Imaging: Causes, Detriments, and Fixes

[RBFC]

To split off the discussion, let's use this thread to discuss imaging and all the implications.

There are objectivists who feel that imaging can be "estimated" by examining certain measured specifications of a loudspeaker. The subjectivists seem to feel that there are yet-unmeasurable quantities/factors that determine the ultimate imaging quality of a speaker. Does that reasonably sum up the opposing opinions under discussion?

For the objectivists:

What measurements are necessary to describe the imaging characteristics of a speaker?

How do different values in those measurements affect the image quality of a speaker as opposed to one with "ideal" measurements?

For the subjectivists:

What are the "missing" pieces of objective information that may help in delineating the imaging ability of a speaker?

Without measurements to assist you, discuss how you adjust/tweak speaker position/performance to achieve the best imaging from a given design.

What certain speaker design philosophies do you feel provide the best imaging?


For all:

What are the characteristics of excellent imaging?

How do you personally go about adjusting your speakers when you have (for example) great center image, but smeared lateral images? (etc., etc.)

Are certain archetypal designs better at imaging, and what special considerations must be given to each design type to maximize its imaging performance?

What are some of your reference recordings that offer excellent imaging qualities?

Just to get things started! Feel free to enter comments pertaining to imaging that weren't mentioned above!

Lee

 

[amirm]

I heard one more thing: that the only thing that messes with the imaging is the speaker, the room or both. I am not sure I agree with that fully .

 

[Ron Party]

Nice channeling of Yogi Berra, Amir!

 

[DonH50]

Ooo, I'd love to get into this one, but am too busy on other things right now... Please keep it going a while!

Since I suspect speaker/room interactions will dominate the discussion (and rightly so, imo), I'll throw out a few talking points about component imaging issues: power amp output modulation with speaker loads (and resulting speaker modulation), ditto source/load interaction among low-level components, and of course crosstalk and noise/nonlinearities within the low level components, all of which can change the frequency response (magnitude and phase) and thus can change the perceived image (perhaps due to the speakers and room and they way the respond at different frequencies)....

This should be fun! - Don

 

[Mike Lavigne]

i see 'imaging' as the ability of a system to render the illusion of a real musical event in your room where the components of that event sound similar to how they should sound in terms of size, weight, dynamics, tonal accuracy, depth, height and width. there should be the ability for the mind to clearly track the action in the soundstage of the various musical parts.

further, imaging should include resolution of the ambience of the recording venue.

we are stretching the term 'imaging' here a little as i see the word 'soundstaging' be a more inclusive word to use. imaging is specifically about shapes, density, dyamics and location of imagined musical parts.

rarely does actual live music image anything like a good recording has the potential to. there are so many varibles in listening to live music maybe the odds are against it and venues are not necessarily set up to optimize imaging.

the recording's imagining is mostly an illusion and a manifiestation of the intentions of the recording and mixing engineer and the artist. personally i have no problem with knowing that live music is different than a good recording in terms of imaging. typically i find recordings with exceptional imaging to be more enjoyable than one's that cannot do that. so keep fooling me please.

regarding objective measurements and how it might indicate the ability of a system to image well, or how a subjectivist might view things; it's hard to look at this issue that way.

you listen and it either images wonderfully or it does not.

my room was built from the ground up to image optimally. so i've been living with that for 6 years and i have strong opinions about the subject. there are aspects of my room performance which have been frustrating and i've been working on changes here and there. but from day once it has really had the ability to separate images wonderfully.

the most significant characteristic of the room is retention of musical energy. it has hard surfaces mostly but that are either curved or diffusive in shape. at the speaker end of the room the floor is hardwood over concrete. the rear 2/3rds of the room is a thick carpet. it is shaped like an oval so there are no opposing flat surfaces. it intentionally resembles a concert hall which also uses mostly diffusion and has a hardwood stage. the audience is like my carpet.

as far as speaker-room interaction i think the subject begins with figuring out whether you have a 'local' or 'global' speaker-room situation. this is assuming a conventional dynamic speaker. a local situation is where the room size dictates that your first refections off the sidewall and ceiling will be short enough in time to cause smearing of the imaging at the listening position. a global situation is where the speaker is far enough from the sidewall and ceiling where the first reflection time to the listener is long enough that it will not cause image smearing. this issue determines how agressively the walls and ceiling needs to be treated. this can also be affected by how close one sits and the distance the speakers need to attain coherence. and with certain speaker types sidewall and ceiling first reflections are not a significant problem.

my room is 21 feet wide and my walls are diffusive; so i don't need anything too agressive for first reflections.

toe-in adjustment is a significant aspect of imaging. assuming a dynamic speaker it will determine height and width and depth. my speaker designer is a firm believer in the equalateral triangle method of speaker listener positioning. the listener's ears is equally apart from both speakers as the tweeters for the speakers are apart. the preferred starting point for set-up is for the speakers to aim at the outside of the listeners shouders. if the image is too short and wide, toe them in slightly to raise and deepen the soundstage.....or vice versa. obviously; every room and listener is different as is the precise dispersion pattern of the various drivers. so where you end up is personal. but that is where i start.

