Early horizontal reflections - isn't there a price to be paid?

[tmtomh]

I have noted that when @amirm reviews a speaker that has good off-axis response - or off-axis response that helps improve the overall estimated in-room response - he writes something like, "off-axis looks good so don't go absorbing the side reflections," or "the speaker seems designed to use reflections to tame the treble so don't go crazy with wall absorption and let the speakers use the room to create a larger image."

I understand the logic of this, but in my system - admittedly just one data point - I find that while limited side-wall absorption narrows the soundstage a little bit, it also improves imaging.

I have a single 2x4 foot, 2" thick panel on each side wall, more or less at the first horizontal reflection point. After reading some of Amir's reviews, I have tried removing the panels. My immediate impression is a slightly wider soundstage, but a more-than-slight reduction in soundstage precision. Without the panels there is a bit more ambience and "air" around the music to go with that perception of wider soundstage - although I detect that mostly when I put the panels back and then I hear the sound again without that bit of added air/ambience.

The effect without the panels has a pleasant aspect to it, but I find myself missing the extra bit of tightness and soundstage precision in the mids and treble when I have the panels on the walls. Something about the imaging just seems to lock in when the panels are there. I don't experience the difference as extreme, but I would not call it subtle either - it's immediately obvious to me, with any musical style or recording I might choose, at any reasonable listening volume I might choose.

This is of course just my subjective experience, and I while I really don't think I'm imagining the difference, I am open to a well-reasoned argument for confirmation bias if someone thinks what I'm saying can't be true. I'm also open to the argument that the increased soundstage width is merely additive and that the soundstage precision is not actually reduced by removing the panels - but again, that doesn't really square with what I think I'm hearing.

At any rate, I'd love to hear others' experiences and/or insights about this.

Thanks!

 

[March Audio]

I have noted that when @amirm reviews a speaker that has good off-axis response - or off-axis response that helps improve the overall estimated in-room response - he writes something like, "off-axis looks good so don't go absorbing the side reflections," or "the speaker seems designed to use reflections to tame the treble so don't go crazy with wall absorption and let the speakers use the room to create a larger image."

I understand the logic of this, but in my system - admittedly just one data point - I find that while limited side-wall absorption narrows the soundstage a little but, it also improves imaging.

I have a single 2x4 foot, 2" thick panel on each side wall, more or less at the first horizontal reflection point. After reading some of Amir's reviews, I have tried removing the panels. My immediate impression is a slightly wider soundstage, but a more-than-slight reduction in soundstage precision. Without the panels there is a bit more of ambience and "air" around the music to go with that perception of wider soundstage - although I detect that mostly when I put the panels back and then I hear the sound again without that bit of added air/ambience.

The effect without the panels has a pleasant aspect to it, but I find myself missing the extra bit of tightness and soundstage precision in the mids and treble when I have the panels on the walls. Something about the imaging just seems to lock in when the panels are there. I don't experience the difference as extreme, but I would not call it subtle either - it's immediately obvious to me, with any musical style or recording I might choose, at any reasonable listening volume I might choose.

This is of course just my subjective experience, and I while I really don't think I'm imagining the difference, I am open to a well-reasoned argument for confirmation bias if someone thinks what I'm saying can't be true. I'm also open to the argument that the increase soundstage width is merely additive and that the soundstage precision is not actually reduced by removing the panels - but again, that doesn't really square with what I think I'm hearing.

At any rate, I'd love to hear others' experiences and/or insights about this.

Thanks!

You are not imagining it, this is precisely what I experience and IIRC Toole comments in his book about it.

With more first reflection reduction the central image and sound positions tighten up and are more precise, but as you say it sort of reduces the ambience.

Just go with what you like the best, no right or wrong here.

 

[andreasmaaan]

+1 for @March Audio's reply.

Strong lateral reflections tend to increase perceive spaciousness and apparent source width. Remove or reduce these reflections and, conversely, you end up with a reduced apparent source width (a tighter image) and less spaciousness. So I think your experience is totally consistent with the research.

Another thing you could try would be to position the panels such that each absorbs the first reflection from the speaker adjacent it, but not the reflection from the speaker nearer the opposing wall. Whether this is possible will depend on your speakers, room, and listening position ofc. But if possible, it may give you a nice balance between spaciousness and image tightness (as the lateral reflection from the opposing wall will arrive later than that from the adjacent wall).

