When we talk about the generally accepted sonic principals to which all audio systems aspire, and by those, I mean clarity, accuracy, dynamics, soundstage and imaging, the last two are really my favorites. Why? Because they make what may otherwise be a boring listening session far more interesting and enjoyable.
While clarity and accuracy lend a degree of realism to recorded music, dynamics gives music power, authority and creates an emotional connection to a song, it is soundstage and imaging that makes sitting in that chair staring at an audio system a fun and gratifying enterprise.
When we talk about soundstage and imaging, we usually do not mention one without the other. Generally speaking, they are in many ways inexorably tied together. Soundstage is defined as "the physical environment in which a recording is or was made, and its acoustical properties." Think a recording studio, a small intimate live venue, or a giant concert hall.
Imaging, on the other hand is defined as "the accuracy with which a stereo system recreates the original sizes and locations of the instruments across the soundstage."
In this instance, imaging refers to where the musicians are located on the soundstage while performing. Pay particular note to the location part of the definition. For brevity, let's consider imaging in this article.
Some systems do a remarkable job of this phenomenon, other less so. Imaging is always a composite of the recording, the audio system itself and the room in which the system is housed. All of these factors affect how well the listener can identify where in the room a particular instrument or vocalist is portrayed and the placement accuracy of that portrayal.
In considering speaker design, attempting to replicate live music, or at least the perception of live music is an obvious goal. One term used long ago was the "pulsating sphere." This speaker design, while theoretical and does not exist in reality, would emit all frequencies in all directions, exciting the room with 100% of the sound, exactly as live sound would behave in a given space. It would also disperse that sound with equal dynamics from the lowest frequency to the highest. That condition is called "dynamic linearity."
Sadly, we do not yet have what is theoretical and must accept our systems based on the previously outlined conditions - the recording, system and room. And because all three of these plays so collective a part in the overall quality of image presentation, failing or a reduction of one or more as compared to the others negatively affects imaging quality and a lifelike presentation.
One mildly debated condition is where imaging should take place - behind the speakers or in front. There are those who prefer imaging to occur behind the speakers, much like early stereo recordings using only two mics. Those mics were placed fairly close together, much like our ears, and the sound field was then recorded as a triangle with the musicians at the rear of that soundstage. Translating that to an audio system directs the image should therefore be behind the speakers.
Conversely, there are also those who champion the condition of hearing music in front of, to the side of, and possibly even behind the speakers regardless of what audio purists might say.
They will even eschew the notion that anytime an image is presented in front of the speaker boundary it is the likely result of drivers out of phase and / or room reflections. I have had it both ways and while I prefer imaging behind the speakers, I have had it the other way and found it equally entertaining. Because remember, we're trying to make listening sessions FUN!
The room plays so huge a role in imaging it cannot be discounted. Depending on the design, speakers tend to radiate sound in a direct pattern but also in a broad pattern that creates reflections.
We have terms like "comb filtering," that can and will play havoc on a sonic presentation. We are talking about the time arrival of sound to one ear as opposed to the other.
And given the ear / brain's remarkable ability to recognize miniscule differences of time arrival of sound to each ear, managing reflections as best as possible makes perfect sense. We cannot change the recording. And with the exception of a different component or speaker placement, our systems are pretty much consistent. Audio rooms, on the other hand, can be manipulated and improved for the ideal sonic picture given the circumstances.
At the beginning of this article I wrote "Because they make what may otherwise be a boring listening session far more interesting and enjoyable." That's what it's really about, isn't it? Making music more fun and enjoyable. In my current set up, I have heard singers move along one side wall, across the front wall (wall behind the speakers) to the opposite side wall just as a vocalist would sound if walking across a stage. Were my room much wider, it would even be more linear and less reliant on side walls.
I can, depending on the recording, identify where in the room an instrument is placed with a high degree of accuracy. Some recordings spread the image presentation from one side wall to the other and all in between. Other recordings will not image beyond the boundaries of the speakers at all, in my case about six feet apart. I routinely have layers of depth, front to back, again, always behind the speakers. My limitations are the recording, the system and the room.
Imaging is hard to accurately pin down. There are so many variables that saying any one presentation is perfect is quite nearly impossible. If perfection is really wanted, better go live. Still, I very much enjoy trying to determine the point from which a particular sound originated. Imaging makes listening to music more fun, more interesting and more satisfying. Short of live music, I can't think of any better attribute.