Hi Amey,
I asked my friend, the recording studio owner and engineer (although he’s more of a musician than a geek), about this question.
Interesting answers:
In one way, you are absolutely right; a live session feed will have dynamic range and other properties that are usually not found on recordings. If you don’t limit DR, don’t filter frequency and just pass what the mic picks up, that’s what one tends to hear ‘live’ as being ‘better’ than a recording.
He explained the mastering process, and how the mastering engineer will apply overall or even bandwidth based compression to the final 2 track mix as he prepares it for creating the CD master.
Besides compression, they occasionally apply low frequency roll-off filters as well as selected EQ (to tame an over-bright high-end for example). But often, the decisions are based on taste just as much on general CD production guidelines.
This compression is designed to keep the music in a dynamic range that works well in cars, radio and other less-than HiFi situations.
So bottom line, a CD has less dynamic range and altered frequency response relative to the final mix-down tracks.
Furthermore, a mic feed is usually post-processed with EQ, gain riding and other ‘effects’ to achieve an artistic result that is unique. Which explains why live sounds so different from a studio rendition.
However, he did clarify that for him, since he hears both ‘live’ source and then his recorded tracks, a Protools HD deck at 24/96 or above are indistinguishable from each other, and that even at 24/48 it doesn’t make a difference in the end.
So my point about a mic going through a system, and 24/96 version of same being equal is sustained.
To help me see the effects of CD mastering, he gave me a CD of a small Italian group he engineered an album for, and a track from that album straight from the proToolsHD, with no post-processing, as a 24/48 stereo track on CD-ROM.
The source mix is a 60 track, highly engineered mix with lots of subtleties in it, so it will be interesting to see what gets lost with the compression and EQ of CD mastering.
BTW- he was not encouraging about Vinyl either (and he's a vinyl fan), which goes through even more mastering steps with stronger compression and more low-end filtering.