I've often seen comments dismissing the accuracy and importance of "holographic" imaging in stereo playback. As always, I have a strong opinion on the matter. The truth is, there's no such thing as "accuracy" when it comes to good sound. Things that are accurate on paper often sound terrible, while those that sound great in subjective listening tests often perform poorly in measurements. My advice? Leave the accuracy debate out of this.

Is holographic imaging important? Absolutely. It serves as a valuable tool for evaluating the true finesse of any stereo system.

The thrill of high-end audio lies in its ability to transcend mere frequency balance and create a space from which sound seems to originate—a space defined by its width, depth, and height, and by the illusions that unfold within it.

Light (eyes) and sound (ears) are more similar than you might think. If you wanted to technically define the process that creates these illusions in a three-dimensional sound space, you could look at the illuminator equations used in ray tracing. These equations define and map a four-dimensional space to create a three-dimensional image on a two-dimensional plane.

A simplified version of an extended (partial) illumination equation is as follows:


N
__
\ n
I = Ia Ka + / IL(Kd cos(theta) + Ks cos (alpha)) + Ks Ir + Kt It.
~~
L=1


The values used in this equation are:

Ia [RGB]: Global ambient light
IL [RGB]: Light contributed by light L
Ir [RGB]: Light contributed by reflection
It [RGB]: Light contributed by transmission (refraction)
Ka [RGB]: Object ambient color
Kd [RGB]: Object diffuse color
Ks [RGB]: Object reflection color
Kt [RGB]: Object transparent color
n [Real]: Phong specular factor
N [Integer]: Number of light sources

If you substitute the word "sound" for "light" and "harmonic" for "color," you're essentially looking at one of the fundamental formulas for imaging.

So, why is holographic imaging important? It's crucial because it effectively squares the amount of information perceived in the recording.

When I evaluate the fidelity of an amplifier, I find that the true indicators separating a great amp from a merely good one are as follows:

Its ability to handle sounds that move within the soundstage. Can a sound move from the right rear to the left front in a linear path? Can it move in complex arcs or circles, gracefully transitioning between vertical and horizontal? Imagine orbs of shimmering sound that hover in the sound space like UFOs. Visualize their flight paths as you listen. How many can your system accommodate simultaneously without losing focus?

This is the quickest way to discern which amp is better, assuming all else—frequency balance and general signatures—are equal.

For example, consider two Zen amp prototypes using different coupling capacitors with nearly identical signatures. Casually set up in an average listening room, both sound identical in every way. However, when evaluated in a system that excels at holographic imaging, the assessment of moving targets within the sound space will reveal that one amp has a speed issue with the orbs. They skate through certain quadrants of the sound space faster than in the surrounding quadrants, distorting their rhythm or pace.

Creating an amplifier with a good (flat) frequency balance is something anyone can do with a bit of effort. Most people who dismiss holographic imaging have likely never truly experienced it.