Diffusing 1st reflections of speakers that measure great on and off-axis - instead of absorbing

[j_j]

Yes. Relative to the direct signal. -30dB is considered definetely to be effectively anechoic (not audible). Obviously the treatment needs to be broadband with high coefficient to Schroeder. A standard ETC/impulse will not reveal that.

The clarity, detail or "resolution" is brought to a completely another level when early arriving specular reflections are strongly attenuated. I find it ironic that people are spending a lot of time on finding electronics with lowest distortion but overlooking this; considering it contributes far more to a "distorted/blurry signal". It will actually often mask differences in electronics and speakers.

What time delay are we talking about, again, between direct and specular reflection? Also, what head angle? (assuming plane for now, but theta/phi is better.)

Oh, and we still disagree on how to interpret small vs. large rooms, and I'd like to know your take on perceptually diffuse vs. analytically diffuse.

BUT you said one important thing:

FIX THE (*(*&*(*& ROOM. 95 vs 96dB SNR is nothing compared to the room. (assuming 16 bits there)


There are days I've gotten a sore throat saying that to people. Yep.

 

[Senior NEET Engineer]

Unless I'm mistaken, it's mainly just headphone people that obsess about SNR.

 

[j_j]

Unless I'm mistaken, it's mainly just headphone people that obsess about SNR.

I's more complicated than that.

SNR obviously CAN matter, one needs to know the system gain and the acoustic noise floor.

 

[Duke]

Who is for diffusing, who’s for absorbing and who is for doing nothing with 1st reflections? But more important: why?

I suggest dodging the early reflections if possible. With speakers like the M2, this can be done with aggressive toe-in so the speaker axes criss-cross in front of the center sweet spot, such that the first significant lateral reflection is the long across-the-room bounce off the opposite wall.

With more conventional speakers, this can be done by setting them up along a diagonal, such that an early same-side-wall reflection is geometrically impossible at the listening position.

Or if budget allows, keep the normal orientation but create angled surfaces at the first sidewall reflection zones which redirect the first reflections away from the sweet spot area. Recording studios often use this technique.

If the choice is between diffusion and absorption, I lean towards diffusion but am open to changing my mind. Here are the issues I have with absorption:

1) Energy which is absorbed cannot come back as beneficial later-arrival reflections;

2) Absorbers attenuate not just those first reflections but all subsequent ones which strike them; and

3) If the absorption isn't broadband (which is expensive to do), it is altering (dulling) the spectral balance of the reflections, in addition to reducing their level.

Remember, there is not an ounce of research using controlled listening to back the claimed benefits of RFZ and all the similar control room schemes cooked up in 1960s and 1970s.

The basic concept of avoiding early reflections while encouraging later ones apparently has anecdotal support from a qualified source.

In 1975 Floyd Toole had a house built with home audio in mind. In the smaller of his two listening rooms he used a diagonal arrangement. Toole explains:

“This was deliberate. I think many people are unaware of the advantages of a diagonal arrangement. There are essentially no sidewall reflections.”

That seems pretty straightforward.

His other listening room was much larger, with a more conventional set-up geometry, and apparently it was his primary classical music listening room. Regarding loudspeaker choice for that room, Toole writes:

“Over the years a parade of loudspeakers went through that room, and all disappointed... Then in 1989, a new loudspeaker came on the scene: the almost omnidirectional, bidirectional-in-phase “bipolar” Mirage M1. They performed well in double-blind listening tests in the small NRCC room, and also in this large one. They simply “became” the orchestra.”

Toole the scientist doesn't wax poetic very often, so that last sentence stands out to me.

It is not evident to me from eyeballing the photo of this room in the 3rd edition of his book that Toole was deliberately minimizing early reflections, but it could be argued that by choosing the bipolar Mirages he was deliberately enhancing the later ones (those arriving more than 10 milliseconds behind the direct sound).

Toole subsequently moved and now uses more conventional wide-pattern Revel speakers, with the right-hand-side first sidewall reflection zone being an opening into another room, and the left-hand-side first sidewall reflection zone being damped with heavy drapes. In other words, there are virtually no early lateral reflections. Writing about this room, Toole reports that “stereo reproduction is very satisfying, but I still employ tasteful upmixing for many recordings to embellish the sense of space.” I agree that sense of space matters to the point of being worth "embellishing", if done well.

