Zu Audio Union Loudspeaker
Young riders dressed in dark clothing dart about the urban industrial landscape on 883's and Forty Eight Sportsters in a Harley Davidson promotional video. My mind pans left into the Zu website where black and white photos of young dudes click in and out; segue to a video of the making of a speaker in their dusty shops. Of course Zu Audio Union speaker is there and noticed it only cost $3000 for what appeared to be quite an impressive speaker. Looking back at the pics, at least the guy in the spray booth wears a mask to protect his lungs. Both Harley and Zu Audio are fiercely American, one an elderly icon and the other just a teenager. Both keenly focused on what they are doing and insistent on doing it their way with their own vision of moving forward while seeking to recapture the thrill and excitement of the past. Music used to be more central to our culture, more fun, and Zu is using modern technology to bring that past into the present.
I'm old enough to be the father of most of these guys. Maybe that's why my first attempts to get review samples of their speakers didn't work out. Nor were my encounters with their rooms at shows always exhilarating. But sometimes they were and it was clear they were into something unique. Having been that young once, I understood the meaning of 101dB/W/m efficiency. Not once, but twice Altec Voice of the Theaters dominated my living room, only to be given up because I was damaging my ears driving them too loud with 1970's vintage Pioneer solid state gear. Motorcyclist, head banger; been there, done that. A large painting of me standing on the salt flats in Utah, reminiscent of the cover of John Lee Hooker's Endless Boogie (1971), each a legacy from my first marriage, hangs in the family room. Decades later I discovered the High End and low powered tube gear. I could hardly believe there was that much music hidden in the grooves.
It was the six watt per channel Triode Lab EL84TT integrated amplifier that led me back to Zu Audio once again. As fate would have it, they had just announced the new Zu Audio Union speaker with coaxial super-tweeter and a 10" full range driver. After a delicate exchange of emails they made a commitment, but production delays put off the arrival until right before the Montreal show. Three weeks of writing the show report, followed by the furniture trade show, followed by the writing of the Triode Lab review and finally the Unions were very nicely broken in.
Difference 99dB/W/m Efficiency Makes!
What you need to read into this is that the Zu are very revealing of the amplification with which they are paired. This doesn't mean you have to have the newest, most expensive gear to achieve a rewarding musical listening experience. My vintage solid state Tandberg 3012A integrated amp with 100 wpc, much of it biased into Class A, sounded very nice with it during the break-in period. The music was warm and inviting, if not the last word in resolution and soundstaging. The Triode Lab with the EL84 tubes was tight from bottom to top, revealing a slight upward tilt on the treble. That it became irritating over time turned out to be due to a slowly failing EL84 tube, a situation that was corrected with a matched pair of new tubes. It was also a very transparent amplifier with a high degree of focus. The Coincident amp was similar providing a fuller sound and it also brought down the prominence of the super tweeter to a more comfortable level.
Hear Me NOW?!!!
The other most obvious characteristic of the Union is their dynamic capability. Take a rim shot or pluck an electric guitar string with a pick. They've got attack. Even pianos have balls when played with ferocity. Xylophones? Not so much. Combine high efficiency with outstanding attack and you should have outstanding dynamic range. And you do, once you get the volume up into the broad sweet spot with musical peaks reaching the 85 to 100 dB range. Lower the volume to late night listening levels and the dynamic range obviously compresses as it does with most dynamic speakers. But hey, you know where the fun is. And the decay? It must be just about right because it didn't come to my attention as being too short or too long. And as I've learned from Paul McGowan's blog, it is the attack that determines the timbre of the note and the Union gets it very, very right. For the most part I would say the Union is capable of excellent tonal coloration if you've got an amplifier that can do it justice. For the one exception I have to rely upon my friend Tom who listens to a lot of classical music. He noted some congestion in the treble with demanding orchestral music, particularly with high violin notes. If large scale classical music is a major item on your menu, you might want to check this out before committing. I had no problem with rock, jazz or electronic music in this regard, except with the prominence of the treble when using the Triode Lab EL84TT with its extended high frequency response. Even string quartet sounded great, until the violins went for the high notes where they sounded a bit like they had steel strings, but only in a narrow high frequency window. Since most tube amps roll off the high end slightly, this should not be a problem. If you have an amp that is bright on top, you may want to pay attention to the output of the super-tweeter.
