Apogee Scintilla - 1 ohm model with all new ribbons by Graz. New steel stands fabricated by True Sound Works.

Plinius SA-250mkIV amplifier and a BAT VK31-SE preamplifier.

Apple iMac 24" running Leopard and Frontrow/iTunes. Pop Pulse Digital conversion device handling the USB to SP/DIF duties. Assemblage D2D-I jitter reducer and up-sampler and an Assemblage DAC-3 fully balanced DAC.

Furutech Evolution Series Power Cables, Furutech Evolution Series Speaker Cables (BiWire), Furutech Evolution Series XLR Balanced cables, PAD Contego digital SP/DIF cable, and CyroParts USB cable.

PS Audio Premier power plant in Limited Edition black and PS Audio power ports.

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Positive Feedback ISSUE 67
may/june 2013


zu audio

Union Loudspeakers and Undertone Subwoofer

as reviewed by Pete Davey


zu union

It's with a heavy heart I write this article about these speakers. Sean of Zu was kind enough to put up with lending me these speakers indefinitely all while we were having our first child. Quite a rollercoaster!

When I say heavy heart, I mean these speakers have really opened my eyes and filled me with emotion; simplicity while maintaining the core product, and the sound that radiates through them. In my tenure with PFO, I have witnessed so many wondrous audiophile-grade gadgets, most in the un-obtanium price range. I tend to equate those expensive products with artwork moreso than high-end audio. Sure, some of them do sound as good as they cost, but most of them end up as eye candy… lying on the floor, glowing—saying, "You want me. You want to show me off to your friends." These Zus are anything but that. Sure, they are aesthetically appealing (that is always subjective), but they are extremely biased towards sound reproduction.

I've gotten to know Sean (of Zu) over the years, and he has my highest respect as a designer—he's down to earth, a family man, and he LOVES music. You may have witnessed this during one of the many trade shows Zu attends, the room being extremely minimalistic and FILLED with amazing vinyl recordings. They typically omit anything digital—keeping the signal simple and as pure as possible. Cartridge, turntable, phono-stage, integrated amp, speakers. It's always a treat walking into a Zu room, the first thing they do is greet you with a nod, then look to see if you brought anything to listen to. No rules here! They aren't looking for that magical disc to appeal to the pixel pushers—they want you to bring what YOU like. I think that is key—and most of the stuff I hear is real music.

I guess I can go on and on about Zu Audio, it really is an experience to be had, and not easy to write down in words. I can say that there is nothing like entering a room full of audio equipment and feeling comfortable enough to plop on a disc and not have to worry about being judged. Sure, some people may walk out, but that isn't their focus, they're focused on whoever is sitting in that sweet spot, eyes closed, feet tapping. And every time I am a witness; that person ends up waking out of that room, smiling, and usually talking with their buds right outside about how cool this company really is!

Sean Casey, CEO of Zu, is a music lover, and an analog genius (just talk to him about tube gear and anything electronic). His knowledge will blow your mind, plus you can talk to him about any genre of music! I remember one year at CES, Amon Tobin came up, and he was like, "Oh yeah man!" Blew my mind… at CES, filled with propellerheads that listened to Patrcia Barber and Diana Krall (snooze), and this guy knows Amon Tobin! I knew I found a friend forever… and the pinch to wake me up out of my dream. 

My journey with these speakers started at the 2012 Newport audio show—I hadn't even heard of them, and they had these (prototype) military green single-driver (coaxial) models playing in their room. It was love at first sight—not only because of the simplicity, but because they actually sounded musical! Until now I've always had a hard time with the single-driver full range sound, but the Unions got it right.

zu union

From afar, the drivers look like the standard Zu fare, a custom made driver sitting in a rectangular box, however upon closer inspection, the drivers are open in the middle; a coax, married to a horn compression driver. I guess I really can't call these single driver speakers as they really are a dual driver, married into one "speaker" if you will. There are ALL sorts of pros and cons with this type of speaker configuration (crossover-less). A few cons being they are extremely revealing (yeah I know, you've heard that before), but there is no magic behind the curtains here. Your amp is directly connected to the drivers, and the compression driver can get hot sounding! It's imperative you match these with the proper amplification.

