[Folsom]

Yup, please enlighten me to what everyone here thinks it is....

I get a lot of mixed reviews on different equipment and music, as to what imaging is playing a role in. Hell some people do not even use the term; it is just not in their library for explaining sounds. Then I have people telling me that my ears are fooling me because of imaging, that I hear odd locations of things (that I later find out have a reason for, of course).

So yeah feel free to explain please, I want to get a general notion of what everyone else considers imaging to be.

[DSK]

Um, do you mean 'imaging'? 

[eric the red]

In Disney terms:
Imagineering has been responsible for more than 100 Disney-owned patents in such areas as ride systems, special effects, interactive technology, live entertainment, fiber optics and advanced audio systems.

Imagining is when people think they can hear sonic differences between power cords or sonic improvements when the Clever Little Crock is placed in their listening rooms .

[JLM]

Imaging is the psychoacoustic phenomenon of defining size and 3 dimensional location for a given source of sound.   Anthropology explains that it was an important development in the survival of our (and other) species.  The offset distance and placement of two ears on opposite sides of our heads can be explained in these terms.  For audiophiles it represents entry into the "high-end" as nearly all low/mid-fi does not try or even recoginize imaging.  It adds a factor of realism versus a typical American "bigger is better" ideal.  Similarly soundstaging is the combination of images.  Proper imaging/soundstaging provides width, depth, height, and size of each aspect of the performance.

Stereo was invented to allow imaging/soundstaging, not to fill our rooms with more equipment that someone could sell to us.  Just as we have two ears, two channels of information should be sufficient to reproduce a "stereo image".  Additional channels, if done right, will enhance the effect.  The "if done right" clause is directed mostly towards the recording industry and could easily invoke it's own thread.  In my experience imaging was somehow better in the days of tape and vinyl.  Exactly how various parts of the audio reproduction chain effects imaging is not well understood.  The current popular interest in headphone use, and listening in the car, has caused most to be ignorant of imaging.

[Ethan Winer]

> please enlighten me to what everyone here thinks it is.... <

You got some good joke answers, and some reasonable info too. I'll add a little more.

First, good imaging is entirely a function of avoiding "early" reflections from the walls, ceiling, and floor. Early reflections are those that arrive within about 20 to 25 milliseconds of the direct sound from the loudspeakers. So regardless of what you may read in audiophile magazines, loudspeakers don't "image" - rooms do.

When a room is set up to absorb (or diffuse) all early reflections, everything becomes clearer and you can more easily discern where in the left-right stereo field a particular instrument or singer has been placed.

The main reason avoiding early reflections improves imaging is because early reflections impart a particular type of frequency response error called comb filtering. This is a series of many peaks and deep nulls that color the sound unnaturally. The reason these peaks and nulls harm imaging is because each ear receives a different frequency response. Once all of the first reflection points in the room are properly treated the response becomes much flatter. More important, there is then much less difference between what the left and right ears receive.

--Ethan

[mfsoa]

Ethan,
I'm sure my acoustics knowhow is zip compared to yours, but I thought that early reflections were bad for imaging primarily due to the ear/brain perceiving the sounds at different times than intended. Aren't sounds within a certain window (I thought 10 ms-ish) were perceived as the same sound as the original, and sound arriving after that is percieved as ambience? So this time-smeared "same sound" can't be localized as intended.

I don't doubt that comb filtering is a bad thing, but isn't localization of sounds caused primarily by time-based arrival differences in each ear?  How will a frequency responce shift affect this time differential?

When I go outside, I can clearly hear birds chirping and can tell exactly where they are - Do Robins  "image" better than Cardinals due to their different frequency responses? Just my $.02 or less.

Seems like imaging is not a matter of frequency response as much as the time delay between the ears.

[Folsom]

Now here is a predicament, what does a “soundstage” play if imaging is primarily the location of all instruments and voices? Would this only refer to how tall, wide, and deep these sounds are confined too?

Yes I have to ask. The definition I get slapped around me all the time of these things is so broad I wonder who is talking about what, and who knows what they are talking about. I can only assume a general consensus is the only way to determine what everyone thinks.

[John Casler]

Now here is a predicament, what does a “soundstage” play if imaging is primarily the location of all instruments and voices? Would this only refer to how tall, wide, and deep these sounds are confined too?

Yes I have to ask. The definition I get slapped around me all the time of these things is so broad I wonder who is talking about what, and who knows what they are talking about. I can only assume a general consensus is the only way to determine what everyone thinks.

DoS,

Sonic Imaging is the same as Visual Imaging, except with sound.

