"They are here" vs. "You are there"

Hi Bryon,

Your last post, while of course highly thoughtful, I would have to very respectfully say strikes me as being essentially a set of hypotheses, which are subject to challenge and skepticism in several ways:

1)Along the lines of some of our discussion earlier in this thread, there is little reason to expect, in general, that omnidirectional presentation in the listening room will augment or better present the omnidirectional information that was captured in the recording space, because of the vastly different delay times that are involved. Those timing differences will cause our hearing mechanisms to respond in completely different ways, per the Haas Effect and the Precedence Effect (for which Wikipedia links are provided in one of my earlier posts).

2)There would certainly seem to be ample empirical evidence, such as in the system descriptions posted here at Audiogon, that high quality directional speakers are not necessarily at a disadvantage, relative to speakers with broad or omnidirectional dispersion characteristics, in creating a reasonably good "you are there" illusion.

3)Omnidirectional presentation in the listening space presents in an omnidirectional manner not only the reflected sound that was captured in the recording space, but also the sound that was captured in the recording space via the direct path between instrument(s) and mics. The directly captured sound, of course, having a significantly earlier arrival time at the mics. Intuitively that would seem, at best, to invoke a significant tradeoff. Among other reasons for that is the fact that the frequency response curves of our ears vary considerably as a function of the direction of the sound source.

4)It seems to me that the major problem with headphones is not that the sound is presented bidirectionally. Per my item 2 above, speakers that present bidirectionally can, at least in many circumstances, present a reasonably good "you are there" illusion. The major problems with headphones are two-fold, as I see it:

(a)The sound we hear from them essentially bypasses the pinnae, thereby altering both frequency response and directional cues.

(b)Nearly all recordings are not mic'd to be compatible with headphone listening. A recording mic'd to be properly compatible with headphone listening needs to be recorded binaurally, which as you probably are aware means it is recorded via microphone capsules inserted in the ears of a dummy human head.

I have two or three binaural recordings, and they can be truly spectacular in their "you are there" realism, when listened to with headphones. Although the degree of that realism can be expected to vary somewhat from listener to listener, corresponding (I believe) to the anatomical differences that may exist between the heads and ears of each listener and the dummy head that was used.

FWIW, I'll add that on normal stereo recordings of classical music, if they are well recorded, minimally mic'd, and minimally processed, I can clearly hear ambient cues and hall effects on my Stax headphones. They do seem somewhat less prominent than when I listen via speakers, but I suspect that is due mainly to the relatively lean sonic character of these particular headphones.

5)

So why don’t we just say that BOTH the listening room and the equipment are important factors in creating the illusion that “you are there,” though neither is as important as the recording. Or we could leave that last bit out, and just say that ALL THREE are important.

I agree with both sentences. By which I mean to imply that in general my feeling is that the recording is the most important of the three variables, at least with respect to the role that ambient cues play in "you are there" realism.

So in conclusion, I have no conclusion :-). At least, beyond what I've said earlier. But those are some thoughts that come to mind in response to your latest post.

Best regards,
-- Al

Your last post, while of course highly thoughtful, I would have to very respectfully say strikes me as being essentially a set of hypotheses, which are subject to challenge and skepticism in several ways…

Al – You are absolutely correct. Nearly everything in my last post I would consider a hypothesis, not a fact. Looking back at my post, I can see how I failed to make that clear. Usually, I am careful to include lots of phrases like “in my view,” “As I see it,” “I believe that” and so on. In other threads, I have often used the words “hypothesis” and “proposal.” But in my last post, there is a shortage of such words and phrases, which could easily give the impression that I regarded its contents as a group of generally accepted facts. I do not. I was struggling more than usual to organize my ideas, and so certain things got missed. In any case, like you, I regard the contents of my last post as a collection of hypotheses. That is to say, they are proposals about what MIGHT be true, proposals that have some evidence to support them, but that, like all proposals, can be defeated by other evidence. Having said that, let’s look at the evidence…

RE: (1) TIME SCALE DIFFERENCES BETWEEN LISTENING SPACE AND RECORDING SPACE

…there is little reason to expect, in general, that omnidirectional presentation in the listening room will augment or better present the omnidirectional information that was captured in the recording space, because of the vastly different delay times that are involved.

