With up-mixing, it is done with algorithms designed and optimized by knowledgeable researchers. Having the sound coming from speakers all around you and when your room is nicely damped, the room effects will be overwhelmed by the surround speakers, and you get repeatable and controllable results. It is much more flexible and can do what you can't get from fixed room reflections, for example controlling the rate of reverberation decay. And if you don't like what you are getting, you can adjust the settings and there is always an off button. You can easily switch settings for different materials, including turning it off, according to your desire at the moment.
Agreed.
I do not criticize upmixing as "adding something to" the original recording, whether or not a case could be made for that characterization. Imo improvements in sound quality and/or spatial quality need not justify themselves against a dogmatic yardstick.
But note that in the scenario you describe, "having the sound coming from speakers all around you and when your room is nicely damped", the ONLY directions spectrally-correct reflection energy will arrive from are directly from the surround speakers, UNLESS the damping in the room is truly broadband (which is expensive). If the in-room damping is removing significantly more of the shorter-wavelength energy than of the longer-wavelength energy, the spectral balance of the reflection energy is progressively degraded each time it bounces off a damped room surface. Eventually the spectral balance may become so degraded that what's left of the reflection ceases to be identifiable by the ear/brain system as "signal" and effectively becomes "noise". So imo there are potential tradeoffs involved with using damping to suppress the in-room reflections.
Also, note that any decent recording ALREADY HAS enjoyable venue spatial characteristics, whether they be real or engineered or both. The fact that we can EVER hear venue spatial characteristics on a recording is proof that they CAN be perceptually dominant over the playback room's "small room signature". What I advocate is taking some deliberate measures which perceptually minimize the "small room signature" of the playback room while enhancing the presentation of the venue spatial cues which are ALREADY ON THE RECORDING.
With speakers that spray sound into the room in random directions, if you want to adjust, you'll have to:
- Move the speaker around
- Move the listening position around
- Change the speakers
- Change the room
There is no off button, and you don't have the capability (or at the minimum highly compromised capability) to listen to native multichannel recordings (videos).
Agreed, upmixing gives you more flexibility in tailoring the spatial presentation to your liking. But note that unamplified instruments also "spray sound into the room in random directions", yet still manage to sound pretty good in most rooms.
I have a question, arising from my lack of experience with upmixing, that maybe you can help me with: Once the upmixer is adjusted properly, are those same settings optimum for all recordings, or is there benefit from adjusting the settings for different recordings? In other words, is upmixing "set it and forget it", or not?