The 10" full range driver is the principal feature of the Union. It is good for 45 Hz to 12 kHz and like the full range (or nearly so) drivers of some other outstanding speakers, it is powered directly by the amplifier without a crossover. The transparency of such crossover-less designs is usually outstanding, and the Zu Union is the most transparent of all that I can recall from memory. This driver is able to resolve midrange lyrics that escape most other loudspeakers with dynamic drivers regardless of price. Other designers have implemented nearly full-range designs by pushing the woofer down to around 200Hz and below and the tweeter up above 7-8 kHz with great success, but Zu has stretched the envelope even further with the Union. And to create a point-source design, they have mounted the super tweeter concentrically with the 10" driver, rather than mounting it on the baffle as they have done with the lower-price Omen or their higher price models (other than the Soul). The result is a coherency that is conspicuous only by virtue of the frequency limitations of the driver itself.
The bass goes down to 45 Hz and it is tight, tuneful and
transparent all the way there. But what makes it better than most is that it
falls off quickly with grace, not groping for another few Hz and muddying the
bass by trying to be more than it is. This bodes well for those of you who feel
compelled to add subwoofers as you can continue to run the Union full range and
bring the sub in at a low level. Apartment dwellers and those with children who
go to sleep early will probably be perfectly happy with the Union just the way
it is. As I looked at the frequency response graph on their website, I was
puzzled by the bass extension below 40 Hz which did not correlate with what I
was hearing. Sean Casey, the main man at Zu, explained to me that they take
their measurements "in room" and that lower hump in bass response represents
room reinforced response. I was probably not getting this result because in my
positioning, the front baffle was 64" from the wall behind it and since it is on
a very long wall, there are no meaningful corners to reinforce the bass. In a
smaller room with real corners, you will quite likely experience more mid-bass
response than I did.
To The Rescue?
I resurrected a pair of prototype Tekton Design subs with concentric 11" drivers the rear driver in a sealed box, the front driver mounted on an extended open baffle in free air. They are driven by an internal 200 watt BASH amplifier and the signal was delivered from the speaker terminals of the Coincident Turbo 845SE integrated amplifier (review forthcoming). The initial result was quite disappointing until I added Boston Audio TunePlates beneath the spikes of the subwoofer. The TunePlates tightened up the focus of the subs, whose spikes were not sharp enough to penetrate the carpet and dig into the flake board below. This brought the speed and clarity of the subs fairly close to the Unions and I was able to cross over nicely at 50 Hz with the subs placed just outside the Unions. While the Unions were really good without the subs, I felt there was a slight upward tilt to their frequency response. In reality, it was just the absence of lower bass to balance out the high extension of the super tweeter. Had the super tweeter been rolled off around 15 kHz, I probably wouldn't have had the perception of an elevated high end. And if you are in a room with real corners, and the Unions are placed a little closer to the front wall to take advantage of the room reinforcement of the bass, you will probably be just fine with the Union alone. But man, it was really sweet to have the full-range extension afforded by the subs. When I added the subs it shifted my attention more squarely on the midrange and I had little or no quibbles with the treble. The downside was the additional clutter of two big boxes with their attendant power and speaker cables that made it more awkward to load the CDs and LPs in my rig. The trade-offs in life never cease.
Another point that needs emphasis is that with the high efficiency of the Zu Union speaker, you will get great bass even with low powered SET amplifiers. The EL84 tubes of the 6 wpc Triode Lab EL84TT integrated amp I recently reviewed are very tight and resolving at the frequency extremes. The more costly Coincident Turbo 845SE integrated and the Tube Magic monoblocks (which use 300B tubes) had a fuller sound that gave added majesty to the mid-bass. You need a high quality amp to get the very best out of the Union, but not a high powered one. The speakers will let you know when you've got the right amp (as well as everything else upstream).
