Mike:
All current recording/playback systems, be they stereo or surround, have a
defined sweet spot and most require the listener to face forward or nearly
so.
In general, the size of the sweet spot is inversely correlated to the
accuracy of the imaging of discrete sound sources (such as singing birds).
In other words, a system with a large sweet spot will usually have poor
imaging and a rather diffuse sound field where discrete sound sources such
as birds are not easily located in space, but still there can be a very
satisfying sense of spaciousness. In contrast, recording/playback systems
with small sweet spots often have excellent imaging along with lots of
spaciousness . . . but the price that is paid is the small size of the swee=
t
spot.
While the quad-type surround I have described still has a defined sweet
spot, it at least allows the listener to turn in different directions and
still experience a stable soundstage, where discrete sources remain in thei=
r
proper positions. The Cooper-Bauck and related crosstalk cancelling
techiques have small sweet spots and if the listener turns his head much
over 30-45 degrees to either side, the soundfield collapses. This is not so
terrible in light of the fact that conventional stereo also requires the
listener to face forward.
Lang
> Lang Elliott wrote:
>
>> The Cooper-Bauck method is one of a number of techniques designed to red=
uce
>> crosstalk for speaker playback of binaural recordings.
>> There is a great discussion of this in Part 2 of the following article:
>> www.harman.com/wp/pdf/HowManyChannels.pdf
>
> Which has this paragraph:
>
>> In the 1980=B9s Duane Cooper and Jerald Bauck focused on the
>> original problem of accurate binaural playback and developed
>> a series of improvements that made speakerbased listening more
>> practical and economical. These patented innovations resulted
>> in a system that is simpler to implement than the Atal and
>> Schroeder original, that is less demanding of the listening
>> environment, that is more tolerant of head movements,
>> and that degrades =B3gracefully=B2 as the listener moves
>> out of the sweet spot. ...
>
> I just played back some of the demo and tried pivoting on
> my chair and notice what happens to the image when the axis
> of the ears is parallel to the center axis of the speaker
> pair. The illusion of wider-than-the-speakers soundstage
> disappears. A little front-back discrimination remains,
> but it sounds like it's coming from a pair of loudspeakers
> off to the side. Rotating 180 degrees restores some of
> the soundstage imaging, but it is not as convincing as
> facing the speakers, and not as wide.
>
> Thinking about how the crosstalk cancelation works, the
> 90 degree rotation would require a different set of
> cancellation corrections -- nearer and farer instead of
> left to right. I suppose it could be done, but anything
> that's based on listener position and orientation really
> isn't reporducing the original soundfield in the listening
> space.
>
> -- Mike
>
>
>
> "Microphones are not ears,
> Loudspeakers are not birds,
> A listening room is not nature."
> Klas Strandberg
> Yahoo! Groups Links
>
>
>
>
>
>
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