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A speaker may not fill a room with bass, resulting in a light, possibly bright sound. The same speaker could also overload a smaller room, yielding a hooded, muddled finish. We might describe the latter condition as 'too much bass'. More likely there are peak nodes far above the baseline level which are masking other sounds. Applying calibration, we find 'more' bass is possible than what we called 'too much bass' before. The reason is that the imbalanced humps can be cut and response dips can be brought up in level if sufficient amplifier power is at hand. In a reasonably treated room, once the passive setup is calibrated, an early impression will be of amazement at just how much bass can be accommodated within the music.


First, in-room response can be set flat. Generally this is not desirable and a gentle rise from 100Hz down to 20Hz is preferable. How steep this slope should be is up to the user. At first, the level will be high as toes feel depth of the pool. Restraint and balance will take over later, revealing deep, controlled, evenhanded reproduction of low frequencies that leave the most jaded visitors shaking heads. Percussive or sustained, electric or acoustic bass potential of these speakers is astounding in quality and quantity. Consider a stand-up bass and its two primary resonating elements. The string is first. Plucked, it is percussive and dynamic. Near following instrumental body is a fast-flowing river of energy. Either one by itself will give some illusion of reality though vague.


Capturing the true dynamic relationship between metal and wood requires speed, power and control. My setup allows the front arrays to animate strings and the rear drivers to energize the body. I run my pair as bipoles from the lower reach of the mains (40Hz) to around 100Hz. To get the relationship perfect, the sub drivers (body) are raised in level to match the mains (strings). This is tricky of course. It requires the front and main arrays to be in phase, meaning acoustic waves are additive rather than destructive. Otherwise clarity is lost. With my setup, proper phase alignment delays the subwoofers by 150 degrees behind the mains.

I found an easy guide from Robert Harley on a chat board on how to determine phase relationship: Invert speaker cables on the mains so the mains and subs have inverse polarity. Play a tone at the crossover frequency and adjust phase until sound is quietest. This is maximum cancellation which is easier to hear than maximum contribution. Once this is determined, turn the cables back to their original position and voilà, you have been phased.


I used an 80Hz test tone and separately checked left and right speakers this way. It was quick and easy. Each speaker obviously produced the strongest null at minus 150 degrees. If I only had a +/- switch, the better setting would have been '-' but in my testing, the difference between -150 and -180 was significant. This testing and adjustment could improve many systems with separate bass system and I wholly recommend continuous phase controls for any prospective purchase.


Before discovering the importance of phase coherence, I had an EQ calibrated. After setting phase, I reduced sub output in the 70 – 80Hz range by up to 20 dB. Cutting 20 decibels of output did not reduce perceived volume but the subwoofer amps and drivers now work much less to produce better quality. Win/win. In my arrangement, the mains and subs share a lot of common output with nearly two octaves of overlap. With correct phase, the overlap is transparent and the hand off range sounds continuous with equal elements of speed and power. Another design element that plays out terrifically in the real world is stereo subwoofers. Subwoofers have a tendency to sound uneven, good in some places in the room, bad in others. Stereo subs are said to load a room more evenly. Duke LeJeune at Audiokinesis has gone even further with this idea, offering the Swarm, a 4-subwoofer array intended to be placed asymmetrically within the room on the theory that each will activate different nodes.
Similarly, the Definition 2s essentially include two dual-10" subwoofers per speaker though tuned differently. The net effect is broadly dispersed bass loading without egregious hot spots or holes. My room is loaded fairly evenly though it has a couple of corners where bass is more pronounced but it is
not severe nor cause for particular concern.


As a final product, the fully configured Zu Definition 2 bass system is capable of tremendously controlled power from 20 to 100 Hz or higher. The end user will decide whether a warmer or more percussive balance is truer. By themselves and properly driven, the bass bins are linear and more tuneful than punchy as a ported speaker would be. With equalization, a simulated port peak could be added if desired.


