Lack of high-end speaker reviews

[Newman]

Pulling speakers out into the room benefits two things that matter when it comes to spatial quality: The direct-to-reflected sound ratio; and the time gap between the first-arrival sound and the onset of many (if not most) of the first reflections.

Both of those factors seem to be emphasising direct sound and deemphasising indirect sound...so why does that favour increased perception of soundstage depth?

A couple of fun quotes on the myth:-

Toole: (when asked if there is such a thing as apparent source depth), "The sense of depth is very imprecise, but most of the evidence points to a proportion between the direct sound and delayed reflections and reverberation. This information is in recordings and the times involved are so large compared to those created by small room reflections that they are not likely to be a substantial factor. Play with a good stereo upmixer to appreciate what augmented lateral reflections can do for a sense of space and envelopment, including depth." (my emphasis)

Linkwitz: "Some audiophiles have claimed that the perceived sound stage depth corresponds to the distance from the loudspeaker to the wall behind it. That claim is mistaken. The wall behind the loudspeakers as well as the loudspeakers themselves completely disappear on many recordings of live events where apparently the venue acoustics are sufficiently embedded in the sound to recreate the sense of space." (my emphasis) - Linkwitz, S., Room Reflections Misunderstood?, AES 123rd convention, 2007

As usual, the likely source of this myth is cognitive bias. "Oh look, I see so much more space behind my speakers, and lo and behold, I'm hearing more depth." And of course, the converse: "Darn, my speakers are flat against the wall, and the soundstage is almost two-dimensional and flat." Now that is some real pudding for the proof-is-in-the-puddingers.

Honestly, one can embed one's speakers flat into the front wall of the room, and one would be entitled to anticipate excellent soundstage depth reproduction, in the sound waves themselves, relative to other speaker placements.

cheers

 

[jhaider]

I have found that to be true particularly of the center channel speaker. Ime a good two-channel system's phantom center image has more depth. Which doesn't really matter on movies, but imo that sense of depth adds to the experience with music videos. I have multiple customers who sold their center channel speakers because they no longer preferred to use them.

This may be the first thing I’ve wholly disagreed with you on. I have yet to have heard a single advantage for 2 channel over 3 channel. I can take or leave heights, sides, and rears, but not the center.

Did these customers do multichannel right, i.e. identical LCR at the same height and orientation, or are we talking about replacing some toppled MTM?

 

[Duke]

This may be the first thing I’ve wholly disagreed with you on. I have yet to have heard a single advantage for 2 channel over 3 channel. I can take or leave heights, sides, and rears, but not the center.

Did these customers do multichannel right, i.e. identical LCR at the same height and orientation, or are we talking about replacing some toppled MTM?

They replaced their existing left and right speakers with ones that I designed, and later sold their center channel speakers. I don't recall what speakers they replaced. In two instances the center channel speaker was more expensive than one of my speakers would have been. But I don't know whether the center channel speakers were "toppled MTM's".

I've also heard the improvement in soundstage depth on a trinaural music system. In trinaural mode the soundstage seemed shallower in the middle with eyes closed, but quite deep when the same recording was played without the center channel speaker. The owner invited me over so he could demonstrate this to me.

I'm not expecting you believe me nor to agree with me of course; I'm just going into a bit more detail about my experience.

In each of these cases the main left and right speakers they switched to were used in a time/intensity trading configuration, the toe-in being built into the speakers sometimes, as seen below.

 

[MattHooper]

As usual, the likely source of this myth is cognitive bias.

As usual, you likely overstate the case for cognitive bias.

There are many factors to consider, and I don't think anyone here has said that, with the right set up a surround system can't image well, and have depth. I already acknowledged I hear depth from my speakers even near the walls.

As I said, since many surround systems are associated with home theater set ups, the L/C/R speakers are usually constrained to near the screen wall. So you are more likely dealing with room lift that can muddy the sound (and of course DSP can help this), near wall reflections, and you have the issue of trying to make the sound totally coherent between the L/C/R speakers, which is far from easy - a good pair of 2 channel speakers do this easily since you don't need to try and get a center channel to match the sound. And again a screen or other issues with using L/C/R speakers can constrain the position of the speakers where you might not be getting as perfectly positioned regarding the listener spot, as you could only dealing with 2 speakers. So IF you have more flexibility with positioning the 2 channel speakers, as I have, and speakers tend to sound smoothest and most coherent when pulled away from my back wall, and THEN there is nothing implausible about the more coherent sound, and more precise, dimensional imaging I mention. (Not to mention in my case the stereo speakers are just better and more open sounding than the home theater speakers).

