[Gary Eickmeier]

Peter -

Without re-quoting the entire thing, which is available above obviously -
another great and interesting post. But let me concentrate on just one
aspect of this speaker-room interface problem.

Most (normal) audiophilles who haven't studied all this will not know the
difference between the "spatial" and the "temporal" characteristics that you
discuss. But we must differentiate the two because the spatial is the much
more important and audible one that has not been studied enough. The spatial
means the angles from which the various sound fields arrive at the listener.
For example, the direct comes straight from the instruments (or speakers),
the early reflected comes from a much wider and deeper set of reflections
from the soundstage area but with a significant and important time delay,
and the reverberant comes from all around, evenly, with (hopefully) a smooth
decay to inaudibility, considered to be 60 dB below the loudest sounds. When
we record we should try to record not just the instruments but also the
early reflected sound as part of the whole soundstage, helping to flesh out
the full sound power of the instruments and giving us the timbre of the
instruments and the perception of spaciousness that we hear live.

This perception of spaciousness - very important to stereo and the musical
enjoyment, live or reproduced, is caused by the physical placement of those
recorded reflected sounds from angles that are similar to the original. I do
it by reflection, but you could do it with extra speakers placed near the
front and side walls of a smaller room. Anyway, it is the directions from
which those sounds arrive that is involved in this perception of
spaciousness. This cannot be reproduced by the direct speakers no matter how
good they are, it must come from the radiation pattern by means of
reflection or from those extra speakers.

OK, so the temporal aspect is also important, but it does not come from the
temporal delay of those reflections we were just talking about above. It was
actually contained in the recording, both the delay of the early reflections
and the full decay of the reverberant field. You will often see the
criticism of a direct and reflecting type of speaker that our home rooms
are not as big as the original, so it can't work. But now I hope you (all)
can see that if we address the spatial part, the temporal will take care of
itself.

Moral of the story, we must learn to separate in our thinking the spatial
from the temporal characteristics of sound fields.

Gary Eickmeier