OB speakers and room acoustics

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Markus,

Nice pictures. But this is not Magic Eye picture.

Magic Eye picture is single flat image which both eyes view entirety. Depth cues exist, and our perceptual process is well equipped to extract them. Picture is construction, as is a stereo recording. In stereo over loudspeakers, both ears hear entirety of sound, and perceptual mechanism is well equipped to construct image of performers and space.

These are linked images from: Easy Stereogram Builder


8364.jpg


8213.jpg


8677.jpg


These images hold much in common with stereo sound. The further back that image is viewed from, the greater the depth. Small motions of head left and right cause similar shifts. Rotations of eyes too far from horizontal plane cause image to collapse.

Casually looking at flat image is akin to casual music listening. Engaged viewing is akin to listening from sweet spot.

Viewing discrete stereo pictures via cross-eyed technique is akin to listening to binaural recording over loudspeakers. Viewing with stereoscope is akin to listening with headphones.
 
Failure of speakers to control early reflections from within, and from diffraction cause imaging degradation that in Magic Eye picture would be adding offset ghosts to images, which would impact recovery of the intended elements, ranging from partial collapse as when eyes are tilted out of horizontal plane, total image collapse, or to partially merged/overlapping image elements.
 
Well, the problem is that binaural information in stereo recordings is missing or distorted. It doesn't allow our brain to reconstruct a three dimensional image of an "atomic lattice", "chess board" or "monster hunting a girl". If you do get a three dimensional perception from stereo then it's either binaural information that was deliberately added (see QSound), unintended distortion or spatial infomation from listening room reflections.
 
No, that's not what the data shows

It does show that
The five-channel arrangement described in ITU-R BS.775-2, shown in (i), performed about as well as any other confi guration.

ITU 5.1 performs about as well as any other configuration, meaning it is not worse than other configurations but also that is not the best configuration.

4 frontal speakers seems to be the best.

So, why would anyone be using 5.1 configuration for music reproduction.


- Elias
 
ITU 5.1 performs about as well as any other configuration, meaning it is not worse than other configurations but also that is not the best configuration.

But you claimed "no better than average" and "average" in that diagram would be worse than b, c, d, e and i.

4 frontal speakers seems to be the best.

No, b, c, d, e and i are equally good when only LEV is considered.

So, why would anyone be using 5.1 configuration for music reproduction.

Because you can add LEV and have sound sources behind the listener at the same time. 4 speakers in the front can't do that.
 
fig (b) and (d) give nearly the same result? :confused:
Yes, 60° forward seems to be as good as 60° backward. If we don't mind the "contralaterality", "d" is like the second approach of Markus in http://www.diyaudio.com/forums/multi-way/235200-ob-speakers-room-acoustics-11.html#post3488613
a lateral reflection is as good subjectively as a rear discrete source? but.. what about delays then?
We don't get the "right" delay for sure, but Markus' approach should give him some delay at least. :)
If we only look at LEV, then yes. ...
... I was talking about the difference in "field of view". Our hearing picks up sounds from everywhere whereas our sense of sight gets "only" the frontal hemisphere.
And I was just looking for LEV enhancement with the front channels only. ;)
Even if sounds solely coming from the frontal hemisphere would suffice for realistic music reproduction, stereo still is limited to two single directions, ±30°.
With OB speakers and room acoustics (isn't that the thread title? ;)) we can stretch those ± 30° a bit to ±45°. From what I hear in my room, my approach doesn't compromise the resolution in the ± 30° area, but expands (while blurring) the information at 30° left and right to the outside.
 
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I have my dipole speakers at ±45° instead of the typical ±30°. The gives almost 50% wider soundstage. In addition, my impression is that the soundstage extends somewhat outside the speakers as well, resulting in almost an 180 degrees full frontal hemisphere. I think that's pretty cool.

In my home theater I have a full 5.1 setup, but the soundstage is not much wider there than with my stereo.

My humble tip of the day is to try a much wider setup than the classic ±30°. :)
 
My humble tip of the day is to try a much wider setup than the classic ±30°. :)

Currently have my speakers at the side walls which results in an opening angle of ±40°. Speakers are 3.25m from the listening position and spaced by 4.20m. That configuration always results in a very realistic and natural sounding auditory scene. Not sure why - the reflections in the recording coming from psychoacoustically more effective angles, the specific room reflection pattern or the size of the stage? Maybe all of it. Anyway, for me this works with very different speaker concepts and radiation patterns.
 
Speakers are 3.25m from the listening position and spaced by 4.20m. That configuration always results in a very realistic and natural sounding auditory scene.

with such a wide separation I bet it is! the reason I went back to 30° was because I do not have enough space to keep everything into place with 45°. But that may change again, who knows..
When I tried two flooders "a la Graaf" separated by 5m, I could well notice an improvement on some recordings that do beg for a wide stage. Now, 4 or 5m with a dipole+reflections means a huge room, back into the dilemma again.. :(
 
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