So...no..it's far from established that I'm just imagining things.

I've done the tests - plenty - my 2 channel speakers vs the surround, my two channel speakers adding a center, you name it, all done closing eyes to see which gives the greatest impression of "being there" and best imaging and sense of openness and depth. The two channel speakers alone win every time. As I said, this is not a claim that all
such comparisons in any system will have the same result. YMMV.

 

[Duke]

Both of those factors seem to be emphasising direct sound and deemphasising indirect sound...so why does that favour increased perception of soundstage depth?

Excellent question! Moving the speakers forward pushes the arrival time of the first reflections further back, but NOT NEARLY far enough to simulate the acoustics of the recording venue! So what's going on?

I think two things are happening: Pushing the strong onset of reflections back in time partially degrades the "small room signature" of the playback room; and pushing the strong onset of reflections back in time also improves the presentation of the "venue signature cues" on the recording, assuming the reflections are spectrally correct. Let's look at these one at a time:

The ear/brain system largely judges the size of a room by three things: The time delay between the direct sound and the first reflections (which indictes distances to the walls); the temporal "center of gravity" of the reflections (how long between direct sound and the "energy average" of the reflections); and the reverberation tails. When we move the speakers forward we delay the arrival of the first reflections and weaken them a bit, and we push the temporal center of gravity back in time a bit. So we have weakened the "small room signature" cues a little bit. (If you're skeptical of this, consider as a thought experiment what would happen to the "small room signature" cues if the first reflections and the temporal center of gravity of the reflections were both pushed to infinity.)

The venue spatial cues are already on the recording (whether those cues be real or engineered or both matters not), and are delivered to the ears by the direct sound and by the in-room reflections. I don't expect the in-room reflections to do a great job of delivering the first venue reflections. The in-room reflections probably do a better job of conveying the temporal "center of gravity" of the venue's reflections. But I DO expect the in-room reflections to do a very good job of delivering the reverberation tails that are on the recording, ASSUMING those in-room reflections are spectrally correct.

Now one thing that degrade this delivery of the reverberation tails would be an insufficient time gap for the ear/brain system to clearly differentiate the stream of direct sound from the stream of in-room reflections (said in-room reflections functioning as carriers for the reverberation tails on the recording). The necessity of this time gap is implied (though not explicitly stated) by acoustician and researcher David Griesinger in something he wrote in the context of concert hall acoustics:

Envelopment is perceived when the ear and brain can detect TWO separate streams:
A foreground stream of direct sound.
And a background stream of reverberation.
Both streams must be present if sound is perceived as enveloping.

So when we increase the time gap between the direct sound and the strong onset of in-room reflections, we help the ear/brain system to clearly differentiate between the foreground stream of direct sound and the background stream of reverberation (in this case, the background stream being the reverberation tails on the recording as delivered by the in-room reflections).

Toole: (when asked if there is such a thing as apparent source depth), "The sense of depth is very imprecise, but most of the evidence points to a proportion between the direct sound and delayed reflections and reverberation. This information is in recordings... ( Newman's emphasis)

Toole is saying that the depth information is on the recording. Yes it is. How do we extract and make it perceptually dominant? Upmixing is what Toole does. Imo that is not the only way. People were hearing depth on recordings long before upmixing was invented.

Linkwitz: "Some audiophiles have claimed that the perceived sound stage depth corresponds to the distance from the loudspeaker to the wall behind it. That claim is mistaken. The wall behind the loudspeakers as well as the loudspeakers themselves completely disappear on many recordings of live events where apparently the venue acoustics are sufficiently embedded in the sound to recreate the sense of space." (Duke's emphasis)

I agree with Linkwitz. And he is NOT using upmixing; he's using a spectrally-correct and fairly well-energized reflection field whose strong onset is at least 6 milliseconds behind the direct sound, if I recall correctly.

As usual, the likely source of this myth is cognitive bias. "Oh look, I see so much more space behind my speakers, and lo and behold, I'm hearing more depth." And of course, the converse: "Darn, my speakers are flat against the wall, and the soundstage is almost two-dimensional and flat." Now that is some real pudding for the proof-is-in-the-puddingers.

There may be some role played by cognitive bias. Imo there is a much stronger role played by psychoacoustics.

