Zu Omen Standard Loudspeaker

      Date posted: April 16, 2012

Zu Audio Omen Standard - frontSugg. Retail: $1875/pr  USD

HxWxD: 36 x 12 x 12″ [92 x 30.5 x 30.5cm]
Footprint: 12 x 12″ [30.5 x 30.5cm]
Weight: 53 pounds [24kg]
Bandwidth: 34—20,000+
Dynamic Range: 117 dB
Efficiency: 98dB 1W/1m
Impedance: 12 ohm
Power Amp Range: 4—300 watt

Zu Audio is a different kind of speaker company.  You’ll know this already if you’ve ever seen them exhibit at shows (more DJ booth/house party than hi-fi demo), had a read of their (extremely frank and detailed) website, or even just had a careful look at one of their speakers.  Their corporate slogan is “a revolution in American hi-fi” and their goal is nothing less than bringing “back the stereo as the most important and rewarding furnishing in the home.”

The attitude is more than a little refreshing.  Here is a company that flies proudly in the face of the snobby, “by appointment only”, ‘it costs more than major surgery so it must sound fantastic’ perceived value school of hi-fi marketing.  No lofty, mythical mumbo jumbo here.  Zu is frank and direct in their philosophy: “For people who love listening to their hi-fi, scrutinizing every aspect of the recording and forensically dissecting the performance, there’s a raft of speakers out there for those lost souls. For people who are still in love with the music, who just want to be at that gig, who really don’t care about ‘audiophile’ recordings and all the attendant crap—for all those enlightened souls, there’s Zu.”

The products of this philosophy have done well for Zu over the past decade or so, speakers like the original Druid and the Definition garnering some great reviews and a fervent, almost evangelical following, particularly among the high efficiency/low power tube amp crowd.  With the Omen Standard, however, Zu wanted to broaden its customer base, designing a speaker that while still true to the brand was not only more affordable but happy to be driven by pretty much any amplifier, tube or solid state.

The Heart of the Omen

Like all Zu speakers, the heart of the Omen is their proprietary 10” full range doped-paper driver, made in-house, like the rest of the speaker, in Ogden, Utah.  The Omen is basically a single driver, crossover-less design with a supertweeter added to fill in above 12Khz, where the full range driver falls off. “Zu designs and builds full-range drive units that cover the widest bandwidth possible and weighted for bass, and loudspeakers that are as dynamic and efficient as possible with bias on the critical human voice.”  Like its brethren, and most single driver speakers, the Standard  is shockingly efficient (98dB) and incredibly easy to drive (12 ohm impedance). Amplifier power range is specified at 4-300 watts!
Omen Standard - rear
What may look, at first glance, to be an incredibly straightforward, reflex-loaded or sealed cabinet, is actually another area where Zu distinguishes itself from the mainstream.  The speaker uses what Zu calls “Zu-Griewe cabinet/room loading”. Inside the box is a large trapezoidal shape increasing steadily in width until it fills almost the entire bottom of the cabinet (see illustration below).  Inside, around the speaker’s edges, are slots which, while not exactly ports, allow the speaker to “see”, as Zu put it, the acoustic space of the room.  As noted by the manual it is important to leave at least the width of a CD jewel case between speaker and floor.  “Zu-Griewe driver / cabinet / room loading technology allows this high efficiency platform to give articulate and deep bass performance—attributes that have never been done in a passive, high efficiency loudspeaker system of this size. (Zu-Griewe is an acoustics technology and model originally developed for high performance competition two and four cycle engine exhaust systems for improving power output through pulse and pressure management, with increased bandwidth, while reducing noise and sound pressure levels over convention”.  In a nutshell, Zu have developed their own novel way to damp and control that big driver of theirs, and no, despite the “engine exhust system” origins of the technology, the Omen does not sound anything like a dirt bike with a Supertrapp on it, but more on that below.

The Sound of a Good Omen

I set the them up in my roughly 14’ x 17’ Toronto living room (my system having changed quite a bit after a year long stint in Brooklyn) driven by my Bryston B100 SST DA integrated amp.  Sources were my tweaked Rega Planar 3 turntable via Audiomat Phono 1 phono stage, and MacPro desktop computer running iTunes/Pure Music (yes indeed, I’ve ditched CDs for a server, but more on that another day).  The Omens displaced a pair of Royd Minstrels that I’ve been using as temporary speakers until I find something more permanent.