I acknowledge that the time scale differences between the typical recording space and the typical listening space can be quite significant. But I don’t know that those differences warrant much skepticism about my view that the omnidirectional presentation of ambient cues in the listening space helps create the illusion that "you are there."

Here are some of the reasons…

(i). You are quite right that the time scale of the first order reflections in a typical concert hall, being somewhere around 25-40 ms, cannot be reproduced in the listening room, since the listening room would have to be the size of a concert hall. However, a concert hall is the worst cast scenario. Many recording spaces are considerably smaller, to the point where the first order reflections of the recording space might be on roughly the same time scale as the first order reflections of the listening room. So the closer the size of the listening space is to the size of the recording space, the closer the time scales will be, and the less of an obstacle differences in time scale will be to creating the illusion that “you are there.” But even in cases where the listening space is much smaller than the recording space, there are still reasons to believe that the listening space can make a significant contribution to the illusion that "you are there." Which brings me to…

(ii). It seem to me, and this again is a hypothesis, that even when the recording space is so large that it is impossible to construct a listening space whose first order reflections can exist at the same time scale, you can construct a listening space that, in important respects, EMULATES the larger recording space. First, you can absorb the first order reflections of the listening space. This will lengthen the time before reflections reach the listening position, and, in effect, acoustically "enlarge" the listening room. Second, you can reflect or diffuse the second, third, and fourth order reflections of the listening space to provide a SUBSTITUTE for the first order reflections in the recording space. Admittedly, an analysis of the order of reflections would be significantly different between the two spaces. But a listening space that sustains higher order reflections with an amplitude and time scale similar to the lower order reflections of the recording space will, by doing so, RESEMBLE the larger recording space. I believe that kind of listening space allows the ambient cues in the recording to be presented in a way that APPROXIMATES the amplitude, time scale, and directionality of the ambient cues as they sounded in the recording space, contributing to the illusion that ‘you are there.”

(iii). Finally, matching the reverberation time of the listening space to that of the recording space can further enhance the illusion that "you are there." This can be accomplished even when the listening space is rather small and the recording space is rather large. This is another respect in which the differences in time scales involved in different spaces is not an insuperable obstacle to an effort to create the illusion that "you are there" by constructing a listening space that presents ambient cues in a way that approximates the way they were presented in the recording space.

In light of this, it seems to me that the approach to creating the illusion that “you are there” by constructing a listening space that provides the omnidirectional presentation of omnidirectional ambient cues is not defeated by differences in time scales, since (a) the time scales of the listening space are not always radically different from the time scales of the recording space, depending on the type of music; (b) the higher order reflections of the listening space can, to some extent, act as substitutes for the lower order reflections of the recording space; and (c) matching the reverberation time of the listening space and the recording space can be done (nearly) regardless of the size of the recording space. In my view, these measures constitute partial solutions to the limitations imposed by differences in time scales between listening spaces and recording spaces, even when the recording spaces are very large, like concert halls. And because of that, I do not feel that differences in time scales create serious doubts about my view that the omnidirectional ambient cues of the listening space can be used to augment the omnidirectional ambient cues of the recording space, and thereby enhance the illusion that "you are there." Having said that, I acknowledge that differences in time scales is something that must be carefully addressed in the listening room, if you are serious about creating the illusion that "you are there."

