I worship at the altar of imaging

[NorthSky]

Stereo Image Depth Test - that's the one. Sounds like a good audio test disc. I have some CDs from that music record label...audiophile label.

 

[Thomas savage]

Stereo Image Depth Test - that's the one. Sounds like a good audio test disc. I have some CDs from that music record label...audiophile label.

That cd tests side to side, front to back and indeed all around...

It's the perfect sound stage test and a known that s repeatable hence worth comparing our subjective experience of.. Anything else is a little inane as there is no 'known' to base things off...

 

[NorthSky]

The first foundation is in the quality music recording itself...by experienced and competent recording engineers...and the artist musicians/opera singers performance of course. Then our hi-fi stereo systems @ home are the last bastion of the chain...with the loudspeakers positioning in the acoustically treated room.
Youtube music videos no need to apply...it's just too lo-res. ;-)

What I'm interested in in addition to lateral/horizontal imaging in front and on the sides and in the rear is vertical/height imaging, in front and in rear, between.
That's for another thread though. Here it's retro stereo imaging, from the last hundred years, or about.

 

[NorthSky]

"I am reluctant to admit this, but I will; praise be, hare hare, amen to imaging One of those most audiophile-iest of things that sucks me in. So I'm not completely playing the 'phool, it does lend to my overall enjoyment as a music listener with my favorite genres, for instance being able to pin point the violin soloing while the rest of the orchestra plays quietly can be quite powerful on the right piece.

I often read about "minimum baffle diffraction" and that may or may not be helpful as a starting point for someone designing speakers but it does not tell us much measurement wise or how we can advance our knowledge further. Linkwitz has some good reading here and here.

I thought maybe I could correlate something with off axis response. Then I went back to thinking about the speakers that imaged particularly well and well... their off axis response is all over the place.

What contributes to imaging? How do we measure it?"
________

First original post ↑ of this thread.

 

[Cosmik]

From Wikipedia:

Stereo sound systems can be divided into two forms: The first is "true" or "natural" stereo in which a live sound is captured, with any natural reverberation or ambience present, by an array of microphones. The signal is then reproduced over multiple loudspeakers to recreate, as closely as possible, the live sound.

Secondly "artificial" or "pan-pot" stereo, in which a single-channel (mono) sound is reproduced over multiple loudspeakers. By varying the relative amplitude of the signal sent to each speaker an artificial direction (relative to the listener) can be suggested. The control which is used to vary this relative amplitude of the signal is known as a "pan-pot" (panoramic potentiometer). By combining multiple "pan-potted" mono signals together, a complete, yet entirely artificial, sound field can be created.

In technical usage, true stereo means sound recording and sound reproduction that uses stereographic projection to encode the relative positions of objects and events recorded.

During two-channel stereo recording, two microphones are placed in strategically chosen locations relative to the sound source, with both recording simultaneously. The two recorded channels will be similar, but each will have distinct time-of-arrival and sound-pressure-level information. During playback, the listener's brain uses those subtle differences in timing and sound level to triangulate the positions of the recorded objects. Stereo recordings often cannot be played on monaural systems without a significant loss of fidelity. Since each microphone records each wavefront at a slightly different time, the wavefronts are out of phase; as a result, constructive and destructive interference can occur if both tracks are played back on the same speaker. This phenomenon is known as phase cancellation.

The later section on recording methods is very interesting. It is clear that some stereo is more 'correct' than others.

However, it has got to be the case that an audio system can do nothing more than be 'high fidelity', surely? Someone earlier said that "It can't be as simple as that", but what more can an audio system do? If it inadvertently creates "pseudo-stereo" it is presumably a pretty poor system:

Bremmers Audio Design (The Netherlands),[60] uses special filters to achieve a pseudo-stereo effect: the "shelve" filter directs low frequencies to the left channel and high frequencies to the right channel, and the "comb" filter adds a small delay in signal timing between the two channels, a delay barely noticeable by ear,[note 2] but contributing to an effect of "widening" original "fattiness" of mono recording.

 

[Sal1950]

From Wikipedia:


The later section on recording methods is very interesting. It is clear that some stereo is more 'correct' than others.

