The ASR "objectivists tribe" ;) has to read the Keynotes at the AES160th by Lars Risbo

[amirm]

When the single speaker was tested at Harman, the distance was far enough to side walls to avoid early arriving reflections, and to my knowledge the rear wall in Harman rooms always have absorption.

What kind of absorption you are talking about? Here is a picture I took:

There is a thin curtain to hide the mechanism for the speaker shuffler. That would filter out high frequencies of which, there is hardly any behind the speakers.

 

[amirm]

thanks @Bjorn, exactly the kind of discussion I was hoping for!

It is a tired discussion we have had over and over again. Some folks want to cling to old ideas in Pro space that came about with zero research and impose it for home listening. None of it was based on any kind of research -- just stuff people made up like live end, dead end, etc. As I responded to, a lot of answers exist which I hope you are aware of if he is not.

 

[amirm]

I don't know why people think 70% of the answer is the same as nothing. We will never get to 100% with speakers or headphones because there are no standards of production. With no reference to reality, then we can only build high confidence models of what works. The last 30% has to be dealt with or ignored, not used as a means to dismiss incredible progress we have made after decades of research.

If folks want to say the research is not good enough, then show up with your research. If you have none, then don't spread folklore.

I thought @Lars Risbo was interested in investigating non-linearities of which, no one has done more work to highlight them than ASR. I plan to do a lot more but throwing rocks at us as not caring is great example of friendly fire.

But now it seems we are going after tired arguments of dead vs live rooms??? Very strange.

 

[Suono]

An informal blind listening test was conducted between M2 and Salon 2 and the latter won

I take it for granted that a less directive, wide-dispersion speaker won, but that doesn't mean that early reflections aren't detrimental to focusing. A speaker with wide dispersion, and above all, coherent, is definitely preferable.

 

[Bjorn]

An informal blind listening test was conducted between M2 and Salon 2 and the latter won.

As I mentioned before: The M2 has pretty strong aberrations in the directivity. It's not a particular constant broadband speaker. A former Harman/JBL employed, Don Keele, called these measurements crap. While that's a strong statement, the directivity is certainly not stellar.


Regardless of this, you still need to consider the acoustics of the room the test was performed in (which you probably don't believe matters), the quantity of listeners, and it would make sense to test several narrow broadband constant directivity speakers before one actually claims anything objective. Science is seeking truth, and turns every stone to do so.

Besides, M2 isn't particular narrow in its directivity either. It would not avoid early arriving side wall reflections. It's a more like a cardioid direcivitity in the area of 120-140°. Most horns are designed with 90° and lower. I wouldn't call the M2 a narrow constant broadband speaker.

 

[Bjorn]

I fully agree to the last sentence.
What I not fully understand is, what you mean by “study on preferences for directivity“. As far as I know there has not been a specific study investigating directivity. And there is no “directivity target“ as a result either. As I see it the main results are “smooth and flat on-axis (no resonances)“ and “smooth of axis sound“.

Then there is the important question in how far the details of the test have an impact on the result on relative preference and what the limitations of the results are. (And Toole did investigate that in respect to many factors.)
However, it is much easier to construct conditions and constellations that the research did not fully account for, than to do the research that takes all these variations into consideration.

So it would be great to have more information on the below (including the limitations of these studies, too).

Before we can arrive at such “results“ as below. (Emphasis by me)

I was refering to Toole's research that wide speaker directivity seemed to be preferred. In practice, we're seing more the opposite though. I think one reason for that is most place their speakers (at least hear in Europe) very close to the side walls. The reflections from these walls will then arrive within a few ms. While Harman tests a speaker in middle of the room with great distance to the side wall, arriving much later in time. The Harman room is also generally much wider (and longer) vs the rooms most people have.

As for the weakness of the studies that went into LEDE, I believe it's mainly that they didn't always use enough listeners to make the tests statistical. A LEDE room would sound considerably more spacious than the Harman room due to all the diffused energy. And also far more accurate and detailed since all early reflections were suppressed below -25 dB. The goal was a combination of accuracy to hear the recorded signal as well as possible, and with delopment and spaciousness to make it similar to the best concert halls. Clearly not something all can achieve in their homes.

Studies of preferences are far more difficult vs accuracy. So many aspects go into "preference", that it's perhaps a bit meaningsless IMO to make science out of it.

 

[Bjorn]

What kind of absorption you are talking about? Here is a picture I took:

There is a thin curtain to hide the mechanism for the speaker shuffler. That would filter out high frequencies of which, there is hardly any behind the speakers.

You're showing what we call front wall in acoustics. I was talking about the rear wall.

In the Harman room, the rear wall is partially covered with 4" (10 cm) absorption panels. Not a good choice when the reflections arrive so late in time and it will effect spaciousness and development in a negative way.

