Oooh, that Horenstein Mahler 3 HDTT release!

[Kjetil]

I bought and downloaded the PCM 24/192 2.0 and 4.0 bundle:

Mahler Symphony No 3 & Strauss Death and Transfiguration - Jascha Hore

Title: Jascha Horenstein, Conductor London Symphony Orchestra Norma Procter, Contralto Ambrosian Singers, John McCarthy, Conductor Wandsworth School Boys Choir, Russell Burgess, Conductor William Lang, Flugelhorn solo Dennis Wick, Trombone solo John Georgiadis, Concertmaster, and violin solo

www.highdeftapetransfers.ca

This particular recording has maybe the best sound of a large orchestra (plus two choirs and a vocal soloist) that I have ever heard. And in 2.0 you hear what two microphones picked up. In 4.0 you hear what four microphones picked up (I haven't heard that one yet).
Things don't get much more minimalist audiophile than this. Props to High Definition Tape Transfers for making a commercial offering of the recording Jerry Bruck did beside the official Unicorn/Nonesuch back in 1970. He really was on to something.

 

[Kal Rubinson]

And in 2.0 you hear what two microphones picked up. In 4.0 you hear what four microphones picked up (I haven't heard that one yet).

N.B.: The 4.0 was not miked with the commonly-expected quad layout as it was recorded in 4 channels with the microphones in a tetrahedral array. Default routing will offer a nicely expanded soundspace with a multichannel playback system but that is not exactly how it was intended.

In the delivered multichannel files, left and right front are as expected. What is conveyed by the right rear channel is from a third microphone that was above the first two and aimed straight up. The left rear channel is from the fourth microphone in the same horizontal plane as the L/R but aimed towards the back of the hall, away from the orchestra. Proper rendition of this requires some rerouting of the signals.

 

[Kjetil]

I was hoping to get to hear the 4.0 played through a normal 4.0 setup this week, but it will have to wait to find out if TM to RR and RM to RL is confusing or not. I doubt it is since these returns should quite diffused, but it should be proven.
(My friend’s rear speakers are not easily moved. All his speakers are heavily modified Maggies with four extra 12” in a baffle, all DSP crossovers, plus a DBA below 120 Hz.)

 

[Kal Rubinson]

I was hoping to get to hear the 4.0 played through a normal 4.0 setup this week, but it will have to wait to find out if TM to RR and RM to RL is confusing or not. I doubt it is since these returns should quite diffused, but it should be proven.
(My friend’s rear speakers are not easily moved. All his speakers are heavily modified Maggies with four extra 12” in a baffle, all DSP crossovers, plus a DBA below 120 Hz.)

Your premise is correct and you will enjoy what it delivers. However, remapping is an improvement.

I don't move my speakers but I have the ability (via a mapping matrix) to reroute channels, sending TM to my center channel speaker and RM to both my SR/SL speakers.

 

[Kjetil]

The same should be possible at my friends’ place. I’m not quite sure if routing TM to C yields the best result one could achieve. I think I would try to route both TM and RM at -6 dB to RL+RR as a test.

I very much look forward to comparing the sound and placement of the off stage Flügelhorn in the third movement. In 2.0 it’s completely diffuse, maybe not so in 4.0.