 

[pozz]

I'd say what you experienced well-established but not universal. Reflection strength and combfiltering go hand-in-hand. The stronger the first, the more severe the second, and the fuzzier imaging becomes. But the total effect is heavily dependent on the proportions and reflective character of your room (direct affecting reflection arrival times and strengths covered in the "precedence effect").

The issue as I see it is that there is no good literature on image or soundstage control at home for stereo or multichannel setups. There are rough guides and numbers, but nothing as far as I know that will tell you the net effect of adding a few absorptive panels. You can measure the ETC and RT60, opine on the quality of decay and evenness of reverb times, or measure FR and do the kinds of analysis we are used to doing here.

The main book on acoustic absorbers and diffusers, Cox & D'Antonio's Acoustic Absorbers & Diffusers, has very, very little to say on the psychoacoustic impacts of treatment. Absorbers make images smaller, and diffusors make them bigger (pretty much a direct quote). Most of it is concerned with the specifics of construction, modelling and prediction of effects, and the difficulty of precise measurement.

 

[richard12511]

I have noted that when @amirm reviews a speaker that has good off-axis response - or off-axis response that helps improve the overall estimated in-room response - he writes something like, "off-axis looks good so don't go absorbing the side reflections," or "the speaker seems designed to use reflections to tame the treble so don't go crazy with wall absorption and let the speakers use the room to create a larger image."

I understand the logic of this, but in my system - admittedly just one data point - I find that while limited side-wall absorption narrows the soundstage a little but, it also improves imaging.

I have a single 2x4 foot, 2" thick panel on each side wall, more or less at the first horizontal reflection point. After reading some of Amir's reviews, I have tried removing the panels. My immediate impression is a slightly wider soundstage, but a more-than-slight reduction in soundstage precision. Without the panels there is a bit more of ambience and "air" around the music to go with that perception of wider soundstage - although I detect that mostly when I put the panels back and then I hear the sound again without that bit of added air/ambience.

The effect without the panels has a pleasant aspect to it, but I find myself missing the extra bit of tightness and soundstage precision in the mids and treble when I have the panels on the walls. Something about the imaging just seems to lock in when the panels are there. I don't experience the difference as extreme, but I would not call it subtle either - it's immediately obvious to me, with any musical style or recording I might choose, at any reasonable listening volume I might choose.

This is of course just my subjective experience, and I while I really don't think I'm imagining the difference, I am open to a well-reasoned argument for confirmation bias if someone thinks what I'm saying can't be true. I'm also open to the argument that the increase soundstage width is merely additive and that the soundstage precision is not actually reduced by removing the panels - but again, that doesn't really square with what I think I'm hearing.

At any rate, I'd love to hear others' experiences and/or insights about this.

Thanks!

You're not imagining it. Absorbing the first reflections definitely improves the imaging, at the expense of soundstage width. I think more data is needed to determine what the majority will prefer. Toole's data does suggest that most will prefer the wider soundstage over the better imaging, but I don't think the sample size is sufficient to give a conclusive answer. I see it as a weak "majority", if that makes any sense; kinda like the preference for the Harman curve in headphones.

 

[RayDunzl]

The effect without the panels has a pleasant aspect to it, but I find myself missing the extra bit of tightness and soundstage precision in the mids and treble when I have the panels on the walls. Something about the imaging just seems to lock in when the panels are there. I don't experience the difference as extreme, but I would not call it subtle either - it's immediately obvious to me, with any musical style or recording I might choose, at any reasonable listening volume I might choose.

Wide vs narrow dispersion here without side or ceiling absorption. There is carpeting.

Unsmoothed sweep at the listening position, no windowing.

Let's just call them interesting differences.

Phase

Group Delay

Impulse

 

[tmtomh]

I guess I shouldn't be surprised anymore at the high quality of the responses one can get here - thank you all!

@March Audio , yes, the center image is probably the thing I'm most attached to with the wall panels in place: center-mixed vocals and snare drums (and I could swear even the higher harmonics of kick drum hits) are just so good and present and easy to localize right in front of me when I have the panels up that I don't want to let go of that benefit.