However, it has got to be the case that an audio system can do nothing more than be 'high fidelity', surely? Someone earlier said that "It can't be as simple as that", but what more can an audio system do? If it inadvertently creates "pseudo-stereo" it is presumably a pretty poor system:

How interesting to find such a detailed description of "stereo" in the Wiki.
Had never given much thought to the "loss of fidelity" when playing back a "true stereo" in mono, but of course this is the true case. But then only a couple in a thousand of the recordings I played back on my mono systems were recorded in a true stereo fashion, the vast majority being pan potted pop and such.

 

[hvbias]

I am not so sure that just the speaker or speaker type is all that is involved. The room and speaker placement, toe-in, etc., I think can play a huge role, which all might need to be optimized for a given speaker to have it image at its best.

I have also had occasions where a change in electronics made a substantial difference. I first noticed this on an amp upgrade I did 30 years ago. That taught me to focus much more on spatial and imaging cues in comparative auditions of equipment. I have also had that experience in upgrading my DAC more recently. These differences were quite noticeable in careful listening.

A lot of things in the system have to be right in order to deliver best imaging. So, listening for that, I find, is the single most revealing characteristic of a system's performance, since it integrates so many other performance characteristics.

But, ascribing imaging quality all to the speakers - horns, etc. - is overly simplistic, I believe.

I'm not a person that thinks all amps and DACs sound the same, however this is ASR where it's commonly accepted that the speakers, room/treatments/placement and DSP contributes to the vast majority of the sound quality. As such this is where I focused the question. And like I mentioned up thread I'm speaker shopping and use some objective criteria to see which speakers I should audition.

My observation on horns was just that, an observation on what I heard, nothing stated as fact. I brought it up since maybe someone had some measurements where those types of speakers shared a common ground.

=======================================================

I would still prefer if this stayed more towards the objective side of discussion. I'll share any IACC findings and hopefully that can put things back on track.

 

[Fitzcaraldo215]

That cd tests side to side, front to back and indeed all around...

It's the perfect sound stage test and a known that s repeatable hence worth comparing our subjective experience of.. Anything else is a little inane as there is no 'known' to base things off...

Interesting. Another technique I use is with classical music Blu-Ray videos of live concerts, comparing the audio to the picture of the ensemble playing. Yes, the video is shot from multiple, shifting angles, but you develop an accurate 3D sense that builds in your mind of where the instruments or singers are physically placed in a specific recording.

The audio soundstage does not shift with changing camera angles. Some find that somewhat disconcerting at first while watching, but I do not. I would find anything else hopelessly confusing and impossible to record. And, a fixed, static frontal camera angle would be boring beyond belief. I do not keep my eyes fixed on one spot at a live concert, though many camera angles in the videos do not attempt to duplicate exactly what would be seen by the audience. The focus of my eyes wanders over the performers and the hall quite naturally live. And, the visual directing of live concert recordings is something of an art form in itself: wide vs. close up, one instrumental section vs. another, conductor or soloist, etc. Some flow with an unhurried, more natural feel. Others do not.

Not all performances use the same layout of the ensemble. Some conductors prefer a modified layout of the orchestral sections, and some stages in some halls require it. Some orchestras perform on risers, some do not. Singers move around the stage in opera. Some string quartets reverse the placement of viola and cello, etc. It is interesting to see this and hear this.

The BD disc can also be listened to with video off, of course. However, I expect that knowledge of the visual layout might unconsciously influence what we think we hear, even unsighted afterwards. The audible image might tend to align itself with the more dominant visual one in our mind. That might even be true with your audio-only test disc based on foreknowledge of what it says it is supposed to sound like.

 

[Thomas savage]

Interesting. Another technique I use is with classical music Blu-Ray videos of live concerts, comparing the audio to the picture of the ensemble playing. Yes, the video is shot from multiple, shifting angles, but you develop an accurate 3D sense that builds in your mind of where the instruments or singers are physically placed in a specific recording.

The audio soundstage does not shift with changing camera angles. Some find that somewhat disconcerting at first while watching, but I do not. I would find anything else hopelessly confusing and impossible to record. And, a fixed, static frontal camera angle would be boring beyond belief. I do not keep my eyes fixed on one spot at a live concert, though many camera angles in the videos do not attempt to duplicate exactly what would be seen by the audience. The focus of my eyes wanders over the performers and the hall quite naturally live. And, the visual directing of live concert recordings is something of an art form in itself: wide vs. close up, one instrumental section vs. another, conductor or soloist, etc. Some flow with an unhurried, more natural feel. Others do not.

