[Gary Eickmeier]

Andrew Haley wrote:
Gary Eickmeier wrote:

The room is 21 x 31 ft, the speakers positioned 5 ft out from the
front wall, 5 ft in from the side walls, for an image model that has
all real and virtual sources spaced evenly 10 ft apart.

The sound is as spacious as it gets, has very sharp imaging, speakers
disappearing entirely and casting a sound field behind, between, and
to the sides beyond the separation of the speakers in a way that
makes it seem like the musicians are right there with you. This is a
sat/sub system with the IMPs doing the satellite part and a Velodyne
F-1800 doing the subwoofer chores. It is balanced, full range,
spacious, and precise.

I have yet to test them against other high end speakers, but I don't
know what else a speaker can do better in any of the audible areas
of speaker performance. Frequency response, radiation pattern, and
room positioning, that's all there is, there is no more.

Questions? Comments?

Okay, I'll bite. I don't doubt that this arrangement would present a
huge soundstage. However, that first diagram, which shows laser-like
sound coming from the rear of the speakers is rather fanciful. In
reality, there will be a dispersal pattern which varies with frequency
and there won't be so much clean reflected virtual speakers as you
illustrate.

Andrew -

No, it doesn't show laser like sound coming from the rear. That is just the
ray tracing technique for showing the path of reflected sound. If you take a
look at the desired radiation pattern at the lower left, you can see how I
wanted the mid to high frequencies to launch from the speaker in order to
achieve the image model above. Low freqs are always omni. But the IMP
satellites have nothing below 100 Hz. Not sure exactly what range it starts
to take on the desired radpat, but all you can do is aim the four panels as
shown and adjust their gains and see if the model takes shape or not.


The other thing is that would worry me is that room looks extremely
lively, and I'm surprised it isn't plagued by flutter echo. Are there
some diffusers (books, etc.) on the back wall we can't see? I have a
somewhat smaller room which had similar properties, and the echo was
mostly cured by filling the back wall with books floor-to-ceiling and
some large pieces of furniture, neither of which your room has.

Andrew.

Good question, and the picture doesn't zoom back far enough to show the wall
treatments. I made a half dozen half round absorber panels and mounted them
on the side walls staggered, not directly across from each other, so that
the laterals would be broken or absorbed before being reflected once again.
There is more and more absorption as you go back, so that most lateral and
diagonal waves will not return to be reflected again. Bottom line, there is
no flutter echo, as indicated by clapping my hands anywhere in the room.
Reflectivity is desired in the front of the room for creation of the model,
which is basically the big secret of most dipoles, bipoles, and omnis. Very
spacious sound with speakers disappearing and leaving nothing but the music.

The caution with reflecting type speakers is that the speakers MUST be
positioned very precisely or else they will lose focus. If those reflected
(virtual image) speakers are not evenly spaced you will get stretched
soloists and no center imaging. If any one of the elements of the model is
missing, radiation pattern, speaker positioning, and room acoustics, you
could miss these qualities and never discover all of the factors of stereo
imaging. I stumbled upon it by accident, then pursued the idea until I
finally figured it all out and had these built to do the concept on purpose
rather than by accident! The whole room was designed around the theory about
25 years ago, and now I am finally there!

Gary Eickmeier