@andreasmaaan , thanks for bringing up the distinction between the adjacent speaker and the opposite-wall speaker. I put the panels up to absorb adjacent-speaker first reflections. I will have to double-check the measurements and calculations I did when I first set up the room (I moved into a new space a little over a year ago), but if memory serves each speaker's opposite-wall first reflection mostly misses the panel and either hits blank wall or CD/bookshelf units I have on the side walls a couple of feet from the acoustic panels. So while I cannot claim to have given a single moment's thought about opposite-wall reflections when I set up the room, it's possible I already accidentally have a version of what you've recommended. Interesting!

@pozz and @richard12511 , thanks for your insights about the research - or lack thereof - on the actual psychoacoustics and people's preferences. I am not at all surprised to hear that there might be a majority preference for greater ambience at the expense of imaging precision: the perception of ambience and air, the feeling of the music being "big" and of being enveloped or overwhelmed by it, I can totally relate to that and can imagine that many people would love that. I enjoy it too - but I've always preferred what audiophiles sometimes dismiss as "clinical" or "analytical" sound (which is why I like this place so much - the dedication to accuracy and transparency). I find the better imaging just feels more accurate to me - it feels closer to what I imagine the artist and engineer likely heard on the monitors in the studio. A subjective preference of course, but on balance i enjoy it more and feel like I'm missing less that way.

 

[Bugal1998]

I have noted that when @amirm reviews a speaker that has good off-axis response - or off-axis response that helps improve the overall estimated in-room response - he writes something like, "off-axis looks good so don't go absorbing the side reflections," or "the speaker seems designed to use reflections to tame the treble so don't go crazy with wall absorption and let the speakers use the room to create a larger image."

I understand the logic of this, but in my system - admittedly just one data point - I find that while limited side-wall absorption narrows the soundstage a little bit, it also improves imaging.

I have a single 2x4 foot, 2" thick panel on each side wall, more or less at the first horizontal reflection point. After reading some of Amir's reviews, I have tried removing the panels. My immediate impression is a slightly wider soundstage, but a more-than-slight reduction in soundstage precision. Without the panels there is a bit more of ambience and "air" around the music to go with that perception of wider soundstage - although I detect that mostly when I put the panels back and then I hear the sound again without that bit of added air/ambience.

The effect without the panels has a pleasant aspect to it, but I find myself missing the extra bit of tightness and soundstage precision in the mids and treble when I have the panels on the walls. Something about the imaging just seems to lock in when the panels are there. I don't experience the difference as extreme, but I would not call it subtle either - it's immediately obvious to me, with any musical style or recording I might choose, at any reasonable listening volume I might choose.

This is of course just my subjective experience, and I while I really don't think I'm imagining the difference, I am open to a well-reasoned argument for confirmation bias if someone thinks what I'm saying can't be true. I'm also open to the argument that the increased soundstage width is merely additive and that the soundstage precision is not actually reduced by removing the panels - but again, that doesn't really square with what I think I'm hearing.

At any rate, I'd love to hear others' experiences and/or insights about this.

Thanks!

My experience is similar to yours... Certainly noticeable but not a massive difference. A few A/B comparisons removed any doubt for me that there's a change.

Possibly semantics, but I find the extra ambiance with treated reflections to make my overall perception of soundstage to be wider while also making the location of instruments in the sound field more precise.

With treatments in place sounds are frequently outside the width of the speakers and extending out into the room giving a sense of envelopment. I percieve the tighter 'imaging' as allowing more space around the instruments (air?). The phantom center is also tighter with reflections treated.

I haven't been able to reach any conclusions on the impact-- if any-- on the sense of depth behind the speakers.

With the exception of a few classical recordings and a Jazz recording or two (which I rarely play) I have a pretty strong preference for a heavily treated room. I do agree with the criticism raised by some that "over" treating makes the room sound dull and muddy, but only until EQ is applied, and then it's just wonderful sound to my ears.

Edit: My comments above pertain to high quality recordings where there is ambience present in the source material... On lesser recordings I find room reflections to be pleasant. A less resolving audio system also tends to be better for lower quality tracks IMO

 

[theyellowspecial]

It seems all the reviews that have the "no treatment" disclaimer are technically well-designed speakers (for use in average rooms with mostly bare walls) with sidewall reflections that have relatively similar FR to the on-axis FR.

