A Broad Discussion of Speakers with Major Audio Luminaries

[Keith_W]

I would like to mention one minor detail: on page 119 of the slides, the spinorama shown is for a 3-way floor-standing speaker (not 4-way); As it is my dream speaker, I am very familiar with its specific spinorama profile and recognized the model immediately

Wow, there is no identification of the speaker on that slide and you managed to recognize it!

Actually, I recognize it too. It's a KEF Blade 2. It is recognizable by the irregularity in directivity at 200Hz, which is where the front drivers transition to the side drivers. I don't know if it's sad or hilarious that we can both recognize a speaker from its Spinorama alone, maybe you and I need to get out more.

 

[Jukebox]

Wow, there is no identification of the speaker on that slide and you managed to recognize it!

Actually, I recognize it too. It's a KEF Blade 2. It is recognizable by the irregularity in directivity at 200Hz, which is where the front drivers transition to the side drivers. I don't know if it's sad or hilarious that we can both recognize a speaker from its Spinorama alone, maybe you and I need to get out more.

It is truly a fine art to recognize a speaker based on the spinorama data alone )
So its ok in my book ...i guess
Also, I am taking my wife on a summer holiday
Starting tomorrow, I will be away from the audio gear, forums and reviews for one week

 

[Sal1950]

OOPS! A typo, because I certainly know better. I think I know how it happened, but that is no excuse. Thanks for noticing - it has been corrected.

"Any man makes typo errors spends a night in the box".

 

[kmanusa]

But I don't think there has been a failure to communicate!

 

[Mart68]

But I don't think there has been a failure to communicate!

It's 'communicake'

 

[krabapple]

If I might be so bold, your book assumes a certain level of technical competence and knowledge on the part of the reader. Hobbyists don't know what an Energy-Time Curve is. Hardly anybody outside of ASR knows what we mean by "minimum-phase", and I would wager a large number of people here don't know either.

If our goal is to expand scientific thinking amongst audiophiles, it has to be clear that acquiring such knowledge will benefit them.

Some journals we've published in encourage the inclusion of a breakout box explaining technical terms used in the paper. This is a good option (as long as the explanations are written to be comprehensible to the nonspecialist reader!)

For a digital text to be read in a web browser, it is easy to add mouseover/pop-up explainers for any word.

For e-books, not so much, though Kindle does have a general 'dictionary' lookup for highlighted words.

 

[Floyd Toole]

a breakout box explaining technical terms used in the paper. This is a good option (as long as the explanations are written to be comprehensible to the nonspecialist reader!)

Aye, and that's the rub. I have used text boxes a few times in my books, but in the end they take space that is necessary for telling the prime story. Something is sacrificed in print books with a limited page count. Even color was not possible in mine. It is very constraining. And then there is the question: how simplistic does the breakout box content need to be? At what intellectual level should the explanation begin? I consumed multiple chapters just to explain what a frequency response curve means - start with dB, loudness, pitch/frequency, the meaning of irregularities, tilts, and so on. In fact, I wrote much of an entire book explaining it. Writing an explanatory text while defining all terms used within it is an encyclopedic endeavour if one is thorough, and it does not, in my opinion, qualify as "For Dummies".

That is why I put some effort into the website accompanying the 4th edition, especially the PowerPoint slide shows that, I think, explain much of the book content in a more digestible format. But even these slide shows have been considered too complex for much of the ASR audience, and simplified "For Dummies" versions suggested.

I have spent decades presenting and discussing this content to audiences ranging from CEDIA members (many are audiophiles) to engineers, and general university students, and listening to the feedback and questions. ASR and other forum discussions have added another perspective which includes input from people of many very different backgrounds. Misunderstandings are frequent, even among people with technical backgrounds.

It seems to me that much more simplification in the "For Dummies" direction, simply will create "Dummies" who think they understand a subject that they really don't. This simply adds "noise" to the discussion.

Amir and Erin measure, present and discuss spinoramas and more - definitive data - in print and video forms. Their opinions have substance. The problem is that they cannot review all products on the market, but spinorama data is available now from other sources. If average audio enthusiasts want to competently interpret those data they will need to do some serious homework. Otherwise, we end up with misleading, seemingly simple, "room curves" as unreliable guides. Loudspeakers are not that simple, and bass problems in the listening room are not even considered - two chapters in my book, and about 30% of one's overall assessment of sound quality.

It is complicated . . .