Honestly, one can embed one's speakers flat into the front wall of the room, and one would be entitled to anticipate excellent soundstage depth reproduction, in the sound waves themselves, relative to other speaker placements.

Absolutely! Flush-mounting the speakers eliminates reflections off the wall behind them because there is no wall behind them, and therefore the normal "small room signature" package of cues is effectively disrupted. This probably works best with speakers that have some radiation pattern control already.

Maybe something like this?

Anybody wanna help finance me bringing a pair of these in-wall speakers to Amir? Anybody wanna help me carry them up his stairs??

 

[boxerfan88]

Another one to add to the list: $750k SF

Sonus faber reveals $750,000 loudspeaker system

The new Sonus Faber Suprema looudspeaker system delivers luxurious quality and sate of the art audio, but it will set you back $750,000.

www.soundguys.com

 

[MattHooper]

I agree with Linkwitz. And he is NOT using upmixing; he's using a spectrally-correct and fairly well-energized reflection field whose strong onset is at least 6 milliseconds behind the direct sound, if I recall correctly.

Also, I presume Linkwitz wouldn't advise that his speakers go up against the back wall for best performance.

 

[Blumlein 88]

Excellent question! Moving the speakers forward pushes the arrival time of the first reflections further back, but NOT NEARLY far enough to simulate the acoustics of the recording venue! So what's going on?

I think two things are happening: Pushing the strong onset of reflections back in time partially degrades the "small room signature" of the playback room; and pushing the strong onset of reflections back in time also improves the presentation of the "venue signature cues" on the recording, assuming the reflections are spectrally correct. Let's look at these one at a time:

The ear/brain system largely judges the size of a room by three things: The time delay between the direct sound and the first reflections (which indictes distances to the walls); the temporal "center of gravity" of the reflections (how long between direct sound and the "energy average" of the reflections); and the reverberation tails. When we move the speakers forward we delay the arrival of the first reflections and weaken them a bit, and we push the temporal center of gravity back in time a bit. So we have weakened the "small room signature" cues a little bit. (If you're skeptical of this, consider as a thought experiment what would happen to the "small room signature" cues if the first reflections and the temporal center of gravity of the reflections were both pushed to infinity.)

The venue spatial cues are already on the recording (whether those cues be real or engineered or both matters not), and are delivered to the ears by the direct sound and by the in-room reflections. I don't expect the in-room reflections to do a great job of delivering the first venue spatial cue reflections. The in-room reflections probably do a better job of conveying the temporal "center of gravity" of the venue's reflections. But I DO expect the in-room reflections to do a good job of delivering the reverberation tails that are on the recording, ASSUMING those in-room reflections are spectrally correct.

Now what can degrade the delivery the reverberation tails would be the lack of a sufficient time gap for the ear/brain system to clearly differentiate the stream of direct sound from the stream of reflections (the in-room reflections being carriers of the reverberation tails on the recording). The necessity of this time gap is implied (though not explicitly stated) by acoustician and researcher David Griesinger in something he wrote in the context of concert hall acoustics:

Envelopment is perceived when the ear and brain can detect TWO separate streams:
A foreground stream of direct sound.
And a background stream of reverberation.
Both streams must be present if sound is perceived as enveloping.

So when we increase the time gap between the direct sound and the strong onset of in-room reflections, we help the ear/brain system to clearly differentiate between the foreground stream of direct sound the background stream of reverberation (in this case, the background stream being the reverberation tails on the recording as delivered by the in-room reflections.



Toole is saying that the depth information is on the recording. Yes it is. How do we extract and make it perceptually dominant? Upmixing is what Toole does. Imo that is not the only way. People were hearing depth on recordings long before upmixing was invented.



I agree with Linkwitz. And he is NOT using upmixing; he's using a spectrally-correct and fairly strong reflection field whose strong onset is at least 6 milliseconds behind the direct sound, if I recall correctly.



There may be some role played by cognitive bias. Imo there is also a stronger role played by psychoacoustics.



Absolutely! Flush-mounting the speakers eliminates reflections off the wall behind them because there is no wall behind them, and therefore the normal "small room signature" package of cues is effectively disrupted. This probably works best with speakers that have some radiation pattern control already.

Maybe something like this?

View attachment 340880

Anybody wanna help finance me bringing a pair of these in-wall speakers to Amir??