zu union

What I mean by this, is that my actual setup here in my listening area consists of a BAT VK-31SE Tube Pre, and a monster Plinius SA-250mkIV. You may know by now that I own this amp due to the nasty drive of my Apogee Scintilla 10hm speakers, a match made in heaven. BUT—using such a monster amp, even one with such finesse and caliber, didn't really work out very well with these speakers. No—they needed something more musical, if you will. I'm not saying solid state will not work! I'm also not saying Plinius is not musical; it just was not the best match. Zu Audio understood this, and they were kind enough to get me in touch with a few amplifier manufacturers, and a few were sent to me to play with, making this journey even more exciting. The one amplifier that I ended up sticking with is the Melody Astro-Black 22, a moderately priced integrated tube amplifier. I won't spend too much time discussing this amplifier, not that it isn't deserved, but there are plenty of reviews out there for this wonderful piece of equipment and well, this is more about the Zu speakers.

zu union

After dialing in the Melody amp, and connecting my phono-stage (currently a Sutherland on loan—amazing piece of equipment which I reviewed not long ago for PFO) I kicked on the power and the tubes started glowing. Let's see… which album to play first?! I'm just now shy of 300 LP's (and growing, please don't laugh; snooty vinyl collectors… vinyl is MUCH more expensive than it used to be, figure $15-$50 a pop and more) so this wasn't an easy decision. How about some Jaco Pastorious from the guys at ORG? Flip the table to 45rpm, drop the needle and have a seat…


zu union

I swear I could hear the wind vortex created by the drummer's hands as he slapped the skins…. Then the bass-line… I could hear the nuances between chords. My feet were tapping, and before you know it, I wanted to get up and dance! But, there was something missing… Deep bass.

Yes—another drawback from these sorts of speakers, you won't get deep extended bass. This is a trade-off from resolution. Zu to the rescue though! With these speakers, also came another huge heavy package. The "Undertone" subwoofer.

zu union

Eww you say! A subwoofer! Blasphemy! Normally I'd agree with you, I have a really hard time with integrated subwoofers in a two-channel system. I'm sure there are readers out there that disagree with me, and that is okay, but that is just my real world experience. But, I had to give it a shot, why not? I will say this didn't come without a challenge; the hookups on the rear of the sub aren't conventional. For example, the high-level inputs share one negative poll. Electrically, it makes sense, but some consumers may be confused by them. The low-level (RCA type) inputs aren't very sensitive, so make sure your preamp has enough level here. I struggled with this until Sean asked me to connect the low-level outputs from the pre-amp into the high level inputs on the sub which wasn't easy because I essentially had to create a custom cable (RCA -> Spade). Once I completed this, and powered up the sub, I heard some bass!

zu union

Interestingly enough—the bass wasn't overwhelming, which is what I've grown to be accustomed to. No flappy warbles, no floor slapping, just invisible complimentary bass. Zu has done it again—they have tapped into the subwoofer department and kept the musicality! There are adjustments aplenty—trust me—good enough for any room or music type.

zu union

So now that I've got those two pieces dialed in, let's hear something… might as well go back to the Jaco album as a reference at this point! Drop the needle… and WOW! My room just came alive—dynamics, resolution—and most of all, music that sounded so real! Then comes the whole "reliving my music collection" thing, drove my wife nuts, but she is so patient (I really am a lucky man—and father now!).

zu union

Record and record, not one of them didn't create a jaw-drooping experience. Mouth agape, feet tapping—involvement! I've also recently obtained some DSD gear, and have been playing with all sorts of DSD goodies, from SACD rips, to downloads, to recordings from a buddy's Korg from his scratch master open tape collection that he was kind enough to share with me. Elton John, The Doors, Loscil, Brian Eno, INXS, Swans, the entire gamut of music fills my room and these speakers have yet to let me down.

zu union

I believe I have finally found a system that I can live with other than my pesky pain in the rear Apogees. It's not that I flock to weird designs, but honestly nothing offered the transparency that I got from ribbon speakers. These Zu's, they take transparency and resolution to another level. Sure, you don't get the "dipole" sound, which is almost impossible to simulate, but in turn they offer realism, resolution, emotion and best of all… music.

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I hope I didn't disappoint you by not listing boring measurements, audio graphs, and impossible math calculations—not really my forte’, I tend to just get caught up in what is (in my humble opinion) the music—the feeling, the nostalgia. And wow, this setup did not disappoint. Don't let your life slip by without hearing anything from the Zu line, especially these little gems. Thanks for listening. Pete Davey

Union Loudspeakers
Retail: $2400 a pair

Undertone Subwoofer
Retail: $1999

Zu Audio