 

[MarkS]

Dr. Toole has been participating recently in the thread on electrostatic speakers; some of his remarks there should be of more general interest. Here is his first recent post in that thread:

https://www.audiosciencereview.com/...trostatic-speakers.19205/page-65#post-2652696

I found this comment of his particularly noteworthy:

Floyd Toole said: The hundreds of loudspeakers and listeners that have been involved in decades of careful research indicate that, when non-auditory biasing influences are controlled or eliminated, most people most of the time prefer non-resonant, uncoloured, neutral, technically accurate loudspeakers. Such loudspeakers can be dipoles, forward-firing cone and dome/horn, bipolar or omnidirectional.

 

[Newman]

The noteworthiness depends on what you think is implied....

Is he saying that all configurations of loudspeaker can be equally preferred if they are "non-resonant, uncoloured, neutral, technically accurate loudspeakers"? I doubt it....or more precisely, I very much doubt that such was his main point.

And all that is left after removing that interpretation, is Floyd saying that "non-resonant, uncoloured, neutral, technically accurate loudspeakers" are preferred to less so, in all configurations. Which is hardly news to his well-versed readers.

Floyd has written extensively on the psychoacoustic preference for delayed in-room sound that meets certain criteria for amount of delay, amount of attenuation (or gain), and directions (or angles of arrival at the head). And also of the merits of dispersion patterns that somewhat resemble dispersion patterns of live instruments and voice.

And the various loudspeaker configurations do not all meet those criteria to equal degrees.

cheers

 

[krabapple]

Well, you could just ask him.

 

[Duke]

Five years ago I asked @Floyd Toole the following arguably relevant question:

"What are your thoughts about steady-state room curves for omnidirectional or polydirectional loudspeakers? Would there be any advantage to reducing the spectral discrepancy between the direct and reflected sound, something your old bioplar Mirage M-1's may have done?"

Here is his reply, emphasis mine:

"My personal experience is too limited to answer with any certainty, and nobody I know of has pursued this as a research question. The well-behaved multi-directional speakers I have heard sound just fine, and are a viable alternative to forward firing designs. They appear to add a bit more "space" to a stereo presentation, and for those mixes that have hard-panned L and R images they might present a 'softer' image. But real investigation is needed to give a certain answer."

Link

So I think it is the specifics - the behavior of the specific speaker - that matters the most, with well-behaved multi-directional speakers not being excluded because of their unorthodox radiation patterns.

 

[RickS]

Five years ago I asked @Floyd Toole the following arguably relevant question:

"What are your thoughts about steady-state room curves for omnidirectional or polydirectional loudspeakers? Would there be any advantage to reducing the spectral discrepancy between the direct and reflected sound, something your old bioplar Mirage M-1's may have done?"

Here is his reply, emphasis mine:

"My personal experience is too limited to answer with any certainty, and nobody I know of has pursued this as a research question. The well-behaved multi-directional speakers I have heard sound just fine, and are a viable alternative to forward firing designs. They appear to add a bit more "space" to a stereo presentation, and for those mixes that have hard-panned L and R images they might present a 'softer' image. But real investigation is needed to give a certain answer."

Link

So I think it is the specifics - the behavior of the specific speaker - that matters the most, with well-behaved multi-directional speakers not being excluded because of their unorthodox radiation patterns.

In my experience (still have Mirage OMD-5s in one my systems), as @Floyd Toole's response to you suggests, results from more omni-directional are dependent on the recording. My CBTs are now in my brother's studio, but I am guessing a comparable speaker array, could offer a more realistic presentation if content was targeted to it. As Floyd has done, also have moved towards surround technology, but I do not see the current approach (more speakers in more locations) as a likely solution that the masses (or even most enthusiasts) are likely to adopt.

I know sound bars are often disdained, but if you have heard one place a sound in 3D space (with the right software), this seems an attainable goal for a more sophisticated set of front speakers with a more holistic approach to delivering content. Atmos with some sort of room adaptive/corrective software might get there, but it will likely take the imminent demise of the current (and forced imo) multi-speaker approach before the industry will deliver a more acceptable offering. I have a good-sized room for home theater and have been doing it for decades now and it is still way too much effort to get realistic presentation. I can foresee a better day. Until it happens, despite the flaws (and most of my current content), stereo still has sufficient merit for me.

 

[Duke]

In my experience (still have Mirage OMD-5s in one my systems), as @Floyd Toole's response to you suggests, results from more omni-directional are dependent on the recording.

It's not obvious to me that @Floyd Toole is saying omni-directional-ish speakers are more recording-dependent, but maybe he is; hopefully he'll clarify if he feels the need.

I think he's saying that well-behaved multi-directional speakers tend to convey more "sense of space", which arguably follows from having a lower direct-to-reflected ratio, though again imo the specifics matter.