The use of some Skyline diffusers in the room (both rear and side walls) is also discussable. They offer high absorption, very little diffusion, and sends half the energy in a direction that isn't beneficial. I assume the curved products are polys. They seem to be too narrow to go as low as such treatment should ideally do, and don't offer any phase grating. Not the best option either.

 

[Bjorn]

You misunderstood NTK's post and seem to not be familiar with the research. He said and I repeat, for the purposes of evaluating speaker preference, the room effect is dialed out as long as listeners are allowed to acclimate to it.

This does not at all mean that the room has no effect on what you perceive. Dr. Toole and crew have done a ton of research in this area and huge sections of his book are dedicated to every reflective surface.

Where this nets out currently is that you must get the on-axis frequency response right. And the right sum of off-axis. Once there, then it is an open debate as to preference for wide vs narrow directivity. It is this research that is unfinished. Not that it impacts preference for speakers.

I have the book, have read it (a good while ago I admit), but we see this differently. I don't think there's far enough evidence that we can say "the room is dialed out in regards to speaker preference".

Did they ever test speakers with a slanting ceiling behind and close to the listening position? There are numerous room dimensions and odd geometries in room that can effect the result quite strongly. With a very low cathedral ceiling, we experience that very limited vertical dispersion for example is highly preferable.

This comes down to having done enough tests in various environments before claiming any science, and this is what we disagree on.

There's also the weakness IMO of the speaker designs they have tested. Naturally, they stick to popular commercial brands. But that's generally not where you find the better speaker designs.

 

[olieb]

I was refering to Toole's research that wide speaker directivity seemed to be preferred.

I understand, but among the “results“ of Toole's research this seems to me to be the point where is most cautious. Please correct me, but there are not that many studies related to that and here is a quote from himself about the issue from another thread. (#105) [Bolding by me]
There seems to be no clear: “narrow is bad, wide is good“ verdict.

Toole:
As I said, to control loudspeaker directivity as a truly independent experimental variable is a challenge - not necessarily impossible, but a challenge. There are examples of manufacturers of loudspeakers capable of varied amounts of sound radiated towards the adjacent sidewall, promoting the virtues of such a feature. I have no problem with the concept, and psychoacoustics would indicate that it would be the adjacent sidewall bounce that would have the greatest effect, not overall directivity of the loudspeaker. It would increase the sense of space and many people find it pleasant, but at the same time it would add ambiguity to the individual soundstage images and other people would find that unattractive. There would be, I can imagine, a significant interaction with the musical genre - spacious classics vs. in-your-face rock.

So maybe you are overemphasising this point a bit.

EDIT: If you want to bring forward the alternative of “narrow is good, wide is bad“, then I suppose someone has to do the work, so we can get some evidence.

 

[Bjorn]

I understand, but among the “results“ of Toole's research this seems to me to be the point where is most cautious. Please correct me, but there are not that many studies related to that and here is a quote from himself about the issue from another thread. (#105) [Bolding by me]
There seems to be no clear: “narrow is bad, wide is good“ verdict.

So maybe you are overemphasising this point a bit.

EDIT: If you want to bring forward the alternative of “narrow is good, wide is bad“, then I suppose someone has to do the work, so we can get some evidence.

Good point. It may be more his followers that have promoted wide directivity as a preference. You can see what Toole wrote about this years ago. But he doesn't mention the arrival time of those lateral reflections, which is important. My guess is that he's talking about reflections arriving after 7 ms and is based on one single speaker tested in the middle of the wide Harman room.

The most debated issue relates to first lateral reflections. Some of those arguing vociferously in favor of eliminating them seem to have a conflict of interest, being providers of acoustical materials. Others have more reasoned arguments. I say up front that there can be no universally satisfactory answer because there is no universal scheme for recording stereo or multichannel signals. Only through controlled listening tests can we get useful insights, and these are in short supply. In the meantime opinions reign supreme, and there are many of them.

In the book I show results of several double-blind evaluations, some done by me, some done by others, showing that listeners tend not to be disturbed by lateral reflections, and many even prefer them. I also point out that the professional side of the industry almost universally feels the need to eliminate them. I suggest, respectfully, that humans have a remarkable ability to learn, to adapt, and that recording engineers spending their days adding, adjusting, and removing - at will - delayed sounds from mixes undoubtedly are more highly sensitized to these sounds than are lay listeners. This probably applies to any audio professional, acoustical consultant or enthusiast who focuses enough attention on this task. We learn to hear things and, once heard, they tend not to go away. I well remember that during the resonance detection experiments, we all became extremely skilled at hearing and identifying resonances. During the tests, and for some time afterward, we were hearing little resonances in everyday life that normally would have been totally unnoticed. From such things paranoia is born, and if we had taken this to an extreme, we would have damped our wine glasses.