It seem to me that part of your skepticism, Al, is focused on my suggestion that, in order to create the illusion that “you are there,” ambient cues must be presented OMNIDIRECTIONALLY. In my last post, I tried to provide several arguments that express why I believe that. What it essentially comes down to is that, in order to create the illusion that “you are there,” the directionality of ambient cues in the listening space must resemble, as much as possible, the directionality of ambient cues in the recording space. And in the recording space, the ambient cues were OMNIDIRECTIONAL. Hence, in the listening space, they must be OMNIDIRECTIONAL. That does NOT mean, however, that the speakers must be omnidirectional (more on this below). Here is a quote from a speaker manufacturer who expresses more or less the same thing I’ve been saying:

…why do anechoic chambers sound so odd and artificial? We are accustomed to hearing the acoustics of the room we are in and spacial cues coming from many directions. Although a recording contains the acoustics of the concert hall, during playback those spacial cues are not coming from the original directions—they are all coming from the two speakers in front of us—very artificial. It is a crude and unnatural way to simulate an acoustic environment. We need to hear those spacial cues coming from all around us. In an anechoic chamber they don't. In contrast, I suspect the reason stereo works as well as it does in our homes is because of room acoustics. In a way, the room reflections are substitutes for the ones we would get at a live event. The reverberant field in our home listening room surrounds us with sound, not as a simulacrum of the actual location of the recording, but as a substitute. Those cues in the recording can then be interpreted as if coming from their original directions.

This is not an appeal to authority. I don’t regard this manufacturer as any particular authority, nor do I necessarily agree with his views on loudspeaker design. It’s just something I found that expresses, in a slightly different way, what I’ve been trying to say.

RE: (2). BIDIRECTIONAL VS. OMNIDIRECTIONAL SPEAKERS

There would certainly seem to be ample empirical evidence, such as in the system descriptions posted here at Audiogon, that high quality directional speakers are not necessarily at a disadvantage, relative to speakers with broad or omnidirectional dispersion characteristics, in creating a reasonably good "you are there" illusion.

I agree with this. In my response to Learsfool in my last post, my point was NOT that omnidirectional speakers are inherently superior to highly directional speakers at creating the illusion that “you are there.” My point was to express doubt about HIS suggestion that highly directional speakers were inherently superior to other designs at creating the illusion that “you are there.” In my view, neither is inherently superior to the other, when considered independent of the listening room. However, I do believe that some speaker radiation patterns will work better than others in PARTICULAR listening rooms.

RE: (3). HEADPHONES

…it seems to me that the major problem with headphones is not that the sound is presented bidirectionally. Per my item 2 above, speakers that present bidirectionally can, at least in many circumstances, present a reasonably good "you are there" illusion.

The bidirectionality of most speaker designs is not equivalent to the bidirectionality of headphones. To state the obvious, once you place bidirectional speakers in a listening room, they create a reverberant sound field. Hence the sound at the listening position is, to some extent, omnidirectional. The only place bidirectional speakers create a completely bidirectional sound field is in an anechoic chamber. In the real world, bidirectional speakers create SOMEWHAT OMNIDIRECTIONAL sound at the listening position. In contrast, headphones always create a COMPLETELY BIDIRECTIONAL presentation. In light of this, the success of bidirectional speakers at creating the illusion that “you are there” is not a reason to believe that headphones can, by virtue of similar directionality, create the illusion that “you are there.” The reason is because the sound field of bidirectional speakers is no longer purely bidirectional, once you put them in the listening room, while headphones remain completely bidirectional, come what may.

I'll add that on normal stereo recordings of classical music, if they are well recorded, minimally mic'd, and minimally processed, I can clearly hear ambient cues and hall effects on my Stax headphones.

Yes, I agree with this, as I mentioned in the last paragraph of my last post. Headphones DO provide ambient cues from the recording. But they do not present them OMNIDIRECTIONALLY, which is how they sounded in the recording space. That is why I don’t believe headphones can create the experience that “you are there” on typically mic’d recordings. Which brings me to...

I have two or three binaural recordings, and they can be truly spectacular in their "you are there" realism, when listened to with headphones.

I have not head a binaural recording through headphones, though I do not doubt, from what I know of the technique, and testimony like yours, that it can create the illusion that “you are there.” So none of my comments about headphones apply to binaural recordings.