When you look at a picture, you can see "images" of things in the picture and where they are.  You can also see the size of the images, and the outlines and colors, etc.

In Sonic Images, you get a sense of size, distance, placement on the soundstage and other clues to cause you to assemble those sounds into an image.

First, good imaging is entirely a function of avoiding "early" reflections from the walls, ceiling, and floor. Early reflections are those that arrive within about 20 to 25 milliseconds of the direct sound from the loudspeakers. So regardless of what you may read in audiophile magazines, loudspeakers don't "image" - rooms do.

I might slightly disagree with Ethan that the "only" thing that causes imaging is avoiding early reflection, but I would agree that reflections can certainly "degrade" imaging.

Imaging has two primary electrical signal elements that cause their creation:

1) Is the amplitude variance between speakers, that places the image within a specific portion of the soundstage.

2) Phase variations that further add to this psychoacoustic placement.

Both of these are rather delicate to the point that interuption, interference, or disruption of them will cause poor imaging.

Ethan's reflection degradation interferes with both the amplitude and the phase you hear and as he noted degrade imaging.

Some mention height and there really is no signal to cause height, other than where the various drivers are located in space. So if you wish a large image, you will need to raise your speakers to a height to achieve that size.

[EProvenzano]

Some mention height and there really is no signal to cause height, other than where the various drivers are located in space. So if you wish a large image, you will need to raise your speakers to a height to achieve that size.

This is interesting to me.
I've often wondered why some speakers give the perception of the band being as tall as midgets while others don't.  When I notice this problem I pay special attention to the tweeter hight and always try to make it ear level.  Still, some speakers suffer this problem 

[Scotty]

I have noticed that image height appears to be dependent on two things.
the electronic equipement must not loose or alter the the phase relationships in the signal and the loudspeakers must be capable of reproducing the information in the recording. I have found that if these two criteria are met, the image height
is independent of the tweeter or midranges vertical location to the point that the loudspeaker can be laid on it's side on the floor and still put an image on the ceiling.
As far as height information being present in the recording is concerned
Chesky records produced a test CD that was used to demonstrate image height
reproduction and evaluate how well speakers performed in this area.
Scotty

[John Casler]

I have noticed that image height appears to be dependent on two things.
the electronic equipement must not loose or alter the the phase relationships in the signal and the loudspeakers must be capable of reproducing the information in the recording. I have found that if these two criteria are met, the image height
is independent of the tweeter or midranges vertical location to the point that the loudspeaker can be laid on it's side on the floor and still put an image on the ceiling.
As far as height information being present in the recording is concerned
Chesky records produced a test CD that was used to demonstrate image height
reproduction and evaluate how well speakers performed in this area.
Scotty

Hi Scotty,

Are you a "new" Scotty?  (I see this is your first post) or the old Scotty and I only mean that in the most flattering way?

If you are a new Scotty, then welcome.  If the old, then welcome back.

I might be suspicious that "height" is a function of phase relationships being retained, but I could be wrong.

Do you have any ideas about these relationships to support what might be happening?

What I'm looking at here, is that everyone knows that we can have phase relationships between L&R speakers, but even though we might have three stacked drivers on each side, the signal going to each speaker is already phased for all those drivers, so the only asymetrical phase relationship we can have is between the L&R speaker and not the speakers in each frequency range.

Or are you saying height "IS" caused by creating an asysmetrical phase that fools the brain, in a single speaker?

I still have a rough time thinking that you could lay a speaker on the floor and still have image height.  Have you heard this phenomenon yourself?

[Scotty]

I am the old Scotty, I had login troubles and had to re-register.
Recreated image height is a function of the captured phase relationships in the recording or a product of phase manipulation in the studio. I am unclear as to how Chesky made their demo recording and encoded height information. I have numerous recordings that will put images at ceiling height clear across front of the room as well as on the floor or in a 360 circle around the listening position all with only two loudspeakers in the front of the room. I think the height information can be passed through good electronics to the speakers but it could certainly be degraded very easily at this point in the chain and the room/ speaker interface could also muck it up. The same information that allows us to tell how high a source of sound is with only two ears should be present in a good recording. And if it is reproduced with high fidelity, height information should be heard by the listener.  As far as the laying the speaker on it's side and having about a six foot tall image, I did this with a small 2way DIY using a Dynaudio 17W75 woofer and a Lineaum tweeter Xover at 2500Hz with a Quasi-second order series network. I was just screwing around one day and decided to see if they would still image laying on their side on the floor and they did. They were 23in. tall by 8in.wide and 10in. deep and did not need stands to recreate excellent height,width and depth. They lobed upward toward the listening position at about a 15degree angle. I am not sure how height information is captured in ordinary recording that is not subject to studio doctoring. A good recording of a grand piano made with the lid up should exhibit
the same image height that you would hear if you were in front of it while it was being played for real. The upper registers of the piano are reflected off of the lid and the higher the note the higher it will appear in the sound stage, conversely
the lower notes will seem to come from a position lower in the piano
and the size of the string and the body of the instrument being involved in producing the sound is obvious. Properly reproduced, the piano will sound life sized in image scale with height, width and depth and the sensation of hearing
a three dimensional instrument recreated in your listening room.
An excellent example of a recording with this information on it is
George Winston, Linus and Lucy The Music of Vince Guaraldi, on the Windom Hill label.
Scotty