Not all performances use the same layout of the ensemble. Some conductors prefer a modified layout of the orchestral sections, and some stages in some halls require it. Some orchestras perform on risers, some do not. Singers move around the stage in opera. Some string quartets reverse the placement of viola and cello, etc. It is interesting to see this and hear this.

The BD disc can also be listened to with video off, of course. However, I expect that knowledge of the visual layout might unconsciously influence what we think we hear, even unsighted afterwards. The audible image might tend to align itself with the more dominant visual one in our mind. That might even be true with your audio-only test disc based on foreknowledge of what it says it is supposed to sound like.

Yea I used to do that when I watch music concerts, I can't say any biases exists when I used the isotek cd though as I am listening for what's not right rather than convincing myself of what I 'want' to hear.

It's a good test but dose not help the op as it does not seek to identify any predictable identifying factors that can reliably predict sound image performance.

 

[NorthSky]

Stereo imaging "refers to the aspect of sound recording and reproduction concerning the perceived spatial locations of the sound source(s), both laterally and in depth. An image is considered to be good if the location of the performers can be clearly located; the image is considered to be poor if the location of the performers is difficult to locate. A well-made stereo recording, properly reproduced, can provide good imaging within the front quadrant; a well-made Ambisonic recording, properly reproduced, can offer good imaging all around the listener and even including height information.

For many listeners, good imaging adds markedly to the pleasure of reproduced music. One may speculate that this is due to the evolutionary importance to humans of knowing where sounds are coming from, and that imaging may therefore be more important than some purely aesthetic considerations in satisfying the listener.

>>>→ The quality of the imaging arriving at the listener's ear depends on numerous factors, of which the most important is the original "miking", that is, the choice and arrangement of the recording microphones (where "choice" refers here not to the brands chosen, but to the size and shape of the microphone diaphragms, and "arrangement" refers to microphone placement and orientation relative to other microphones). This is partly because miking simply affects imaging more than any other factor, and because, if the miking spoils the imaging, nothing later in the chain can recover it.

If miking is done well, then quality of imaging can be used to evaluate components in the record/playback chain (remembering that once the imaging is destroyed, it cannot be recovered).

It is worth noting that only a handful of recordings are miked for optimal imaging, and what usually passes for stereo, while being two-channel recording, is not true stereo because the imaging information is incoherent. ←<<<

Imaging is usually thought of in the context of recording with two or more channels, though single-channel recording may convey depth information convincingly."

 

[Blumlein 88]

I am pretty sure very much layered depth is actually a coloration of stereo. I also know from using various target curves for room correction one can adjust depth, soundstage size/shape and imaging somewhat with minor response anomalies. Ye olde triode amps can create layered depth, space, and a 3D quality not present in the signal.

So my thoughts would be purchase good speakers without regard to imaging. Fed the appropriate signal with the right room positioning and they will provide it.

Further the great majority of recordings are recorded in a manner that any depth or imaging that seems to make sense must be an artefact.

Theoretically, a crossed-pair of figure 8 pattern mics for recording and playback with speakers at 90 degrees would reproduce recording position most accurately. Blind listening tests of various miking techniques confirmed that as true. Most people don't setup speakers at 90 degrees separation and a negligible number of recordings are miked this way. So this info doesn't really help all that much.

 

[Blumlein 88]

https://acousticstoday.org/wp-content/uploads/2014/10/Leo-Beranek-and-Concert-Hall-Acoustics.pdf

Here is an article from one of the authors of the IACC paper mentioned earlier in the thread.

https://biblio.ugent.be/publication/2041657/file/2041664.pdf

This is also interesting use of that info for the purpose of evaluating outdoor locations for rock concerts.

 

[TBone]

Over the years, I have become less and less impressed with the production on this album. I think the mixing and balancing is highly manipulated and unnatural.