So in the first room Toole was geometrically eliminating the first sidewall reflections without using absorption so that energy was still around to contribute as later reflections; in the second room Toole used speakers which intentionally enhance the amount of spectrally-correct later-arriving reflections; and in the third room Toole avoids/absorbs the first sidewall reflections and "embellishes" the later ones. One might see a progression or evolution, with the third room arguably combining the best characteristics of the first two.

Toole's implementation specifics are very different from an oldschool RFZ approach, but there seem to be some conceptual similarities: Minimizing early reflections while enabling (or even "embellishing") later ones.

 

[Lorenzo74]

I suggest dodging the early reflections if possible. With speakers like the M2, this can be done with aggressive toe-in so the speaker axes criss-cross in front of the center sweet spot, such that the first significant lateral reflection is the long across-the-room bounce off the opposite wall.

With more conventional speakers, this can be done by setting them up along a diagonal, such that an early same-side-wall reflection is geometrically impossible at the listening position.

Or if budget allows, keep the normal orientation but create angled surfaces at the first sidewall reflection zones which redirect the first reflections away from the sweet spot area. Recording studios often use this technique.

If the choice is between diffusion and absorption, I lean towards diffusion but am open to changing my mind. Here are the issues I have with absorption:

1) Energy which is absorbed cannot come back as beneficial later-arrival reflections;

2) Absorbers attenuate not just those first reflections but all subsequent ones which strike them; and

3) If the absorption isn't broadband (which is expensive to do), it is altering (dulling) the spectral balance of the reflections, in addition to reducing their level.



The basic concept of avoiding early reflections while encouraging later ones apparently has anecdotal support from a qualified source.

In 1975 Floyd Toole had a house built with home audio in mind. In the smaller of his two listening rooms he used a diagonal arrangement. Toole explains:

“This was deliberate. I think many people are unaware of the advantages of a diagonal arrangement. There are essentially no sidewall reflections.”

That seems pretty straightforward.

His other listening room was much larger, with a more conventional set-up geometry, and apparently it was his primary classical music listening room. Regarding loudspeaker choice for that room, Toole writes:

“Over the years a parade of loudspeakers went through that room, and all disappointed... Then in 1989, a new loudspeaker came on the scene: the almost omnidirectional, bidirectional-in-phase “bipolar” Mirage M1. They performed well in double-blind listening tests in the small NRCC room, and also in this large one. They simply “became” the orchestra.”

Toole the scientist doesn't wax poetic very often, so that last sentence stands out to me.

It is not evident to me from eyeballing the photo of this room in the 3rd edition of his book that Toole was deliberately minimizing early reflections, but it could be argued that by choosing the bipolar Mirages he was deliberately enhancing the later ones (those arriving more than 10 milliseconds behind the direct sound).

Toole subsequently moved and now uses more conventional wide-pattern Revel speakers, with the right-hand-side first sidewall reflection zone being an opening into another room, and the left-hand-side first sidewall reflection zone being damped with heavy drapes. In other words, there are virtually no early lateral reflections. Writing about this room, Toole reports that “stereo reproduction is very satisfying, but I still employ tasteful upmixing for many recordings to embellish the sense of space.” I agree that sense of space matters to the point of being worth "embellishing", if done well.

So in the first room Toole was geometrically eliminating the first sidewall reflections without using absorption so that energy was still around to contribute as later reflections; in the second room Toole used speakers which intentionally enhance the amount of spectrally-correct later-arriving reflections; and in the third room Toole avoids/absorbs the first sidewall reflections and "embellishes" the later ones. One might see a progression or evolution, with the third room arguably combining the best characteristics of the first two.

Toole's implementation specifics are very different from an oldschool RFZ approach, but there seem to be some conceptual similarities: Minimizing early reflections while enabling (or even "embellishing") later ones.

I really Thank you Duke. That’s more than average available On this site and on the web. since I read his (FT’s book) your summary perfectly resonate to me. I land, in my little journey, so far to same conclusions. that’s why I found speakers like kii3 or D&D standing out respect to the others.

if I may ask, how would you address ceiling reflections? diffusing with proper skyline is not possible due to diffuser height impact (min 40cm to reach 400Hz...), foam or absorption panels struggles below 1-2 kHz... at the end how to deal with 100-1000kHz region where the voice and music energy typically is?

psycho acoustic says we are much easier to be fooled if the early reflections (<10ms) are from same direction, it smears the definition of image reconstruction in our brain While lateral, if “properly delayed“ might be even beneficial to someone.
it reminds me the Mgr-1 exercise: direct sound, cardioid the 20ms delayed from lateral direction!

