There will always be discussions which DVD or LD has 'the most
bass', or which version (LD or DVD, DD or DTS) of a film 'sounds
best'. An analysis of the latter is impossible, because its of totally
subjective nature. What we can do, though, is measure the
SPL (sound pressure level) of the individual channels in a DVD or
LD soundtrack to make a quantitative instead of a qualitative
So, while we can't really measure whether track A has a 'wider
soundstage', 'tighter bass' or 'more air between the instruments'
than track B, we can show for example that one track has
more bass in a certain freqency range than another. Or that
one track still has the highs boosted, like the original theatrical
mix, probably requiring THX's CinemaEQ to tame them, while the other
might already be mixed for a near-field home presentation, with
the proper reduction of the highs.
It has to be noted that comparing two tracks doesn't really show
which one is correct per se. If one track has more bass than
the other, then there is the possibility that the weaker one is
correct and the stronger one is boosted beyond the sound
mixers original intend. But its also feasible that the stronger
one is untouched, while the weaker one is toned down for home
use, which is unacceptable from a audiophile perspective.
So the measurements and graphs can only be a tool to investigate
the differences. Its up to the experience of the investigator and
his proverbial educated guess to come to likely conclusions.