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Aries Cerat Stentor. Though being a smaller 10-inch sealed 3-way costing just a G more than half of the €22.000/pr 12-incher, its Carbon-fiber woofer reaches lower than the bigger Fostex paper driver of the Gladius. As such I didn't think it could benefit from any subular assist. Even so setting the Submission's low-pass to 10Hz(!) still produced more audible space, crisper bass transients and more realistic kick drum. This admittedly came closest to gilding the lily than any previous combination. On my type of music however, its efficacy was particularly evident at volumes below those where this speaker's 88dB inefficiency fully awakes. The difference between real or synthesized drums and their interactions with the recorded venue for example was far more apparent, hence the intended musical effect appreciably more convincing and stirring.

If your primary musical fare consists of Baroque orchestra, string quartets and girl+guitar, the sub now would have been inaudible. For this type music the Stentor is perfectly sufficient. Here your musical tastes are simply easier on raw bandwidth. Once you cross over into even light ambient fare—rather than gothic dark full-on electronica—such as the paisley music of sitarist Al Gromer Khan where appeal rides on opium-den minimalism of deep space, slow pulse and melodic fragments, the tables turn. Maximally developed infrasonics become necessity, not gold-plated luxury. And since ambient music is often used as a mood setter rather than primary room filler where playback volumes are low enough to hear yourself think rather than feel drowned out, active bass once again has the discrete attenuator advantage to compensate for those effective Fletcher-Munson curves.

My takeaway from this encounter was two-fold. One, bass that at 20Hz is up a few dB at the ear sounds better and more natural than flat but isn't achievable even with endowed passive speakers unless—by very unlikely chance—they interact with your room acoustics in the desired fashion. Two, ported low bass is far more likely to become woolly and ringy and sound like room boom when in the very same location a sealed speaker will play far cleaner and more linear. Porting's entire rational is to get lower louder bass from boxes that are smaller than sealed equivalents. Why not go after a non-ported speaker with sufficient far cleaner reach to blend perfectly with a subwoofer that allows you to strategically dial in the desired infrasonic boost whilst avoiding all port problems altogether?

Conclusion. Bob Carver's tiny 'walk-about' Sunfire subs with their heavy drivers, massive bullnose surrounds, kilowatt class D power and high distortion plus all subsequent clones competitors felt forced to launch in their wake did precious little for the breed's cred as an audiophile species. Zu's giant Submission has just as little to do with that subject as does the ultra-compact sub's silliness of brute force. It's not about pushed alignments and idiotic internal air pressures. The Submission is about easeful elegant extension and output which in this game mean big size. The downfiring orientation with its instant floor reflection creates immediate omnipolar dispersion. This eliminates directional cues which front-firing subs retain from their directive wave launch. Absolutely vital for proper integration in the '1st-octave-only' game is the continuously adjustable low-pass filter down to 10Hz. So is the EQ function to build out infrasonic lift.

The upshot of all this is very basic. Particularly if you love electronically enhanced music with its unnatural (non-acoustic) extension and power, active bass is pretty much a prerequisite. But low bass is so much more than just low bass. It's primarily about a more successful suspension of disbelief. It's about greater realism, about more audible space, about heightened ambient retrieval, about keener venue cues, about higher contrast and deeper colors and tacitly greater overall scale and gravitas. What an outboard subwoofer adds over most integrated active bass systems are more flexible adjustments, physical isolation and greater freedom of placement. It's a well-known fact that with passive speakers the 20-40Hz band is the costliest to secure. All else being equal, a model that hits 40Hz vs. 20Hz might only have to cost half as much. It'll also be substantially smaller and thus visually easier to integrate. Bass reach to about 55Hz would seem perfectly sufficient to seamlessly add infrasonics with a true subwoofer. In practical terms and from the top down, this would make the third rather than second model in a given speaker catalogue most ideal (and in this context forget about the priciest model altogether).

Such deliberate downsizing for better performance—what a perfectly contemporary bumper sticker—should have another fringe benefit. Your smaller main speaker ought to be perfectly happy with a smaller amp. Once you minimize high power needs with their reliance on endlessly paralleled output devices, cascaded gain stages and corrective feedback, the doors open to simpler better-sounding amplification circuits. Now spend your big-amp money on a more sophisticated small amp from a better maker; or save money by buying a smaller model in the same amp catalogue. Either way you win.

Size is relative as Marja & Henk's personal Submission shows between their giant Arcadian Audio Pnoe horns.

Isn't the Submission overkill? Wouldn't a half-priced Undertone accomplish the same? Not having auditioned the latter, that's really my only unanswered question. A fair assumption? The main part of the documented journey into greater sonic realism should be equally well served by the smaller sibling. Where I expect the Submission to reign is on ease, specificity of low-bass detail and subsonic reach. It's here where personal demands for ultimate performance plus considerations about what your music library consists of the most become the final deciders. Either way it's my considered opinion that the genus of subwoofer must once again be included in serious audiophile discussions. To have subwoofers condemned to home-theater exile as imposed by ill-informed snobbery and unfit samples of the breed is ultimately costly on your wallet and counterproductive for the 'high' in hifi. Kudos to team Zu for swimming against the prevailing tide and offering not just one but two dedicated quality subwoofers. Their stout Submission should get this process of reacquaintance with the genre started even if by no other means than outraged dissent with my review of it. I for one feel cured from the stupid ambition to do it all with passive boxes no matter what their pedigree might be. It only took me 11 years of intense reviewing to arrive at such a belated realsization. Better late than never though. And perhaps talking about it saved you a few years? Cheers to that!...
Quality of packing: Good.
Reusability of packing: A few times.
Ease of unpacking/repacking: Requires two.
Condition of component received: Flawless.
Completeness of delivery: Perfect.
Human interactions: Good.
Website comments: At publication date this model wasn't yet listed.
Pricing: Costly but considering
comprehensive performance enhancements—and what it would cost to achieve the same from bigger passive speakers (impossible!)—very good value in fact.
Final comments & suggestions: The amp's transformer is highly sensitive to DC on the power line. If you encounter hum, consider adding a DC blocker.

Zu Audio website