The Bill Evans Trio's The Complete Village Vanguard Recordings features bassist Scott le Faro at the height of his career. It's an excellent recording effortlessly served by the Definitions. They capture string tension released and bent on the fret board. The nimble but trailing mass of the instrumental body lags half a breath behind and underneath, dynamic relationships hold true as if dealing in easier midrange. Moby's Hotel includes two discs, the second of which is 'ambient' and composed entirely of synthetics. There is no proper relationship between the sounds, i.e. nothing is natural. I have a Steroid Setting on the dbx for music of this style which eschews convention and skews low bass skyward. Some of the synthesized effects positively shake my basement's foundation. I doubt Moby would mind. This setting also works quite well for movies. Boosting low bass has no effect on higher ranges.
Standard setup
As they come from the factory, the Zu Definition 2s are ready to roll. The jumpers connecting subwoofer amplifier outputs to the driver inputs are in place, the speaker only needs to be connected to the mains amplifier and AC power. Listen and season low bass to suit via the rear panel attenuators. Crossover settings for the internal bass amplifier include a 12Hz subsonic filter (high-pass), 4th- order (24dB/octave) L.R. filter, 6dB of gain at 33Hz and a low-pass L.R. 3rd-order filter (18dB/octave) at 50Hz.


These are rather different settings than I use in my customized setup but they are quite effective. It is possible to change the stock settings but I would be cautious in doing so as accessing the panel is not terribly convenient.


DBX setup
To run the passive arrangement, AC to the speaker is unplugged and jumpers are disconnected. The first preamplifier output is
connected to the mains amplifier, then to the front array as before. The second preamplifier output is routed to the parametric equalizer which feeds the outboard subwoofer amplifier of your choice. I'll make your life easy there. I've tried six audiophile amplifiers on the subwoofer array. None had satisfactory control. I'm sure there are decent, even good choices but for what they would cost, there is no reason not to favor a pro unit.


I had a Crown K2, a cool-running 500wpc monster with a sterling reputation among bass mongers. At $850 used, it did a terrific job. It resided in my rack for 18 months with no complaints. Then, I got the itch as the audio curious are wont to. Everyone has heard active speakers are 'better' and a corollary notion posits shorter speaker cables enhance damping factor and driver control. It turns out Bryston agrees.

I ordered a pair of new Behringer A500s for $350 delivered. Yes two amps. They are rated at 500 watts peak into 8 ohms bridged. They need an 8-ohm or higher load when bridged but the Def 2s offer an 8 ohm load in the sub section. The amps have never even gotten warm in loud sessions. I have them set up immediately adjacent to the speakers and use twelve inches of un-terminated 10-gauge solid-core copper Romex wire to connect to the speakers. At less than half the price of the previous best, this setup performs significantly better. They even have real transformers. I can't vouch for their cred as full-range amplifiers but under 100Hz, they are ideal. The dbx is a 6-channel brain intended for managing live venues. We will only use two channels and some features will go unused. Others are invaluable. The unit features high-pass and low-pass crossover points and slopes to set the subwoofers' effective range.
It also allows fine adjustments down to a 10th of a decibel over every aspect of output response. There is a fine art to dialing in the equalizer. Results will improve with practice. Even initially, the improvement over a strict plug-and-play system will be utterly obvious.


Sound
I've had discussions debating whether these can properly be called single-driver speakers. Omega makes single-driver speakers. They also make subwoofers. Would a customer pairing a bottom-end extender with Louis' mains undermine the sanctity of the original idea? What if a super tweeter were added?
Such mental gymnastics are primarily academic. I doubt many among us place any great stake in whether a speaker has one driver or twenty if it sounds great. Some of our number have gravitated to the sonic virtues more commonly associated with single drivers. To me, the single driver term speaks to a design philosophy gravitated toward the center and treating the outlands in the best ways possible given all design considerations. By this
measure, the Zu Definition 2s are single-driver speakers though likely the most confounded to ever grace the earth.