Do well-designed speakers like this reduce time-effects from first reflections that lead to poorer imaging? In other words, how important is it that first reflections reach our ears at least 5ms after the direct sound (or else should be absorbed) with these types of speakers?

EDIT: Nevermind. Just read "Delaying Room Reflections: Constraints on Room Size and Loudspeaker Placement". Seems like exploiting the precedence effect requires reflected sound to be of similar content to the direct sound, so absorption techniques apply regardless.

 

[FeddyLost]

If you prefer analytical sound with better imagery, it's good solution to walk around some good studio control rooms and find out well done measurable preferences. Maybe it will help you to make better treatment without experimenting with your exact room.
I'm also fan of 3D and clarity, so I went into some crude "non-environment" approximation. Can't recomment this solution to anyone, because it's too dry, but by the way scene heavily depends on record and speaker placement, and sometimes definitely much wider than speakers.
It's all about preferences. Usually, fans of live performances don't care much about imaging, because there's no imaging in orchestra. I've almost literally grown in headphones, so I just like good imaging, soundstage and layering, but don't really care how realistic this sound event is.
If you have big room, you can diffuse early reflections and it will be good compromise.

 

[napilopez]

I have noted that when @amirm reviews a speaker that has good off-axis response - or off-axis response that helps improve the overall estimated in-room response - he writes something like, "off-axis looks good so don't go absorbing the side reflections," or "the speaker seems designed to use reflections to tame the treble so don't go crazy with wall absorption and let the speakers use the room to create a larger image."

I understand the logic of this, but in my system - admittedly just one data point - I find that while limited side-wall absorption narrows the soundstage a little bit, it also improves imaging.

I have a single 2x4 foot, 2" thick panel on each side wall, more or less at the first horizontal reflection point. After reading some of Amir's reviews, I have tried removing the panels. My immediate impression is a slightly wider soundstage, but a more-than-slight reduction in soundstage precision. Without the panels there is a bit more of ambience and "air" around the music to go with that perception of wider soundstage - although I detect that mostly when I put the panels back and then I hear the sound again without that bit of added air/ambience.

The effect without the panels has a pleasant aspect to it, but I find myself missing the extra bit of tightness and soundstage precision in the mids and treble when I have the panels on the walls. Something about the imaging just seems to lock in when the panels are there. I don't experience the difference as extreme, but I would not call it subtle either - it's immediately obvious to me, with any musical style or recording I might choose, at any reasonable listening volume I might choose.

This is of course just my subjective experience, and I while I really don't think I'm imagining the difference, I am open to a well-reasoned argument for confirmation bias if someone thinks what I'm saying can't be true. I'm also open to the argument that the increased soundstage width is merely additive and that the soundstage precision is not actually reduced by removing the panels - but again, that doesn't really square with what I think I'm hearing.

At any rate, I'd love to hear others' experiences and/or insights about this.

Thanks!

To supplement what's already been said: the quantity of sidewall reflections are a matter of preference. This applies to both speaker directivity and the reflectivity of your room. What you prefer is what you prefer.

The important thing to remember about sidewall reflections is that it's not like frequency response and directivity quality, for which striving for flatter and smoother is almost always a good thing (with diminishing returns past a certain point, of course). The current research seems to suggest people can have a marked preference for stronger or weaker sidewall reflections, but one isn't obviously better than the other.

I markedly prefer having louder sidewall reflections. A few dozen speakers tested over the course of a couple of years with nearly-bare sidewalls have made that trend obvious, in which I consistently feel I would buy wider-sounding speakers over narrower ones that might seem technically better.

You seem to prefer the opposite, and that's fine. And of course, these are independent viewpoints. Perhaps our rooms are just very different, and our preferences not so much. =]

As for what the research actually says...

You're not imagining it. Absorbing the first reflections definitely improves the imaging, at the expense of soundstage width. I think more data is needed to determine what the majority will prefer. Toole's data does suggest that most will prefer the wider soundstage over the better imaging, but I don't think the sample size is sufficient to give a conclusive answer. I see it as a weak "majority", if that makes any sense; kinda like the preference for the Harman curve in headphones.