May I ask you (pls) a comment on below article?
https://www.stereophile.com/content/acoustic-research-mgc-1-loudspeaker

my Best Regards
L.

 

[tuga]

if I may ask, how would you address ceiling reflections? diffusing with proper skyline is not possible due to diffuser height impact (min 40cm to reach 400Hz...), foam or absorption panels struggles below 1-2 kHz... at the end how to deal with 100-1000kHz region where the voice and music energy typically is?

Have you though of deflecting towards the back of the room (if short wall setup or sides if long wall)?

An example:

 

[Duke]

I really Thank you Duke. That’s more than average available On this site and on the web. since I read his (FT’s book) your summary perfectly resonate to me. I land, in my little journey, so far to same conclusions. that’s why I found speakers like kii3 or D&D standing out respect to the others.

Thank you Lorenzo. The Kii3 and D&D 8c both look very good to me. I have heard neither, but eyeballing the two, I am drawn towards the smooth waveguide of the D&D.

Iif I may ask, how would you address ceiling reflections? diffusing with proper skyline is not possible due to diffuser height impact (min 40cm to reach 400Hz...), foam or absorption panels struggles below 1-2 kHz... at the end how to deal with 100-1000kHz region where the voice and music energy typically is?

Given free reign, I'd probably hang boards from the ceiling to break up the first reflection. Imagine boards that looks like a support joist, only not as thick (maybe only 20 mm thick). Earl Geddes does something like this on his ceiling. Then he has a coffee table placed to disrupt the floor bounce.

Note that a comb filter notch can be perceptually filled in by energy which arrives within about 10 milliseconds of the notching reflection. Since the floor bounce notch and the ceiling bounce notch occur at different frequencies and typically arrive well within 10 milliseconds of the direct sound and of one another, they may perceptually fill in for one another to some extent. I have not actually read anything which says they do, so this is just a speculative extrapolation on my part.

May I ask you (pls) a comment on below article?
https://www.stereophile.com/content/acoustic-research-mgc-1-loudspeaker

In my opinion Ken Kantor's Acoustic Research "Magic" speaker was absolutely brilliant. I believe its basic approach is more psychoacoustically correct than just about anything that has been done since, as it focuses on two things:

1. Getting the first-arrival sound right; and

2. Getting the reflections right. This includes getting their spectrum, arrival time, and arrival direction right.

Unfortunately the marketplace did not reward Acoustic Research with success; they went out of business not long after the MGC-1 came out. I suspect it was conceptually too unfamiliar for people to wrap their heads around. I never heard a pair, they say it had weak bass for its size and cost, and that alone could have doomed it: We learn from Toole that about 30% of our perception of sound quality is attributable to the bass region.

One issue the article mentions is a blurring of the center image when the supplemental arrays were active. I think this is a side effect (no pun intended) of the strong sidewall reflections: They increase the apparent source width (ASW), but they can degrade image precision.

What my company does is arguably a passive embodiment of the concepts embraced by the Magic speaker: We use a directional main array which is supplemented by additional drivers dedicated to the reverberant field. We typically get a bit more than 10 milliseconds time delay by aiming these supplemental drivers up-and-back, which results in at least one wall bounce and a ceiling bounce before their output arrives at the listening area. We don't get the increase in Apparent Source Width that comes from strong sidewall reflections, but in return I think we retain imaging precision. It's all a juggling of tradeoffs.

 

[localhost128]

As you walk around the house and hear your loved ones, their voices are "mashed in" with their direct sound. If you think you are bothered by such thing, you would go crazy in everyday life.

yes, and speech intelligibility suffers dramatically. try having a conversation in a stairwell (exaggeratedly-live environment): even with the person right in front of you and thus gain (SNR) is not an issue, intelligibility through articulation is heavily degraded as the indirect reflections smear the perceived speech to the point where one can hardly make-out what is being said.

although your example is not really relevant seeing as voices in a house are not "reproduced" via that of a loudspeaker with other ambient cues on recorded on top.

and yes, some people really do in fact "go crazy in everyday life" with poor acoustics from live sources such as humans speaking freely within a room. modern city lofts/apartments are extremely susceptible to this, as most have concrete ceilings, brick walls, hardwood floors, and thus very little porous absorption inherently applied. host a social gathering or event party and really focus on the level of acoustic energy in the room when there are multiple conversations taking place, and you will quickly understand how subjectively dis-pleasurable this is. now "treat" the room (not for stereo reproduction, but for room acoustics for speech) and it becomes much more flattering. numerous, distinct conversations can be had in parallel, without the "positive feedback loop" taking place of those speaking louder and louder to account for the SNR issues from others' conversations. it also dramatically reduces listening fatigue, as one is no longer mentally straining to hear what is being said. it's akin to how "cold" and negative an empty house may sound, but more "warm" and pleasing once furniture and other porous objects are added.

