Mind Stretchers
On Tue, 12 Jun 2012 04:07:31 -0700, KH wrote
(in article ):
On 6/11/2012 6:07 AM, Gary Eickmeier wrote:
wrote in message
...
Yes, that is the problem. The signal presented to the listener, in the
venue, has angular, temporal, and level clues that, in conjunction with
the HRTF of the listener, create a spacial image. That information was
not, however, encoded into the recording except as temporal and level
information. No matter how that information is played back, the signal
reaching the listener cannot be the same as in the venue. Reflecting the
sound cannot, except in the context of listener preference, ameliorate
this constraint.
Keith, I'm not sure what exactly your conceptual problem is,
I'm tempted to believe you. Not convinced, but tempted. I would posit,
however, the conceptual difficulty appears to be yours.
but everyone
knows that stereo operates on temporal and level differences between
channels. You have noticed how those differences can cause the perception of
phantom images between the speakers, right? That spatial information is
encoded into the channels by means of temporal and level differences in the
signals.
Then quit asking questions like "where did the information go?". The
spatial information you are describing is left/right - that's it. That
information *is* encoded in the signal. Up/down, front/back, that
information is not present in two channel recordings. You can create an
illusion of depth and height - not the same thing.
I can't agree with you 100% here. Not the "stereo is an illusion" part. That
is certainly true enough, but the part about up/down, front/back, I have to
take serious issue with. I have been making true stereo recordings of
ensembles of all sizes and types, from small, jazz ensembles to large wind
ensembles (concert bands) to full symphony orchestras for many years and I
always use some kind of stereo pair. I either use A-B, X-Y, a coincident pair
or a single stereo mike in M-S mode. All of my recordings have image height,
and front-to-back layering of instruments. How, you ask? It's simple, true
stereo is phase coherent. It properly captures the phase relationships
between two closely-spaced microphones that tells the listener (on playback,
through speakers) that one sound is emanating from in front of or from behind
another. It can also tell via these phase cues that, for instance, the brass
are up in risers and the woodwinds are at stage level. Also, in a true stereo
recording the triangle in the percussion section "seems" to hover over that
section just as it does in a real concert hall situation. These aren't
anomalies or "illusions" as in trickery, these are repeatable phenomenon that
take advantage of the phase coherent nature of true stereo recordings and is
well covered by papers from Alan Blumlein et al.
Now, I have observed that reflecting a part of the sound from room surfaces
can cause an image shift toward the reflecting surfaces. This has a twofold
perceptual impact. One, it causes the sound to go outside the speaker boxes
and appear as an aerial image somewhat behind the plane of the speakers,
seeming like the instruments are right there in the room with you, rather
than coming from speakers.
And I have noticed that this sounds contrived, oversized, diffuse, and
not at all realistic. It is, inarguably, inaccurate since the new
spatial distribution of the reproduction cannot possibly be anywhere
close to the actual event.
This type of "slap" reflection that Mr. Eickmeier refers to tells me that his
listening room is way too live. It looks to me like he needs to add some
acoustic padding at strategic locations to knock-down this type of room
interaction.
Secondly, it causes an impression of spaciousness
in recordings that contain such information, such as correctly miked
symphonies in a good hall. Most of us have experienced this very audible
difference between directional speakers and more omni type speakers.
Yes, we have. Some of us think that's realism, some of us don't.
OK, fine, now between those two types of sound, one is likely to sound
closer to live than the other. If you think that is just a preference and
worth no further study, then that is the bed you shall l ie in.
Taking umbrage at a strawman of your construction is hardly helpful.
If I think
this is a significant point and worth further study, and try to get others
to notice these effects and help me out, then please don't tell me it is all
pointless because you are not interested.
Yet another strawman. Please provide a quote that even intimates any
such thought. As I've said, ad nauseum, and as you've ignored rather
perniciously, is that you are ignoring the role of preference, and want
to divorce it from the process. Ignoring preference is as egregious an
error as ignoring the physics or engineering involved.
Especially since the BEST we can do is so far from reality. Audiophiles tend
to gravitate to some smaller part of the whole enchilada and obsess over it
to try to get it right - often at the expense of other parts of the complete
picture. This is 100% preference. One listener obsesses over imaging and uses
small book-shelf speakers on stands because they image best, while ignoring
the fact that such speakers are often deficient in bass. Another listener
requires that the midrange be right, and the rest of the spectrum be damned.
Still another might be a bass freak with huge sub-woofers that pressurize his
listening room in what he sees as a realistic manner. To pretend that these
choices that disparate audiophiles make aren't personal preferences, is, at
the very least, an arrogant approach to the question. Were it a question of
one speaker system designed according to the precepts of one man (such as our
Mr. Eickmeier, here) then there wouldn't be thousands of different models and
designs of speakers available.
Audiophiles have been trying to
figure out what causes these effects for decades. They have complained about
boxy sounding speakers and the hole in the middle effect and wondered what
makes some systems sound more realistic than others.
And where are all these audiophiles complaining about "hole in the
middle"? I've counted exactly one...you.
Hole in the middle? Then your speakers are too far apart. Put them closer
together until the "hole-in-the-middle" disappears. Easy.
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