It seems pretty clear that there is an overall preference for louder sidewall reflections, but I agree with the weak majority thing -- I see it as a favorite color. Most people prefer blue, doesn't mean there shouldn't be other colors too.

That said, in Toole's book his/harman's own research is just a small part of the evidence pointing in favor of louder sidewall reflections. Though of course, Toole is summarizing the research, his references are mostly to the works of others on sidewall reflections, much of them research into recording studios and the like. I started this post by listing all the studies, but then it got too long =]

I think you already know this, but the interesting trend is that for recreational listening sidewall reflections it seems more sidewall reflections are preferred, but at the same time it seems that many recording professionals have a quite strong preference for a more direct soundfield. For mixing in particular, while mastering leans more towards loud sidewall reflections again.

One interesting tidbit looking back at this chapter (7) of Toole's book revealed was from a Klippel study in 1990:

"Figure 7.17 shows that there is an optimum amount of reflected sound; there can be too much and too little, depending on the nature of the program. This is in line with the evidence in my own research, reported earlier, that the recording itself is a major factor. The smallest amount is required to provide a satisfying setting for speech, more is required for music, and music has many varieties. The optimum difference between the direct and reflected sound fields is about 3 dB for speech, 4 dB for a mixed program and 5 dB for music. There is no frequency dependence considered in these numbers, and we know that most loudspeakers do not exhibit constant directional behavior at all frequencies.

A good loudspeaker for this purpose would therefore be one that has two qualities: wide dispersion, thereby promoting some amount of reflected sound, and a relatively constant directivity index, so that the direct sound and reflected sounds have similar spectra. The essence of good design in this respect would be to deliver the optimum proportion of reflected sound for the program being auditioned."
"

It would be interesting to see how much those figures for ideal reflection SPL translate to preference. Maybe the speaker/treatment that has the best soundstage in our homes is the one that yields roughyl 4dB down reflections.

EDIT: I'd also like to add that I think I find myself gravitating towards constant-directivity-ish behavior too, and that might contribute to my preference for more sidewall reflections. Wider speakers are often closer to constant directivity throughout the majority of the range before they drop off steeply. Big waveguided speakers tend to have that deep tilting off axis and I think something about that just doesn't jive as well with my ears.

Yet that wasn't as much of a problem with the D&D 8C, which exhibits strong horizontal CD behavior. Similarly the JBL L100 Classic is one of the best imaging speakers I've heard, and while it's quite wide up top, it's also narrower than usual at the bottom due to big woofer design. Just a thought.

 

[richard12511]

"Figure 7.17 shows that there is an optimum amount of reflected sound; there can be too much and too little, depending on the nature of the program.

I read his book a few years ago, but it seems people are always quoting parts of it that I don't seem to remember. It was a long book, so I guess I really need to read it again(and take notes this time).

That there is "an optimum amount of reflected sound" is something I had hypothesized on my own(though maybe my subconscious was "remembering" this section of the book ) to try and explain a discrepancy between my own blind listening test results and the Harman results.

We did a mono, stereo, and multichannel(5) blind test between 2 wide dispersion speakers and 1 narrow dispersion speaker. The weird thing about the result was that the wide dispersion speakers dominated the mono test, but lost the multi channel test quite badly. This goes against the Harman/NRC science, which says that the same speakers that win in mono will always also win stereo and multi channel tests. Struggling to come up with an explanation, my best guess was that maybe there was an "optimal amount of system dispersion". The wide dispersion speakers were closer to that optimal amount in mono, but were far exceeding it in the multi channel test.

I need to repeat the test, though, as I now see aspects of the test I could have done better.

 

[andreasmaaan]

Another aspect of it is a fair amount of ambiguity as to what Toole means by “wide dispersion”. In the main discussion of this topic, which is in chapter 7 of the book, he most commonly uses “wide” and “narrow” to contrast what I’d call average-directivity, non-controlled directivity 2-way monopoles on one hand (“wide”), with dipoles that produce almost no output whatsoever 90 deg to either side (“narrow”). Having re-read the relevant chapter recently, I’m not convinced Toole’s characterisation of “narrow” would extend to some speakers commonly categorised as “narrow” on ASR.

