Space... The Final Frontier

[1_sufferin_mind]

I just had to borrow this thread's title from the article written by J. Gordon Holt in March of 1994. It was too clever to pass up! But "space" on an AV forum doesn't refer to a vast void filled with stars; instead, it refers to the expanse of a recording space, concert hall, or other venue. It's the icing on the cake, but it can be spread thick or thin depending on the capabilities of the equipment, room, and source material.

The article begins by surmising that: "the ultimate soundstage is doomed to failure: we're trying to reproduce three-dimensional space from a two-dimensional system, and it simply can't be done." It goes on to present arguments for the spaciousness afforded by surround sound, spaciousness attributable to comb-filtering, and spacial differences between recording and reproduction rooms.

Now this is where the article takes an interesting turn, and the author's intention to support a migration from 2-channel to multi-channel music listening. He claims that the two configurations actually call for different speaker types: editorialized for 2-channel, and accurate for multi-channel. In conjuction with room treatment to acoustically isolate multiple channels, the speaker/room system then allows all manner of spatial information to shine forth, including height and depth.

Mr. Holt urges: If you're skeptical that spatial information is largely a product of system and speaker type, then listen to a large-scale work with bass in mono.

"The first thing you'll notice, of course, is that the soundstage has collapsed. The second thing you'll notice is how much thinner the sound has become. Much of the upper bass/lower-midrange warmth and richness are gone, and the sound seems almost pinched in comparison to the stereo reproduction.

Psychoacousticians seem unable to explain why this is so. The consensus appears to be that the phenomenon is related to auditory masking---the tendency for sounds to obscure softer sounds of similar frequency coming from the same perceived direction. In mono, all sounds come from the same direction, so the hall reverb, being softer than the direct sounds, is largely masked by them. In stereo, the instruments producing those reverberations are heard to image at specific locations across the soundstage, while the reverberant energy comes from two spatially separated sources, offsetting some of the masking effects of the direct sounds. The result is that the reverberant energy becomes more audible---it sounds louder, even though, as mentioned previously, frequency-response measurements will reveal no differences that could begin to account for the extent of the perceived difference."​

To what extent do you agree or disagree and why?

 

[Sonnie]

I need to absorb what he's saying and get a better grasp on it. He is referring to bass in mono... which we do all the time with bass management. All frequencies under the crossover (in many cases 80Hz) are redirected to a single sub or two subs acting in mono, not stereo. Never had my sound stage collapse. I also get a very large spacious soundstage with my ML's... one reason I like them so much. I can get a good sound stage with smaller speakers as well... maybe not quite as spacious, but it's no where near collapsing. This is with nothing more than two speakers. If the material is recording in multi-channel, it can sound very good as well, but I don't want multi-channel (all channel stereo) if the recording does no decode it.

Am I misunderstanding what he is implying?

 

[1_sufferin_mind]

No, I think I may have miscommunicated.

Instead of saying, "Mr. Holt urges: If you're skeptical that spatial information is largely a product of system and speaker type, then listen to a large-scale work with bass in mono," I should have said, "then listen in mono to a large-scale work with bass." I think the point he is trying to make is that spatial cues and bass content are diminished when listening in mono, "proving" that our ears respond to hall ambience differently in stereo than they do in mono. He then tries to pin missing or diminished ambience on the masking effect.

Maybe my question should be: For 2-channel systems, do you agree that direct sound masks reverberant/ambient energy? Traditional practice is to isolate each speaker in a multi-channel system by treating 1st reflection points. Ambience is then provided through the surround/back channels. How are we to retrieve/preserve delicate ambient information for 2-channel systems?

 

[Sonnie]

I can't say I will argue with him on our ears responding differently when listening in stereo vs mono. Our ears are processing two different environments between those two.

I think I get this delicate ambient information with my ML's... Wayne did a really good job of setting up my ML's where we get direct reflection from the back wave, delayed of course, which not only helps with superb sound stage and imaging, but also that delicate ambient sound. It is by no means the same as listening to Pink Floyd WYWT on multi-channel SACD, but then I don't think the recording engineers intend it to be anything resembling that sound with two-channel recordings.

This will give you an idea:

 

[Leonard Caillouet]

I have to disagree with the premise. It really oversimplifies the most amazing and complex system that exists in any organism, the human perceptual system. At the most basic level what people who make this argument forget is that we hear with two ears. Those same ears are hearing sound from a musical performance in a hall or from our audio systems at home. What hits the ear canal is also affected by the shape of our ears, their orientation and location, and the subtle differences in phase and frequency response in three dimensions. Add to that the incredible capability that our brains develop to recognize patterns and decode fine detail from. Think of some of the amazing things that the blind can do in terms of perception to navigate and locate things.

What clarified and closed the book on this argument recently for me was the Smyth Research demo at AXPONA. It confirmed in dramatic terms what I believed, that we can perceive three dimensional information from stereo. Lot's of people will still disagree, claiming that it is only our imagination recreating the perception. This is, of course, correct to a degree. What we hear, or experience, is ALWAYS mediated by what we have experienced before and associate to the current stimuli. But to dismiss experience to this degree is less than useful, in my view.

It is not uncommon for writers to scoff at experiences that are difficult to explain with a simple set of variables, trading their inability or unwillingness to engage in trying to understand complex systems for apparent expertise shrouded in a cloak of understanding of basic physics or electrical properties. We see it all the time in the objectivist/subjectivist debates. I take a more humble approach and prefer to try to figure out why people experience what they do, and how it might be explained with physics and electrical theory. But just because it is not obvious how to do so does not mean that it can't be done. Particularly when the external physics are only part of the system. The rest is the complex system of our bodies and brains, and our psyche and emotional systems.