What is the biggest ramification of effectively separating main and bass circuits? Why, placement flexibility of course. The main array does project significant energy below 100Hz but it is more of the plucked bass string variety, not power. They will not overload a room. Being sealed, near-wall placement is perfectly acceptable. I've listened to mine for periods of time literally two inches from the wall. Currently, they're all of six inches from that wall. My room is fairly large but placement options are limited. I've had them as much as eighteen inches into the room but that compromised room utility and the sonic improvement was negligible.


In a normal or less constrained space, this means the speakers can be placed where imaging is best and bass tuned to that spot. I can't imagine many domestic placements which the bass bins couldn't fill. It will be helpful to revisit previous moonbeams on earlier models as the central design mission has not changed. Detailed sonic notes on them still apply. The new measures equate to a much deader box, however. With the Pros I was only able to run the subs up to around 70Hz. Above that, the boxes became quite resonant. This was my biggest complaint about the old speakers. My room is bass hungry and the main drivers are not strong in the power zone in my room. There was always a 75-110Hz hole in the response that could not be corrected.


The new boxes remain quiet no matter how high the low-pass is set. As a practical matter, I do not set this function much higher than 100 H because this is around the lower reach of the male voice, better reproduced by the mains alone. Occasionally, the old speakers would get peaky in the presence band. The new speakers have cured that problem completely. It's easy to forget the Definition 2s are based on hugely efficient wideband drivers.
It helps to have some experience with wideband paper drivers as these speakers are undeniably such. From the obvious oversized 'midrange' drivers on the front faces to the sounds from them, these are proud examples of the breed. Some aspects are quintessential to this speaker type. They excel with instrumental tone, dynamics and coherence. I think of dynamics on 4 levels – Bombast, Transitional, Nuance and Vibration. Bombast speaks for itself. Transitional is scale, pressurization through the saxophone reed. Nuance reveals small variations in technique, minor finger movements on a fret board. Vibration is the instrument's living breath.


Each of these ideas manifests in sliding, like ice on ice. Discrete sound includes originating event and tonal trail. Maintaining these relationships is at the core for me. Quiet or escalated, keeping proportions symmetrical to the original defines mettle.


In broad strokes, efficient wideband speakers do Vibration and Nuance. They might Transition but few will scale Bombast. Conversely, big complex speakers sound large and dynamic at high volume. They probably will transition quickly and effectively between quiet and loud and might convey nuanced expression. They have a harder time with the woody or brassy glow hiding behind the leading edge.


Owing to incredible radiating area, high efficiency and miniscule/no crossover, the Definition 2s ace all four categories of dynamics. Miles Davis' Live at Newport, 1958 showcases explosive range. Quiet-to-loud transitions are bombastic, a real test for any system at volume. Sufficiently amped, the Definition 2s will play this disc at live volumes comfortably. This disc includes layered horns, gliding stop to stop. The speakers start, slide and freeze without slowness or overhang that might be expected from such large main drivers.


Cowboy Junkies' Trinity Sessions Revisited was released this year on the 20th anniversary of the original. It's a brilliant evolution of the old play list featuring deft guitar work. Minor string bends, plucks and the tangible wooden vibration of an acoustic guitar transform air into viscous hydraulic fluid. Minor pressures at the speaker transmit to the listening seat intact.


There are aspects of this sound not common to wideband paper drivers: loud-play ability, 20Hz – 20 kHz+ frequency extension, even-handed frequency response and lots of drivers. Loud means exceedingly clean, house-party capability with 50 watts. At volume, proportions of frequencies stay defined and correct. There is no compression or breakup. Room effects become stronger at higher volumes and are the biggest SPL consideration, not whether thermal or crossover compression or loss of amplifier headroom are killing the buzz.

This is not faint praise and should not be construed as a comparison with Cerwin Vega of yore. It's not a pro-sound feel. All volumes convey evenhanded frequency response without the peaky signature sometimes accompanying the genre. There is no PA-type shouting or hyperactivity. These notes apply regardless of subwoofer option.