For stereo listening I have found that it very much depends on the program. Music with lots of decorrelated sounds, classical for example, is sometimes enhanced by reflections, although coincident-mic recordings may benefit from a lack of reflections - letting the direct sounds be more dominant (the Blumlien stereo effects work best in an almost anechoic situation). Pan-potted recordings (the majority of pop) end up delivering essentially monophonic sounds from left and right loudspeakers, and these may well benefit from a bit of spatial enhancement. Otherwise we are left with what really annoys me about stereo: a relatively spatial set of phantom images created by both loudspeakers, and two "anchor" images created by the left and right loudspeakers playing solo. In some recordings we hear a whole string section emerging from a single loudspeaker. Not realistic, and not even pleasant. In the past, I have recommended that serious stereo listeners hang absorbent drapes along each side wall, pulling them out and pushing them back to suit what they are listening to. Our listening room at the National Research Council in Canada had this feature.

Absorbent drapes would be very bandlimited type of treatment BTW.

Too bad he didn't test proper diffusion to battle what annoyd him about stereo. This lead him to multichannel music, something I personally don't like.

 

[kyuu]

In the Harman room, the rear wall is partially covered with 4" (10 cm) absorption panels. Not a good choice when the reflections arrive so late in time and it will effect spaciousness and development in a negative way.

View attachment 536987

The use of some Skyline diffusers in the room (both rear and side walls) is also discussable. They offer high absorption, very little diffusion, and sends half the energy in a direction that isn't beneficial. I assume the curved products are polys. They seem to be too narrow to go as low as such treatment should ideally do, and don't offer any phase grating. Not the best option either.

I'm quite certain that's not the room that was used for speaker preference testing.

 

[krabapple]

I don't use EQ at all in my reference setup. I used Dirac to set up my sub(s) where it belongs best, and to not be totally unused (as would be my natural preference, honestly).

I really shouldn't be interested in this but...your reference setup does not include subwoofers?

 

[krabapple]

I can't tell whom you're referring to by "he,"

Lars in his talk, obviously, given the context of my reply.

but if @Floyd Toole , he has written in multiple editions of Sound Reproduction text like "Ando et al. (2000) found that musicians judge refl ections to be about seven times greater than ordinary listeners, meaning that they derive a satisfying amount of spaciousness from refl ections at a much lower sound level than ordinary folk: “Musicians prefer weaker amplitudes than listeners do.” It is logical to think that this might apply to recording professionals as well, perhaps even more so, because they create artificial reflections electronically and manipulate them at will while listening to the effects. There can be no better opportunity for training and/or adaptation. In fact, it is entirely reasonable to think that acousticians who spend much of their lives moving around in rooms while listening to revealing test signals can become sensitized to aspects of sound fields that ordinary listeners blithely ignore. This is a caution to all of us who work in the field of audio and acoustics. Our preferences may reflect accumulated biases and therefore may not be the same as those of our customers" (this is from the second edition). Two groups

Also Toole: "In Fig. 14 the author has modified the original data to separately show the result of evaluations by trained and untrained listeners. This is compared to the small room prediction from Fig. 13(a). The “all listeners” average curve is close to the predicted target, except at low frequencies where it is apparent that the strongly expressed preferences of inexperienced listeners significantly elevated the average curve. In fact, the target variations at both ends of the spectrum are substantial, with untrained listeners simply choosing “more of everything.” An unanswered question is whether this was related to overall loudness—more research is needed. However, most of us have seen evidence of such more-bass, more-treble listener preferences in the “as found” tone control settings in numerous rental and loaner cars. More data would be enlightening, but this amount is sufficient to indicate that a single target curve is not likely to satisfy all listeners..."
http://www.aes.org/e-lib/browse.cfm?elib=17839. Two groups that they smooshed/averaged into one

If @Sean Olive , https://www.audiosciencereview.com/...er-preference-curve.50602/page-4#post-1845069. You can see some of my issues with what's commonly quoted as "research" in this forum at https://www.audiosciencereview.com/...er-preference-curve.50602/page-3#post-1819700 and https://www.audiosciencereview.com/...er-preference-curve.50602/page-5#post-1848097. Three groups? I'm still skeptical about the way this is presented

If @j_j , I'm sorry, I'm super-foggy on the details, but I seem to recall that he's written about certain groups of listeners being more sensitive to pre-echo or other artifacts of encoding. I can try to find it at a later date.

Distinct groups of listener preference go all the way back to concert hall acoustics: https://www.audiosciencereview.com/...cert-hall-acoustics-links-and-excerpts.51487/

I didn't think 'he' was that much of mystery.