Every credible investigation into this seems to indicate, the recording overwhelms any room effects from pulling out from the wall. It would not overwhelm a better more even distribution below 200 hz if that is the case pulled out. Otherwise despite how reasonable it seems the recording is more important than other details regarding depth and space. I too think it is mostly just a visual bias, but one that works. If it works to have you perceive more depth, then fine.

I have used panels in a configuration that might make delays from the walls far enough away to matter. Tall ESL panels, positioned on the long side of a very long not terribly wide room. Angled in a fair bit which meant the backwave bounced far down the wall behind, then traveled quite a distance to the end walls and then had to travel all that distance back to your ears. And that put the null of the panel at higher frequencies in a place that nearer parts of wall reflections were mostly out of the picture.

I'd say whether or not a center is better for depth, it depends upon how the recording was done. A true three channel recording is very good. It is a direction I wish music had gone more. Many more people would manage a center speaker than those who simply are never going to add speakers to the rear or sides. One also should remember when doing something in stereo that center phantom image has some FR disturbances that are in a place likely to create some false depth with wide Left and Right spacing of your speakers. One thing that stereo never can compete with 3 channels on even with stereo recordings is anchoring the center for off center listeners. Most of the time when I've heard 3 channel stereo the center is not equal to or identical to the side speakers and that can make stereo seem better.

 

[MattHooper]

Every credible investigation into this seems to indicate, the recording overwhelms any room effects from pulling out from the wall.

Hmmm....

I'm not sure if this speaks specifically to the point you are making, but I've found that playing with positioning and room acoustics affect all sorts of characteristics
of the recording. If I allow lots of room reflection, it starts to overwhelm fine details in the recording itself, such as the recorded acoustic. If I cut down reflections a lot I get a "wet" sound in which I hear the very finest aspects of the recorded reverb or ambience, including that of a large or small hall. If I leave my room a lot more reflective I get a much more 'dry' and "instruments happening in the room" effect. That's why I have often played with that balance. When I get it just right, I get the maximum combination of hearing the acoustic contained in the recording and a sense of open spaciousness.

Just to add: I've heard speakers, and room set ups, that just didn't portray the depth right in orchestral recordings. So for instance string sections sounded extra "dry" of hall sound, and the effect was not that of hearing a large string section from a distance, but rather like a miniature toy string section had been brought in to the room a few feet from the speaker. So while there's certainly the info in the recordings, not all set ups are the same for exploiting that sonic info.

Most of the time when I've heard 3 channel stereo the center is not equal to or identical to the side speakers and that can make stereo seem better.

Yup that was a point I was making. It's not that a surround system can't sound coherent or do depth. It simply throws more challenges to do so - center channels are notoriously, often not completely coherent with the mains. Can be done, but two channel speakers just tend to be more easily coherent than adding a lot more speakers that cover the above-room-modes range as well.

 

[restorer-john]

All the data we have shows that speakers which are preferred relative to other speakers remain so regardless of if they are compared in mono or stereo.

What specific up to date 'data' do you 'have' that shows that?

Imaging, image stability, balance, and crossover matching is not discussed, tested or even acknowledged by proponents of the single speaker audition.

It's a glaring hole in the testing of loudspeakers, which are sold in pairs, to be used in pairs, listening to stereophonic content by humans with two ears.

There is nobody who should be purchasing a pair of loudspeakers without listening to them as a pair.

 

[voodooless]

What specific up to date 'data' do you 'have' that shows that?

Did you sneak the words “up to date” in there to discredit the work of Toole?

Imaging, image stability, balance, and crossover matching is not discussed, tested or even acknowledged by proponents of the single speaker audition. There is nobody who should be purchasing a pair of loudspeakers without listening to them as a pair.

It's a glaring hole in the testing of loudspeakers, which are sold in pairs, to be used in pairs, listening to stereophonic content by humans with two ears.

Show us with data that this is true, and I’m sure people will jump on it to create a new scoring system for stereo sound. Until then, it’s just speculation on your part.

Around 9:25

Does that mean you should not audition speakers in stereo pairs? Probably not. This research is not about how people should audition speakers, it’s about how to unlock the highest preference score out of a speaker, ultimately to make it sell better. And to do that, you do not need to evaluate a stereo pair. Since the reasoning goes both ways, listening in stereo should be just fine, just realize that it will not give you more insights. It will however make for a more natural way of auditioning, which is probably more comfortable for most people.

 

[Newman]

What specific up to date 'data' do you 'have' that shows that?