First We Take Manhattan(CD1227) ... Stevie Ray Vaughan's absolutely killer guitar riff (& Roscoe Becks bass line can be tricky to reproduce properly) always sounds inviting in my system. That said, but 1 song, and I'm an admittedly big SRV fan. An early digital recording (DDD,1986), the first time I heard it was on LP. It offered impressive dynamic contrast, enough so, few LP owners questioned its digital provenance.

 

[NorthSky]

The auditory cues are all in the recording. Evolution has meant that our hearing is extremely adept in deciphering what the sounds our ears pick up mean, including a quite exact location of the source of the sound - even when the sound is highly "mangled", say, just coming from two speaker boxes. All the echos from the space in which the recording was done are coded information that tell the story, and all that has to happen is for that information to reach the brain, without extra scrambling from system deficiencies. A particular system will show more and more space, precise localisation, and imaging, as it is improved - it's just an automatic process, and happens every time ...

- if the reproduction is good enough then the ear/brain adjusts for the path discrepancies between the stereo speakers and where you happen to be, and the imaging remains rock solid as one moves around in the room. Also, the sound picture always exists from the plane of the speakers, and behind them - never in front; the illusion is exactly what the microphones saw, that recording space is recreated in the area behind the speakers, to whatever width the sound elements "lived in" when the track was put down.

It was a remarkable sensation when I first encountered it - and made it clear what the end goal should always be ...

I would rephrase this - Everything in the system has to be right in order to deliver best imaging. What kills the quality of the imaging is the one thing in the setup that hasn't been sorted out, optimised - whatever it happens to be. I find speaker positioning to be irrelevant - if the acoustic output from the drivers is clean enough then the mind has no problem "seeing" an illusion, because there are no significant audible anomalies disrupting the acoustic clues.

Frank, you gave us some good clues from your above quotes. I very much agree with those points.

 

[NorthSky]

https://acousticstoday.org/wp-content/uploads/2014/10/Leo-Beranek-and-Concert-Hall-Acoustics.pdf

Here is an article from one of the authors of the IACC paper mentioned earlier in the thread.

I perused through that pdf paper, and found it informative and enriching.

And I like this, very ↓

| Reminiscences from Friends and Colleagues Ten Things I Learned from Leo Beranek |

Leo Beranek helped to form my basic thinking and approach to architectural acoustics in many ways. His writing, speaking and design work has been a continued inspiration and example to me since 1979 when Bert Kinzey, my professor at the University of Florida, introduced me first to his work and then to Leo himself. Here is my list of ten things I learned from Leo (though he may not know he taught me these).

1. The importance of theory. Once Bert Kinzey introduced me as a young student of architectural acoustics to Music, Acoustics and Architecture in 1979, the idea that one could develop an architectural theory based on something as intangible as the perception of musical sounds in architectural spaces yet rooted in science was both fascinating and challenging.

2. Think broadly about sound. In my first year of study with Bert we read Acoustics, Noise and Vibration Control, Music, Acoustics and Architecture, and Noise Reduction by Leo. These books which covered sound systems, noise control, sound transmission, HVAC system noise control, vibration, room acoustics and the perception and meaning of sounds among other topics introduced us to the breadth of acoustical thinking in architecture.

3. Always be a student. Leo remains an inspiration to me when I see him seated in paper sessions at ASA, CHRG and other meetings from early in the morning until the end of the session, listening intently and engaging in the discussion like a young graduate student. His enthusiasm and engagement with current research in acoustics is an example to us all.

4. Listen carefully and often. Leo sits and listens everywhere he goes. His writings convince all of us that this is the reason for the science.

5. The qualitative is important. A reading of Music Acoustics and Architecture and its subsequent derivations demonstrates the importance for dialogue among participants in the soundscape of concert rooms to develop a science of architectural acoustics about the shared experience of listening to music in world class venues.

6. Test, Design, Build, Listen, Test, Design Build, Listen, etc. Sharing the viewpoint that the science of architectural acoustics is rooted at once in science, acoustical testing with new metrics, analysis of data, designing, building, listening and then further testing, analysis, designing, building in iterative sequences is essential to the growth of the field. Build may be the biggest distinguishing factor here. Leo and his colleagues built the field of architectural and environmental acoustics building by building, project by project, year by year in amazingly creative and interesting ways. What a portfolio of work!

