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Beyond stereo?


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1 hour ago, gmgraves said:

I'm afraid that you are wrong sir. A pair of the right mikes in the hands of someone who knows what they are doing, are very much "adequate". And I have made enough recordings using only two mikes to know.

Right, if I got to grade all my own tests I'd be a straight A student. ;)

2 mics are woefully inadequate for any semblance of soundfield reconstruction. That is a physical fact, not conjecture.

At best, one can do a binaural recording for headphones. For speakers and listeners in a room, forget it.

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14 hours ago, gmgraves said:

 

I do it with MS miking using figure-of-eight microphones, but one can also do it with crossed figure-of-eights and get really nice ambience using spaced omnis (but this requires a fairly live venue). At any rate, I find two carefully chosen and well set-up microphones are more than adequate to make an ambience-rich 2-channel recording.

A 2 mic sample of any soundfield is inadequate to capture both onset and diffuse portions, so that any realistic rendering with loudspeakers can occur. Again, binaural doesn't work with loudspeakers and is inferior to actual soundfield reconstruction rendering methods. I would post all the links yet again, but we are at Einsteins insanity definition here.

The characteristics of the diffuse portion cannot be played back simultaneously with plane wave onsets and be perceived as one would live. That is a physical fact, not conjecture.

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Since folks are having trouble reading links

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In the usual stereo audio presentation, a partial sound stage consisting primarily of the front elements of the sound stage is created by two channels, either sampled from several microphones set in the original sound field or more often by a mixdown of many microphones placed both in proximity to the performers and out in the hall to capture the ambience. The information presented by the two channels, in either case, is a small fraction of the information in the original sound field. Additionally, this fraction is presented to the front of the listener. The presentation does not create an envelopment experience, where one is immersed in the original sound field, as the information is not present. While some processors mimic the effect, such effects are not based on the actual venue but rather on some hypothetical model of a venue. : In holographic or auralized two-channel presentation, a presumed human head-related transfer function (HRTF) is used to create an impression of sound arising from other than the front of the listener. This works well in headphones or with interaural cancellation for one listener facing directly ahead and on the central axis between the loudspeakers. This method can, with some difficulty, produce an immersive effect for one point in the sound field, assuming that the subject maintains the proper head position, and the subject's head has an HRTF like that of the presumed functions. The ultimate form of this is, of course, binaural recording, where an actual head model is used to capture the information for one head location. : Beyond two-channel presentation, one can think of analytically capturing an original sound field to some degree of accuracy. This would require the use of many channels, perhaps placed in a sphere about the listener's head in the simplest form, requiring very high data rates (1000 to : 10 000 channels, perhaps) and creating a very high probability of influencing the sound field in the space with the microphones and the supporting mechanisms. As a result this technique is currently infeasible, and is likely to remain infeasible, for basic physical reasons as well as data-rate reasons, and actual analytic capture of the spatial aspects of a sound field in this fashion is unlikely.

 

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31 minutes ago, NOMBEDES said:

Wow. I have problems with WAF just for four speakers.  Unless you have unlimited space in your backyard for an underground anechoic chamber to be constructed, good luck.

Great news for you:

http://www.aes.org/tmpFiles/elib/20170625/13880.pdf

Figure 5

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If two pairs of loudspeakers are arranged in the following manner — the front pair at an angle of around 60 degrees and the rear pair at an angle of 120 to 180 degrees — four loudspeakers can reproduce the spatial impression of a diffuse sound field.

 

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25 minutes ago, gmgraves said:

AJ, from your picture, I'd venture to say that I've been doing live, location recording of classical music and jazz longer than you've been alive.

That's George Clooney not me. Regardless, that's a long time to have not picked up anything regarding basic perception of soundwaves.

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You are entitled to your opinion, but my experiences tell me otherwise. I guess we're going to have to agree to disagree on this point. 

I'm not posting opinions. All those links are scientific facts, not opinions, such as you are posting.

If yours aren't, please post the files or links to your 2ch recordings that correctly capture the soundfield so that they can be rendered and perceptually reconstruct the original, TIA.

It is impossible to sample combined direct and diffuse with 2 mics that can then be rendered separately, because they are no longer separate. The leading edges of the planar waves cannot be simultaneously played back from the same speaker producing an unlocalizable diffuse field. If you don't understand any of this, no shame in saying so.

A bare minimum of 4 loudspeakers is required for envelopment as one would have in a live soundfield. Again, scientifically established fact, not fictional opinion.