the other thing is that it's all about software and source quality. yes; the speakers and the room are ulimately limitations but as you improve the quality of the recording and even the format imaging can go off the charts comapred to a previous reference.

i don't want to light the digital-analog fires here (we could have a separate thread to argue imagining between digital and analog maybe); but those of us who are listening to RTR 15ips master dubs know about how they can image. and vinyl. and SACD. and then PCM. i bring this up because i have an opinion that imaging has alot to do with phase accuracy to the original recording. tape is tape. a tape copy of a tape might lose a touch of bandwidth or add a slight bit of noise but otherwise all the timing stays the same. therefore it has the most potential to recreate the original event. and on down the format food chain the varoius formats image less and less effectively.

in any recording the first moment prior to the music starting there is an ambient bed of air and a pressurization of the room that occurs. the degree of this happening, which i consider the foundation of any imagining as it defines the space, is directly related to the format. tape being easily the best, vinyl next, sacd/dsd next, hirez pcm next, then redbook. no question redbook can do this thing, just not nearly as well as tape, and so on. is this an artifact or reality? i know i like it the more it exists in any recording.

i listen to all these formats daily in a room built to optimize imaging so my 'opinions' are not lightly taken.

anything that can lower the noise floor of a system, anything that can lower the noise floor of a source, allows for a better soundstage and imaging. the noise floor varies with my three tt's and therefore the imaging and even image stability varies between them. when i added custom output electronics on my RTR deck the noise floor dropped and imaging improved.

sorry if i have rambled here but again my perspective on imaging is strongly held. i've tried to stay on topic as best i can.

as i progress with my system's maturation process every step seems to yeild imaging improvements. any improvement to the signal path improves the ability of the system to recreate a more real image. my Equitech balanced isolation transformer that was installed last Wednesday has caused everything to take a huge step forward.....including imaging. so quality of power can be a big factor too.

 

[Ethan Winer]

For all:

What are the characteristics of excellent imaging?

Yes, this must be defined first because what Mike said above is not my definition of imaging. To me, imaging is very simple: The ability to point to a place in space and say "This is where that instrument is located" with no ambiguity.

So my definition of imaging has nothing else to do with realism other than the location of sounds. A perfect example is the common reaction many people have when they first hear stereo music in my living room system. I sit them on the middle seat of the couch and start a CD playing. Invariably they walk up to the center speaker and put their ear there to be sure no sound is coming from that speaker. You'd swear that speaker is playing, but it's not. To me, that is good imaging.

--Ethan

 

[Randy Bessinger]

Guess, I should now put this in this thread

http://v3.espacenet.com/publicationDetails/originalDocument?CC=US&NR=5778087&KC=&FT=E

 

[Ethan Winer]

^^^ The link doesn't work from here.

 

[MylesBAstor]

Yes, this must be defined first because what Mike said above is not my definition of imaging. To me, imaging is very simple: The ability to point to a place in space and say "This is where that instrument is located" with no ambiguity.

So my definition of imaging has nothing else to do with realism other than the location of sounds. A perfect example is the common reaction many people have when they first hear stereo music in my living room system. I sit them on the middle seat of the couch and start a CD playing. Invariably they walk up to the center speaker and put their ear there to be sure no sound is coming from that speaker. You'd swear that speaker is playing, but it's not. To me, that is good imaging.

--Ethan

I'm sorry but you're confusing the definition of imaging with perspective. And perspective should vary among recordings depending upon the miking and music. To wit, a trio should be closer than an orchestra. Imaging is simply can you tell where the instruments are and are they separated in space eg. is there space between the musicians. Having the speakers "disappear" as you describe it has nothing to do with imaging and any properly set up speaker should disappear eg. I can't remember the last time I heard a pair of speakers where the musicians were in the speaker or on the front of speaker. OK one. The AVG horns where I always felt the singers was in the horn. That said, speakers vary in how they present an orchestra. The Alon/Nola are famous for placing the musicians behind the speaker. I find that planars and my estats are a slightly closer perspective. Wilsons, at least when I had the WP, are somewhere between. Imaging is simply the recording engineer's blueprint of where the musicians were and that picture can be shifted around so it's more forward or back.

And imaging begins with the choice of mike setup. Som setups are better at capturing imaging and others not as good. Take RVG's famous Blue Note and Impulse recordings (we're talking vinyl here, not the drek that was put out out on CD-and not the recent digital from Acoustic Sounds). Closely miked and great imaging. Not much in the way of spatial information save if some reverb was added to say the voices. Take the original Deccas. They played around first with directional mikes as they used with their classic opera recordings and later switched mikes and perfected their tree to capture more ambience. And then there's people like KOJ who does different things to capture instrumental placement; unfortunately, the only release that does justice to KOJ's technique and ability to capture the sense of a real event are the 15ips/2 track R2R releases issued by the Tape Project. Not only does all else, vinyl and digital pale, but you have not heard how good his recordings are.

