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At 1.30m tall, the Submission is a true tower of power. Only as a corner plant stand with Rapunzel-type leaf cover would it visually 'disappear'. It's perfectly inaudible powered up without any annoying transformer hum. With its 32cm square foot print rotating the business end to face the listener whilst one sorts out the perfect settings is as easy as turning things around in the end to look at just smooth lacquer skins (or wood veneer if that's what you opted for). Though the controls are self-explanatory and unmistakably marked, here is how Zu recommends to get going. With LF boost at max but set to about 26Hz, one assures proper infrasonic in-room power without muddying up the higher ranges. As I found out with Martin Gateley's Wave 40 widebanders, it works an obvious treat also with other 'single-driver' speakers. The ability to set the low-pass as low as 10Hz and from there up in very easy 5-cycle increments or less allows for perfect integration with speakers that mostly lack just the bottom octave (or even less).

The sub-level input is  3dB higher than a single left or right line-level input. Left + right line-level inputs approximate the gain structure of the single sub-level input. In practice the loudspeaker-level input gain approximates a typical home-audio variable line-level feed. Left and right line-level inputs sum and running both is highly recommended if you are using a single sub. A single input will drop Submission's output level by 3dB. Ditto the speaker-level inputs. If you are using Zu floorstanding speakers, the above initial settings are recommended and equal the median of the black curves within the data below (speaker-level in and just one channel is where I usually start). Purple curves are line-level input using the above recommend initial settings. Volume setting will vary quite a bit depending on room, main speakers and system gain as will other settings. Adjusting phase is best done with some acoustic measurement equipment. This affords a user or engineer to really dial in timing relative to the main speakers, room/listening area and other possible phase/polarity considerations within the electronics.

Undertone is the stripped-down smaller version giving up parts and assemblies that contribute less to sound. The three areas we skimp on are size, cabinetry and machined aluminum work. The overall sound and function of Undertone is similar to Submission but it won't dig quite as deep and isn't as calm, collected or agile by having more cabinet talk and microphonic noise. Undertone's cabinet doesn't feature the extensive internal bracing and uses half the cabinet material of the Submission. Both are made from Comp-60 high-density composite fiber board. Submission bolts the LAB-12 into the machined aluminum alloy base like Definition IV which then bolts into the cleats of the cabinet. Undertone's base is a sandwiched layup of Comp-60 with the the LAB-12 mounted directly into it. That means it's not as quiet and well behaved as Submission. Undertone has its electronics mounted to an open plate whereas Submission seals them within its machined casework.

with soundkaos Wave 40 and Bakoon AMP-11R, Submission set to volume click 3 and 40Hz low-pass

If you wonder what exactly lives in those murky depths of 20 cycles below 40Hz, it's quite the handful. I'd propose the following sequence - overall scale; soundstage depth; breath; color saturation; transient impulsiveness. Let's cross these improved qualities off one by one. Scale and depth are intertwined and related. It seems that very important but subtle ambient data about the recording venue are encoded in very long wavelengths albeit at quite subliminal levels. When reproduced on what's a more guttural instinct than primary hearing level, these wavelengths create a very specific spatial expander action. Audible space rolls out in general but particularly in the depth domain. It's dead obvious and of surprising magnitude even on material that—we think—shouldn't contain any such infrasonic information like girl plus guitar. This is a very basic case of not knowing what one doesn't know (until one finally does).

Breath too relates to scale. There's more ebb and flow, more cresting and easeful gushing as though a belt was loosened and music on a whole began to perform deep diaphragmatic breathing. More extended powerful low bass also deepens the black level of the color palette. This saturates tone intensity and heightens contrast. Finally transient impulsiveness particularly on kick drums and bass but even on higher-pitched instruments gets more acute and incisive. The obvious upshot is that rhythmically driven fare shifts down a gear for higher RPM because the major time keepers in the drum and bass section gain in potency and slam. A good word for this would be increased vitality. More pep in your step. Greater kick.

Of vital importance in the proper harvesting of "the murky depths" is the subliminal factor. Dial up the sub attenuator too high and bass becomes obvious. This might impress the boom-truck brigade but nobody else. You thus might be very surprised to discover just how far you can throttle the sub's output back to still get all the above goods in an otherwise perfectly 'invisible' fashion. This means perfect clarity, clearly discernable dry pitch and full intelligibility to strike the word 'murky' from the bass vocabulary. Verification that you aren't imagining this novel underworld is a simple power down of the sub or turning its volume to mute. Compare by contrast. Then turn off the main amp and listen to just the Submission. This will be a crash course in observing what the various controls do. As soon as you've gotten used to the full picture, bypassing the sub causes this scale, grandeur, ease and enhanced grippiness to collapse upon themselves. Once you have proven to yourself how without proper infrasonic presence some very important elements go missing which transform how we relate to the music from spectator to participant, you'll henceforth consider a Submission-type subwoofer essential.