The extracts from Toole that I posted earlier today are relevant.

re: "up to date", Toole often mentions that a lot of audio research has enduring currency. Not all, of course. But he doesn't hesitate to say so when new data leads to new conclusions.

cheers

 

[Duke]

Every credible investigation into this seems to indicate, the recording overwhelms any room effects from pulling out from the wall.

Well of course! There is enormous variation in the sense of space from one recording to the next. What I'm advocating is, unmasking the spatial (ambience) cues which are already on the recording.

Otherwise despite how reasonable it seems the recording is more important than other details regarding depth and space.

Again, of course! We want to hear the depth and space that is already on the recording, and not have that masked by the "small room signature" depth and space cues of our playback rooms!

I too think it is mostly just a visual bias, but one that works. If it works to have you perceive more depth, then fine.

I'm NOT claiming that the following is universally true, but it has been my experience with some types of speakers:

Move the speakers out from the wall a little, and you get a little bit of improvement in depth. Move them a bit more, get a bit more improvement. And so on. Then at some point you move them a bit more and this time the change is dramatic. The presentation transitions from "they are here" to "you are there". And each recording sounds like you are in a different space, maybe not precisely the space on the recording but still it's quite an enjoyable addition to the listening experience.

 

[Pearljam5000]

It looks like an awesome vintage lamp
But no doubt it's cool
Probably the most unique looking speakers

 

[MattHooper]

"you are there"

That is the goal I have cultivated and feel I have achieved. An immersive space that changes with each recording.

 

[MaxBuck]

Due to the nature of ASR and how it obtains products for review, it is understandable that Amir, et al don’t receive very expensive speakers for review, either from owners or manufacturers.

Therefore do we think that the ASR database of reviews is not representative enough of the loudspeaker performance landscape?

Are there some examples out there of truly exceptionally well engineered (and measuring) speakers that are in the >$100k category?

As a former employee of Meridian Audio in the UK I spent a lot of time listening to their flagship speakers at the time, the DSP8000SE (circa $100k/pair I believe). The company’s design goals were always for reproduction accuracy. Whilst not my favourite speaker of all time the 8000SE are hugely impressive and sound very lifelike.

Companies asking those prices for their products should run the tests themselves and publish the results.

 

[Duke]

That is the goal I have cultivated and feel I have achieved. An immersive space that changes with each recording.

Yup! And that "changes with each recording" thing doesn't get old, does it?

 

[restorer-john]

The extracts from Toole that I posted earlier today are relevant.

re: "up to date", Toole often mentions that a lot of audio research has enduring currency. Not all, of course. But he doesn't hesitate to say so when new data leads to new conclusions.

Listeners are firstly listening to a pair of loudspeakers, sitting I presume, in a central(ish) location (as per his pictures), presented with a 2 channel stereophonic recording reproduced on a pair of loudspeakers.

Then they are presented with the 'monophonic test' which is what exactly? We have no idea. It could be one of 4 (possibly more) things:

• A genuine single microphone mono recording, completely different to the stereophonic recording, but recorded at the same time and in the same space.
• A summed 'mono' version of the stereophonic recording with all the issues that occur in phase and cancellation when that is done.
• One channel only of the stereophonic recording (which would seem like a really dumb idea to me).
• An electrically summed 'mono' signal derived from the stereo recording.

Then the subjects were subjected to "only the left loudspeaker". So, why not the right speaker? And why were they forced to listen to the left speaker only? Did they stay seated or could they get up? Were they allowed to move so both ears got largely the same content/level or was it offset as is suggested. None of this is clear in his book.

The 1985 test seems to state they were "stereo 2 channel recordings" which means you cannot create a "mono" recording from those recordings as they already contain the left and right difference signals in phase, level and FR baked into each channel- combining it creates a whole new beast that is not monophonic.

 

[Newman]

Excellent question! Moving the speakers forward pushes the arrival time of the first reflections further back, but NOT NEARLY far enough to simulate the acoustics of the recording venue! So what's going on?

I think two things are happening: Pushing the strong onset of reflections back in time partially degrades the "small room signature" of the playback room; and pushing the strong onset of reflections back in time also improves the presentation of the "venue signature cues" on the recording, assuming the reflections are spectrally correct. Let's look at these one at a time:

The ear/brain system largely judges the size of a room by three things: The time delay between the direct sound and the first reflections (which indictes distances to the walls); the temporal "center of gravity" of the reflections (how long between direct sound and the "energy average" of the reflections); and the reverberation tails. When we move the speakers forward we delay the arrival of the first reflections and weaken them a bit, and we push the temporal center of gravity back in time a bit. So we have weakened the "small room signature" cues a little bit. (If you're skeptical of this, consider as a thought experiment what would happen to the "small room signature" cues if the first reflections and the temporal center of gravity of the reflections were both pushed to infinity.)

