Frontal reflections, depth of soundstage, and dipoles

[Blumlein 88]

I did some experimentation using recordings of some friends who have a musical group. All acoustic instruments. The recordings were all close miked. No delay, reverb nothing just the dry signal. I assigned one feed to one speaker with speakers for each musician. I placed the speakers in different locations in my room near the front. You could even move a speaker and it was like the guitarist moved from here to there. This makes for an excellent very real sounding "they are here" reproduction. This is not a "you are there" sound, but a they are here in your room sound.

This is not really surprising as you have a real as opposed to phantom or mixed sound source for each instrument. Your hearing of course finds it natural to use the reflections in the room with a real sound source to hear it as being there because it is there. Despite the fact the directionality of instruments vs the microphone pickup differ greatly the result is startlingly real sounding.

Now doing this with an orchestra is not practical. The promise of systems like Atmos or similar is being able to create and place large numbers of virtual sound sources. If it really worked it could duplicate an effect for an orchestra. Of course it is virtual and it doesn't fully reach the claims made for it.

 

[Duke]

That may be correct, but I think a very important factor in detecting those low-level reflections, and for us to separate them from the direct sound, has much to do with hearing different directional cues. Those different directional cues can only be heard in the stereo illusion, but will not be present in reverberation that occurs in the listening environment as those reflections are generated by the two speakers and by that have lost the directional cues present in the stereo illusion.

Agreed, there are no useful directional cues in the in-room reflections of the reflections on the recording, but there are spatial cues - ambience, hall reverberance, distance cues - in those reflections of reflections.

I believe the reverberation tails in the recording are only heard in the direct sound, which represents the stereo illusion where the directional cues are present.

But I believe the reverberating tails from the recording get completely lost in the diffuse reverberation field (that we hear as envelopment), and that is just a "mess" of everything in the recording as there are no longer any differences when it comes to directional cues, as everything (recorded direct sounds and recorded reflections) are now generated from only two positions, the position of the two loudspeakers.

Thanks for clarifying your position.

I don't think we're going to agree on all the details, and I hope that's okay.

I thank you for having this conversation with me, and for disagreeing without ever even a hint of being "disagreeable". I hope I have done the same, and let me know if I have not.

Do you ever get to any audio shows in the US? I would like to meet you.

 

[tmuikku]

You didn't mention Griesinger's "proximity" in so many words, but imo "proximity" and "envelopment" are not necessarily mutually exclusive in a playback setting, the key arguably being a significant time gap between the direct sound and the strong onset of reflections... which happens to be something big electrostats can do if given sufficient distance from the wall. I noticed the transition to "you are there" at 5 feet (about 152 cm) from the wall, and 7 feet (about 213 cm) seemed to be "optimum" to my ears, but unfortunately was not practical.

Hi,
yeah I've got Griesinger card out so many times left it out this time As I understand Griesinger's proximity and envelopment always come together, both are result of single phenomenon, the stream separation. Proximity is basically the foreground neural stream, and envelopment the background stream. These happen when auditory system can pick out the direct sound as something important when it sticks out loud enough from "noise"*, basically separating an important sound above unimportant. So, there is both proximity and envelopment, or neither. Proximity is umbrella for things like engagement and sharp localization because brain pays great involuntary attention to direct sound and it surely feels like so.

I guess that if front wall reflection is the loudest one it could be such a loud noise and the last one that prevents stream separation happening. I kind of assumed toe-in was used to eliminate most of it, as that's the forte of a dipole. I do not have dipole speakers so my posts regarding them is just based on information collected and processed, so second hand knowledge at best.