The result is that the back side of the speaker cone sees very little internal noise and consequently, almost all of the musical energy radiates forward from the outer face of the driver, unlike with most other ported systems where the bass is augmented by music coming from the port at a slight time delay. Furthermore, the porting system of the ZuGriewe system is tuned over a larger frequency range than typical speaker ports which operate over an octave or less. It also increases the efficiency of the bass a claim that is verified by the excellent results achieved with even very low powered tube amplification.
What It Sounds
It was a Friday night at this point coming up on midnight, but I summoned enough energy to hook up the Tekton subs in preparation for Tom coming over the next night. I dared not listen to a single song, fearing what I knew would happen since Saturday is an important day at work. It's always fun when Tom comes over because he brings with him a different palate of music that gives me fresh insight beyond what my own reference music affords. We started out with his compilation CD with stuff like Tower of Power's "Diggin on James Brown", some Tito Puente, Jennifer Warnes singing Leonard Cohen's "First We Take Manhattan", Clifford Jordan from Live at Ethel's on Mapleshade, one of Todd Garfunkel's recordings of new tango music from the group Sera una Noche, and moved on to some LPs including Sonny Rollins' Way Out West and from Count Basie, 88 Basie Street as well as a direct-to-disc LP and some classical stuff. I also dug up some really clean live recordings from the American Folk Blues Festival '70, some Chinese drum music from Yim Hok-Man, and from John Marks' Glass Bead Game a string quartet piece from Zoltan Kodaly and from his Pipes Rhode Island CD, Howell's "Master Talllis's Testament" with some monstrously low organ notes that sounded as real as the organ recital I attended recently at my 45th college reunion.
We were all over the map. And we both loved what we heard, save for Tom's apprehension about their suitability for classical music. He regularly attends concerts with the Rochester Philharmonic Orchestra (12th row, center), whereas for me, that is a rare occasion. Adding the subs brought the system to full range by anybody's standard although I have heard much more expensive subwoofers that might provide more subtlety in the lowest bass. Quantity was not an issue here. The subs brought the tonal balance to even keel allowing the music to supersede the equipment and draw me in to the music sometimes even the venue of the music. Incredulously, I give this evaluation from the recliner beside the official listening chair. With the TubeMagic monoblocks the soundscape did not collapse to the speaker in front of me, though it did lean heavily in that direction. When I sometimes swapped seats with Tom everything fell into perfect perspective. On a good recording the orchestra would be perfectly laid out, left to right and front to back. Furthermore, the tweeter seemed more properly balanced once the bass was extended and the midrange was more accurately centered between the bass and treble. Overall, it was pretty close to Being There. The piano sounded like a real piano. I could hear the hammers hitting the strings.
My Love, Could Carry Us Higher. (Barbara
The rectifier tube is a NOS Mullard GZ32 favored by many, but easily replaced thanks to Triode Lab's unique "Uni-fy rectifier stage" to tune the amp to your preference. And the 6SN7 tubes are OTK Military Grade which is the cheapest 6SN7 you can buy but accurate, neutral and laid back. The amp is Class A with an auto-bias circuit and unusually, it is AC heated by preference. Triode Lab also makes a hot rodded 2A3-S special edition for $3888 CDN with premium transformers and a chassis that will likely satisfy your desire for audio jewelry. The S version is for the connoisseur who not only likes to roll tubes, but roll amplifiers as well.