Again, from the Zu website:  “Zu products do the following or they don’t get released: voices will sound human, instruments genuine, impact and resolution of musical details will be consistent from deep base [sic] through extended treble, and dynamic scale will not be hindered.  Zu is about tone, texture, stereophonic and dynamic realism… Zu products will allow the color and fidelity of other components in the system to come through, especially amplification.  Full-spectrum color and shading will be unmasked and music will sound alive and compelling.” Again, pretty direct, and relatively hyperbole-free too, as marketing copy goes.  More importantly, from what I heard of the  Omen Standards in my system, pretty accurate as well.
Zu Omen Cutaway
Let’s start with the bass.  It’s easy to look at that big ten incher and make assumptions about what this speaker might sound like on the bottom.  Don’t.  I don’t care if it came from motorcycle exhaust research or primate research, the cabinet/room loading works. Banish any notions of big, flabby, flaccid bottom end from your mind. These are startlingly tight, articulate for sure, but the keyword here is “IMPACT”.  These speakers positively devour drums.  Not just quick, they’re some of the fastest sounding speakers I’ve heard, electrostatic or otherwise.  Transients in general jump out of the speakers with lifelike speed, the driver so well controlled that it seems to stop the instant it needs to.  There is zero overhang, zero smear, zero ringing.  Despite what appears to be a somewhat live cabinet when you give it a rap with your knuckles, the Standard sounds incredibly un-boxy.

I hesitate to call any speaker that can rock this hard polite, but they were incredibly well controlled and coherent, even at ear-splitting levels.  Bjork’s “The Hunter” can be a torture test for big speakers with aspirations for great bass, with its relentless deep synth lines, but the Omens sailed through this track without hardly breaking a sweat.   Ditto for one of may favourite albums of late, Brothers by the Black Keys, where it’s the drums that are relentless (and fantastically well recorded).  The Omens adored this record as much as I do, serving up big, dirty, noisy, raucous blues so enthusiastically and convincingly you could imagine you were in a hot, grimy little club somewhere hearing it live.  These speakers can play effortlessly loud without being aggressive or fatiguing.  And, no matter how loud it gets, coherent enough that you can hear every little thing that’s going on in the mix.  And, chances are, they’ll play louder without a fuss than you’ll ever want to play them.

The corollary of this fantastic control, impact and slam appears to be some tradeoff of lower extension.  I was expecting a little more bottom octave out of the Omen Standards, but found them a touch light at the bottom extremes.  They didn’t manage to load up the room the way my old Energy Veritas 1.8’s did. Over the long term I’d probably consider a subwoofer to augment them, or trade up to the Omen Definition, which, with two 10” drivers rated down to 30 Hz, should provide a little more bottom octave oomph.

The good news continues in the mids, where true to intent, tone, texture and immediacy are indeed the dominant themes.  The Omens are no wallflowers.  This is an upfront, very direct, very present, very involving speaker.  It wants your full attention, and chances are, it will get it.  They really shone on the latest (gorgeous) Fleet Foxes record (Helplessness Blues) with gobs of subtle midrange color, detail and nuance.  Voices were decadently rich, well centered in space and completely free of the speaker boxes. These speakers “throw” images and voices into the room in a way that I’ve never heard before. Ali Farka Toure’s “Rouky”, an intimate little African blues track, is downright spooky when well reproduced and I’ve never heard it as gripping as through the Omens.  With these speakers the music is happening right in front of you.  The sound is in your face, and very intimate. And, not surprisingly since it’s all coming form the same driver as the bass, the speed, control, freedom from overhang and immediacy carry forward through the mids and lower treble.