ps.
here is fun listening test for stream separation using your mobile and stereo:
put mono pink noise playing on your stereo, take your mobile and put pink noise on that too about as loud as your stereo but not louder, and position it behind you for example, or side of you. Now move yourself to Limit of Localization Distance and the mobile seems to mute. In other words when you are closer to stereo than LLD brain pays attention to sound of your speakers provide suppressing all the noises in the room, including effects of reflections, appliances, what have you, the mobile in this case. Your attention is on the sound of your stereo now. If you move yourself further than LLD you'll hear both the mobile and your stereo. Or the other way around, if your mobile is louder than stereo, or If you switch your mobile to different kind of noise, like white noise, the LLD is now closer to speakers. If you do these you need to get closer to speakers before the phone mutes from perception, position of LLD moved. There is a lot of things to take note from this test, for example it indicates that early reflections that are similar to direct sound brain can suppress them more easily, at lower SNR. I could very well mix things here, like what precedence effect does and so on, perhaps precedence effect is part of the stream separation mechanism I don't know. Nevertheless it's fun test to hear your own auditory system switch state to provide different perception.

* "noise" here means all sounds around us that are present all the time. Imagine brain paid attention to everything all the time, you couldn't get anything done as you'd be distracted and focus kept on everything. Brain helps us out, delegates focus on what is important, and suppresses other things so there is possibility to focus, supresses the "noise".

 

[tmuikku]

BTW, it's really fast and easy to use VituixCAD to try and estimate how much front wall affects with some particular positioning and toe-in.

Make ideal dipole like so:
when the program opens, copy the ideal point source there is, flip it's polarity and move Z 1mm to make an ideal dipole. Then add a low pass filter to flatten the response for easier visuals and hook it all up.


Now head to the room tab and start playing with front wall or any other boundaries. Use toe-in and reference angle to emulate listening triangle you want. Toe-in turns the speaker and ref angle means at which angle the "listener" is in relation to the speaker on-axis. The graphs show response at listening position. Listening distance is adjustable there on room tab, just like distance to the boundaries.


Enable front wall reflection, or any of them that are of interest. Now the yellow "in-room response" line in Power & DI window shows interference pattern due to reflection(s) interfering with direct sound. You can estimate how loud the reflection is from how much the amplitude variation is. As an example, here with and without toe-in. With toe-in the sidelobes are more toward the specular reflections so the interference variation drops in amplitude.


Or how it is with reduced listening distance


These do not show directly what the audible effect is, but it's quite easy to test how to reduce a reflection in amplitude, to build intuition how polar pattern with toe-in, positioning in general, affects early reflections.

For example test series like this is really fast to do and indicates that toe-in is far more important regarding front wall reflection than distance of listener to speakers, and distance of speaker to front wall:



Dipole is about as flexible as it gets to utilize / reduce front wall to anything, just change toe-in to increase / reduce front wall reflection SPL. Change distances to decrease / increase path length difference of first specular front wall reflection in comparison to direct sound. For example, with the toe-in used in these examples the front wall is more and more to the null the closer the speaker is to frontwall, which is kind of unintuitive at first but apparent from the tests. This is compensated by increaing path length difference, so the front wall reflection stays about the same amplitude no matter what the distance from speaker to wall, when the dipole is toed-in like so, even when listening distance is maintained. Delay would of course vary, and affect perception.


Without toe-in the distance becomes important, but I think this would be silly use of dipole? would it sound better or worse than something else, likely depends on what you wanna perceive.


Without toe-in the listening distance has to reduce to get similar front wall reflection amplitude as with toe-in:

 

[goat76]

Do you ever get to any audio shows in the US? I would like to meet you.

I have never visited an audio show, not even in my country. I’m not gear hungry enough for that type of thing.

 

[Duke]

here is fun listening test for stream separation using your mobile and stereo:
put mono pink noise playing on your stereo, take your mobile and put pink noise on that too about as loud as your stereo but not louder, and position it behind you for example, or side of you. Now move yourself to Limit of Localization Distance and the mobile seems to mute...

I would expect the ear to localize the sound source at wherever location it first arrived from (assuming an arrival time difference of at least .68 milliseconds and no significant intensity difference favoring the later-arriving signal) due to the Precedence Effect (or Haas Effect or Law of the First Wavefront). My understanding is that the later-arriving signal would still contribute to timbre and loudness, but its localization cues would be largely ignored.