We put the CD into forward, listened for a brief moment, looked at each other and simultaneously broke out into laughter. This is a seriously good amplifier in spite of its humble appearance. The top end is rolled off. The presentation is dark, being centered on the lower midrange with a full, sumptuous bass. Attack is good, decay is long, midrange focus is very good and the holographic music grabs your gut and pulls you right into the collective soul of the performers. Forget about a subwoofer. With the highs rolled off and the ripe mid-bass you don't miss the lowest octave because you're so emotionally engrossed in the music. In fact, if I wasn't so indoctrinated in the philosophy of the so-called high-end audio, I could call this an end game and move on to another hobby called high fidelity all the while enjoying the music. Should I put this paragraph to rap music? No wonder Carl tells me a lot of his customers with Zu speakers own this amp. These could be the 3.5 most important watts on the planet. And if not these watts, I'd be tempted to ante up for the 2A3-S. (Can you hear me now, Carl?) Combined with the transparency, dynamics and focus of the Zu Union, you get all the pace, rhythm, timing and timbre that's on the recording. You ask about the Chinese Drum cut? It barely required more than the first watt yet the Triode Lab delivered as much slam and more delicious timbre than I've ever heard from this piece. Tom went home about 11 pm and I fell into bed at 2 am after "just one more song".
The other major factor in the design is the ZuGriewe acoustic technology which dictates a tall slender design with a rather square footprint. This allows the speaker to have a minimal visual presence in the room, though this can certainly be offset by your choice of stain or paint if you wish to make them more prominent. In spite of the high placement of the driver, with the overall height being about 37" (with spikes), it doesn't seem to require outriggers for additional stability. (It comes with both rounded feet and carpet piercing spikes that allow for tilting the tower backward a bit. I simulated accidentally bumping into them as might happen at a party and they were reasonably stable but they can be taken down if seriously tackled. The single coincident driver arrangement gives the Union a very clean, understandable look that was very easy to live with and attractive enough not to become boring. The fit and finish are of a high standard and it does indeed look like it will last a hundred years as they claim.
"In terms of value, I was trying to think about other speakers that I've heard that I think can compare with the combination of the Zus and the Tekton subs. The Coincident Total Victory might be a contender. I remember that they sounded quite magical on my Sonny Rollins LP, and I think that was with your CAT preamp, the Mahis, and the unmodified Linn with the Clearaudio cartridge. Other than that, I think that you'd have to go to the level of the Wilson Sashas, the Magico S5s, and the MBL 116s, all about $28k. You can probably come up with your own list. I think that it's an interesting exercise that highlights the value of the Zus."
In terms of transparency and jump factor, the Union might even top these esteemed speakers. In terms of ultimate refinement it comes up a little short, probably because of the minor resonance of the cabinet, but the difference is small enough that poor set-up skills or unfortunate room dimensions could easily reverse the outcome. Whether you get it right or not could be a $25,000 gamble. The issue of suitability for classical music may be linked to the Union coming up a little short in ultimate refinement. As much as Tom liked the Unions with other material, it did not come close to his experience of live music at the RPO, which rules them out of contention for his next purchase. As good as the ZuGriewe tuning is in the Union, the cabinet is still rather light weight in comparison with the Coincident, Wilson and Magico mentioned above, or my reference Kharma speaker. With those speakers the music completely gets out of the box. With the Union, some of it seems to get tripped up. Or maybe the issue is asking the 10" driver to handle the music all the way up to 12 kHz, something that could cause Tom to complain about the violin strings sounding steely. In my house, classical music is rarely heard and opera is banned. Oh, I may have a token Pavarotti LP somewhere, I suppose. For everything else, the Union provided a transparent window that let the music jump right through. If you have the courage to spend a little less for your speaker and a little more for a good tube amp, the Union is an incredibly good value.
I've skipped over technical discussion of the Zu driver and their relationship with Eminence, a major pro audio speaker manufacturer. Nor have I mentioned their proprietary cable design, also used in the internal wiring of the speaker. It is so proprietary I have nothing to say about it save that it's copper and apparently it does a lot of things very right. Combing through their website I came to appreciate that Sean Casey and Zu are a lot more steeped in science than their casual presentations at audio shows suggest. It also documents the significant technical evolution of this relatively young company which bodes well for their future. Consider their website recommended reading, for sure.
As The Sun
Sets Over The Bonneville Salt Flats...