The only real quibble I have with the Omen Standard resides at the top of the frequency range.  While I wouldn’t describe the speakers as dark sounding I could have used a little more air and sparkle on top.  If your tastes run to string quartets and chamber music, these are not likely the speakers best suited to you.  Zu says itself that its speakers are “built around the critical human voice (A1, 55Hz, through A6 and all the possible harmonics, to approximately 10kHz)”.  It’s a philosophy that prizes tone, impact, emotion, and involvement, but it does so at the expense of treble extension.  If serious openness and utter transparency are at the top of your speaker priorities list, then the Omens may not be a great fit.  On the other hand, if immediacy, soul, impact, speed and involvement are what you need to get your toes tapping, these are speakers you need to hear.  It’s a great deal of speaker for under $2K, and if your philosophy of hi-fi jibes with Zu’s, just may be a giant killer.

Aaron Marshall

Andrew Marshall Measures the Zu Omen Standard:

Omen Standard Frequency Response
My measurements may look  quite different initially from those published on the Zu web site, but there are some good reasons for this. First of all, their graphs show 10-dB major divisions vertically, while ours are 5 dB; this tends to make theirs seem flatter, when they actually aren’t. It also looks as if their response below 60 Hz is a spliced nearfield response, since our 1-metre in-room results in a 32-foot long room were quite different, but more on that below.

Our graphs come from a camera screen capture, because our LMS program refused to save the file or print it directly for some reason, so I simply took pictures. The small amount of horizontal distortion at the very top of each is not reflected in the actual chart, where  the lines can be seen to be horizontally straight, thus accurate.

That said, a closer look reveals a quite smooth reproducer in terms of frequency response. Let’s look first at the range above about 600 Hz, which is quite linear, sloping gradually by 3 dB to 18 kHz. This is excellent timbral balance through the midrange and treble area to the conscious limits of human hearing (we may hear higher subliminally as a primitive warning mechanism, for perhaps that sense of air that audiophiles talk about). The Zu’s gradual slope may also account for Aaron’s perceived lack of “air”. And this slope increases at 15 and 30 degrees off axis as shown below, partly because of the horn loading of the tweeter, perhaps, but because of the acoustic crossover design, this will also involve the dispersion characteristics of the large driver and its large centred phase plug.

Below 600 Hz we see a rise in response to a plateau of 5 dB that is quite smooth from 400 down to about 70 Hz, with a gentle rolloff below that reaches par with 700 Hz at 50 Hz, and is -3 dB at 35 Hz, quite good bass extension. But the bass character is defined not only by its perceived tightness and speed, but also by its extra energy in the mid-bass and into the lower midrange area. Perhaps this could be better described as “bumpy” rather than “thumpy”.

The tapered interior slot loading is shown in a cutaway drawing that can be seen above, and this technique should provide consistent bass response in different rooms to a greater degree than front or rear reflex porting would, though it depends on at least a CD’s height of air space beneath the speaker cabinet (and above a rug, I presume), according to Zu. There is another Zu  model, the Soul Superfly ($3750 pr), that mounts the same drivers oppositely, the tweeter above, and I am curious if this might in itself improve the perceived bass-to-treble balance at the listener position, though that can only remain speculation. But that character of the Omen Standard, which covers a slope of 8 dB (50 Hz-10 kHz) even in their own measurement, has to be described as somewhat mellow, if otherwise fast and quite accurate. And that slope is identical to that seen in our measurements, if you look closely at the curves and corresponding numbers.

Omen Standard Impedance/Phase

Our impedance numbers closely parallel Zu’s, too, ranging between 10 and 20 ohms, with a matching phase curve with smooth values that indicate good coherence through mid and treble ranges. As an audio old-timer, I will note that a good old Baxandall slope tone control with an axis around 800-1000 Hz could turn this speaker into a very flat reproducer, because of its evenness of response above and below. If there were ever an argument for such a tone control, the Zu Audio Omen Standard  is it in spades.

Finally, my measurements also suggest that this Zu also lives up to its sensitivity claims of 98 dB, as I found when setting them up for an acoustic level of about 85 dB at 1 metre from our AKG 460B ULS calibrated microphone. This opens the possibility of using low-wattage amplifiers, and a nice, sweet-sounding single-ended under 10-watt design might just even out the overall frequency balance a bit. Then you might find even more “happening at the Zu” (thanks, Paul Simon).

Andrew Marshall

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