it is also a common issue in fine dining restaurants, where one must strain to hear another speaking from just across the table, as acoustics are commonly overlooked in such environments when visual consumes most of the funding.

i personally apply room acoustics and treatments in everyday living quarters, as it dramatically increases overall pleasurability of operating within the space as well as reduces mental fatigue - especially now that so many are forced to be working from home. it's no different than interior decorators applying diffuse lighting and other management techniques in the visual domain, to reduce fatigue, increase ambience, etc. acoustical treatments aren't for home stereo systems alone!

Remember, there is not an ounce of research using controlled listening to back the claimed benefits of RFZ and all the similar control room schemes cooked up in 1960s and 1970s.

could you please qualify this statement, as on its face is appears to be an outright lie.

LEDE and subsequently RFZ was not a "cooked up scheme of the 1960s and 1970s". Don/Carolyn Davis' LEDE was first introduced in 1982 (first studio constructed by Chip Davis), and Peter D'Antonio's RFZ (a geometric approach to achieving the LEDE psycho-acoustic response) in 1984 and there-after as tools, understanding, and science evolved.

control rooms are intended to be neutral reproduction spaces, with primary requirements dictated around accuracy of the direct signal such that mix/mastering decisions can be made that will translate to a myriad of other listening environments. these same requirements can be used to construct a home listening space, if one so prefers.

Syn Aud Con during that time hosted a myriad of workshops, all revolving around "science" of physics and psycho-acoustics of reproduction spaces - which took a quantum-leap forward with Heyser's introduction of the TEF as it allowed the real-world understanding of the high-gain indirect specular energy arrivals that were deemed destructive to localization, imaging, and intelligbility. the rooms were put through rigorous tests from musicians, studio engineers, and of course real-world subjective results such as whether the mixed material translates. one workshop i have here from 1987 details heavily the use of Doug Jones introducing the Knowles in-ear microphones to understand IACC for a myriad of tests - all rooted in science and measurements.

implying control room acoustical models are "scheme cooked up" does a great disservice to the science, audio, and acoustics community. they also wouldn't still be constructed today (or have many of the principles such as attenuation of early reflections, and diffuse later-arriving sound-field being recommended for home listening spaces) if they did not "work".

 

[localhost128]

I don't think concert halls have early reflections arriving shortly after direct sound or sparse reflections, like you would see in an untreated domestic room. LEDE goal is not to treat a domestic room like a concert hall, but to not mask the concert hall spatial cues in the recording.

concert halls have early reflections, the difference is unlike in small rooms there is no reverberant sound-field to mask them.

indirect specular reflections are still troublesome and must be isolated, most commonly from the rear-wall (large room "echo" reflecting back to the musicians on stage as a secondary auditory event) and specular reflections from seating elements (if reflective). i have numerous studies and workshops from concert halls detailing time-domain analysis and "hunting down" these destructive indirect reflections and their subjective perception pre/post.

 

[j_j]

For all of these discussions, can we please have some impulse responses, or the Hilbert envelope of these. Without more information there's not a lot of productive discussion to be had, beyond "yes, 1/4 second specular reflection back to the stage is a pretty terrible thing indeed". Let's not try to get into semantics or "rules of acoustics" because they are all over simplifications, in my experience.

 

[tuga]

Why has the discussion suddenly moved from listening rooms where recorded music is reproduced to concert halls where music is produced, listened to and recorded?

It makes as little sense as comparing a loudspeaker with an instrument...


A very interesting topic nonetheless, and one which is worthy of a dedicated thread.

 

[j_j]

Why has the discussion suddenly moved from listening rooms where recorded music is reproduced to concert halls where music is produced, listened to and recorded?

It makes as little sense as comparing a loudspeaker with an instrument...


A very interesting topic nonetheless, and one which is worthy of a dedicated thread.

Actually, the effect of overlaying one on the other, and the time domain aspects of hearing, make this less than a complete separation to say the least.

It also leads directly to 1933 work by Steinburg and Snow that still points the way to real "stereo" which does not mean "2 channel". All of these problems are mixed into one actual acoustic mish-mash. Floyd Toole's work on speaker directivity is headed in exactly that direction, and, with some understanding of the interaction between hearing and (I am tempted to say vs. in some cases) acoustics, helps to start sort things out. Needless to say this is not a short, simple discussion.