[Russell Dawkins]

spheroids

[lonewolfny42]

As far as height information being present in the recording is concerned
Chesky records produced a test CD that was used to demonstrate image height
reproduction and evaluate how well speakers performed in this area.
Scotty

This is the Chesky release. Its a good recording....

[jon_010101]

Recreated image height is a function of the captured phase relationships in the recording or a product of phase manipulation in the studio.

Preservation of phase/time information definitely seems to play a huge role, but I also think there is a certain psycho-acoustic effect which is important: We expect the piano to "image" in a certain way, therefore we tend to arrange it that way in our mind.  I'd be curious if demos of height "work" if the listener isn't told (and doesn't know) what to expect, i.e., if they could be created for arbitrary sounds without providing any visual hints.  Years ago I bought an "Aureal 3D" sound card that used HRTFs to position sounds in space via headphones.  For up-down effects, it was really only effective if you had a visual cue, such as in a 3D game. 

An additional concern for me is that the geometry of the speaker array strongly affects my own perception of vertical imaging.  For example, I have MTM style speakers (GR Diluceos) and sit about 8' away with 8' speaker separation in an equilateral triangle.  If my ears are above the tweeter, the image tends to "project" upwards from the speakers, if my ears are aimed at the tweeter, the image loses some height but gains width and clarity, and if my ears are below, the image projects mostly downwards. 

My personal theory is that given a vertically symmetric array, speaker, and seating position, only recognizable sounds (e.g, toe-tapping=down, cymbals=up), or sounds coupled with visual cues (e.g., home theater), should be distinctly placed in the soundstage above or below the center of the speaker array.  Given perfect vertical symmetry, up and down become completely ambiguous and no repeatable engineering trick should be able to simulate vertical imaging without playing upon the listener's expectations.  Perhaps one possible counter to this argument could be that we subconsciously assign heights to frequency ranges, regardless of phase or point of origin in space  .

There are some recordings, of course, which seem to preserve (or simulate) spatial information.  Nick Drake's Pink Moon, the piano is far, far up and far, far to the left.  It is so apparent and distracting to me that I usually picture my room being replaced by some synaesthetic reality, with a ghostly image of a piano hovering 10' diagonal up and left beyond my wall .  But, notably, the piano tends to be left and not up when my ears are aligned with the horizontal plane of the tweeters.  Another example is Knots by Gentle Giant... a xylophone (I think?) projects perfectly across the entire soundstage, about halfway between the listener and the speakers, usually a few feet up.  THAT is definitely one that impresses the guests  .  But, again, my perception of height varies greatly with my ears' vertical position relative to the speakers.

This is a great thread... much to think about 

[JLM]

D of S,

Soundstage describes the extent (typically width and depth) of the collection of images. 

Forgot to mention that improved imaging and improved detail go hand in hand as one improves the other.  My experience is that as images focus (using a visual analogy) from a large fuzzy blob to a smaller more discrete object and separates from the other fuzzy blobs the detail also improves.  This is most noticable of small sound sources like triangles or wooden blocks.  Overall smaller sounds seem smaller and bigger ones bigger with improved imaging. 


Ethan,

Adding first reflection diffusion/absorption does expand the soundstage.  With the usual recommended setup across the narrow wall the width of soundstage is constricted, but noticably improved with treatments.


jon,

Good points regarding psychoacoustics and how expectations play into vertical imaging.  This brings up the whole concept of "active" listening.

The entire recording process must be considered as well.  Modern techniques use too much close miking that forces imaging to be artificially recreated during mixing.  Using fewer mikes farther back would allow some venue ambiance to be picked up.  (Hard to though with many of the "tricks" of the industry uses like adding tracks later or the lead vocalist doing their own backups). 


Scotty,

Good points regarding phasing (which support the use of simplier circuits and crossovers).  Fodder to start several threads.


