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"KH" wrote in message
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On 11/8/2013 8:07 AM, Gary Eickmeier wrote:


radiation patterns of the speakers

Gee, where did this happen? Did you invent the piano speaker, bass
speaker, and drum kit speaker? This isn't feasible. Nonetheless, let's
assume you have these perfect speakers for discussion purposes.
-
what do you know - zing ping pow happening all over again right in your
room! The drum sound will reflect off the front and right side walls, the
bass off the left walls and the piano will remain mainly centered.

Well, let's do a bit of an arrival timeline here. Let's say that in the
new room, the smaller playback room, that new room first arrival and new
in-room zing ping and pow are now only separated by 0.2ms. So what
happens when you play back in the room? Let's see, to be simplistic, you
play one pure tone from each "instrument", in sync.

Sorry, I don't want to trash all of your work on the X, A, B, C diagram, but
I'm getting Deja Vu all over again here.

I said that all of the foregoing just scratches the surface, so permit me to
elaborate just one more level.

There are two stereophonic recordings being made at the live event. One, the
direct sounds and their directions, left to right. Two, the reflected sounds
have been recorded in stereo as well - as you have agreed. Both the
directions and the timings of those reflections, plus the reverberant tail
as the sound dies out during the reverb time of the hall.

No, we cannot find enough channels to do each reflection with a direct
loudspeaker, nor could we do a new setup for every recording. What is
important to audibility is that these reflected sounds NOT come from the
same directions (sources) as the direct sounds that were recorded. This is
why you cannot just wipe out the room and listen to the speakers only, in
near field or any other manner.

Nor is it necessary to have precisely the same radiation pattern as each
musical instrument - just a general pattern will suffice, one that is
oriented toward the model, not the live sound itself, in a general way, not
for each instrument and each recording.

The main requirement is to get the spatial patterns more correct and
separate the later arriving reflected sounds from the first arriving direct
sounds. This will be done simply by time delay. In the model, a matrix of
real and virtual speakers is set up equidistant from each other such that
the loudnesses of all 8 of these sources is about equal and there will be a
summing localization among them all, in depth as well as width, so that the
recorded sounds come from a region within this structure somewhere behind
the plane of the real speakers and from wall to wall in width. This
structure, a spatially arrayed, temporally delayed, spectrally shaped sound
field simulator then becomes the "canvas" on which the recorded sounds can
array themselves.

The main point is that the reflections from the recording come from correct
spatial angles on playback, which MUST be different from the direct sounds.
Your whole timing discussion is mostly irrelevant to this spatial
requirement. The fact that the timings of the reflections in your room are
shorter than those in the recording matters not. Those timings remain as
recorded, but now come from spatially similar angles during playback if
properly recorded.

At this point you declare that Eickmeier is full of it once again, because
there is no way to separate out the reflections from the direct sound in the
recording in order to make this fantastical model work. You would be wrong.

It is all done with time delay. Much like a Hafler or Dolby Stereo playback
system can extract the ambience from a recording and wrap it around to the
sides and rear, the time delay of the reflected sound in your room can
decode the reflected in the recording for the frontal soundstage. How? There
can be only one first arrival, and that HAS to be from the actual speakers
in the model. Later arriving, longer duration sounds will come from the
virtual sources or reflections in your listening room if the balances are
all about right.

The audible result is that for tight dry recordings with none or little
reverberance contained in them, the direct sounds just take on a harmless
image shift toward the reflecting surfaces and form themselves as an aerial
image slightly behind the plane of the speakers. More reverberant recordings
take on the spaciousness and depth similar to the live situation and for
similar reasons. As long as zing ping pow happen within the fusion time, we
perceive them as part of the direct sound but with the spatial signature of
the model, which has been designed to be similar to the live model.

Probably a few gaps in all that, but I am tired and at least I tried!

Gary Eickmeier