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the recent 2-channel 3D sound formats and their viability for actual f
BearcatSandor
post Jul 13 2011, 18:54
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(I posted this on the [SurSound] list but i'd like to get more takes on it.)
I'm interested in the idea of 360 horizontal surround sound but more interested in a sphere recreation.
-------------
Folks,

I've been reading up on the various proposals for 3D sound from a set of
stereo speakers. The 3D Audio Alliance is working on such a system.
Astound Surround is getting ready to market, Edward Choueiri is working
on the same idea (see:
http://www.studio360.org/2011/apr/29/adventures-3d-sound/ ) and there
are others. I used to have a Carver pre-amp with Carver's Holography
button but i could never get it to do much.

Has anyone heard a truly 3D/360 surround effect from 2 speakers using
this stuff? Ever heard a fly buzzing around your head, or an object in
the back far-left of you or some such? Can any of this do as good of a
job as Ambisonics? Is all of this just related to head transfer
function mathematics?

I've listened to some of the headphone applications of this like
binaural and whatever these folks are doing here
http://www.3d60.co.uk/index.php That demo on the 3D60 page sounds
really cool, however nothing ever sounds like it's more than a foot from
my head and nothing is ever right in front of me. Why can't they create
an effect of something coming from a long distance away and getting
closer and closer behind me? If it's all related to head transfer
function you'd think you could create any sound your ears can hear.

I'm looking at my audio system building options and I'd love to throw my
money/space decor at 2 really good speakers and a good 2 channel pre-amp
instead of 12 speakers in an ambisonic system with all the associated
electronics.

Any thoughts on all this 3D through 2 channel stuff?

Thanks,

---------
Further thoughts i've had are that i don't understand how this works given crosstalk, the differences in everyone's rooms, the differences in everyone's hearing, outer ear/head shapes ect. If this is relying on head position to create the same sounds as they would be after HRTF isn't that one hell of a sweet spot?

In review (and i've only read one) of the system put out by the 3D Audio Alliance the person listening to it described hearing the sound of a dog off to his back right. From two speakers. That's really awesome..if it works.

Bearcat


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Music lover and recovering high end audiophile
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BearcatSandor
post Aug 1 2011, 06:45
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That was a very informative post. Thank you. I used to have a Carver pre-amp with the "Sonic Holography". I couldn't get it to do much either.

One thing that i don't understand: recording engineers must be taking the cross-talk into account when they record things, right? So if you reduce the cross-talk, aren't you messing things up further?

I donno wether "3d" recordings are done with out any crosstalk or how they differ in that regard.

This post has been edited by BearcatSandor: Aug 1 2011, 06:46


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dc2bluelight
post Aug 1 2011, 08:13
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QUOTE (BearcatSandor @ Aug 1 2011, 00:45) *
That was a very informative post. Thank you. I used to have a Carver pre-amp with the "Sonic Holography". I couldn't get it to do much either.

The "Sonic Hologram Generator" was very sensitive to acoustic issues. If you had a really good room, it was spectacular, but didn't work at all in a bad room.
QUOTE (BearcatSandor @ Aug 1 2011, 00:45) *
One thing that i don't understand: recording engineers must be taking the cross-talk into account when they record things, right? So if you reduce the cross-talk, aren't you messing things up further?

I donno wether "3d" recordings are done with out any crosstalk or how they differ in that regard.


The monitoring environment in a mixing room is fairly standard, though hopefully attention has been paid to acoustics, in particular early reflections which strongly degrade a normal stereo image. Since acoustic cross-talk is a fact of life, especially in two-speaker stereo, it's not compensated for during the mix. A good mixing engineer knows that proper acoustic cross-talk compensation is highly situational, and it does little good to try to deal with it at all in the mix. It's assumed the target audience will have the normal acoustic cross-talk issues.

Some 3d sound processing has been done during mixdown. It's usually an "effect", a temporary one. I have a CD with one track where 3D sound processing was used. Frankly, I never even noticed it until I read the booklet notes! It's a fine line between making a 3D effect "noticeable" to everyone, and making it overpowering, which is why it's hardly ever done in the mix, but is better applied as a playback function. However, this makes precision 3D placement and panning impossible.

But, to the rescue comes multichannel audio! A 5.1 channel system adds a tremendous amount of dimensional capability. These days there are millions of 5.1 channel systems in homes, most of which are never used for music only entertainment. But 5.1 music is really very good.

But lets not stop at 5.1. It seems every time the channel count is doubled (or slightly more than doubled), every listener can hear the difference without question. Enter 10.2, and it's outgrowth 11.2. To gain true 3D dimensionality, yet retain a huge listening sweet spot, you have to add channels and speakers. Systems like Audyssey DSX, with three front channels, plus two wide channels, plus two height channels, then the usual surround compliment really does succeed in presenting a fully dimensional acoustic environment. Yes, it's impractical. 5.1 is impractical too, but we do manage it because it's clearly an improvement over 2 channel. Currently, Audyssey DSX is a synthetic post process, as there is no true 11.2 channel material easily available. However, BD has the capability of lots of high bit rate, uncompressed audio channels, and the players are now connecting to existing systems. There's your delivery medium, and your reproduction system. All we really need is the content, and a nice way to fold 11.2 channels down to 5.1, which as I understand it, DSX is all set to do.

So, the problems with 3D audio systems from two speakers are: a narrow listening window, poorly controlled directional placement, somewhat random amounts of reproduced 3D effects due to system design and acoustic issues, and more. Multichannel systems solve the listening window issue, the placement issue, are consistent, easily auto-calibrated, and much more immune to acoustic issues.

I doubt 3D from two speakers will ever really be widely accepted. But 20 years ago there were only a few home 5.1 systems. Today there are millions, and thousands of 7.1 systems, with numbers growing all the time. Though none of these concepts, 3D or multichannel, present true "sonic holography", the multlichannel approach is, for the foreseeable future, the only reliable and practical way of presenting 3D sound at home.
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