Am I missing something?

 

[tmuikku]

Hi, yeah could be that, it's very easy to do simple emulation of a "singular early reflection", attempt to wonder auditory system ability to completely mute sounds favoring others. The mobile mutes very suddenly as I move closer to speakers, and I can move back and forth to toggle it on /off from perception with very little movement. This is bit off topic though This listening test is me fooling around and relates to my personal curiosity towars perception of sound and the Griesinger LLD in particular, which is basically the transition between "you are there" and "they are here" perception in my opinion. It is very similar toggle effect. Transition between the two is very short in physical distance like Griesinger explains it, which is why I think it is what I'm hearing and what makes the "you are there" and "they are here" distinction. Brain either pays attention or doesn't. I have no idea what the delays and such are, but all that needs to happen must have since it happens. My mobile test might be something else completely, it's just another example that it's very powerful thing to move the listener.

ps. this kind of simple tests make it very apparent that perception does not equal sound that hits ear, because it filters through auditory system. It is very cool to be able to perceive auditory system working, and although I cannot affect it directly by "thinking" I can still affect it indirectly by moving myself and basically forcing it to provide me perception I want it to, in this case I can choose whether to perceive noise from mobile or not by moving a little. Very powerful thing, and it's all about this with speaker positioning. And when speakers have found their place I can actively adjust perception to my liking by moving myself, for exanple swap between "you are there" and "they are here" in an instant by moving myself a bit.

 

[Bugal1998]

If things are out of phase in the recording, any widening or envelopment effects that may occur will come exclusively with the direct sound, and be part of the stereo illusion that tricks your hearing that things are coming from positions outside the speakers. It will most likely not have any significant effect on the diffuse late reflections that occur in the listening room.

Okay, let me try again.

First, my thoughts are predicated on three statements that may or may not be true, but which seem to be true in my anecdotal experience.

1) In a room with relatively more late reflections and longer decay times, there can be a pronounced increase in perceived reverb and ambiance compared to the same tracks in a room with more absorption, as well as headphones (possible exception being the HD800s but requires more testing). This seems to hold true even when the systems have a similar timber (so I don't believe it's purely an artifact of frequency response).
2) Dry recordings still sound dry, but without the hyper-clarity that comes with a damped room.
3) Wet recordings sound extra "wet" (relative to a damped room), and the spatial differences encoded in various tracks are still easily discernable, with spacious recordings sounding extra spacious/deep relative to a damped room.

I agree that widening or envelopment effects have to be in the direct sound heard from the speakers, otherwise statement 2 above couldn't be true; the mere presence of late reflections doesn't create envelopment/spaciousness/reverb. So the question remains, how do late reflections increase the audibility of reverb and spaciousness (assuming they do)?

My thinking...

Psychoacoustic tests have demonstrated that--in the brain--early reflections are spatially linked to and contribute to the perceived volume of the direct sound from the speaker when the spectral content is similar; what I'm hypothesizing is that the presence of out of phase sounds in the direct sound from the speakers (typically reverb and spatial effects that are perceived as coming points wider/higher than the speakers and even from behind the listener) triggers the brain to spatially link and integrate ALL sounds--including direct venue sounds--with similar spectral content that are perceived to be coming from wide a variety of angles (e.g. all spectrally similar sounds in the late reflections approximating a diffuse sound field).

Said succinctly, early reflections of similar timbre are spatially perceived as adding to the direct sound from the speakers, late reflections with similar timbre as the out of phase sounds--regardless of whether they were originally in-phase, out-of-phase, direct venue sound, or ambient sound--are spatially perceived as adding to the loudness of ambient out of phase sounds in the recording.

I'm probably way off base here, but if I'm following the discussion between you and @Duke the hypothesis above may reconcile the differences about how late reflections contribute to the perception of depth/ambiance/envelopment. I think the test I proposed earlier (identical tracks, but one with the reverb in phase, and one with the reverb out of phase) my be a valid way to do preliminary testing.