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8 minutes ago, gmgraves said:

 

Theoretical "fact" your posting may be

Not "theory", along established science facts. Direct field. Plane waves. Diffuse field. Perceived very differently by 2 ears.

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but the reality of the situation is that a very accurate sound field can be captured by two mikes.

Science fiction.

 

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Now, I certainly agree that you can't capture a complete sound field in such a way that the ambience cues come at the listener from all directions, as in a multi-channel system. That should be obvious to even the most casual of observers of this debate

Bingo!

 

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but the ambience can be captured with two microphones; it just emerges from the two stereo speakers along with the actual sound stage, that's all.

Right, what emerges is a tiny, maybe 10% of the original soundfield.

Here https://secure.aes.org/forum/pubs/conventions/?elib=9136

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In the usual stereo audio presentation, a partial sound stage consisting primarily of the front elements of the sound stage is created by two channels, either sampled from several microphones set in the original sound field or more often by a mixdown of many microphones placed both in proximity to the performers and out in the hall to capture the ambience. The information presented by the two channels, in either case, is a small fraction of the information in the original sound field. Additionally, this fraction is presented to the front of the listener. The presentation does not create an envelopment experience, where one is immersed in the original sound field, as the information is not present. While some processors mimic the effect, such effects are not based on the actual venue but rather on some hypothetical model of a venue. : In holographic or auralized two-channel presentation, a presumed human head-related transfer function (HRTF) is used to create an impression of sound arising from other than the front of the listener. This works well in headphones or with interaural cancellation for one listener facing directly ahead and on the central axis between the loudspeakers. This method can, with some difficulty, produce an immersive effect for one point in the sound field, assuming that the subject maintains the proper head position, and the subject's head has an HRTF like that of the presumed functions. The ultimate form of this is, of course, binaural recording, where an actual head model is used to capture the information for one head location. : Beyond two-channel presentation, one can think of analytically capturing an original sound field to some degree of accuracy. This would require the use of many channels, perhaps placed in a sphere about the listener's head in the simplest form, requiring very high data rates (1000 to : 10 000 channels, perhaps) and creating a very high probability of influencing the sound field in the space with the microphones and the supporting mechanisms. As a result this technique is currently infeasible, and is likely to remain infeasible, for basic physical reasons as well as data-rate reasons, and actual analytic capture of the spatial aspects of a sound field in this fashion is unlikely.

 

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8 minutes ago, semente said:

 

All (2 channel or processed multi-channel) are approximations, which is why you very well wrote "perceptually reconstruct the original".

Correct, but >2 does so much better than 2.

It's really only audiophiles stuck on 2 with their rock music. Nice explanation here: https://www.stereophile.com/asweseeit/1107awsi/index.html

 

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More mics/channels/speakers may confer a more "realistic" soundfield but will also add complexity, problems, and cost.

We all have our excuses :)

 

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The link about some reviewer describing JA wetting his pants is not a fact.

How do you know he didn't wet his pants??

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19 minutes ago, STC said:

 

That paper was written in 2000. At that time, Ambiophonics was still using physical divider. That was long before BACCH. 

11515bacch.jpg?itok=60A3S-bu

 

images?q=tbn:ANd9GcQkdm3zcokA0F6UIF1ARY4

 

I get a bit claustrophobic with the head vice/limited head movement sweet spot thing :)

 

have you heard a BACCH demo?

The fly around head thing was cool, but an orchestra is a different affair.

Would love to hear though...

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31 minutes ago, STC said:


What limited head movement?

As defined by binaural without head tracking. The system photos seem to confirm this.

 

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Did you listen to BACCH in a proper setup? Did you even listen to classical music with BACCH?

No!, not yet, that's why I said I want to.

 

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I am not sure who is in the picture, but if you actually listened to BACCH like that than you have been conned. 

My favorite droog, but that was a tad bit of embellishment to highlight "head in vice" imaging..:)

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12 minutes ago, STC said:

 

I am not going to speculate based on a picture. I can tell you that the speakers were placed far too wide to be effective without head tracking. That what BACCH does. if you do not want the head tracking than move the speakers closer. 

Ok, I think we are in agreement.

This is what I found online https://www.google.com/search?q=bacch+3d&source=lnms&tbm=isch&sa=X&ved=0ahUKEwj_76KInNrUAhWLOCYKHRMZCJgQ_AUIBygC&biw=1517&bih=708#imgrc=OO6WdobEhfysoM:

Speakers waaaay out in a heavily treated room, couple chairs dead center.

