Some imo relevant quotes from acoustics and psychoacoustics expert David Griesinger, inventor of the original Lexicon processor, which (based on a conversation with an advocate of "tasteful upmixing" whose name has become controversial in this thread) was the best there ever was:
Envelopment is perceived when the ear and brain can detect TWO separate streams:
A foreground stream of direct sound.
And a background stream of reverberation.
Both streams must be present if sound is perceived as enveloping.
In a small room there is almost never sufficient late reflected energy to contribute to the background [reverberation] perception.
Presence depends in the ability of the ear and brain to detect the direct sound as separate from the reflections.
When presence is lacking the earliest reflections are the most responsible.
The earlier a reflection arrives the more it contributes to masking the direct sound.
Imo these statements offer insight into why omnis (and most speakers) produce better clarity and a better sense of acoustic space when their first-reflection path lengths are fairly long, with one of the statements offering insight into why one might want more late-onset reflection energy than conventional speakers normally deliver (and upmixing is one way to accomplish this).
Ime good two-channel (which includes "getting the reflection field right") is "set it and forget it", though I concede that the performance potential is probably higher for upmixing.
In two-channel setups which enable the venue spatial cues on the recording to be perceptually dominant, I find the oft-unexpected and oft-dramatic variation in the sense of space from one recording to the next to be extremely enjoyable, in that it approximates listening to music performed in a corresponding variety of acoustic settings. Which leads to my next question:
Is there a great deal of variation in the sense of space from one recording to the next with upmixing?
Envelopment is perceived when the ear and brain can detect TWO separate streams:
A foreground stream of direct sound.
And a background stream of reverberation.
Both streams must be present if sound is perceived as enveloping.
In a small room there is almost never sufficient late reflected energy to contribute to the background [reverberation] perception.
Presence depends in the ability of the ear and brain to detect the direct sound as separate from the reflections.
When presence is lacking the earliest reflections are the most responsible.
The earlier a reflection arrives the more it contributes to masking the direct sound.
Imo these statements offer insight into why omnis (and most speakers) produce better clarity and a better sense of acoustic space when their first-reflection path lengths are fairly long, with one of the statements offering insight into why one might want more late-onset reflection energy than conventional speakers normally deliver (and upmixing is one way to accomplish this).
Thank you! That's what I suspected.It [optimal upmixer settings] is highly dependent on the recording and mixing technique. So the answer, IMHO, is a strong no. One of the first job of an upmixer is "directional decoding", which is to determine where the placement of the sound is.
For example, if you are adding a center channel to a 2 channel (stereo) mix, and there is a sound panned (using amplitude panning) to the right but not all the way. There you'll have the same sound in both the left and right channels, with the left channel weaker than the right. If you upmix by simply mixing the center channel with the sum of the left and right channels, the resultant image will be pulled toward the center. To "accurately" upmix it (not changing its perceived location vs the 2 channel playback), you'll need to reduce its strength in the left channel. Needless to say, this directional decoding process is far from simple. If the sound location info is encoded using time delay panning, as in recordings using spaced mics, it is almost hopeless. Therefore, a "successful" upmixing is highly depending how the source material is prepared. I believe you'll have a better chance of success for materials recorded/mixed for multichannel, downmixed to 2 channel (for distribution), and then upmixed again.
Ime good two-channel (which includes "getting the reflection field right") is "set it and forget it", though I concede that the performance potential is probably higher for upmixing.
In two-channel setups which enable the venue spatial cues on the recording to be perceptually dominant, I find the oft-unexpected and oft-dramatic variation in the sense of space from one recording to the next to be extremely enjoyable, in that it approximates listening to music performed in a corresponding variety of acoustic settings. Which leads to my next question:
Is there a great deal of variation in the sense of space from one recording to the next with upmixing?
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