Zu Audio Union 6 Supreme

I thought I would post my experiences listening to a new pair of Zu Union 6 Supreme in my home system.  I wouldn’t call this a review. As of today, I’ve had these speakers in my home for a little over two weeks and they are still changing. 

I have a “main” system consisting of a Kuzma Stabi R table, Pass labs phono and pre feeding a Vandersteen HPA-5/Vandersteen Quatro Wood speakers. My ears are used to the amazing imaging, full range, mid-hall perspective that this system delivers. The living room space is open but untreated and acoustically challenging. This is the system I have documented on Audiogon.

In a second basement system, where acoustics are much better for a more first row presentation, I have been enjoying a system consisting of a Lyra Etna SL on a Kuzma Stabi arm feeding a Sutherland mini loci pre or a Bel Canto E1X streamer/DAC as front end.  These signals go to a Decware Torii MK IV and a pair of Lii Audio Fast 15 mounted into nice wooden cabinets with a front port.  This presentation works best when augmented by a pair of subwoofers as the Lii drivers don’t output much below 50hz.  What I love about this combo was the amazing clarity of the Decware-> Lii crossoverless combo. It is holographic an immersive and fun.  All the clichés about hearing new things in the recording and meaningful music information apply here. The high frequency extension isn’t there but not missing enough to sound dull, complex music can get a little congested but not distractingly so. The drivers in this speaker cabinet can have a boxy sound in the upper bas region that was improved with additional speaker  The main issue is the need for subs which eliminates the ability to go direct from phonostage to the Decware as my current subs require a home theater processing (that the Bel Canto can do).  The sound of the phono digitized through the Bel Canto isn’t as nice as the clarity of the direct all analog connection.

Fast forward to Apona last year where I got a chance to hang out in the Zu Audio/Kimber cable room. Here, a cable switching system had ben set up with duplicate Pass XA25 amps and Zu DWX to demonstrate differences between different “kable” looms. I had a chance to talk with Sean Casey of Zu and was able to get a morning demo of the pair of Union 6 speakers without all the cable switching shenanigans.  This demo peaked my interest in the Zu approach of high efficiency, crossoverless design.  I liked the clarity, big soundstage, excellent bass integration and energy of the system.  I got the feeling they would work well as a full range speaker in my current second system with the wide variety of music I like to play (similar to what Sean likes to listen to as well). 

Although Sean warned that the Union 6 Supreme version of the Union 6 (Jupiter caps on the tweeter high pass and their Event internal cabling) requires a longer break in and can be ruthlessly revealing of upstream amplifier quality (I believe he described them as a “mother bitch”), I ordered a pair this October (2024).  I received the pair in mid November and they are beautiful speakers. Zu had excellent communication of the process and ships these speakers in individual boxes.

I subbed out the Lii Audio custom speakers and did some basic speaker placement maneuvers to get the frequency balance and imaging optimized. The speakers are about 8 feet apart and I am sitting about 8 feet in front. They are 32 inches from the side wall and 48 inches from the front wall. The speakers are only slightly toed in. I have been playing them frequently and they are coming along nicely.  Here is what I have noticed so far. They image spectacularly, they have excellent bass response without the need for sub augmentation in my system.  They have a slight warmth to them that brings out color and tone of the music. Maybe the result of putting everything through a 10 inch driver? On digital recordings, I employ the subs below 80 Hz and roll off the bass to the mains below 80Hz. I prefer the all analog Lyra/Kuzma/Sutherland path for its clarity and coherence which has no subs or mains crossover.  My impressions are that these speakers mate well with the Decware ~26watts of Class A push-pull and zero negative feedback. Decware amps are not warm or "tubey" sounding.

On both digital or analog paths, I am hopeful that the Union 6 Supremes will mellow out with further break in. They can sound quite forward on certain recordings which would be more pleasant if they didn’t also have a harsh edge to them. From what I've read from other Zu model reviews, this quality can be tamed with time, so I am hopeful. This forwardness necessitated a swap out of PSVANE PH EL-34s in the Decware to Tube Audio Doctor KT-66s.  These KT-66 are too mellow for my tastes with the Lii Audio speakers but make 90% of the recordings sound great with the Zu Union 6 supremes. My next move may be to swap out my Etna SL with a Koetsu Rosewood Signature Platinum I have in the main system. I'll give them more weeks of play regardless.

To summarize.  I made a move to Zu Audio and am excited about what I hear in a second tube based system.  They have some breaking in to do but I’ll continue to post on this thread about how they are morphing.  Hoping to hear from others with experience with Zu, tube amplifiers and high efficiency speakers as well.