Audio Physic Virgo loudspeaker Page 3

In addition, the midrange and tweeter are isolated in their own specially damped triangular chamber via a wooden member angled from right below the midrange unit to the rear upper corner of the cabinet.

If the massive, gleaming, black NHT 3.3 is a V8-equipped American muscle-car speaker, the Virgo is a Porsche 911, I thought to myself as I secured the chromed feet to the bottoms of the cabinets. As I wrote in my review of the 3.3 a year ago (footnote 1), for this kind of money the holes should be fitted with threaded inserts (NHT now includes them).

Cinerama setup
When was the last time you heard someone tell you to set your speakers up along the long wall of your listening room? In Joachim Gerhard's view of things, the long wall is the way to go. What's more, he wants his speakers set up in the middle of the room and your listening position dead against the back wall. "What about room-boundary bass reinforcement? What about slapback echo?" I hear you cry.

According to Gerhard, while American hearing research is keyed on amplitude recognition and frequency response, European research has focused on another aspect of hearing—one pretty much overlooked in the US. As we all know, aging takes its toll on our ability to hear high frequencies, because, as with the rest of us (well, with one exception for guys), our parts stiffen over time.

This other property of hearing is involved in "event" identification and image localization. A direct nerve-link between the anvil, stirrup, oval window—the drum-like membrane that pushes fluid against the cochlea—and brain tells us that an event has occurred. This "event" information reaches the brain in 14-20 microseconds. By comparison, it takes some 80 milliseconds for us to identify a sinewave pitch. According to Gerhard, this "something's happened" aspect of hearing is basic to, and far more crucial in determining, evolutionary survival than is pitch identification, which is almost a luxury by comparison.

By comparing new sounds to aural memories, the brain establishes whether the event is glass breaking or a twig snapping; then, based on differences in arrival time at each ear, it determines the event's location. Thus, the brain plays a much greater role in our hearing, and in the "believability" factor in sound reproduction, than we previously understood.

Good news, old-timers: this ability does not deteriorate with age. In fact, over time we become more accomplished listeners as the brain sets up more patterns of texture recognition. For example, as children, we may learn to distinguish the sound of breaking glass from breaking plastic. Later we may learn to distinguish a lightbulb breaking from a pane of glass breaking.

This form of pattern-recognition hearing is said to extend far beyond 20kHz and helps explain why we can sometimes "sense" the absence of ultrahigh frequencies. Is that why our quiet listening rooms grow even quieter when we shut down our systems—particularly our digital components?

Our ability to localize events is thought to be good to within inches throughout about a 6' radius. Is it any wonder moving one speaker an inch relative to the other causes us to hear profound spatial differences?

This research profoundly affects Gerhard's speaker designs, cone material choices, and placement strategies. With the concept of "event identity" fixed in his mind, Gerhard went about choosing materials for his cones. His use of paper for the woofers and midrange drivers and his crossing over to the tweeter at 3.5kHz are choices predicated on this research.

The "event" of paper generating musical soundwaves is more natural than moving plastic or some other synthetic, he contends. Gerhard literally sat around listening to various cone materials by dropping them from a distance onto a table and listening to the "event." Gerhard told me that paper is very efficient and offers higher resolution than plastic.

The problem with paper is one of control—of shaping and damping it to behave properly. The paper-cone midrange driver used in the Virgo has a special S-shaped surround that helps it to perform flat out to 10kHz. The 3.5kHz crossover was chosen because it's near the highest note produced by the violin. The metal-dome tweeter therefore handles overtones and not fundamentals.

Up against it
So, why does Gerhard want you to sit with your back against the wall? The wall is a node—where pressure is highest and velocity lowest—where you'll feel maximum bass pressurization. That's basic, and that's why putting speakers against a wall generates maximum bass. Unfortunately, putting speakers against a wall is not ideal for other reasons—like for generating a three-dimensional soundstage. So, better to put your head against a wall.



Footnote 1: The Abso!ute Sound, Issue 97, August 1994, p.98.
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