 

[Randy Bessinger]

attachment

 

[Ron Party]

Thanks, Randy. Excellent reading.

 

[Ethan Winer]

Thanks Randy. That seems to agree with my view of what imaging is, and it shows a good way to minimize comb filtering due to content panned to the middle arriving at your ears at different times. I'm not sure what part is patentable, since even back in 1998 comb filtering caused by delays was well understood. But that's beside the point.

--Ethan

 

[Ethan Winer]

I'm sorry but you're confusing the definition of imaging with perspective.

Wow, I'm glad we have this thread because it never occurred to me that people would have different definitions of imaging!

a trio should be closer than an orchestra.

What if the trio is on a stage in an auditorium and you're in the last row? What if the orchestra is in a Broadway pit and you're in the first row?

--Ethan

 

[The Smokester]

...Imaging is simply the recording engineer's blueprint of where the musicians were and that picture can be shifted around so it's more forward or back...

Myles, The problem I see with this definition of imaging is it now presents a moving target. You wouldn't be able to characterize a stereo system with it because every recording is different.

Every recording has a different "perspective" if you will. I like the idea of a perspective but I think it is comprised of both how the sounds were recorded and also how the stereo is set up. The final perspective is a combination of the two.

I will support Ethan (I think) and Dunlavy's notions of a stereo system's imaging: Namely, it is charcterized by the degree to which identical, time-coherent waveforms interfere with each other at the listening position.

 

[MylesBAstor]

Wow, I'm glad we have this thread because it never occurred to me that people would have different definitions of imaging!



What if the trio is on a stage in an auditorium and you're in the last row? What if the orchestra is in a Broadway pit and you're in the first row?

--Ethan

Well I don't sit in the last rows for a trio. Besides which, we are talking about the best perspective for a recording. Would you mike a harpsichord from a distance? Would you listen to a harpsichord from the back of a hall? You might but you'll lose 3/4 of the instrument. Harpsichords just don't project and the musician has to resort to "trickery" give the impression of dynamics on the instrument.

 

[Ethan Winer]

^^ Okay, that's fine, and I agree that a good recording will aim to capture a realistic and typical sound stage. Of course, that's an artistic decision unrelated to the gear or playback environment. Then the problem still remains that some people consider imaging as meaning more than localization. To me, the air around a singer or instrument is due to "ambience" or reverb. And ambience and reverb in turn are derived from reflections in the performing room. So I still consider imaging to refer only to whatever location cues are embedded in the recording.

--Ethan

 

[MylesBAstor]

^^ Okay, that's fine, and I agree that a good recording will aim to capture a realistic and typical sound stage. Of course, that's an artistic decision unrelated to the gear or playback environment. Then the problem still remains that some people consider imaging as meaning more than localization. To me, the air around a singer or instrument is due to "ambience" or reverb. And ambience and reverb in turn are derived from reflections in the performing room. So I still consider imaging to refer only to whatever location cues are embedded in the recording.

--Ethan

Ethan,

No one I know misconstrues what imaging is. Not sure who you are referring to?

As far as capturing "ambience" goes: that is rapidly becoming a lost art. What most people hear as "ambience" on digital recordings, even those of the classical persuasion, are post production digital effects. I know of one leading digital and high-end audio designer who Sony hired several years ago to create digital ambience effects eg. put the orchestra in any hall in the world, for recordings. It is unfortunate that but a few labels such as RR both talks the talk and walks the walk.

 

[Phelonious Ponk]

Isn't imaging the sum of everything that goes into recording and everything that goes into high-fidelity playback? At the recording end, the placement of the individual performers in the audio image - both left to right and front to back - and the ambient space around those performers is effected by almost everything from mic choice to mic placement to panning to relative volume levels to eq to spacial processing (reverb, etc). All of those things don't have a positive effect on imaging, but any one of them can screw it up. I would think that the playback system could do the same. I'm sure you can have good imaging and imperfect frequency response, but you're not going to get pinpoint placement if the FR doesn't match very well left to right. And if the system is imbalanced, a big 80hz hump, for example, won't the imbalance mask critical midrange frequencies and booger up the image? It seems to me that I always hear the best imaging in systems that also have the best clarity. Similarly, wouldn't a high noise floor flatten out the dynamic range and make it more difficult to place instruments in the depth field? And of course there is the room. You could have a system that images perfectly in theory become a blurred mess in the wrong room, from the wrong seat.

I think this may be the hard part, and unfortunately, it's the part that really floats my personal boat. I love pinpoint imaging. The kind where, as Ethan said, you can point to a place in space and say with confidence that the hi-hat is there. The kind that is more hi-fi than realistic even, as that kind of imaging almost never exists in a live performance.

And what's the difference between imaging and sound stage?

P

 

[FrantzM]

And all this time I thought I knew what "Imaging" in the context of sound reproduction was .. Not that this long thread is moving the knowledge in any direction ...

 

[JackD201]

The soundstage is where the images reside. Localization can be very good (good imaging) or not (bad imaging). You'll still have a soundstage regardless.