The IMP Arrives
The whole theory requires a certain speaker positioning scheme (1/4 of the=
=20
room width in from the side walls and out from the front wall) in order to=
=20
keep the reflected images from clustering together in an uneven manner to=
=20
destroy the lateral or depth imaging. If you draw an image model of that=20
positioning scheme you can see what I mean. My room for example - it is 20=
=20
ft wide, so I place my speakers 5 ft in from side walls and out from front=
=20
wall and that makes all real and virtual image speakers exactly the same 10=
=20
ft apart from each other.=20
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Interesting. Back in the day when AR had their listening room at Grand Cent=
ral Station, they handed out literature by the ton, and spec. sheets by the=
freighter-load. Remember one could not purchase anything there. One thing=
they handed out was a white-paper on speaker placement with all sorts of t=
ips and tricks based on many often-not-considered stuff. And it should also=
be understood that AR put a center-channel output on their receivers as ea=
rly stereo recordings often greatly exaggerated separation. This is somethi=
ng of a nested issue - center channel/stereo, as even in the mid-late 1960s=
, the concept of 'stereo vs. mono' was as much a hot issue as the concept o=
f CD vs. Vinyl is today.=20
In any case, and highly distilled, AR posited that speakers should be place=
on the long wall of any given room, with one speaker being somewhere betwe=
en the 1/4 and 1/3 points, the other placed asymmetrically to it about half=
-way between the first speaker and the far corner. Then, the speakers were =
to be moved closer together until the best sound-stage was achieved - but s=
till kept asymmetrical to the corners. After which, at that point, they wer=
e to be moved as a fixed pair closer to or further from the nearer corner u=
ntil the best (clearest) bass was achieved. Oh, and the woofer centers were=
to be at least two woofer diameters from the floor. The backs were to be a=
gainst the wall. At no time were the speakers to be symmetrical about the l=
ong wall.=20
I have done that with my 3as (also driven by an AR receiver), and I will st=
ate for the record that even moving the pair (or either one) by a few inche=
s is easily perceived. We have a three-person couch facing the speakers abo=
ut 10 feet away, and the speakers are about 8 feet apart on a 17 foot wall.=
(room is 17 x 14 x 10). This is the "wife-friendly" stereo. All self-evide=
nt controls and very few of them. But the sound at either end of the couch =
or either flanking wing-back is quite remarkable. The two wing-backs and th=
e couch describe the same virtual ellipse I noted previously.=20
So, I am quite sympathetic to how sensitive any system might be to speaker =
placement, and most especially to reflections and refractions as created by=
room acoustics, materials and even canvas vs. glass-front paintings on the=
wall. Controlling all the variables is the key, and you have apparently in=
troduced many more potential variables with, I am guessing the potential fo=
r much better results if those variables are controlled adequately. What ha=
ppens if those speakers are in a more difficult location? Do they have basi=
c requirements such as minimum distances from a wall? Must they be symmetri=
cally placed or is there sufficient adjustment that they need not be?=20
Again, I see transducers in general and speakers specifically as about the =
last frontier of audio. Amplification is pretty much 'done' since the 60s f=
or tubes and the 80s (a stretch, probably the 70s) for solid-state. Vinyl, =
Tape, CD, whatever are also pretty much done. Speakers and cartridges. Spea=
kers everyone needs. So, if you do have a cutting edge design that also suc=
ceeds in its intent, that would be truly remarkable.=20
Peter Wieck
Melrose Park, PA
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