The venue spatial cues are already on the recording (whether those cues be real or engineered or both matters not), and are delivered to the ears by the direct sound and by the in-room reflections. I don't expect the in-room reflections to do a great job of delivering the first venue reflections. The in-room reflections probably do a better job of conveying the temporal "center of gravity" of the venue's reflections. But I DO expect the in-room reflections to do a very good job of delivering the reverberation tails that are on the recording, ASSUMING those in-room reflections are spectrally correct.

Now one thing that degrade this delivery of the reverberation tails would be an insufficient time gap for the ear/brain system to clearly differentiate the stream of direct sound from the stream of in-room reflections (said in-room reflections functioning as carriers for the reverberation tails on the recording). The necessity of this time gap is implied (though not explicitly stated) by acoustician and researcher David Griesinger in something he wrote in the context of concert hall acoustics:

Envelopment is perceived when the ear and brain can detect TWO separate streams:
A foreground stream of direct sound.
And a background stream of reverberation.
Both streams must be present if sound is perceived as enveloping.

So when we increase the time gap between the direct sound and the strong onset of in-room reflections, we help the ear/brain system to clearly differentiate between the foreground stream of direct sound and the background stream of reverberation (in this case, the background stream being the reverberation tails on the recording as delivered by the in-room reflections).



Toole is saying that the depth information is on the recording. Yes it is. How do we extract and make it perceptually dominant? Upmixing is what Toole does. Imo that is not the only way. People were hearing depth on recordings long before upmixing was invented.



I agree with Linkwitz. And he is NOT using upmixing; he's using a spectrally-correct and fairly well-energized reflection field whose strong onset is at least 6 milliseconds behind the direct sound, if I recall correctly.



There may be some role played by cognitive bias. Imo there is a much stronger role played by psychoacoustics.



Absolutely! Flush-mounting the speakers eliminates reflections off the wall behind them because there is no wall behind them, and therefore the normal "small room signature" package of cues is effectively disrupted. This probably works best with speakers that have some radiation pattern control already.

Thanks to Duke for the extensive consideration of my question and references.

I think a cornerstone of your commentary (best read when interleaved with my original post) is your belief that the delays in small rooms, with speakers moved away from walls, are sufficient to create a perceptual impression of more depth. That is not in accordance with my reading of Toole.

I think Toole is clear enough that small rooms (ie domestic listening rooms) are manifestly inadequate for that task, and cannot do anything but get in the way. Close to walls or distant, same-same. The delay thresholds for depth perception are much longer than domestic rooms can do.

cheers

 

[Newman]

View attachment 340881
Listeners are firstly listening to a pair of loudspeakers, sitting I presume, in a central(ish) location (as per his pictures), presented with a 2 channel stereophonic recording reproduced on a pair of loudspeakers.

Then they are presented with the 'monophonic test' which is what exactly? We have no idea. It could be one of 4 (possibly more) things:

• A genuine single microphone mono recording, completely different to the stereophonic recording, but recorded at the same time and in the same space.
• A summed 'mono' version of the stereophonic recording with all the issues that occur in phase and cancellation when that is done.
• One channel only of the stereophonic recording (which would seem like a really dumb idea to me).
• An electrically summed 'mono' signal derived from the stereo recording.

Then the subjects were subjected to "only the left loudspeaker". So, why not the right speaker? And why were they forced to listen to the left speaker only? Did they stay seated or could they get up? Were they allowed to move so both ears got largely the same content/level or was it offset as is suggested. None of this is clear in his book.

The 1985 test seems to state they were "stereo 2 channel recordings" which means you cannot create a "mono" recording from those recordings as they already contain the left and right difference signals in phase, level and FR baked into each channel- combining it creates a whole new beast that is not monophonic.

Think of it this way: if an expert researcher designs and executes an experiment, then forms a conclusion, then his interpretation of it is vastly superior to the casual observer.

For example, it is easy for a sceptical observer to say the results indicate that listening in stereo makes a big difference to some speaker types more than others. (People have repeatedly said as much on ASR.) But Toole, with deeper understanding, has clarified that the main thing it shows is that listening in stereo hides the differences between speakers, and hides the preferences.

cheers