Where the Submission leaves passive speakers of any persuasion and price—and lesser subs—completely in the dust is the PEQ facility. Depending on the size of your space, 20Hz signal really might take that 6dB boost to become sense-able yet you wouldn't want 40Hz or higher to be equally potent. The half-octave boost width prevents the usual mud to become a very strategic surgical address instead. The efficacy of what 20-cycle infrasonics without boom at the ear do to our psychoacoustic perception of sonic realism cannot be overstated. It's quite intangible on a 'hard data' level since you can very rightly dispute just what type of tones occur on regular music at those frequencies. Yet it's very tangible on a soft experiential level. And sorely addictive. I'll be perfectly blunt. It's something you'll not want to be without once you've heard it without any of the so very common negative side effects. The Submission might be of hulking proportions but it behaves like an Olympian foil fencer with lethal speed, accuracy and poised elegance. With this active and flexible giant I hands-down had the very best bass I've ever enjoyed in 10 years on the job.

Given the unusual scope of today's assignment, I'll cut submissional reporting short to reserve deeper reportage for a separate feature with a broader variety of partnering main speakers. Since Zu's catalogue has grown quite confusing relative to the various options a buyer has at specific price points, let's survey some of these possibilities according to Sean Casey.

Navigating the options. $10.000 Soul Supreme + Submission or $11.500 Druid V + Submission? This is a similar sound but packaged into a smaller design to fit the architectural and art desires of those who might be turned off by Druid's unique and somewhat tall presence. The smaller size of Soul Supreme and Soul Superfly better fit certain stylistic preferences. Soul Supreme and Soul Superfly also have a bit more cabinet coloration. If you don't need bass below the kick drum region Druid V will give more resolution of detail and tone than Soul Supreme whilst the latter with the same new Radian 850-based tweeter as the Druid V is a significant step up over the Soul Superfly. For me the nexus is Druid around which to build your system. If your wife doesn't like the Druid's geometry and you don't want to get relegated to the basement, go with one of the Soul series which are visually much less demanding.

$11.500 Druid V + Submission or $12.000 Message? Message is the form and build of the Definition without the active subwoofer. It uses the entire cabinet for the two full-range drivers. From the front it looks exactly like a Definition. If you don't need really deep bass and don't like the idea of a standalone sub but prefer a larger soundstage, Message is your answer. It will give you the presentational scale of a Definition without quite its bass depth.

$16.500 Druid V + 2 x Submission or $16.000 Definition IV? Definition IV is the easiest full-spectrum loudspeaker we make. It's easy to set up, dial in and capable of all music (16Hz–20kHz) at levels both low and concert. It excels at large music and big spaces. Definition is also more of a sit-down speaker. Its improved resolution in the presence region only works when seated. The magic is far less less when the listener is standing or moving about preparing food in the kitchen.

Large orchestra, big rock, dramatic film scores, techno and close-mic'd blown-up recordings are where the Definition really comes into its own. Druid V + Submissions are equally full-spectrum but with the simple wave front development allow for more stable whole-room stereophony seated or standing or working in the kitchen because here Druid V's character remains stable. The sweet-spot listener with an average-sized room where the seat is about 8-10' from the speakers will likely find Druid to play well to full-bodied blood'n'guts music like folk, country, singer/songwriter, soul, R&B, blues, blues rock, alt./trad. country, hip hop and garage rock. It's still very compelling for big orchestral, ambient, most film scores and techno but trades a touch of expansive quality for intimacy and emotional sincerity.

Polarity parity.
Zu speakers enjoy polarizing an audience. Those in the fold won't go elsewhere. Consider vocal supporter Phil aka 123cobra: "No Magico at any price can deliver Druid’s pure unity of behaviors regardless of what you try to drive them with. No Magico is as musically satisfying with such a wide range of amplifiers. Druid V laughs at the cacophonous disunity of a Wilson speaker. Druid V ridicules the dynamic choke points imposed on Focal speakers at the crossover points. In the same way that no one appreciative of the unity of the Quad ESL heard any musical value from the Infinity IRS or a Duntech Sovereign back in the day, a Druid V owner today can pretty much ignore the rest of the alleged 'high-end' speaker market inflicting damage upon our hearing - with the exception of other Zu speakers."