 

[Duke]

Actually, the effect of overlaying one on the other, and the time domain aspects of hearing, make this less than a complete separation to say the least.

It also leads directly to 1933 work by Steinburg and Snow that still points the way to real "stereo" which does not mean "2 channel". All of these problems are mixed into one actual acoustic mish-mash. Floyd Toole's work on speaker directivity is headed in exactly that direction, and, with some understanding of the interaction between hearing and (I am tempted to say vs. in some cases) acoustics, helps to start sort things out. Needless to say this is not a short, simple discussion.

It seems to me that there is, in effect, a "competition" between the spatial cues on the recording (whether real or engineered) and the spatial cues of the playback room. What we hear is an acoustic mish-mash of the two, usually dominated by the playback room cues... we are aware of listening in a small room. The illusion of being enveloped in the acoustic space of the recording is... elusive, at least for two-channel.

My understanding is that the earliest in-room reflection are generally the ones which most strongly convey the playback room's undesirable "small room signature", and that the ear is capable of picking out the recording venue reverberation cues from the later reflections, assuming they are spectrally correct. The implication being that we can nudge the perceptual scales towards the venue cues by minimizing early in-room reflections while preserving the later ones.

We will still at best end up with a poverty of cues relative to an actual live performance in a good venue, but with a good recording, from that poverty of cues the ear's "best guess" may be some version of the recording venue's spatial signature. In other words, "envelopment"... not perfect, but still enjoyable.

Anyway you mentioned the "time domain aspects", and ime creating an approximately reflection-free time gap in between the first arrival sound and the strong onset of reflections is desirable (for enabling the illusion of envelopment), though it is not clear to me that Toole's research points us in this direction. What are your thoughts on the subject?

 

[tuga]

Actually, the effect of overlaying one on the other, and the time domain aspects of hearing, make this less than a complete separation to say the least.

It also leads directly to 1933 work by Steinburg and Snow that still points the way to real "stereo" which does not mean "2 channel". All of these problems are mixed into one actual acoustic mish-mash. Floyd Toole's work on speaker directivity is headed in exactly that direction, and, with some understanding of the interaction between hearing and (I am tempted to say vs. in some cases) acoustics, helps to start sort things out. Needless to say this is not a short, simple discussion.

I agree.
In my view, reducing room interaction through narrow directivity and early reflection zone treatment increases the system's ability to "recreate" the acoustics of the venue where the original event was recorded (possible only with classical music and minimalist mic'ing); in other words there is less interference of the listening-room (a room within a room).
But I understand that many would rather enjoy increased envelopment even with the downsides of some image blur and a rather confusing mix of recording- and listening-room cues, particularly with studio recordings where there were no venue acoustics to begin with.
I have no experience with multi-channel, mostly because of practical (space) as well as monetary reasons but also because over two thirds of my recordings are 2-channel stereo.
I have no interest in upmixing nor 3D processing, I find that too much emphasis is given to the spatial aspect and the musicality gets thrown away with the baby water.
Ultimately it's down to personal preference, one must weigh the pros and cons carefully.

 

[j_j]

Anyway you mentioned the "time domain aspects", and ime creating an approximately reflection-free time gap in between the first arrival sound and the strong onset of reflections is desirable (for enabling the illusion of envelopment), though it is not clear to me that Toole's research points us in this direction. What are your thoughts on the subject?

Toole's work points to the need to control the timbre of the reverberant/reflected sound in the listening room. A natural effect you learn in any acoustic setting is to compare the direct vs. the indirect timbre. Odd comparisons create different sensations in different people, but that can also interfere hearing "through" the listening room. The time domain issue in that is the arrival of the direct (first) vs. the rest of the signal from the loudspeakers. This isn't something that is easily dissected in a paragraph.

 

[j_j]

I agree.
In my view, reducing room interaction through narrow directivity and early reflection zone treatment increases the system's ability to "recreate" the acoustics of the venue where the original event was recorded (possible only with classical music and minimalist mic'ing); in other words there is less interference of the listening-room (a room within a room).
But I understand that many would rather enjoy increased envelopment even with the downsides of some image blur and a rather confusing mix of recording- and listening-room cues, particularly with studio recordings where there were no venue acoustics to begin with.

In fact, there seem to be distinct sets of listeners. Some people like a very diffuse sound, some prefer "pinpoint" imaging, some want an illusion of soundstage plus source acoustics. These result in very different room setups. There is no 'right' or 'wrong', in terms of stereo imaging, you simply set up the one you prefer. All stereo is an illusion, pick the one you like.

