[KH]

On 6/9/2012 2:09 PM, Gary Eickmeier wrote:
To the group:


snip

If you and I disagree about which grape is the most realistic, is one of
us wrong? If you and I disagree about whether a specific stereo
implementation is realistic or not, is one of us wrong? If your answer to
either question is "yes", further discussion is pointless as you're now in
the realm of ideology not acoustical theory.

OK, you are saying designing or selecting speakers is like selecting ice
cream flavors at Baskin Robins. Well, I have another analogy for you, and I
think it is quite apt.

No, I did not present an analogy. I asked a very simple, probative
question and your analogy does not address it. Why continue to duck the
question?

I have said that the stereo signal is a concentrate, to be mixed with the
playback room acoustic in a certain way, a way that models itself after the
real thing.

That you have *said* in no way makes it valid.


snip
(where did the recorded ambience info go)

It got converted into two dimensions. Basically, level and arrival time.
How do you think incident angle information is coded into the signal?
That's the HRTF information that is lost in the process. Not because it
wasn't in the venue, and not because the microphone didn't pick it up, but
because it was transduced using a very different instrument than WE use to
hear.

Here you have a technical misconception.

No, here you have a communication issue.

Stereo has nothing to do with HRTF.

As has been stated repeatedly. You asked "where did the recorded
ambiance go?". The answer is that the "ambience" is related directly to
the HRTF of the listener in the venue. Sans listener, there is *ONLY*
temporal and level data available for recording, and when recorded as
such, this data cannot subsequently be used to accurately reproduce
incident angle information. That information is lost in the translation.

That is a binaural, or head-related, process. With stereo, a field-type
system, we are reproducing the object itself in front of us and using our
own natural hearing mechanism and HRTF to listen to it.

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.

snip

OK, here comes my main point of this whole discussion, my "closer."

We have discussed all of the audible parts of the listening experience in
the EEFs, What Can We Hear. We said that the spatial part is the main
stumbling block, the main difference between the reproduction and the real
thing. Think of it as pure physics.

Feel free to present some, please.

If the spatial qualities I discussed are
audible, then we must make some attempt to reproduce them.

We can't reproduce them, they are not on the recording. What we can do
is to produce an illusion, the efficacy of which is clearly a function
of both engineering efficacy and listener preference.

The "real thing" comes to us as a primarily reverberant field from a
multiplicity of incident angles.

No, it does not, except in a narrow subset of live events. Many times
the direct component (lets think of outside live events for example,
shall we?) is the dominant component, and sometimes by wide margins.

The reproduction comes to us from just those two points in space.

That difference is seriously audible; they CANNOT sound the same. This is
not a matter of taste, it is a fundamental error in the theory of
reproduction.

It is not an *error* in theory, it is a physical constraint. You need to
understand the difference. The fact that the reproduction cannot be the
same as the original necessitates that listener preference play a
pivotal role in assessment of the realism of the reproduction.


What to do, what to do? Look at the spatial problem from the standpoint of
the image model of the real thing and the reproduction. If you can separate
out in your mind the spatial from the temporal for a moment,

The distinction is clear in my mind, but that differential information
is not present on stereo recordings. You need to clarify, in your mind,
that there is no spacial information in a stereo recording. All spacial
clues are translated to temporal and level information. If you disagree
with me, then pray tell me, what portion of the recorded electrical
signal - which is all we have after all, come reproduction - represents
spacial information, *separate and unique* from temporal or level
information?

and if the
recording really does contain some of the early reflected sound from the
venue,

It does contain it; translated into TEMPORAL and LEVEL information.

then it is more correct to reproduce that part of the sound by
reflecting it from the similar surfaces in your listening room.

You are not reflecting *that part of the sound*, you are reflecting ALL
of the sound, and in doing so, you reflect the DIRECT portion of the
signal as well. That is clearly inappropriate - it doesn't come to you
that way in the venue does it? If the spacial is as important as you
maintain, then reflecting the direct portion of the signal is at least
as egregious an error as ignoring the reverberant part of the signal.

Keith