Archived from groups: rec.audio.high-end (
More info?)
In article <c620vf09mp@news4.newsguy.com>,
Philip Meech <macmeech@adelphia.net> wrote:
>What is the cause of the holographic soundstage? The push of amplifier
>power, the positioning of speakers in a small room, the quality of the
>tweeter and mid bass driver, the quality of the recording re:separation
>and detail?
What follows is my semi-informed opinion, not Gospel by any means.
All of the above are probably contributors. The process of learning
(yours - the listener's) is another part.
Fundamentally, a "holographic soundstage" from a stereo source and
stereo reproduction system is a psychoacoustic illusion. It's not
actually possible for a stereo system to accurately reproduce the
actual sound field of an orchestra or other sound source in
3-dimensional space. The stereo record-and-playback system will
always introduce anomalies (e.g. delayed and reflected sound-paths)
which weren't present in the original sound-field.
[Picture the sound paths from the instruments to your ears, as if you were
sitting in the original venue. Then, picture the sound paths from
those instruments to any set of mikes, located wherever you choose,
and then picture the paths from your stereo speakers to each of your
ears. You'll see that there's no way to reproduce the original-venue
sound paths with complete accuracy.]
Creating a playback sound field which _seems_ three-dimensional to
the human ear/brain systems is a tricky thing. From what I
understand, it's partly a matter of providing sonic cues which promote
the sense of a three-dimensional space larger than the listening room -
e.g. a balance of direct and reflected sound present in the original
venue, which conveys a sense of the size of the original venue. This
particular cue system is one which comes via the original recording
and mastering.
Similarly, the recording ought to reflect the sonic characteristics of
instruments which are "near" and "far" from the listener... in a real
venue, instruments which are towards the back of the stage might have
a different frequency balance (a bit more attenuation of the treble
due to the distance), and the direct-path sound level from those
instruments would be lower than for instruments towards the front of
the stage. This will help create the proper illusion of depth. Once
again, this is a matter for the original recording and the mastering.
The playback and reproduction equipment should, I believe, generally
try to be as honest as possible - not introducing its own sonic
character any more than is strictly necessary. In particular,
maintaining an even frequency balance (and dispersion, if possible) at
a speaker's crossover point(s) can probably make a big difference in
the naturalness of the soundstage. If there are abrupt changes in
amplitude or in horizontal or vertical dispersion patterns of a
speaker system at any frequency, an instrument may seem to "wander" in
space as it plays up and down across the anomaly, or might seem to be
stretched or pulled if (e.g.) the bass notes seemed to come from a
different direction than the midrange or treble notes. This will tend
to spoil the illusion.
A speaker with abrupt horizontal or vertical lobing in its dispersion
patterns may present other problems... an overly-small "sweet spot".
If you move your head back and forth by a foot or so, you might find
that the soundstage changes abruptly, with instruments seeming to
"move around" in an unrealistic fashion. Speakers with a somewhat
more even dispersion pattern might not have this problem.
Speakers with low distortion levels, and wide dynamic-range capability
probably do a better job than more limited speakers. The sounds of
individual instruments will be less likely to interfere with one
another (e.g. a bass-drum whack or tuba blatt won't cause the apparent
character and position of a viola to wander).
The amplifier is, I think, less critical. As long as it's got enough
clean power to drive the speakers to the desired playback level
without clipping or distorting, and has no other objectionable
characteristics, then you'll probably be fine. More power probably
won't help matters.
Setting up the room so that you avoid excessive "early" reflections
can be helpful... e.g. put a rug on the floor between you and the
speakers, to tame any reflections from the floor. The brain can learn
to ignore "early" reflections to some extent, but they might tend to
spoil the illusion of having a coherent sound-field. Similarly,
moving speakers around or experimenting with wall treatments may be
beneficial in managing the inevitable reflections created by your
room's walls.
Finally, learning and training are probably quite important. When you
"break in" a new stereo system (especially if it's in a new room) you
are often breaking in your own ear/brain system as much as you're
breaking in the equipment (or even more). Over time, your ear/brain
system will adapt to the sound field being created by your system -
it can learn to ignore some of the anomalies created by your listening
room and equipment, and pick out those characteristics of the sound
field which create the satisfying perceptual illusion you're looking
for.
--
Dave Platt <dplatt@radagast.org> AE6EO
Hosting the Jade Warrior home page:
http://www.radagast.org/jade-warrior
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