7. Work in the “in-betweens.” The interdisciplinary gaps between the fields of music, acoustics and architecture are where much of Leo’s work falls. He chose to dedicate his life to the exploration of the gaps between three traditional fields of knowledge to form a new discipline that he helped to raise to a sophisticated science and a high art.

8. Collaborate. To work or labor together. At Harvard, BBN and in later years with many others collaboration and sharing was at the heart of much of Leo’s work. His colleagues in all of these endeavors are a who’s who of those who shaped architectural acoustics from the middle of the 20th century to the present day in so many different ways, places and forms.

9. Ask Questions. Leo shows everyone around him that it is worthwhile to ask questions as a way to learn. He eagerly engages everyone he meets and the authors of the papers he listens to in active participation with the topics they have discussed.

10.It keeps getting better. Anyone who has been to one of the recent halls Leo has worked on or listened to one of his recent papers can attest to the fact that it just keeps getting better.

| Best wishes on your 100th birthday with profound hope that it just keeps getting better. Gary W. Siebein University of Florida School of Architecture |

 

[TBone]

I heard an interesting and big contrast, between the traditional and well-known stereo mix w/reverb vs the original dry mono mix; Jefferson Airplanes Surrealistic Pillow. Go ask Alice if she's heard White Rabbit without the reverb. The RCA Gold edition includes both stereo/mono tracks. Steve Hoffman once called Pillow one of the worst recorded "classics" albums of all time, and my no-noised RCA certainly hints at such. I've not heard many pressings, this RCA isn't considered highly by any means, especially the mono tracks (which apparently are best served w/LP). Despite that, Babin's Comin' Back To Me still haunts ...

 

[TBone]

I am pretty sure very much layered depth is actually a coloration of stereo ...
Further the great majority of recordings are recorded in a manner that any depth or imaging that seems to make sense must be an artefact.

Artifacts certainly with the vast majority of my music, esp w/prog-rock, but even the well mastered Trinity Sessions (the way Margo was mic'd) wasn't recorded naturally. I now consider depth more a function of overall transparency. If I can hear deeper into the mix, that-in-itself recreates a greater illusion of depth in my brain. Better yet, those deep bass clues in which depth is felt as much as heard ...

 

[Kal Rubinson]

First We Take Manhattan(CD1227) ... Stevie Ray Vaughan's absolutely killer guitar riff (& Roscoe Becks bass line can be tricky to reproduce properly) always sounds inviting in my system. That said, but 1 song, and I'm an admittedly big SRV fan. An early digital recording (DDD,1986), the first time I heard it was on LP. It offered impressive dynamic contrast, enough so, few LP owners questioned its digital provenance.

I never said that I didn't like the recording, only that I did not find it natural. Have you ever heard the radio-only remix of that track that focusses on SRV's guitar? It is also quite impressive but entirely different and, in its own way, equally unnatural.

I do not like to judge imaging or soundstaging with studio-produced recordings because they are, overwhelmingly, manipulated to create desired effects, sometimes quite successfully.

 

[Blumlein 88]

Artifacts certainly with the vast majority of my music, esp w/prog-rock, but even the well mastered Trinity Sessions (the way Margo was mic'd) wasn't recorded naturally. I now consider depth more a function of overall transparency. If I can hear deeper into the mix, that-in-itself recreates a greater illusion of depth in my brain. Better yet, those deep bass clues in which depth is felt as much as heard ...

The problem with that approach is the idea deeper is better. The triode amps I mentioned earlier will typically give deeper soundstaging, with enhanced see thru transparency and yet do so by coloring the signal fed to them. That is how they work such magic even on highly produced recordings that aren't natural. So you would be lead away from fidelity. That is okay, it is enjoyable. It can be confusing if you don't realize that when trying to deduce fidelity to source.

As for Trinity sessions it actually was recorded naturally, but Margo's voice was unnatural as it was going thru a PA system. Still the recording of that PA was natural as it was done thru a single Calrec microphone. Same as it recorded naturally the sound of the electric guitar being played in that space through a guitar amp.

 

[TBone]

I never said that I didn't like the recording, only that I did not find it natural. Have you ever heard the radio-only remix of that track that focusses on SRV's guitar? It is also quite impressive but entirely different and, in its own way, equally unnatural.

I'm not certain I've heard that particular remix.