A related shortfall on the Zvox 425 is its complete dearth of digital audio inputs. Likewise, the Zvox doesn't decode any Dolby Digital or DTS surround signals, accepting instead only two-channel analog stereo. In other words, if you've worked to build an all-digital system (using HDMI and optical or coaxial audio connections), you'll again have to settle for using the analog "monitor out" output from your AV receiver or TV--or simply opt for Yamaha's better-equipped (and more expensive) Digital Sound Projectors instead.
The other unique feature of the Zvox 425 is the SANE control (Sudden Audio Noise Eliminator). It's a variable-dynamic range compressor that might come in handy to reduce the "sudden noise" extremes of explosions and special effects for late-night home theater sessions--what's otherwise known as a midnight mode in AV receivers. We didn't find it to be all that effective, but it couldn't hurt.
Zvox offers a two-year warranty for the model 425; that's more protection than usual for virtual surround speaker systems.
We used the Live Free or Die Hard DVD to push the Zvox 425 to the limit of its performance capabilities. The sound was really big, dialogue clear as could be, and after we adjusted the PhaseCue control, the sound was remarkably spacious. Better yet, as we pumped up the PhaseCue, we didn't detect any added processing artifacts. But the 425 is still nowhere as visceral as a decent 5.1 speaker system. For instance, in one scene where an airborne car was about to crush Bruce Willis, the dynamic punch was lacking.
That said, the Zvox 425 stands tall among competing single-speaker products in the same price range. It was notably more powerful and dynamic than the Yamaha YAS-70 Air Surround soundbar speaker ($500 list). Yes, the Yamaha had the advantage of the separate full-size sub, so its deep bass was bigger and louder than that of the Zvox. If you want a lot of bass, go for the Yamaha. But it's a quantity-over-quality deal: the Yamaha's big bottom was boomy and bloated compared to the Zvox's more controlled bass. The Zvox 425 even produces more and better bass than Yamaha's flagship YSP-4000 ($1,600 list) that doesn't come with a sub.
Our current favorite speaker-busting music DVD, Eminem's Live From New York City, didn't faze the Zvox 425 one bit. (By comparison, the Sony DAV-X10 virtual surround home theater system didn't survive unscathed.) We cranked the volume way up, and the Zvox's sound just got better and better--the hip-hop beats were deep and nicely defined. The surround mix puts the audience in the surrounds, which the Zvox 425 projected forward a few feet ahead of the speaker. Zvox doesn't promote the 425 as a "virtual" surround system, but it's certainly on a par with most of them. The Yamaha YSP-4000 is still the reigning virtual-surround champ, though: it can project surround effects much farther out into the room than the Zvox 425 or any other brand's speaker that we've heard to date.
CD sound was also excellent and--after adjusting the PhaseCue control--the stereo spread well beyond the edges of the speaker. The I'm Not There movie soundtrack on CD has a wide range of music types; everything from hard rock tunes such as The Black Keys' "The Wicked Messenger" to Mason Jennings' acoustic folk take on "The Times They Are A-Changin'" sounded great.
Summing up, we were mightily impressed with the Zvox 425's sound on movies and music. Sure, it's big, but it's still a lot less intrusive than a 5.1-channel system.
Editor's Note: The rating on this product has been dropped slightly from 7.9 to 7.6 due to competitive changes in the marketplace.