Anyway, right, I mentioned multi-modal (which IIRC Lars implies) and bi-modal models (the ones I was thinking of, from having read publications by Toole & associates). Thanks for providing specifics. (The Purifi post of the talk is down right now so I can't quote Lars verbatim)

 

[Bwaslo]

I doubt anyone here thinks "the room doesn't matter". After all, there are extreme cases, even in USA. Here's the space I have to work with, very early reflections at left, open space to the right, high ceilings.
At the moment I'm leaning toward Orbit11 speakers over Ascilab C6B + subs. Not because I think Orbits are universally better, but because, being cardioid, they avoid more early reflections from the left for two more octaves of range beyond the directivity of the C6Bs. I'm much less aware of the L/R asymmetry. In a larger or more symmetric room, preferability could be different.
Directivity can be a tool you don't need in every case.

 

[krabapple]

You've also got a reflective table in front of you?

Speaker design can be leveraged to advantage to deal with reflections, and/but so can toe-in.

 

[Bwaslo]

You've also got a reflective table in front of you?

Speaker design can be leveraged to advantage to deal with reflections, and/but so can toe-in.

It's the situaion I have (though removing the coffee table doesn't seem to make a great improvement, certainly none in perceived symmetry

Toe in only works when there is sufficient and, preferably uniform, directivity. Below where it all goes omni toe-in is no help.

 

[Duke]

And no, it [early sidewall reflections] is not "highly audible." But audible in the way it widens the perceived location of the speaker -- a good thing. This is extensively research by Dr. Toole and crew and also by others such as Clark.

"Early sidewall reflections are a good thing" (or something to that effect) may be the majority position, but it is not a universal conclusion among those with expertise in the subject:

"The earlier and the greater in level the first room reflections are, the worse they are. This aspect of sound perception is controversial. Some believe that all reflections are good because they increase the listeners' feeling of space – they increase the spaciousness of the sound. While it is certainly true that all reflections add to spaciousness, the very early ones (<10 ms.) do so at the sake of imaging and coloration." - Earl Geddes

"The earlier a reflection arrives the more it contributes to masking the direct sound." - David Griesinger

"Presence depends in the ability of the ear and brain to detect the direct sound as separate from the reflections... When presence is lacking the earliest reflections are the most responsible." - David Griesinger

"Transients are not corrupted by reflections if the room is large enough - and 10 ms of reflections free time is enough." - David Griesinger

"Image perception is dominated by the very earliest sound from the speaker, i.e. the direct sound (first arrival), and the sound that arrives in the first 5-10 milliseconds. The ear simply integrates this all into one lumped sum. This includes the speakers’ anechoic response along the listening axis, cabinet diffractions, and diffractions and reflections from nearby objects like equipment cabinets or televisions. Basically what one wants for good imaging is a pseudopoint source response, i.e. a single direct sound free from any diffractions or reflections for at least 5, but hopefully a full 10 milliseconds." - Earl Geddes

My point being, it is not bad science to prioritize minimizing the early reflections, including the first sidewall reflections. Doing so may not be the position supported by the majority of the published research and analysis, but that can be a reflection (<- no pun intended) of differing valid priorities rather than wrong thinking.

My understanding is that @Bjorn aims for even more reflections-free-time than the 10 milliseconds Geddes and Griesinger mention, and that would be even better.

In my opinion.

 

[Bwaslo]

Agreed that reflections are beneficial. Provided they aren't all from one side!

Intensifying direct sound over reflections can make it seem pretty "dry", little immersion. I think it comes down to having sound come from different directions (with some balance that is). Other than when outdoors, sound coming from only one direction doesn't sound natural. I use ambience radiators and dsp to add well delayed reflected sounds, those radiators can be level adjusted without screwing up the balance of the direct sound. Artificial ambience is better than little ambience

 

[olieb]

Basically what one wants for good imaging is a pseudopoint source response, i.e. a single direct sound free from any diffractions or reflections for at least 5, but hopefully a full 10 milliseconds." - Earl Geddes

For me the point here seems to be whether the focus is on imaging (+coloration) or on spaciousness.
For imaging early reflections apparently are on the detrimental side.
But they tend to increase spaciousness. So it seems to be a question of individual preference and compromise, as is often the case.
[And there is the question of use case, too. Listening for recreation or studio room as a tool for inspecting the details of a recording.]

However, is spaciousness always a good thing? Or can there be a “wrong“ kind of spaciousness?
Maybe the spaciousness of my listening room is appropriate and preferred for “Fast Car“, but it does not work so well for a Mahler symphony? Or more generally, can the wrong kind of (small room) reflections negatively impact the impression of concert hall sound? Then it might be better to have less of it and let the (hopefully) recorded concert hall reflections do their thing.

 

[Chr1]

Sorry if I am being a dufus...
Surely the amount of preferred room reflection/reverb is somewhat subjective?
For home hifi at least.