[Gary Eickmeier]

Peter Wieck wrote:
Gary:

You mention the Bose and DBX speakers as your springpoint - I will
not insult you by suggesting they were your inspiration. It has been
my experience with a number of speakers of (mostly) conventional
design that what arrives at one's ears is perhaps, and at best, a
third-cousin to the live experience, and for any number of obvious
reasons. fixed-point microphones for the most part do not sit where
one's ears sit, nor do any given pair (with a few deliberate
exceptions) sit so either.

Nor does the typical conventional speaker duplicate the original
sound producer. A piano string may be from a few inches to several
feet long, be made of drawn, hardened steel and often be wrapped with
hardened brass wire. This is hardly duplicated by a speaker coil
which, at best, might be in the 12" - 14" (diameter) range. Further
to this, each producer has its unique characteristic, all of which is
co-mingled by the reproducer.

Nor does the typical speaker duplicated the subtle, for lack of a
better term, "elliptical" nature of live sound. As an analogy,
consider even a small orchestra of perhaps 10 instruments. One sits
in an audience dead-center (such as the 'ideal' (term used very
loosely) listening room) to the orchestra and one is just as far from
the base viol as from the brass. Put a virtual thumbtack on each of
those instruments, and extend a string to each of your years. Draw it
across the back of each tack so it is a complete loop from each ear
to the instruments, then across the orchestra. If one now moves off
dead-center, the string will slide and your ears will describe an
ellipse. Hence the term. And, the basis of the much-misunderstood
term "soundstage".

A properly designed performance stage will not be subject to
standing/interference waves as might a poorly designed stage - and
back in the day (dating myself here) I was exposed as a grade-school
student to the teething problems of Avery Fisher Hall at Lincoln
Center - all kinds of interference and standing waves - and where I
first learned of the term and began to have the inklings of
appreciating good sound. This cannot be said of the typical
rectangular listening venue. Which _WILL_ have such issues even if
identified and minimized by good placement, design and other means.

This is a long way of stating that I am fascinated by your design and
how your longer-term impression of their performance has evolved. A
few years ago, when we moved into our "new" (built in 1890) house, my
wife graciously permitted me to 'set up' in the largest room the
library, 16 x 28 x 10. Walls are plaster, floor is hardwood, four
french doors, lots of glass. The two short walls are mostly shelves,
there is a fireplace. The furniture is soft and there are Afghan
carpets on the floor. In any case, she also permitted me to install
Maggies - the MG-IIIa as it happens, rebuilt to as-new specifications
and with new ribbon tweeters. Pretty amazing beasts. And the closest
thing to a live experience I have been able to produce outside of a
pair of first-issue AR9s that left me when we moved into our previous
house with no possible venue for them. Most of the appeal with the
Maggies is that I may sit in any number of places (imagine that
ellipse) with about the same sense-of-place one gets in a moderately
sized concert venue moving about the 'house'. The volume equals the
virtual 'string length' if you will, so that sense of place/movement
about the stage is much greater at lower volumes than higher. I see
that you have set up a 'sweet spot', something that Bose (at least)
advertised early on as being unnecessary with the 901 design. How
does your set-up respond to more than one listener, or perhaps even a
few of them not sitting on the ideal arc? That, to me, is the single
largest problem with so-called 'high-end' installations. They are
designed around a single head at a single position at a given
distance and height. Not very user-friendly and in my *opinion* far
too high a price to pay for a perhaps dubious result. Although you
do seem to have such an installation in place, perhaps your speaker
design is to increase your options? Might that single chair evolve
into a couch?

Thanks in advance!

Hi Peter -

A most interesting post. I can't answer it all at once, here, but permit me
to give the basic idea or ideas.

First and foremost, I wrote a paper in 1989 (An Image Model Theory for
Stereophonic Sound) in which I tried to relate my discovery that stereo
doesn't work like most of us seem to think, by the lateral localization
alone setting up an "image" by fooling your hearing mechanism into hearing
"through" a large portal into another acoustic space. In my paper I proposed
that stereo is rather a "model" rather than a picture, a model that is
reconstructed within your listening room. This model is composed of the same
parts as the live model, namely a number of real (direct) sound sources
placed upon a model soundstage, surrounded by several virtual images of
those sources as reflections from the other side of the nearby walls. This
is nothing unknown to architectural acoustics, but describing stereo as
working like that is rather different and revolutionary in hi fi circles.
Bose proposed the same effect, but explained it as an "enhancement" more
than a whole new theory of sound, which called for a new approach to our
thinking about stereo theory. The DBX Soundfield One was a refinement on the
direct field portion of the model, which proposed a certain radiation
pattern that could stabilize the central imaging with what is now called
distance/ intensity trading which makes the farther speaker louder to
balance out the nearer speaker's closeness and move the image back to
center.

The whole theory requires a certain speaker positioning scheme (1/4 of the
room width in from the side walls and out from the front wall) in order to
keep the reflected images from clustering together in an uneven manner to
destroy the lateral or depth imaging. If you draw an image model of that
positioning scheme you can see what I mean. My room for example - it is 20
ft wide, so I place my speakers 5 ft in from side walls and out from front
wall and that makes all real and virtual image speakers exactly the same 10
ft apart from each other.

My room surfaces near the front are specularly reflective (another
difference from standard thinking) but with more absorption and diffusion as
you go back into the room. The direct to reflected ratio is adjusted to more
in the reflected domain, until the imaging "pops" outside the speakers
themselves and they disappear, leaving only the soundscape which extends
from wall to wall, across the entire front of my room, rather than just
speaker to speaker. NO sounds are EVER heard to be coming from the speaker
boxes themselves, an artifact which destroys the suspension of disbelief for
me. The worst speakers suffer the imaging of the extreme L or R instruments
collapsing to the speaker grills.

If you think about it, your Maggies have most of these same properties if
you position them correctly and aim them to cross in front of you, so that
if you move left of center the right speaker gets louder, and so that the
backwave is sent deep and wide, returning to you from front and side walls
as a massive secondary reflection from the corners, delayed more than 10 mS.
When the delayed sounds are done by reflection like this, the perspective on
the instruments changes as you walk around the room, just like a mirror
image would change visually.

This is pretty much my "ultimate" design, taking in all of the factors that
are audible about speaker reproduction. These are radiation pattern and
frequency response, positioning in the room, and power, or dynamics
achievable. There is nothing more you can manipulate about speaker sound in
rooms*. Not all speakers up to this point have done that, and no other
speaker in the world has this particular radiation pattern, nor does anyone
else say much about speaker positioning except as relates to frequency
response, which is not the basis of speaker positioning but rather imaging
should be the only criterion. I also use surround sound in my playback,
again under the principle of reconstructing all of the sound fields within
my room to mimic the live fields as much as feasible.

So yes, my longer term impression is still holding, but I still need to get
some people in here to give me their impressions and to get some other
speakers to compare them with in an AB fashion.

* The only other factor is room size, a larger room sounding more like the
original because tghe model is more like the size of the original.

Gary Eickmeier