Just a side note:
I don't know exactly what you mean when you say "on-axis direct sound", as "on-axis" and "direct sound" have nothing in common. No matter in what direction you point your loudspeakers relative to the listening position, the "direct sound" will always be the straight path between you and the loudspeaker.

Edited the prior post to clarify; edits are in [closed brackets].

 

[goat76]

Okay, let me try again.

First, my thoughts are predicated on three statements that may or may not be true, but which seem to be true in my anecdotal experience.

1) In a room with relatively more late reflections and longer decay times, there can be a pronounced increase in perceived reverb and ambiance compared to the same tracks in a room with more absorption, as well as headphones (possible exception being the HD800s but requires more testing). This seems to hold true even when the systems have a similar timber (so I don't believe it's purely an artifact of frequency response).
2) Dry recordings still sound dry, but without the hyper-clarity that comes with a damped room.
3) Wet recordings sound extra "wet" (relative to a damped room), and the spatial differences encoded in various tracks are still easily discernable, with spacious recordings sounding extra spacious/deep relative to a damped room.

I agree that widening or envelopment effects have to be in the direct sound heard from the speakers, otherwise statement 2 above couldn't be true; the mere presence of late reflections doesn't create envelopment/spaciousness/reverb. So the question remains, how do late reflections increase the audibility of reverb and spaciousness (assuming they do)?

My thinking...

Psychoacoustic tests have demonstrated that--in the brain--early reflections are spatially linked to and contribute to the perceived volume of the direct sound from the speaker when the spectral content is similar; what I'm hypothesizing is that the presence of out of phase sounds in the direct sound from the speakers (typically reverb and spatial effects that are perceived as coming points wider/higher than the speakers and even from behind the listener) triggers the brain to spatially link and integrate ALL sounds--including direct venue sounds--with similar spectral content that are perceived to be coming from wide a variety of angles (e.g. all spectrally similar sounds in the late reflections approximating a diffuse sound field).

Said succinctly, early reflections of similar timbre are spatially perceived as adding to the direct sound from the speakers, late reflections with similar timbre as the out of phase sounds--regardless of whether they were originally in-phase, out-of-phase, direct venue sound, or ambient sound--are spatially perceived as adding to the loudness of ambient out of phase sounds in the recording.

I'm probably way off base here, but if I'm following the discussion between you and @Duke the hypothesis above may reconcile the differences about how late reflections contribute to the perception of depth/ambiance/envelopment. I think the test I proposed earlier (identical tracks, but one with the reverb in phase, and one with the reverb out of phase) my be a valid way to do preliminary testing.


Edited the prior post to clarify; edits are in [closed brackets].

Here is how I think things work...

A higher amount of late reflection can be a pronounced increase in perceived ambiance, but it likely depends on how late those late reflections arrive compared to the direct sound from the speakers, and that in turn depends on the size of the listening room relative to the listening distance to the loudspeakers.

I'm sure @tmuikku can explain more in-depth how he thinks this works (and I share his view on this).
He often talks about something he calls the "critical distance", which is about reducing the listener's distance to the speakers to the point where the direct sound "shells itself" as the main sound, and that the late reflections that occur in the listening environment come late enough to "shell itself" as a distinct secondary sound. In a small to average-sized listening room, the listening triangle will likely have to be fairly small for the late reflection to be perceived distinctly as a secondary sound. In contrast, a much larger listening room can probably get away with a larger listening triangle and maintain a clear separation between the main sound (the direct sound containing the width and depth of the recorded venue) and the secondary sound (which adds the envelopment).

I don't think the sound that creates the sense of envelopment necessarily contains any recognizable details from the recording if we had the chance to hear it in isolation from the direct sound, it's likely just a sort of diffuse field of sound somewhat similar to underwater sounds, but that at least gives the listener a sense of envelopment. I don't believe out-of-phase things in the recording have any bearing whatsoever on how this diffuse field will sound, as it's likely just close to an unrecognizable mess on its own if it was heard in isolation.