This goes against the Harman/NRC science, which says that the same speakers that win in mono will always also win stereo and multi channel tests.

If I’m not mistaken, the Harman/NRC tests didn’t say anything as to preferred directivity in multichannel, and Toole has stated elsewhere that wide directivity is less important or unimportant in multichannel setups.

 

[tmtomh]

Another aspect of it is a fair amount of ambiguity as to what Toole means by “wide dispersion”. In the main discussion of this topic, which is in chapter 7 of the book, he most commonly uses “wide” and “narrow” to contrast what I’d call average-directivity, non-controlled directivity 2-way monopoles on one hand (“wide”), with dipoles that produce almost no output whatsoever 90 deg to either side (“narrow”). Having re-read the relevant chapter recently, I’m not convinced Toole’s characterisation of “narrow” would extend to some speakers commonly categorised as “narrow” on ASR.

This is fascinating - thanks! So based on what you're saying it would appear that most listeners would prefer monopoles to dipoles because of the former's wider dispersion, and (stating the obvious I know), would likely prefer monopoles with waveguides or some other design feature to increase tweeter dispersion and minimize beaming, yes?

It would also seem that side-wall treatments would become more advisable with wider-dispersion monopoles, as the dispersion characteristics of the speaker itself would tend to made side reflections less important for establishing a satisfactory soundstage width. (This does not take into account speakers designed based on the assumption of significant side reflection contribution to their overall perceived frequency balance.)

 

[thewas]

If I’m not mistaken, the Harman/NRC tests didn’t say anything as to preferred directivity in multichannel, and Toole has stated elsewhere that wide directivity is less important or unimportant in multichannel setups.

I even think of remembering reading in his book at that for multichannel setups dryer acoustics are recommendable as the envelopment and spaciousness comes from the various surrounding channels, which is quite something in the direction of higher directivity loudspeakers.
Wide dispersion is rather needed for the limited stereo to make its illusion work well.

 

[detlev24]

Especially when looking at room acoustics, I would suggest to read some of Ethan Winer's explanations.

Although many people seem to disagree with his opinion, (as far as I know) nobody could prove him wrong by presenting contradicting repeatable measurements.

Well, let's not get too philosophical. This shall not become another thread of dis-/belief... It is a science, at last:

Early Reflections Are Not Beneficial

 

[andreasmaaan]

This is fascinating - thanks! So based on what you're saying it would appear that most listeners would prefer monopoles to dipoles because of the former's wider dispersion, and (stating the obvious I know), would likely prefer monopoles with waveguides or some other design feature to increase tweeter dispersion and minimize beaming, yes?

I’m pretty sure Toole would agree with this with regard to stereo listening, yeh.

 

[andreasmaaan]

Although many people seem to disagree with his opinion, (as far as I know) nobody could prove him wrong by presenting contradicting repeatable measurements.

Well, afaik nobody disagrees with his measurements. It’s the psychoacoustic relevance of them that the discussion turns on

 

[detlev24]

[...] It’s the psychoacoustic relevance of them that the discussion turns on

Absolutely. How the brain processes information and what is being perceived to be pleasant is a totally different, just barely understood, aspect of the ongoing research.

In these regards, one would have to experiment to find the personal likings.

 

[napilopez]

I read his book a few years ago, but it seems people are always quoting parts of it that I don't seem to remember. It was a long book, so I guess I really need to read it again(and take notes this time).

That there is "an optimum amount of reflected sound" is something I had hypothesized on my own(though maybe my subconscious was "remembering" this section of the book ) to try and explain a discrepancy between my own blind listening test results and the Harman results.

We did a mono, stereo, and multichannel(5) blind test between 2 wide dispersion speakers and 1 narrow dispersion speaker. The weird thing about the result was that the wide dispersion speakers dominated the mono test, but lost the multi channel test quite badly. This goes against the Harman/NRC science, which says that the same speakers that win in mono will always also win stereo and multi channel tests. Struggling to come up with an explanation, my best guess was that maybe there was an "optimal amount of system dispersion". The wide dispersion speakers were closer to that optimal amount in mono, but were far exceeding it in the multi channel test.