I have no experience with multi-channel, mostly because of practical (space) as well as monetary reasons but also because over two thirds of my recordings are 2-channel stereo.

In addition, finding multichannel recordings that simulate an acoustic, as opposed to ones that are designed to be "impressive". Very often the idea of capturing a performance acoustic does not, in fact, exist. There are ways to provide a hall simulation that can be tailored to taste or material, but they don't seem to have any substantial representation in the actual recording market.

I have no interest in upmixing nor 3D processing, I find that too much emphasis is given to the spatial aspect and the musicality gets thrown away with the baby water.
Ultimately it's down to personal preference, one must weigh the pros and cons carefully.

Upmixing is trying to make a 50 dollar bill out of two 10's.

And preference is king in any case. It's your ears, your system, your choice.

 

[Igor Kirkwood]

But I understand that many would rather enjoy increased envelopment even with the downsides of some image blur and a rather confusing mix of recording- and listening-room cues, particularly with studio recordings where there were no .

OK.
The envelopment and the clarity of a listening room are 2 opposite settings.
It's a compromise betwenn that 2 settings.
But you can have a low level quality compromise or a high level quality compromise

A very hight level compromise is called High Fidelity.

 

[Plcamp]

My system being OB...does not load the room 90 degrees off axis like a non OB would.

When I scan for early reflections, with a measuring tape I can find every one of them...a pillar in the room, the corner of a pool table...they all show up clearly. I want to attend to any that arrive sooner than 6 ms, or that disturb the uniform frequency content of reflections when they are longer than 6 ms.

I think the right (maybe only) working approach, presuming WAF isn’t a factor, is diffusion panels behind and to the forward side of an OB, with an absorptive panel behind the listening position. I have seen users that have setup this, and they universally swear by it.

There is a gent publishing designs for fractal dispersion panels (you can make from scrap wood) for this purpose, and while they are pragmatically limited to higher frequencies, they should work quite well. I will undoubtedly try this at some point.

 

[Duke]

Toole's work points to the need to control the timbre of the reverberant/reflected sound in the listening room. A natural effect you learn in any acoustic setting is to compare the direct vs. the indirect timbre.

Thank you for taking the time to reply.

Imo the speaker's radiation pattern is effectively part of the "acoustic setting", at least in home audio. So the room can be acoustically great, but if the speaker's off-axis response sucks, then the indirect timbre will not track the direct timbre.

If I understand correctly, Toole finds that the indirect timbre should have less top-end energy than the direct, (conveniently) by a margin which corresponds with typical radiation pattern narrowing due to driver beaming. My own amateurish investigations have led me to a different conclusion: That the timbral discrepancy between the two should be minimal (even less discrepancy than Toole's findings indicate), and that BOTH should be gently downward-sloping. You are obviously vastly more experienced in real-world acoustics than I am, so I'd welcome your comments and corrections.

May I ask you this: When you speak of comparing the direct vs indirect timbre, HOW exactly do you do so?

Odd comparisons create different sensations in different people, but that can also interfere hearing "through" the listening room.

Could you go into some specifics about what intereferes with hearing "through" the listening room? THAT's the experience I'm aiming for, and any insights you can share would be greatly appreciated.

The time domain issue in that is the arrival of the direct (first) vs. the rest of the signal from the loudspeakers. This isn't something that is easily dissected in a paragraph.

Any generalities or specifics you can share would be greatly appreciated. I have drawn on Griesinger for my generalities and Geddes for my specifics, but am (hopefully) still learning. (I'm already spending money on custom parts but would rather course-correct now than learn expensive lessons the hard way further down the road.)

One source (which unfortunately I did not make note of) spoke of the arrival-time "center of gravity" of reflections playing a role in our perception of room size. I'm under the impression that a large playback room is more conducive to "hearing THROUGH the listening room" than a small one. So, if we can trick the ear/brain system into thinking the playback room is larger by manipulating the reflections to push that "center of gravity" back in time somewhat, perhaps we will hear "more of the recording" and "less of the playback room". Does that make any sense to you?

 

[Plcamp]

Open Baffle speakers attempt to reflect, with a minimum 6 ms delay, a full spectral replica of the primary wave...as per Linkwitz, this delay isn’t perceived as distortion only if it is at least 6 ms and full spectrum.


That’s what I have always thought governed this...seems it isn’t so simple?