"Nihil est in intellectu quod non sit prius in sensu"? Great philosophers have debated these notions for centuries. We should have learned by now that the answers are not simple, nor are they meaningful without the context of the individual asking the question and the context of the individual having the thoughts and experiences. I fall back on my universally correct answer to all questions, "it depends," not as a way to trivialize or sidestep the question, but as a start of a more interesting discussion.

 

[AudiocRaver]

I have to agree with Leonard's comments that the human perceptual system is truly a marvel.

Let's leave out for the moment the fact that it is also susceptible to beliefs and imagination and is easily distracted or fooled. Common / shared experiences, A-B and blind comparisons, and various checks-and-balances approaches help us keep it honest.

I marvel that two signals, only slightly different, properly reproduced and presented to that perceptual system, can produce such a delightful experience in the psychoacoustical brain as the soundstage and imaging (SS&I) we can experience.

Maybe my question should be: For 2-channel systems, do you agree that direct sound masks reverberant/ambient energy?

To quote my good friend Leonard, "It depends." Properly understanding and managing that early ambient energy is important and tiny differences in approach can make the difference between a vague, confusing soundstage and a blow-your-socks-off soundstage. Later reflections and ambience are more easily differentiated by the ear and contribute to spaciousness without messing up the SS&I.

Traditional practice is to isolate each speaker in a multi-channel system by treating 1st reflection points. Ambience is then provided through the surround/back channels. How are we to retrieve/preserve delicate ambient information for 2-channel systems?

All I can tell you is what has worked for me, and I have spent the majority of my audio research time over the last 5 years on this very topic, FWIW.

Early L/R Mains reflections that

• are delayed equally (L & R)
• each come from the same L/R angle as the originating speaker

will contribute to the production of a 3-dimensional soundstage with precise imaging. Reflections that arrive delayed later than around 15 ms or so contribute to spaciousness that does not disrupt the imaging. This all involves the primary soundstage from the L/R Mains. The addition of surround and height information is useful for cinema and surround music mixes and does not have a significant effect, positively or negatively, on the primary soundstage.

 

[Sonnie]

Early L/R Mains reflections that

• are delayed equally (L & R)
• each come from the same L/R angle as the originating speaker

will contribute to the production of a 3-dimensional soundstage with precise imaging. Reflections that arrive delayed later than around 15 ms or so contribute to spaciousness that does not disrupt the imaging. This all involves the primary soundstage from the L/R Mains.

That's what I said...

 

[1_sufferin_mind]

This will give you an idea:

View attachment 739 View attachment 740

Most creative! I remember seeing those panels when I was there for the DAC shootout, and reading about them in a few of the SS&I threads on HTS. I can't say I'm well-versed in their theory or positioning, but kudos to Wayne for developing them!

I have to disagree with the premise. It really oversimplifies the most amazing and complex system that exists in any organism, the human perceptual system. At the most basic level what people who make this argument forget is that we hear with two ears. Those same ears are hearing sound from a musical performance in a hall or from our audio systems at home. What hits the ear canal is also affected by the shape of our ears, their orientation and location, and the subtle differences in phase and frequency response in three dimensions. Add to that the incredible capability that our brains develop to recognize patterns and decode fine detail from. Think of some of the amazing things that the blind can do in terms of perception to navigate and locate things.

The author did go a bit overboard with his argument on masking, and I can't say that I support his view of offset reverberant energy. But I can say I'm on board with the concept of our brains' capability to focus on a single stimulus to the exclusion of other senses. When deprived of sight, for instance, one's sense of hearing becomes elevated. That's why it's so rewarding to listen to our systems with our eyes closed (not to be confused with "our hands tied behind our backs"). Many of us have experienced that for ourselves.

Properly understanding and managing that early ambient energy is important and tiny differences in approach can make the difference between a vague, confusing soundstage and a blow-your-socks-off soundstage. Later reflections and ambience are more easily differentiated by the ear and contribute to spaciousness without messing up the SS&I.

All I can tell you is what has worked for me, and I have spent the majority of my audio research time over the last 5 years on this very topic, FWIW.

Early L/R Mains reflections that

• are delayed equally (L & R)
• each come from the same L/R angle as the originating speaker

will contribute to the production of a 3-dimensional soundstage with precise imaging. Reflections that arrive delayed later than around 15 ms or so contribute to spaciousness that does not disrupt the imaging. This all involves the primary soundstage from the L/R Mains. The addition of surround and height information is useful for cinema and surround music mixes and does not have a significant effect, positively or negatively, on the primary soundstage.

Helpful summary! Five years is a significant effort and contribution! No doubt the subtle nature of reflections seem second nature to you now. I've followed some of your work, and hope to gain more insight and experience with reflections

 

[Flak]

From our point of view we think that the new object based formats are a step in the right direction towards the "Perfect Sound System" but there is ample room for improvement:
https://www.dirac.com/dirac-blog/perfect-sound-system-with-3d-sound-reproduction

Ciao, Flavio

 

[Allen Rumbaugh]

One thing that I have experienced that flies in the face of a lot of positions is what happened at Quad Studios in Nashville once doing a demo. The engineers had of course spent many man hours mixing in the "sweet spot" a place they held their head in to judge the imaging of the mix. I walked in and placed a large diffuser at the rear, and one on each side wall at the reflection point. The engineers hit play of the same mix, and their jaws hit the floor. They walked all over the control room with shocked expressions. Their observation? The sweet spot was widened to include the whole room! How can this be explained? I have no idea. But clearly there is a lot that can be heard, but not measured.