A U D I O... P A P E R


HOLOGRAPHIC IMAGING
MARCH 2002
by Steve Deckert

 

Many times I've seen comments about "holographic" imaging that discount it's accuracy and or importance in stereo playback.  As always I have an unrelenting opinion about that.  There is no such thing as accuracy when it comes to good sound.  Things that are accurate on paper generally sound like crap and things that are accurate by subjective listening evaluations generally measure like crap.  My advise is leave the accuracy argument out of this.

Is holographic imaging important, yes it is.  It makes for a wonderful measuring tool when evaluating the true finesse of any stereo system.  

The thrill of high end audio is it's ability to go beyond great frequency balance and create a space from which sound appears to originate.  A space that is judged by it's width, depth, and height and by the illusions that take place from within that space.



Light (eyes) and Sound (ears) are more similar than you think.  If you wanted to try to technically define what happens to create the illusions in a 3 dimensional sound space you could look at the illuminator equations for ray tracing.  This is where you have a 4 dimensional space defined and mapped to create a 3 dimensional image on a two dimensional plane.


A simple 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 speculator factor.  
N [Integer] Number of light sources.  

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

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

When I evaluate the fidelity of an amplifier I find the real telltale indicators that separate a great amp from a just a good one are as follows:

It's ability deal with sounds that move in the sound stage.  Can a sound move from the right rear to the left front in a linear path.  Can the sound move in complex arcs or circles, going anywhere between vertical and horizontal with grace.  Picture orbs of shimmering sound that hang in the sound space like UFO's.  Visualize their flight path as you listen.  How many can your system accommodate at the same time without loosing focus.  

This is the fastest way to hear which amp is better when all else is equal as far as frequency balance and general signatures are the same.

Example, Two Zen amp prototypes using different coupling caps with almost matching signatures.  Casually set up in the average listening room both sound identical in every way.  However if evaluated in a good system that promotes holographic imaging the evaluation of moving targets within the sound space will reveal one amp has a speed problem with the orbs.  They skate through certain quadrants of the sound space faster than they do in the surrounding quadrants distorting their rhythm or pace.

Anyone with a little effort can create an amplifier that has a good (flat) frequency balance.  Most people who discount holographic imaging by no fault of their own have simply never really heard it.

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