Just thinking out loud...
It would have been highly interesting to hear the diffuse sound field generated by 4-6 real instruments spread out in a venue, and then compare that to the diffuse sound field generated by two loudspeakers in a listening room, both isolated from respective direct sounds. Would the separation of the spread-out real instruments generate a diffuse field with a more "discernable nature" of the instruments, than what the diffuse field generated by the two loudspeakers (which in reality don't make any separation between the sounds in the recording no matter how many instruments the recording contains)?

 

[tmuikku]

Hi,

yeah I talk about "critical distance" a lot, which is a phenomenon that happens in my auditory system I can detect and utilize to listen and reason with this kind of stuff.

Short story, few years ago I was doing all kinds of listening experiments with my stereo system, mono noise in particular to inspect how I perceived the phantom center to somewhat participate on some discussions about phantom center. I noticed that at a particular listening distance the phantom center changed perceptually, quite dramatically. If I was close to speakers phantom center sounded clear and well defined spatially, but if I was beyond this distance it was quite undefined in size and not so clear, bit hazy sounding.

It took me quite some time to find this phenomenon in literature / written format. Then I found David Griesinger work and what he describes as Auditory Proximity and for example Limit of Localization Distance, these concepts very accurately seemed to correlate what I perceived so I took his work as a map, or handbook, an encyclopedia to perception almost.

Main problem we have is that we read all kinds of perceptual effects and phenomenon from forums or in books and studies, like what is envelopment and that so and so milliseconds of delays should integrate and so and such should make reverb, but if you ask yourself do you actually know how to listen this stuff? What does 2ms reflections sound like? Have you heard envelopment? How to hear it? This stuff I was reading and understanding literally, but I just had no clue whether I would hear it and how and what part of perception is the two milliseconds and so on, basically how to understand what I perceive and how to connect written concepts to perception and vice versa.

Since I perceived the phantom center change quite dramatically I though this is it, a chance to do this stuff the other way around, I had perceptual effect which I could not connect to any written concept. Very profound, key to unlock understanding of what I perceive and I still think it really is. So, I think I know what envelopment is because I can link it from Griesinger papers to my perception by using the "critical distance". Closer than critical distance auditory system separates the direct sound as foreground neural stream, while the reverberation, or all the other sounds in the room get another stream the background stream, which is basically the envelopment. This all can be connected with the single perceivable event, "the critical distance", and relating written concepts to that. Reading Griesinger you now understand what is envelopment, and how to listen to that reliably! It also means there is no envelopment when one is listening beyond this "critical distance"! Assuming Griesinger work is relevant of course.

This stuff is very important for many reasons, like how we communicate perceived stuff with each other especially on audio forums, how we understand audio perception in general, how we can improve our playback systems if we wish to, how we can get best seats on a movie theater or at any live event, how we can remember a lecture if it's an important one or make sure our important words to kids get their attention to make it a lifetime lasting lesson. Audio is really big part of our lives and shape us every day and this is really important stuff in general, and at the very core with home stereo hobby stuff as well.

Example from home hifi stereo context and envelopment: turns out my place, a normal living room, the envelopment is actually very poor so I would have never actually "heard it" as such and surely would have confused word envelopment to something else! Now with Griesinger I know when envelopment is audible and how to listen to it, and I perceive it very low in level in my place but also know how to improve it if I wish: I change D/R ratio to minimum still maintaining proximity and adjust toe-in, and when it's not enough due to poor room I could use additional sound sources to enhance it. Drawing from most images of hifi setups at peoples homes the same situation is likely in most living rooms, which I can logically pursue and relate to people to better understand what they might hear as I can now relate my situation quite reliably to theirs. This kind of reasoning could yield lot's of false assumptions of course, but it is heck of a lot better to have some understanding on perception than none at all, a small chance to communicate peceptual effects successfully.

