Some interesting notes regarding the various soundmixes of Alien in Widescreen Review: http://widescreenreview.com/hddisc_detail.php?recid=12316
The "Alien" soundtrack, while encoded in the DTS-HD Master Audio™ 5.1-channel format, still is dramatically less dynamic and sounds dated. The previous DVD's Dolby® Digital soundtrack had no split surrounds and very weak .1 LFE enhancement, making it a 4.1 mix. Our reference Dorrough meter bridge showed aggressive split surround signals on the discrete LaserDisc version reviewed in Issue 18, but monaural surround on the DVD version. Both were THX digitally mastered for "optimum performance," but the THX standard of quality was not heard on the previous DVD. This new encoding has electronically enhanced split surrounds, but they still are at subtle, inconsequential levels.
The DVD Dolby Digital 5.1 audio on the Alien Director's Cut reviewed in Issue 81 was a new remastering effort, sounding a bit louder in overall level than the previous DVD. There was also some more low-end content and refinement in spatial articulation, but the .1 LFE presence was inconsequential. Otherwise, the general characteristics of the audio were similar to the previous soundtrack remastering. The fidelity is certainly dated, and some distortion is to be expected. The soundstage tends to be conservative in nature, with an adequately compelling sense of holosonic® spaciousness throughout. The low end is inherently reserved and weak. The Dolby Digital version seemed to have just a bit more to offer in the low end, but the DTS® Digital Surround™ audio (new to that release) sounded a little more “open” in the midrange and articulated in dimension. Dialogue sounded natural and spatially integrated, with a spread across the three front channels, with emphasis on the center channel.
On D-VHS® D-Theater™, the Dolby Digital soundtrack sounded just slightly smoother in the midrange than the DVD "Alien" Quadrilogy version reviewed in Issue 81. Like the DTS version for the DVD, the DTS audio for the D-VHS D-Theater (encoded at the full 1509 kbps) sounds a little more “open” in the midrange and articulated in dimension. The Blu-ray Disc version is that remastered soundtrack encoded in the lossless DTS-HD Master Audio 5.1-channel format. The enhanced refinement in fidelity, clarity, low-level resolution, and spatiality are evident, but .1 LFE impact is virtually nonexistent and distortion is heard throughout. The sound is inferior to the subsequent three films sonics, always sounding dimensionaly and dynamically reserved. (Gary Reber)
The 4.1 track isn't mentioned but I find the bold part very interesting, I need to take a listen to the 5.1 track on my old DVD, it's been a very long time since I did.