... despite the flaws, stereo still has sufficient merit for me.

Yup, I'm still hoping to squeeze as much juice as possible out of stereo. And imo spatial quality is one of the places where there may still be a bit of juice left.

 

[Newman]

Yup, I'm still hoping to squeeze as much juice as possible out of stereo. And imo spatial quality is one of the places where there may still be a bit of juice left.

I gather that you are trying to "squeeze" from stereo delivery ... because there are more effective ways to squeeze more out of stereo source .. but they involve more-than-stereo delivery.

Apparent source width (ASW) and envelopment are the major perceptual spatial qualities that impact preference ratings.

Of these, ASW is minimised with dipoles and narrow-dispersion speakers, and even omni is not going to increase ASW compared to a wide dispersion front-firing speaker, because it is actually directing less energy at the near side walls (for a given SPL). And for squeezing spatial from a stereo source, upmixed stereo will easily exceed any of these for ASW by directing energy to side (and front wide) speakers.

As for envelopment, it is dominated by energy from the sides and rear. None of the unconventional speakers, used as a stereo pair, deliver more of that energy than wide dispersion front firing conventional speakers. Some of them increase the front:rear energy ratio, which is quite unhelpful to perceptions of envelopment. And again, same as ASW, upmixed stereo will easily exceed any of these by directing energy to side and rear speakers.

I think it is helpful to acknowledge Toole's repeated mentions that perceptions of spaciousness are dominated by the recording's mixing and mastering. It feels like one may be looking in the wrong direction to seek these gains from unconventional stereo pairs.

cheers

 

[john61ct]

Yes my inferred general sense is that the effectiveness of ALL the various techniques for adding spatial perceptions, vary by the content's mixing/mastering.

Pure stereo content to stereo-only playback equipment, really how radical could that get?

Upmixing to multichannel hardware from stereo-only content, more promising but I suspect will always be hit or miss by mixing/mastering used.

The ideal level of impact I think will always come from the evolution of encoding (unfortunately proprietary), the recording sessions' specifically targeting the specific matching layout of playback equipment.

But maybe not, no one knows the future

 

[MattHooper]

It's not obvious to me that @Floyd Toole is saying omni-directional-ish speakers are more recording-dependent, but maybe he is; hopefully he'll clarify if he feels the need.

I think he's saying that well-behaved multi-directional speakers tend to convey more "sense of space", which arguably follows from having a lower direct-to-reflected ratio, though again imo the specifics matter.



Yup, I'm still hoping to squeeze as much juice as possible out of stereo. And imo spatial quality is one of the places where there may still be a bit of juice left.

And here’s to you for pursuing that aim !!!


Missing from some analysis is that, given the practicalities of real life living situations and budgets, etc. A simple pair of speakers often fit the bill better than a full surround system.
There are scenarios in which, for various practical reasons, one may achieve better and more coherent sound with stereo speakers. Despite advances in surround sound, there remain some sensible reasons that the market for stereo speakers is still so big among audiophiles.

I’ve got a two channel system and a very good surround system. Both sound fantastic. Each does certain things better than the other. I wouldn’t like to give up either system.

If somebody wants to push for as much spatial goodness or realism as they can squeeze out of a stereo presentation… that’s great stuff. I have done so simply in my own ways playing with different speakers and set ups in my room. (I’m amazed how sometimes the sound seems to go off way into the distance beyond the width of the speakers, especially in symphonic recordings).

Actually designing loudspeakers with such a goal is taking it to the next level and I totally admire the skill and effort. I look forward to the day when I can get out to a show to hear your speakers.

 

[Duke]

I gather that you are trying to "squeeze" from stereo delivery ... because there are more effective ways to squeeze more out of stereo source .. but they involve more-than-stereo delivery.

Yes, yes, and yes.

Apparent source width (ASW) and envelopment are the major perceptual spatial qualities that impact preference ratings.

Is image precision also a major perceptual spatial quality? I have been assuming so, but now that I think about it, I don't actually know whether it's generally considered to be "major" or not.

What about soundstage depth? Maybe that falls more under "envelopment".

Of these, ASW is minimised with dipoles and narrow-dispersion speakers, and even omni is not going to increase ASW compared to a wide dispersion front-firing speaker, because it is actually directing less energy at the near side walls (for a given SPL). And for squeezing spatial from a stereo source, upmixed stereo will easily exceed any of these for ASW by directing energy to side (and front wide) speakers.

That sounds right to me.

