KEF KHT 9000 ACE
British brand KEF has a long and eminent history of serious speaker design. Its current engineering keystone is the Uni-Q driver, which puts a compact dome tweeter in the center of a woofer/midrange cone. This coaxial arrangement allows all of the sound to come from a common point and also helps to disperse the sound evenly across the listening area — both Very Good Things according to the Hogwarts Manual of Speaker Design . KEF's new flagship on-wall speaker is the KHT 9000 ACE, a slim, Uni-Q tower just 5 inches deep that's designed to hang on a wall or mesh with a selection of equally slim stands to form dramatically thin towers. ACE stands for Acoustic Compliance Enhancement, a new KEF enclosure technology aimed at coaxing more bass from small boxes (see www.kef.com/technology/acoustic/acoustic.html for details).

We used the KHT 9000 ACE for all five main channels. One advantage of a coaxial driver array is that the sonic character and coverage change very little whether the speaker is vertical or horizontal. And KEF's clever mounting system lets you orient it either way, on the wall or on a stand.

Clever as it is, however, struggling with the mounting system was no fun. The parts are nicely machined and very attractive, but the wordless manual full of cryptic pictures, the curved, almost-symmetrical parts that might go this way or that, and screws that were about two threads too short for one of the configurations made for a hair-tearing experience. Do yourself a favor — let a professional installer set these up!

Once they were in place, though, the KEF speakers looked elegant flanking my plasma TV. The KHT 9000 ACE can be used with or without a subwoofer, but for real home theater action you should definitely use a sub. Nonetheless, the 6 1 / 2 -inch Uni-Q driver flanked by two 6 1 / 2 -inch woofers produced enough low bass to be fairly impressive from a speaker this small and shallow — presumably a credit to the ACE enclosure technology.

PERFORMANCE Played without a sub, full-range stereo pop music — like Elvis Costello's orchestral-jazz ballad-fest North on Super Audio CD (there's also a surround mix) — sounded impressively detailed and clear, with big, rich bass. I did note that the KHT 9000s sounded slightly but distinctly better at higher volumes powered by my 150-watt-per-channel separate amp than they did fed by a midprice 100-watt A/V receiver. (This proved to be true of the M&K and Thiel systems as well.)

Either way, what I heard sounded very smooth and slightly warm, but with outstandingly even, open, uncolored vocals. Some thickness in the lower midrange tinged what was otherwise a nearly ideal tonal balance. But that's what happens when you put speakers on the wall instead of out in the room, and I've heard the same effect from almost every on-wall I've listened to.

With a subwoofer in the mix, though, I could get close to the ideal by controlling the balance between the sub and the satellites. We chose to test this system with the compact PSW 2150 sub, but you could also use one of KEF's larger and more powerful (and more expensive) models — or any other suitable sub. I used a standard 80-Hz crossover with the 2150, which tightened things up discernibly, adding another full octave to the system's deep bass.

The KHT 9000 ACE proved to be a marvelously capable center speaker, sounding almost identical to its vertically oriented front L/R companions. And this stayed true even when I sat well off to the side of my usual listening position — like that spot you get stuck with at the end of the sofa when you arrive last after thoughtfully grabbing the chips and dip. The only real changes were that the sound became slightly brighter and more focused when I moved directly in front of the Uni-Q tweeter. This was especially apparent with treble-rich music. But there were none of the shifts in the lower-midrange sound — most easily heard on male voices — that you'll hear with most horizontal center speakers sporting a classic woofer/tweeter/woofer layout.

The KHT 9000 ACE's ability to sound essentially the same whether positioned horizontally or vertically made it an especially good surround speaker — particularly for someone like me who usually prefers the more diffuse sound of dipoles and bipoles for movie watching. The surrounds did a fine job with ambient sounds like the storm in Chapter 7 of Kevin Costner's unabashed compendium of Western clichés, Open Range . The thunder rolled realistically while sheets of rain moved convincingly across the sound field.

The PSW 2150 subwoofer was a competent performer, with solid extension (down to about 35 Hz in my room) and good output — plenty to match the KHT 9000s for movie listening in a moderate-size room. With multichannel music at rock-club levels, the five KHT 9000s could outstrip the PSW 2150, though by a relatively narrow margin. So for really no-holds-barred home theater, you might want to consider a more powerful subwoofer.

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