Audio Physic Virgo loudspeaker Page 4

Those who suggest that the reflection off the rear wall will confuse imaging are incorrect, according to the Haas primacy effect, which demonstrates that the ear prefers the direct wave over the reflected and can only process the time delay between the direct and reflected sound when the distance is greater than the circumference of your head, which is about 2'.

If that seems like only watermelon heads are involved, get out your tape measure—we're all a bunch of fatheads. So as long as you sit closer than 2' from the back wall, the ear/brain will not process the reflection, giving preference to the direct sound from the speaker; though, of course, if your back wall is glass, it will for other reasons affect what you hear. Clearly some treatment of the back wall will be of some value.

With you sitting against a wall, where is the best location for maximum bass pressurization? According to Gerhard, at the room's exact halfway point, with the speakers against either side wall. That's the second node. The next best position is at the quarter point in the room in both axes.

In fine-tuning the room for both frequency response and imaging, Gerhard first divides the room into two grids. One is even divisions—halves, quarters, sixteenths, which represent reinforcement nodes; the other is odd—thirds, sixths, ninths, which represent cancellation nodes. These measurements should be done to the inch with a tape measure and not be guesstimates. Ideally, you'd draw out each grid in a different color and overlay the two.

If your room is such that you can put your speakers at the halfway point in the room with the speakers against the side walls, the next move would be to move them laterally closer together to the quarter point on each side. That would be your ideal starting point for maximizing bass pressurization and creating a credible soundstage.

Now begins the battle of optimizing imaging and frequency response. If bass is too strong, you could go to an anti-node that could either be forward or back or side to side to one of the "third" points. While the trend is toward more bass as you move the speaker closer to the back or side walls, there are cancellation points as you go toward the walls.

Unfortunately, I can't sit against a wall in my room. I can't even set the room up with the speakers and listening position on the long wall. The solution, according to Gerhard, is to locate the listening position in the exact middle of the room and put the speakers at the exact quarter points: a quarter into the room and a quarter from the side walls.

That, my friends, in a 16½' room like mine, is a Cinerama-width, nearfield listening experience—and that's another Gerhard/Audio Physic listening preference. And if you think about doing that on the long wall, you have an even wider stage. Gerhard's ideal setup is you against the long wall (room permitting), speakers 8' apart and 6' from the listener. This way the speaker is closer to you than it is to any wall: the first thing you hear is the speaker, not the room—thus, the room is effectively taken out of the equation. The only wall in play is behind you and closer than 2', so it's effectively out of play.

Stuck in the middle
So I'm sitting around with these Virgos 6' (on the diagonal) from my ears, 4' and change into the room, and I'm stuck in the middle. To me, this looks odd—almost uncomfortably in my face.

I'm going to go through the rest of the setup procedure before I tell you what I heard with these speakers, because when you're through reading, you might want to try it yourself with your speakers in your room—although be forewarned: Gerhard claims it works best with first-order crossover designs using tightly matched drivers.

With the speakers toed-in, tweeter pointing directly at your ears, play a mono record—jazz or vocals—and listen for the center image. Move the speakers apart symmetrically until the center image begins to break up (assuming your room is wide enough). Move the speakers together until it solidifies again.

This ideal center-fill placement may put the speakers in additive or subtractive nodes. Whether you leave them there or move them will depend on the bass response you hear. Using the even/odd grids, move the speakers slightly to add bass (into the nodes) or subtract bass (out of the nodes). Inch changes will have surprisingly great effects on the balance from your exact starting point. Front-to-back changes have a more profound effect on bass, side-to-side on "warmth."

Once you're comfortable with the bass response/frequency balance and you've got a firmly focused center image using a mono record, toe both speakers out until the tweeter axes cross about a foot behind your head.

You're pretty close now. Moving only one speaker on one axis (ie, the forward inside edge of the four), point the speaker inward and outward, listening for the smallest, tightest, most focused image using (ideally) a mono recording of a jazz combo. At one point in your trials and errors, the images will "stack up" in the center—that is, you'll hear the drums, cymbals, bass, vocals, and other instruments locked in the center. That's the ideal position, and it doesn't matter if the two speakers are not symmetrical relative to toe-in. If at that point you notice the center image isn't precisely centered, move the same speaker you've been rotating, forward or backward, to center the image.

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