Why I think people like to listen too far out with lots of early reflections is because that gives spacious feeling sound very easily, just put speakers in room and listen anywhere and that's it, but that's actually the poor hazy sound as brain is not paying attention to the sound. Better spacious sound would be when brain pays attention but because that also needs the envelopment to work people do not easily get this good spacious sound at their homes, so it's mostly found on meticulous random positioning and luck by some in some rooms with some speakers. If one knew how to reliably listen to it, and AB toggle it on / off to evaluate it, it would be easier to improve, right? This stuff enables to improve listening skill, which I define as understanding of what I perceive.

There is all kinds of stuff that can be reasoned from perception of "critical distance" and Griesinger paper, I have million posts on this subject on various threads and also on diyaudio.com. But, as this all could be just false, as it's just me one person trying to decipher what I perceive and how it connects to written concepts, and doing reasoning on top of it, I might be wrong many times. I do not have extensive experiment doing this, I don't know all speakers and rooms but I put a lot of weight on assumption that most people should have this "critical distance" with their speakers with their room, as it's not property of speakers or room but our auditor system we share from evolution through millions of years even. Main thing here is that I did the experiments and learned something, so I think everyone has to do this stuff them selves, learn their own perception as it's yours and only yours.

So, I urge everyone to read Griesinger studies and try and figure out a listening test to learn to hear "critical distance", to notice auditory proximity, to hear your own auditory system switch state. This is the only way I've found so far how to understand my own perception quite reliably. Then figure out whether this is something useful or not to you, by yourself. This was a lot to write, so hopefully it's good enough text to be worth your time reading through. Have fun!

edit. Here one paper specifically about spaciousness and envelopment https://www.researchgate.net/publication/2591262_Spaciousness_and_Envelopment_in_Musical_Acoustics

Unfortunately his website doesn't seem to load most of the time, I rarely can get it to load... Anyway, google finds most of his stuff, some in Youtube as well if you prefere to listen / watch https://www.youtube.com/@davidgriesinger3180

 

[Blumlein 88]

Is Greisinger's critical distance the point where direct and reflected sound is of equal level?

 

[tmuikku]

Nope, please read this paper it has some sentences about actual critical distance and auditory proximity on some concert halls. https://www.akutek.info/Mitt Bibliotek/IOA Auditorium Acoustics Hamburg 2018/Additional/papers/p35.pdf

"In Boston symphony hall the critical distance, where the D/R is one, is only about 17 feetfrom an omnidirectional source. On the floor the best seats can be forty to fifty feet from the stage,and the great seats in the front of the first balcony are more than 110 feet from the stage. But in thesmall classroom the reflections come much sooner and a higher D/R is needed. LOC was notdesigned for this type of room."

At home it could be quite close, due to small room acoustics.

 

[Blumlein 88]

Here is a related paper.

https://acousticstoday.org/wp-content/uploads/2019/09/CLARITY-COCKTAILS-AND-CONCERTS-LISTENING-IN-CONCERT-HALLS-David-Griesinger.pdf

I haven't had time to read the paper you linked obviously. Skimming it he is referring to critical distance as the point where direct and reflected sound is equal. In this paper it relates to imaging vs delayed sound and where the imaging collapses in concert halls. 40, 50 or 60 milliseconds. Then looks at small rooms. I do wonder about his male voice vs violins. The region of male voice we can locate via timing differences while the range for violin will be where we localize with level differences and angles of reflection on our pinna.

Again I've not had time to absorb the paper.

How does the critical distance in your room with your speakers compare to the point where you find the transition between you are there vs they are here envelopment?

 

[tmuikku]

How does the critical distance in your room with your speakers compare to the point where you find the transition between you are there vs they are here envelopment?

Hi, I think it's the same thing, as I understand these concepts they are the same thing. "You are there" is when auditory system pays attention to the direct sound and does the stream separation, perceptually this is as if I stepped into the venue, literally inside the sound. "They are here" is when auditory system doesn't pay attention, direct sound is perceptually fused with early reflections as if the source is in my room in front of me, as if I steped out of the soubd and it is in front of me now. Literally this is one physical step, I literally can step inside the sound, or out of it, switch vetween these at will just by moving myself a bit. If I put listening position to location where this transition happens, tot he "critical distance", leaning back gives me they are here, and if I lean forward I'm there, like poking my head through a bubble to hear what's inside. I can do tgis at will, I can change sound to which I want to perceive. Do this repeatedly for few years and you start to almost see your room acoustics.