Memorable examples,

Heart's "Dreamboat Annie", a bar "scene" where a coin rolls off the bar to the floor and rolls around on the floor.  The coin can easily be followed.

A xylophone played on a HT system where the image was superimposed with the TV.  As the instrument was played from top to bottom the imaging disappeared and the sound lost coherence as it passed "through" the TV.


Regarding speaker design,

I'm not a fan of MTM for the reasons Scotty mentioned.  Probably helps comply with HT standards, but bad for audio.  I'm an old fan of Irving Fried's expanding sound source (tweeter on top, woofer on the bottom) idea.

I'm not a fan of dipole either as an unnatural of out of phase backwaves, but it's not much worse than most box designs that allow the out of phase back wave to reflect right back to the backside of the driver and muddy the sound.

[PEB]

If we can agree that imaging is essentially recreation of time/space effects from the original recording then here are my opinions ...

Imaging is a "fragile" recorded quality that can only degrade as it progresses through the reproductive chain.  Electronics and cables affect it, but not as much as speakers/rooms.  So headphones could actually allow us to hear the depth of image on the original recording, and thus take out speaker & room effects.

There is left/right imaging, and front/back (depth of image).  Left/right imaging is an easy/no-brainer thing to achieve with careful setup of two speakers in a symmetrical room.  The depth of image is the harder one.

Yes, some speakers image better than others.  For example, a rough SPL response, or poor inter-driver phase coherency will smear the acoustic signal and thus degrade the image depth.  You can even take the left/right aspect and the room aspect out of the picture by listening outdoors to a single speaker.  Match the levels, and you can still hear that one speaker reproduces the recorded depth of image as determined by some sounds seeming to eminate from farther away than others.  Another great sound with which to judge depth of image is any that exhibits echo, or a trailing off of a percussive sound.  References available...

Back into the room.  Careful setup and room treatments will "preserve" more image depth.  Refer to Everest's Master Handbook for more on phantom sources, early/late reflections, pyschoacoustics, etc.  Also the Cardas and Audio Physics sites are great for setup tips.  They really work!

Phil

[Scotty]

jon_010101,regarding image height, the George Winston recording exhibits this
with your eyes closed. The other imaging effects I mentioned are more easily perceived with your eyes closed eliminating visual distractions.
My speaker system has WMTMW design which seems to work as well or better than the top down approach.  The think execution of the design may play a bigger part in what you hear rather than the baffle layout itself.
Height information can be captured successfully, and given high fidelity reproduction of the original information can be experienced in your listening
room. If this aspect of the listening experience is missing or lackluster in performance something is amiss in the reproduction chain.
 Scotty

[sunshinedawg]

I have a simpler approach to these issues.  If you want to eliminate reflections, sit closer to your speakers. I sit about 3.5 ft from mine.  I don't need much room treatment.  I do use a lot of base panels to help out on the low end. If you want perfect imaging, use crosstalk cancellation.  CTC can be done with software or by placing your speakers very close together and placing a divider in between them. My speakers are about 6" apart. I simply use an extra base panel as the divider. I haven't found a really easy way to do it with software, although it can definitely be done.  Maybe if someone comes up with a CTC plugin for the squeezebox now that I use that as my exclusive source, I'll give it a try. I don't think a lot of people will embrace this kind of setup, but I will never go back to a triangle speaker setup sitting 8 or 10 ft away. YMMV.

[Ethan Winer]

Folks,

> Aren't sounds within a certain window (I thought 10 ms-ish) were perceived as the same sound as the original, and sound arriving after that is percieved as ambience? <

Yes, but because the direct and reflected sounds arrive so close together, the dominant contributor seems (to me) to be the skewed frequency response.

> How will a frequency responce shift affect this time differential? <

Because the response can be very different at each ear.

> Seems like imaging is not a matter of frequency response as much as the time delay between the ears. <

It's both, and I probably should have been clearer. But lately I've been shifting my "opinion" more toward the skewed frequency response theory than the different arrival times.

> Phase variations that further add to this psychoacoustic placement. <

Yes, but unless you're using different model speakers on each side, any phase shift will be the same for both ears so that's a wash. The only times phase shift is even audible at all is either:

1) When the original and shifted versions of the same signal are combined.

2) When the left and right channels have different amounts of shift.

Regardless of the underlying cause, the key point is that imaging is always "made right" when all the first reflection points are treated with absorption or diffusion. Likewise, without absorption or diffusion imaging always suffers unless the side walls are far enough away from your ears and the ceiling is high enough. Since sound travels at about 1 foot per millisecond, those surfaces need to be about ten feet or more away.

--Ethan