I need to repeat the test, though, as I now see aspects of the test I could have done better.

Did you read the latest (2017) edition @richard12511 ? There are a few updates to the directivity stuff, I believe, including a couple of recent studies, but I never read the earlier edition. As @andreasmaaan mentioned, Toole suggests multi-channel negates the need for wide dispersion a few times.

Chapter 7.4.6 "Although side wall reflections are approved of by many for recreational stereo listening, in a multichannel system they truly are optional."

11.5: "In movie sound, the goal is to give the listener the impression of being in the space portrayed on the screen. Consequently, the acoustics of the cinema should not dominate the artistic space portrayed in the soundtrack, whatever it is. For this reason, cinemas in general need to be, and usually are, relatively well damped acoustically, demonstrating reverberation times that are similar to homes at least over the mid- to high-frequency range (Figure 10.1)."

I'm pretty sure there's at least one more quote to this effect, though I can't recall where. There is though also the fact that confidence in speaker ratings gets reduced the more channels one adds.

'Tis why I like the kindle edition overall though.. I can look up terms and bookmarks and make sure I'm not spewing complete nonsense

Another aspect of it is a fair amount of ambiguity as to what Toole means by “wide dispersion”. In the main discussion of this topic, which is in chapter 7 of the book, he most commonly uses “wide” and “narrow” to contrast what I’d call average-directivity, non-controlled directivity 2-way monopoles on one hand (“wide”), with dipoles that produce almost no output whatsoever 90 deg to either side (“narrow”). Having re-read the relevant chapter recently, I’m not convinced Toole’s characterisation of “narrow” would extend to some speakers commonly categorised as “narrow” on ASR.

Hmm, I didn't really get that impression. My impression of what he normally means 'narrow' are large horns, and he has the historical impression of a time when they were more common, probably.

"In those days the powerful main monitor loudspeakers were moderately directional mid- and high-frequency horns, and side walls were usually angled to direct the residual first lateral reflections into the broadband back wall absorber. Recording engineers preferred to be in a strong direct sound field, and that is what they got."
(Talking about recording control rooms)"On the more distant loudspeakers some directional control is desirable to deliver sound to the listening area, not the room boundaries. Horns are common. "
"In Figure 18.3a a classic large horn loudspeaker exhibits evidence of acoustical interference and high directivity, both typical of the genre, but the underlying spectral balance was well maintained on and off axis."

He also implies a few times that the spin is mostly meant to deal with conventional forward-firing speakers, so it doesn't make much sense that he'd be talking about dipoles otherwise.

"Examples in this book have emphasized loudspeakers of the most common configuration: forward firing cone/ dome or cone/ horn. It needs to be asked: What about other designs, like dipoles, bipoles, and omnidirectional? Do the rules change?"

That said, I don't totally disagree with you. Most of what's tested here would probably be on the 'wider' side. The question then becomes what's optimal for most people.

It would also seem that side-wall treatments would become more advisable with wider-dispersion monopoles, as the dispersion characteristics of the speaker itself would tend to made side reflections less important for establishing a satisfactory soundstage width. (This does not take into account speakers designed based on the assumption of significant side reflection contribution to their overall perceived frequency balance.)

Not andreasmaaan, but directivity and sidewall reflections are two sides of the same coin. So it's somewhat the opposite of what you are saying. The more sidewall reflections are absorbed, the less significant the dispersion characteristics of the speakers become.

After all, the dispersion characteristics of the speaker are meaningless for a stationary listener without sidewall reflections.

Imagine listening in an anechoic chamber -- you only hear the direct sound and directivity becomes meaningless. It is similar to listening to open-back headphones. There is no soundstage width beyond what is already in the recording. This is one of the reasons recording engineers may prefer being in a stronger direct sound field. Regardless of whether having louder or quieter reflections is more pleasant than the other, one certainly lets you hear more of the music and less of the room around it.

Ultimately you just need to find the balance between dispersion and reflections that works for you.

I forget whom I stole this from, but I generally describe it as such: narrow directivity/high room treatment transports you to the recording venue, while wide directivity/reflective sidewalls brings the musicians into your home.

It depends on the music and how much spatial information it has built into the recording itself, but I think it helps get the idea across.