Ime there is a trade-off relationship between ASW on the one hand, and image precision, soundstage depth, and envelopment on the other. But the latter three tend to be fairly subtle compared with how enjoyable it is for sound sources to appear laterally beyond the speakers. I am well aware that many listeners would and do opt for increased ASW in a trade-off situation.

Note that the strong early same-side-wall reflections which expand the Apparent Source Width are deliberately avoided in a Reflection-Free Zone (perhaps more precisely "Early-Reflection-Free Zone") studio control room:

As for envelopment, it is dominated by energy from the sides and rear. None of the unconventional speakers, used as a stereo pair, deliver more of that energy than wide dispersion front firing conventional speakers. Some of them increase the front:rear energy ratio, which is quite unhelpful to perceptions of envelopment.

That's what I would have thought too! But psychoacoustics can be highly counter-intuitive. You see, there is arguably a window of opportunity for mult-directional loudspeakers to present enhanced envelopment relative to conventional monopoles, and this is revealed in Figure 7.8 on page 202 of the 4th edition of @Floyd Toole's book.

The higher the little marks, the greater the perceived envelopment. Configuration (a) is two loudspeakers set up normally. But look at configuration (b), which has four loudspeakers in front of the listener, two at +/- 30 degrees off centerline, and the other two at +/- 60 degrees off centerline:

Notice that configuration (b) is competitive in perceived envelopment with the best of the configurations having sound sources located behind the listener, including the 5-channel one, configuration (i).

Does that surprise you? It surprised me too!

A multi-directional loudspeaker can be designed (and set-up) such that the arrival directions of the secondary arrays' reflections approximate the arrival directions of the outer two speakers in configuration (b). Again, the specifics matter; ime in this case they matter a lot.

I think it is helpful to acknowledge Toole's repeated mentions that perceptions of spaciousness are dominated by the recording's mixing and mastering. It feels like one may be looking in the wrong direction to seek these gains from unconventional stereo pairs.

What would be the most effective way to convey the perception of spaciousness that is already on the recording? THAT is what I'm seeking, within the constraints of stereo playback.

Imo the "holy grail" of spatial quality would be the sensation of "you are there", wherein the sense of space on the recording is perceptually dominant over whatever "sense of space" arises from the playback room itself. So THAT is what I am seeking, by presenting the information on the recording in a way that minimizes the "small room signature" of the playback room while simultaneously effectively presenting the "venue spatial cues" on the recording (whether said "venue cues" be real or engineered or both). Will bore you with details on request.

Back to ASW for a moment: Ime one enabler of "you are there" is a fairly long time interval between the first-arrival sound and the strong onset of reflections (see the RFZ control room drawing above; that's probably the best way to do this). Unfortunately those same strong, early same-side-wall reflections that broaden the Apparent Source Width tend to arrive too early for "you are there" to result. In other words, imo "you are there" is one of the things that tends to be traded-off in exchange for increased ASW.

cheers

And cheers to you to, my friend who keeps me on my toes, or doing my song and dance, as the case may be!

 

[goat76]

What about soundstage depth? Maybe that falls more under "envelopment".

No, depth is simply the distance to the recorded source or to a distant reflective boundary in the recording. Envelopment is exactly what the word says, sounds that seems to surround you to the sides or maybe even appear to be coming from behind you in the main listening position.

 

[Duke]

No, depth is simply the distance to the recorded source or a distant reflective boundary in the recording. Envelopment is exactly what the word says, sounds that seems to surround you to the sides or maybe even appear to be coming from behind in the main listening position.

I think you're right.

 

[Duke]

And here’s to you for pursuing that aim !!!

Thank you very much for the encouragement.

If somebody wants to push for as much spatial goodness or realism as they can squeeze out of a stereo presentation… that’s great stuff. I have done so simply in my own ways playing with different speakers and set ups in my room. (I’m amazed how sometimes the sound seems to go off way into the distance beyond the width of the speakers, especially in symphonic recordings).

Unfortunately expanding the soundstage width is not something I'm good at. The things I do hopefully improve the spatial quality in other ways, but NOT in that way. I chose to pursue a package of characteristics that goes in a different direction... why? Because that's where I think I can make a contribution.

Actually designing loudspeakers with such a goal is taking it to the next level and I totally admire the skill and effort.

Well, thus far I haven't offered up anything remotely approaching what might constitute "proof" in the context of this forum. Maybe one of these days.

I look forward to the day when I can get out to a show to hear your speakers.

I would love to get your feedback. If that day ever comes, be brutal. I learn more from my mistakes than from my successes, and I don't mind making course-corrections. I'm in the midst of exploring a course-correction right now based on some interesting feedback I got earlier today.