JBL Performance surround speaker system Page 2
The PT800BE wasn't particularly critical about height relative to the listener; its vertical dispersion was smooth and uncolored from a few degrees below the woofer axis to about 30° above. Placing it with its center at ear height was about ideal, but anything much higher than that caused significant treble loss. This will be a problem if you put the PT800BEs on high stands (which is where I normally put satellites, to minimize front/back balance changes with changes in listening distance), so I turned them upside down. Unfortunately, this put most of their weight at the top, making them even less stable.
I should have taken my own advice about attaching them to the stands—partway through my tests, an accidental jolt that would never have fazed my Tannoy 10-DMTs pitched one of the PT800BEs off its stand and onto the floor. After that, I used adjustable straps to stabilize them. (There are no convenient threaded holes on the top of the enclosure.) A better solution for a permanent installation would be to wall- or corner-mount the surrounds, but because of the below-woofer treble loss, the supplied brackets should be attached to an angled board fastened to the wall, so as to aim the speakers down at the middle of the listening area.
The tower and center speaker are magnetically shielded, but imperfectly. The PT800BE could be placed within a few inches of a direct-view screen without messing up the color, but no closer. The PC600BE center speaker, which in JBL's setup diagrams is pictured perched atop a large direct-view monitor, has far too powerful a magnetic field for such placement, but would work fine atop a rear-projection television (the magnetically sensitive parts of a rear-projection set are located below the screen).
The PT800BE had very broad, smooth dispersion. Perhaps because of the unusual diaphragm shape, and certainly because the drivers are stacked in a vertical line up the center of the front panel, a pink-noise test signal (a very demanding indicator of timbral change) through one speaker revealed no significant change in timbre until I was almost 55° off the horizontal axis, although there was a gradual diminution of level off-axis, as there should be. This ideal directivity characteristic allowed the PT800BEs to be toed-in as much as necessary to stabilize the image, without coloring the sound for listeners across a wide seating area.
I was pleasantly surprised to find that the PC600BE center's horizontal dispersion was very nearly as wide and smooth as the PT800BE's, despite the horizontal driver placement. Vertical dispersion was more modest but completely acceptable: from 10° below to about 20° above the midrange axis. The PC600BE also sounded very much like the PT800BE, which permitted the front speaker array to deliver an almost seamless soundstage from edge to edge. (Small irregularities in the balance of each front speaker can cause audible response aberrations called "picket-fencing" as you move across the listening area.)
The JBLs' removable grilles were acoustically transparent enough to have very little effect on the sound. They did soften highs, but so subtly that you'd have to be a compulsive type to care. If you're more fanatical about sound than appearance, you'll probably leave the grilles off just to be safe, but if you do, expect your guests to leave fingerprints all over the driver diaphragms. It's virtually impossible to tell by sight what shape they are—they're rather like one of those optical illusions that keeps changing perspective.
As usual, I placed the front PT800BEs at the edges of my 84-inch screen on 30-inch stands (which put their woofers just a bit below ear level), and the PC600BE center-channel on an 18-inch stand under the middle of the screen. The PT800BE surrounds went on 6-foot stands behind the listening area, and the PS1400BE subwoofer (I needed only one for my smallish room) went close-in to the front left corner of the room. I set the sub's crossover to Separated, used the Lexicon CP-1's crossovers to select Small and 80Hz for all the upper-range speakers, then calibrated the sound levels for all channels with my trusty RadioShack analog sound meter. No further tweaking of woofer level was needed.