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Why do some speakers produce holographic stereo and why others don't?

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dknguyen

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Your question is flawed to begin with because it is based on the premise that speakers are the only factor involved. There are many other confounding factors like the rest of the equipment, placement, and room treatment.
 

rjenkinsgb

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I think it down to the cabinet they are in rather than the speakers themselves..
I'd say that plus having the speaker cabinets far enough away from the listener so they are no longer perceived as individual sources.

No matter how well any system is set up, if you get too close to any single speaker your hear that as a direct source.
 

kubeek

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What is a holographic stereo speaker? Have you encountered speakers that even though they produce audio, they create a visual hologram in mid air?
 

rjenkinsgb

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What is a holographic stereo speaker?
It's a silly name someone came up with, probably for advertising.

It basically means something like, you can hear the stereo (or surround) sound field with the sources (instruments & vocals etc.) in whatever relative positions across that, without the speakers themselves appearing to be direct point sources.

Pretty much any good and properly set up stereo or surround system in other words.
 

alec_t

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What do you understand is the difference between normal stereo and 'holographic stereo'?
 

AnalogKid

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They don't, it's just a stupid advertising gimmick.
No, it's a real thing. Actually, it's a mind game that mimics the real thing. And, as above, it has nothing to do with the speakers. The physics and psychology are very well known, and documented in both peer-reviewed scientific journals and patents.

The round hole in a guitar is a version of a "Helmholtz resonator", named after a *really* smart guy in the 1850's. His protoge was the father of experimental psychology, and performed the first laboratory-controlled investigations into acoustics and hearing perception. Modern psycho-acoustic experiments date back to the 40's, but Bob Carver brought things out of the lab in the 70's with some of his high-end stereo gear. He had a demo box at the Consumer Electronics Show with a switch, and you could select the acoustics of 4 or 5 famous opera houses around the world when playing back a record. Of course no one knew if the replicated acoustics were accurate to those houses, but there definitely were differences among the options. Bob called this "Sonic Holography".

The overall effect is built on a combination of delays, frequency-shaping filters, and selective combining of the two channels. I think National Semiconductor had a chip for this, and Sanyo or Panasonic almost certainly did. I have an old, small Panasonic boom box, medium-priced at the time, that has a switch marked "Mono", Stereo", and "Stereo Wide", and the little puppy really does expand the perceived stereo image.

Separate from this is "matrix audio", where multiple physical audio channels are encoded at the source into two signals that are then decoded back into the original channels in the receiver. This is a much more complex process and is not always fully backward-compatible with standard two-channel analog stereo that Blumlein invented in 1931.


ak
 
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audioguru

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When stereo speakers are spread apart properly and the signal has good stereo separation then I can hear with both ears left, right and all sound positions in between. With only one ear I do not hear stereo.

With two eyes I see near, far and all object positions in between. I do not see positions with only one eye.

When I first heard surround sound and saw a 3D video I was amazed.
 

crutschow

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If you are interested in learning about reproducing stereo sound with an accurate soundstage and minimum room interaction, where the speaker's location becomes not apparent, then read the articles and speaker designs for that by Sigmund Linkwitz.
No gimmick circuits or signal processing are involved.
Next speakers I build will be a pair of his LXmini speaker designs.
 
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What is a holographic stereo speaker? Have you encountered speakers that even though they produce audio, they create a visual hologram in mid air?
What do you understand is the difference between normal stereo and 'holographic stereo'?
It doesn't show visual hologram in mid air but you can feel depth(in addition to width) of instruments and their placement on y and z axises. Normal stereo is spread on x axis.
 

shortbus=

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The round hole in a guitar is a version of a "Helmholtz resonator", named after a *really* smart guy in the 1850's
While he got the name it was used back farther than that. Don't remember if it was Greeks or Romans that used many different size clay jars placed in certain spots in their ampitheaters The jars made speech so it was able to be understood in the whole area.
 

AnalogKid

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While he got the name it was used back farther than that.
True. What Helmholtz did was work out the math that makes it work, and made it possible to *design* one with specific performance characteristics rather than just use trial and error.

ak
 

rjenkinsgb

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That's pretty much the "expanded stereo" effect that stretches the sound field beyond the width of the stereo speakers.
It is quite a common option with ghetto blasters / boom boxes, as the speakers are so close together.


Separate from this is "matrix audio",
eg. Dolby Pro Logic encoding, for the commonest one.
A very large percentage of "stereo" audio is actually surround encoded; TV, movies and music - I reckon once the various studios set up for surround when Quadraphonic LPs were introduced, they kept the surround gear and just switched to using Dolby analog encoding when that became available.

It's extremely obvious on a lot of music going back decades, when played through a pro logic surround decoder.
And obvious on tracks that don't have it, the rear speakers stay near enough silent..


That is a totally different system to Dolby Digital and the analog surround encoding is even retained in MP3 stereo audio files.
 
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