Like I said, would love to hear, but nearly the opposite of what I prefer physically, i.e regards to speaker placement and "living" room decor. Nothing on head. YMMV

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7 minutes ago, STC said:

 

 

Guess you too don't read the links. :)  

I did

52617bacch3.jpg

 

That looks like a very confined sweet spot...as expected from the physics of crosstalk cancellation. Note speakers way out in room and treatments everywhere, including chunks on floor!!

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To answer your questions...

Submitted by Michael Lavorgna on May 26, 2017 - 2:07pm
...the sweet spot is defined by the user, more or less. For this demonstration, the sweet spot was defined for one person sitting and that person could move their head a few feet in either direction without disrupting the 3D effect.

 

I don't see how the person in the front chair can move their heads "a few feet" with that chair...but this is all semantics. The fact is crosstalk cancelled binaural with loudspeakers is a small sweet spot and lots of room conundrum. The pic says it all. I have no doubt the sound is super...for the one person in front chair.


 

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46 minutes ago, STC said:

 

Show me one stereo audiophile system where the chair is not in dead center. 

Not without advertising.

 

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Sweet spot is sweet spot. That is only one spot. Even in concert hall, you will find a spot albeit larger where it sounds best. 

I've posted this already http://www.linkwitzlab.com/Links/Optimized-listening-area-Davies.pdf

imaging2.jpg

 

When demoing my large CD system at audio shows I will have attendees get up from the sweet spot and walk to the sidewalls outside the speakers while playing music with vocals...which remains centered behind speakers

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8 minutes ago, STC said:

If you move away from the sweet spot ( in a non realtime headtracking BACCH) , you will hear the normal stereo sound that will sound like any stereo when you moved away from the stereo's sweet spot. 

Right.

 

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Now room treatment is bad! Don't tell me you have not seen heavily treated stereo room.

No, I've stated many times that the iso-ward look/approach is very appropriate for audiophiles/studiophiles

 

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At least, I have tried both method to know now the difference. Have you?

Sorry, what 2 methods? The thread is about 2 vs >2 ch

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7 minutes ago, STC said:

So called world greatest system with "minimum"treatment 

???

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Your criticism about dead center and room treatment is not relevant at all to OP.

Ummm, I am the OP... 

 

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Yes, proper DTS, 5.1 SACD vs 2 channels. 

???

 

Are there some invisible quotes being addressed there?

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10 hours ago, STC said:

AJ, I skimmed through the PDF link. Is there anywhere in there it is suggestion the best stereo effect is not in dead center?

What the image got to do with Davis paper?  That image got nothing to do with the link. What's the relevance here?

In the image, the best position is still in the middle. The four green circles. Same as BACCH or Ambiophonics.

Yes, it's clear you didn't like what's in it. The paper and the image coincide. The paper describes the required loudspeaker polar pattern that given a much wider/larger sweet spot than can be realized with any form of binaural with crosstalk cancellation, like BACCH and Ambiophonics, which basic physics dictates cannot be effective over a wide area, again, unless with head tracking to adapt. The Davis method does not require any head tracking and the image does not collapse to the L and R loudspeaker as one moves off center as happens with typical loudspeaker polar response. Like the ones used in the BACCH photos. The Davis approach requires a physically large speaker to control the directivity and resulting polar pattern. Unless one was to use the B&O approach with multi-drivers and lots of DSP. I get that you don't understand this stuff I'm linking, but that's ok.

The image is from a large 15" waveguide 2 way by Geddes, that partially creates the Davis polar response and much wider sweet spot than an binuaral based system can. It can be improved further if the directivity control extends downward of the waveguide.

Of course, if one is an audiophile who prefers to be constrained in a tight sweet spot by oneself in an iso-ward room, this approach would be unnecessary. YMMV.

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10 hours ago, STC said:

We could so easily fooled when we have others to suggest where the sound is coming from.

So you weren't there but assumed this was suggested? Interesting.

 

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In no way, I am suggestion that your speakers couldn't  do that because I have not heard them. 

Right.

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3 hours ago, semente said:

 

That's my point exactly.

No matter how many channels/ speakers you add, no matter how much processing sci-fi messing you do, the speakers will always be reproducing both instruments and room cues.

So you don't understand how it's possible to encode each separately and then render using different driver compliments separately with each signal. Nor apparently comprehend the research about 4ch minimum for envelopment and the separate encoding already linked.

Ok then.:)

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