two-channel system to fill in the "phantom" middle is, well, not really practical for most source material -- psychoacoustically speaking. Yes, if you start with Blumlein coincident figure-8 mics and arrange the speakers closer and pointed towards your head, you will achieve significant spacial accuracy. But no one does that -- other than Robert Greene, apparently.
Then there is the problem of the "sweet-spot." If TP subscribers are interested in sharing their music, that would be greatly enchanced by having a center channel. Unless, you insist that your friends all sit on your lap. <g>
Btw, has anyone ever listened to TP tapes played back through Ralph Glasgal's Ambiophonics system? It takes a two-channel input and cross-cancels the L/R and then adds hall ambience. Quite a powerful acoustic statement, with a multi-person sweet-spot to boot.
Mark Stahlman
New York City