Quote Originally Posted by kexodusc
Three of my friends and I performed a little test this weekend, comparing 5 albums of various music types. We used my friend's setup: a Yamaha RX-V1400, with Paradigm speakers - 6 Studio 20's, a PW-2100 and the CC-470 for playback. Older Yamaha CD player and Panasonic DVD player were used. The goal was to determine if DD/DTS audio tracks sounded better than CD audio.
Here's what we collectively came up with:
Metallica (Black Album) - Definitely better in DD than CD audio in stereo
Diana Krall - Live in Paris - Again, DTS better than the CD audio version
Pink Floyd - Dark Side of the Moon - 5.1 DD has won the test already.
Neal Young - Harvest - Don't know if it was the recording or what, but 2-channel stereo won out over 5.1 audio
The Eagles - Hell Freezes Over - 3 votes to 1 in favour of DTS over CD Audio.

Now, is there some technical information I can use to support the results of this admittedly subjective test? Is it bit rate/sec, sampling rates, 16 vs. 24 bit "word length"? Or do we just subjectively prefer the added ambience a 5.1 music source delivers?
Any comments?
Very interesting results, although I would caution that you're comparing surround tracks with two-channel tracks, and there are lot of other variables at play other than the formats themselves. For example, in order to put together a 5.1 soundtrack for an older recording, the mixing engineer needs to actually go all the way back to the multichannel master tape, which might have significantly different tonal characteristics than what ultimately made its way down to the original two-channel master tape (a lot of vinyl masters had EQ and/or compression applied, and the CD transfers were done from these without compensating for this). Also, keep in mind that a lot of CDs have had multiple remasterings done, so different versions of the CD releases can also sound different (a lot of the early transfers were not done properly).

I've done similar comparisons with all sources folded down to two-channel, but even that method is flawed given that the channel balances between two-channel and repurposed 5.1 mixes can be very different, and create a dissimiar sound overall even in two-channel. In general, I've noted that DD can come very close to the audio quality of the CD versions, and can be superior in some cases (these were all two-channel direct comparisons). These differences could have more to do with the mastering or other source differences. In cases where I know that the DD and DTS tracks were encoded simultaneously at identical levels, the DTS track typically sounds subtly better.

I think for now, it's a good subjective comparison for the various versions of those specific recordings. Whether or not those listenings can be applied more widely is where some caution's in order.