Our auditory system does thisbstuff many times all day every day, it pays attention to sounds that are close enough, but we just don't pay attentiin to it! if you subject yourself to it and start to actively listen your perception, you'll notice it and perhaps understand it's importance. Our auditory system functions without conscious cobtrol, so all you have to do is pay attention what you perceive to notice this kind of stuff.

 

[Blumlein 88]

You can measure where the critical distance is for your speakers. Send them some pink noise (maybe filtered with a drop of 12 db/octave below 500 hz and above 2000 hz). Start at one foot and keep doubling the distance with a sound level meter. Phone will probably work for this. At first it will drop nearly 6 db. Later it will drop only 3 db for twice the distance. You'll be around the critical distance for your room and speakers at that point.

 

[tmuikku]

Yes of course, but this measurement is outside auditory system and doesn't correlate with perception in this sense. Details like this, any techical equipment, numbers or calculations, all keep your attention in other things than listening.

Put your phone away for few minutes, close your eyes and pay attention to what you perceive, and how it changes if you move closer or farther from your speakers. It's irrelevant what technical details go into perception changing, because when it changes everything happened that needed to happen. You can listen where the actual critical distance is, measure afterwards and see whether you got it right. This would help improve listening skill. Checking it with phone you learn where it is technically, which is not useful alone, you have to listen to it to learn how your numbers and perception correlate.

 

[JanRSmit]

Yes of course, but this measurement is outside auditory system and doesn't correlate with perception in this sense. Details like this, any techical equipment, numbers or calculations, all keep your attention in other things than listening.

Put your phone away for few minutes, close your eyes and pay attention to what you perceive, and how it changes if you move closer or farther from your speakers. It's irrelevant what technical details go into perception changing, because when it changes everything happened that needed to happen. You can listen where the actual critical distance is, measure afterwards and see whether you got it right. This would help improve listening skill. Checking it with phone you learn where it is technically, which is not useful alone, you have to listen to it to learn how your numbers and perception correlate.

Basically is what i do when listening to music, i close my eyes, even in concerts or even in a movie.
Interesting to hear effects on perceived soundstage by direct reflections. F.i. a direct reflection coming from left wall can cause the subject in soundstage shift to the right. ( the reverse can be used to stabilize the lateral aspect of soundstage when listening left or right from the MLP)
Also that making system phase-linear made the proximity effect stronger when listening a bit further away than the critical distance. ( and other improvements as well)
Unfortunately i cannot switch between old and new system, so it is just my memories.
The only thing that is the same is the room(and its arrangement) , the position of the speakers in the room and the enclosures(so drivers on same location in space).

 

[JanRSmit]

In addition, i found it very interesting to hear from visually impaired persons what they heard in the same situation. It is a main reason for me to close my eyes when listening.

 

[Bugal1998]

Just thinking out loud...
It would have been highly interesting to hear the diffuse sound field generated by 4-6 real instruments spread out in a venue, and then compare that to the diffuse sound field generated by two loudspeakers in a listening room, both isolated from respective direct sounds. Would the separation of the spread-out real instruments generate a diffuse field with a more "discernable nature" of the instruments, than what the diffuse field generated by the two loudspeakers (which in reality don't make any separation between the sounds in the recording no matter how many instruments the recording contains)?

I wonder if auralization software could be tasked to render the sound exclusive of the direct sound and any reflections within n seconds? It could perhaps be a useful tool to explore some of these perceptions.

 

[Blumlein 88]

I wonder if auralization software could be tasked to render the sound exclusive of the direct sound and any reflections within n seconds? It could perhaps be a useful tool to explore some of these perceptions.

Sort of what software like rew does with gating for measuring sweeps.