Jingoist shilling? Ideology manifesto? Gonzo love? Whatever your personal reaction, in certain quarters such color is emblematic of how Zu owners voice their support. I expect that Sean Casey shudders at times. To my ears earlier Zu designs always were exceptionally fun to fire up. Their straight-for-the-gut approach bypassed calmer reasoned assessments which, whilst finding certain audiophile faults, also had to admit that those didn't intrude on the fun. Tone density and dynamic responsiveness were already locked.

The new Druid massages the same fun quotient further but adds considerable seriousness. Costlier better parts and costlier more complex cabinetry add up to a more serious sticker and greater physical weight plus clearly more serious performance - more bandwidth, more focus, more resolution, more dynamic gradations. Unlike the Punk rep Zu has cultivated, first-class electronics well above the Druid's sticker are sensible and proper company.

I hit full seriousness of stride with in-room SPL about two clicks above my AudioSolutions Rhapsody 200 or Aries Cerat Gladius. Their less efficient smaller dedicated midranges got lucid sooner. Once the Druid 'arrived', its visceral physicality as the polar opposite of ethereal sonics became quite addictive. It nearly silenced remnants of desire which wished for just a bit more in-sight into the presence band. Yet a Rethm which does that also generally goes after a different aesthetic: aural spiritualism, not Zu's sonic materialism. Rethm is built on a super-modulated hellaciously transparent immediate upper midrange. For proper integration that mates to an equally quick lean bass. My wiring correlates with this the higher mind and entering the zone on perhaps the abstract architecture of a massive Bach fugue or the otherworldly transcendence of a Bruckner Adagio. The Zu aesthetic is centered in the power region. Think gut or lower and saucy Brazilian samba for an obvious example. Any notion of grafting Rethm's trademark flavor atop the Druid would up-end its special allure. It's really a vanilla/chocolate thing.  
Rethm Saadhana

For the 16Ω Druid V, those into 85% pure cocoa might wish to pursue maximal tonal saturation with a valve amplifier. 20wpc 845 or 211 variants are said to be ideal. Those after greater lucidity in the upper vocal range coupled to optimal bass control might consider an infusion of cayenne pepper for dynamic kick and energetic after burn with a superior small transistor amp from FirstWatt, Bakoon or Vitus perhaps preceded by a superior (even DHT) valve preamp.

Being good to about 35Hz, the addition of the Submission for true infrasonics transforms the Druid V's scale and ambient recovery in particular. True subbing at 30Hz and below might seem mostly theoretical amusement to fuel testosterone-poisoned bragging rights. Once acquired it's far from. Obviously bass gets better whenever there's actual primary data that low. That's not the chief attraction however. The main benefit are 'tertiary' data which render recorded space more expansive. This triggers some nearly animalistic psycho-bio sense where we relate to playback as more tacit and grand like moving up a slider on the reality meter. Key of course is proper room integration. Grotesque lumpy boom from waves of LF resonance must be avoided at all costs. Enter placement freedom and the ability to dial down infrasonic output until at the ear it approaches the subliminal. That's when the real (bass) magic happens [Eminence LAB12 woofer at left and below].
This is not a sat/sub compromise or band aid. It's moving what for a 2-way tower is already full-range sound—technically it's a 1.5-way—into true LF bandwidth. Whilst more palatial spaces will respond differently, a room like mine (5.5 x 12m or ca. 15 x 35') set up in short-wall orientation doesn't normally warrant more than one centrally placed Submission or half-priced Undertone. Having moved through six rooms in the past 10 years of reviewing has me quite certain. After conjugal visits with far more speakers than rooms over that same period, I'd also consider it extremely unlikely that one could achieve anywhere near equivalent 20Hz performance from a passive $11.500/pr multi-way. Franck Tchang's ASI Tango for example proved too bass potent for my current space. Being passive meant no means of taming.

Finally a two-stage acquisition in the Druid+ scheme is easier on the pocket book. This shouldn't imply that the Druid V without sub is incomplete. It simply means that with the Submission, scale and soundstage freaks in particular arrive at the end of their road without qualification. And that's very serious indeed. In short, all the talk of nano treatments and hi-tech enclosure laminations wasn't techno babble. The improvements from the Essence days are real. Even a casual A/B confirms it. With the Druid V, return of a classic doesn't quite capture it. I'll leave it to you then to pen a better byline...
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