Having said that, it seems to me that the success of binaural recordings at creating the illusion that “you are there” SUPPORTS the things I’ve been saying about the importance of the DIRECTIONALITY OF AMBIENT CUES in creating the illusion that “you are there.” Unlike typical recordings, binaural recordings contain robust information about the DIRECTIONALITY OF AMBIENT CUES. That is the reason, I believe, that they can create the illusion that "you are there." For the vast majority of recordings, which are not binaural, the directionality of ambient cues must somehow be recreated IN THE LISTENING ROOM, if you want to create the illusion that "you are there." Or that is my hypothesis, anyway. :)

One more thing about binaural recordings…

While binaural recordings, literally speaking, are bidirectional, they nevertheless RECREATE the same information that results from the OMNIDIRECTIONAL arrival of ambient cues. That is precisely the point I have been trying to make about the listening room, namely, that it must RECREATE, to whatever extent possible, the same information that results from the OMNIDIRECTIONAL arrival of ambient cues, if it is to create the illusion that “you are there.”

Now I will pause for a brief resumption of my life.

Thanks very much, Bryon. With the clarifications, qualifications, and further exposition you have provided, I find little or nothing to disagree with. Although as we both agree, a lot of what has been said remains in the realm of hypothesis, that is conceivably refutable or subject to further qualification.

When you have time to return here from the real world :-) please take a look at item 3 in my previous post, which I added in some time after initially submitting the post. I believe you may not have seen it when you composed your response, and I'd be interested in your comments on it.

Best regards,
-- Al

Bryon and Al, you both make some very interesting points! In general, I agree with most all of them, particularly Al's. Regarding this bi-directional vs. omni-directional subject, though, I do think it is very important to remember that in a good concert hall, sound is really not coming from EVERY direction at exactly the same moment. Acousticians try to design the overall space so that as much of the sound as possible goes directly to the audience, and that the reflected sound is channeled in such a way that it interferes with this as little as possible. So although sound does come from many different directions, it does not come from all of them anywhere near equally, and the overall effect is not PRIMARILY omni-directional, only secondarily so. Again, this is assuming a well-designed hall, and I am admittedly over-simplifying. I think the point I am trying to make here is similar to Al's point no. 3 he asked you to reconsider. (On a side note, this is why some musicians I know claim that even stereo reproduction sounds fake, and do as much of their listening as possible to older mono recordings! I don't go that far myself, but I have been exposed to a truly great mono set-up, and had to admit that it was at least as realistic as the best stereo set-ups I have heard.)

This point leads to another - listening rooms do not come anywhere near capable of recreating the original recording space, if this space is a concert hall (or a good jazz club, for that matter) - so this means that the listening space will ALWAYS be fundamentally different from the recording space, as I believe you put it, in these cases, and this is why I believe you are overestimating it's importance. It must be a very good listening space indeed, beyond the capabilities of the vast majority of us, to come close to recreating the sound of a concert hall in their listening room. I am not suggesting the room is unimportant (it can definitely help in the ways you suggest), but merely not as important as the speakers, and certainly not as important as the recording itself, which is by far the greatest factor.

Another point I would make, per our discussion of speaker types, is that while I think I understand your comment that "neither [speaker type] is inherently superior to the other, when considered independent of the listening room," in practice, one cannot listen to the speaker independent of the listening room, so while that statement may be true in theory, it doesn't have any practical value.

As for the binaural recording issue, I have absolutely no experience with this - I have never heard a binaural recording. The subject is interesting, and I would like to hear one sometime, but until then I will remain skeptical, for the reasons I already stated. And I still remain convinced that though the very best types of headphones out there may be able to provide some ambient cues, they will not be of anywhere near the quality of normal speakers. I do not claim to know the scientific reasons behind it, but it has much to do with what Al alluded to about the ears not picking up the sound in the same way. I read a very good article about this subject a few years ago written by an engineer, but have no recollection of where, unfortunately. I may try a Google search, and if I can find it, I will share the link.