Zu Audio UNION 6 User manual

PRELIMINARY
OWNERS MANUAL [PRELIM V2]
UNION 6
12.0"
12.0"
36.0"

UNION 6
ZU AUDIO | 3350 S 1500 W | OGDEN, UTAH — USA [DESIGNED AND MADE BY US]
WWW.ZUAUDIO.COM
ZU AUDIO UNION 6 & UNION 6 SUPREME OWNER’S MANUAL
[PRELIMINARY V2]
PRELIMINARY
TABLE OF CONTENTS
WELCOME AND THANK YOU 3
INCLUDED WITH LOUDSPEAKERS 3
DANGER - RISK OF SEVERE INJURY OR DEATH 5
WARNING - RISK OF INJURY 5
CAUTION - RISK OF MINOR INJURY OR PROPERTY DAMAGE 6
CAUTION - RISK OF PROPERTY DAMAGE 7
UNION’S DESIGN OVERVIEW 8
UNION / UNION SUPREME DIFFERENCES 9
BREAK-IN / BURN-IN 10
INITIAL UNION 6 PLACEMENT 14
CONNECTING YOUR AMP AND SPEAKERS 16
ZuB3 CONNECTOR DETAIL 17
AMPLIFICATION GUIDANCE 18
LOUDSPEAKER CABLE GUIDANCE 19
LOUDSPEAKER/ROOM TUNING 21
UNION-6 LOUDSPEAKER SPECIFICATIONS 27
WARRANTY 29

UNION 6
ZU AUDIO | 3350 S 1500 W | OGDEN, UTAH — USA [DESIGNED AND MADE BY US]
WWW.ZUAUDIO.COM
ZU AUDIO UNION 6 & UNION 6 SUPREME OWNER’S MANUAL
[PRELIMINARY V2]
PRELIMINARY
WELCOME AND THANK YOU
Thank you for your purchase of Union. They are designed and built for a lifetime of trouble-free high-
performance playback. It is our desire to exceed your expectations in product performance, quality,
durability and customer service. If we have fallen short we would sincerely appreciate knowing how we
may improve. If we have exceeded them we hope you will let your family and friends know.
David Toop in his book Ocean Of Sound paints a powerful image of today’s musical creativity, “...Starting
with Debussy in 1889, is an erosion of categories, a peeling open of systems to make space for stimuli,
new ideas, new now, this environment included sounds of the world—previously unheard musics and
ambient sounds of all kinds, urban noise and bioacoustics... unfamiliar tuning system and structuring
principles, improvisation and chance.”
The quantity and qualities of music the modern world has at its ngertips is unfathomable—we want to
amplify your nds and choices and extend the time you immerse yourself in them.
Thanks again, and welcome.
–Zu Audio
Included with each pair of Union 6 loudspeakers
(2x) slip-t hard plastic driver covers - installed as packaging
(8x) 1” long [26 mm] 3/8–16 stainless-steel oval-end feet - installed
(8x) 9/16” [14 mm] hex 3/8–16, stainless-steel thin (jam) nuts - installed
Additional Items Included In Package
(8x) 1-1/2” [38 mm] hardened carpet spikes
(1x) nish cleaning cloth
Packaging is double-wall cardboard with closed-cell foam frames and end-caps
PUBLICATION INFORMATION
INCLUDED WITH LOUDSPEAKERS
This is version PRELIM V2 of the Union 6 Owner’s Manual. The latest version of the manual can be found
at www.zuaudio.com/downloads
© 2023 Zu Audio All rights reserved. No part of this work may be reproduced in any form or by any
means for other than your own use without the written permission of Zu Audio.
Products that are referred to in this document may be either trademarks and/or registered trademarks of
the respective owners. Zu Audio make no claim to these trademarks.

UNION 6 OWNERS MANUAL [PRELIM V2]
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PRELIMINARY
Read and follow these precautions to use Union loudspeakers safely.
Zu Audio is not liable for any failures, damages or problems caused by the use or misuse of Union
loudspeakers by the purchaser or any third party.
This mark indicates the possibility of hazardous situation, which if not avoided
could result in serious injury or death.
This mark indicates the possibility of hazardous situation, which if not avoided
could result in serious injury.
This mark indicates the possibility of hazardous situation, which if not avoided
may result in minor injury or property damage.
This mark signies prohibited action, which must not be done to use this
product safely or to prevent premature wear.
This mark signies required action, which must be done to use this product
safely, to get good sound or to prevent premature wear.
DANGER
WARNING
CAUTION
REQUIRED
PROHIBITED
SAFETY PRECAUTIONS TERMS

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DANGER - avoid electrocution by making sure your amplier is powered down (or the amp’s
power cable is disconnected) prior to disconnecting/connecting loudspeakers to it.
Electrocution through touching of bare metal amplier output posts, bare metal loudspeaker
cable connectors when connected to amplier, or bare metal loudspeaker connectors when
connected to the amplier is possible. Ampliers designed to output enough power to cause
electrocution while operating will feature touch-proof contacts such as Neutrik® speakON®
connectors.
DANGER - place your loudspeakers so there is little to no chance of them falling or tipping over
on someone.
Union loudspeakers are very stable when oor standing and footers adjusted so there are four
points of contact. Nevertheless, children, and especially infants and toddlers, should not be left
unsupervised near them.
DANGER - Union loudspeakers are moderately heavy at about 80 pounds packaged [35 kg]
and should only be handled and moved by the physically able.
Those lifting and moving the Union loudspeaker should practice good lifting techniques (lift with
your knees and not your back—and ask a friend to assist.) While not acutely at risk of death,
back injuries can and often do cause chronic pain, sometimes reaching unbearable levels.
DANGER - RISK OF SEVERE INJURY OR DEATH
WARNING - potential shock hazard exists when touching of bare metal loudspeaker and
loudspeaker cable contacts. To avoid this make sure your amplier is powered down prior to
connecting or disconnecting cables to your amp or loudspeaker.
WARNING - Union loudspeakers are capable of extreme sound pressure levels, play
responsibly—consider your neighbors and consider your hearing.
WARNING - again, when moving or lifting Union loudspeakers, be careful with your back—lift
with your legs, not your back, and ask a friend to assist you.
WARNING - the drivers of the Zu Union loudspeaker create stray magnetic elds that extend
beyond the boundaries of the cabinet. We recommend you keep magnetically sensitive
electronics and media at least eight inches [20 cm] from the loudspeaker.
WARNING - RISK OF INJURY

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CAUTION - RISK OF MINOR INJURY OR PROPERTY DAMAGE
CAUTION - corners are fragile, do not set or pivot your Union loudspeaker on the corner of
cabinet. Pivoting them on the installed footers or spikes is not a problem as they are designed
to take those forces.
CAUTION - with wood nishes we recommend you keep the loudspeakers out of prolonged
and frequent direct sunlight. How long is prolonged and frequent? Well, three hours a day of
direct sunlight every day will cause some color changes after a year or two. Painted nishes
will not. While we use materials and top coats with the highest levels of UV resistance and
absorption, some color changes to wood nish is going to happen when sitting in direct
sunlight day after day.
CAUTION - amplier may be damaged if the loudspeaker outputs are shorted, i.e., the red (+)
and black (–) contacts of a loudspeaker cable come in direct contact with each other while the
amplier is switched on.
CAUTION - turn your audio equipment o anytime you leave your home. Yeah, yeah, solid-state
electronics sound better warmed up and not being turned o every time you go out—while
the risk is very low there have been house res from all forms of electronics, including the best
designed audio.
CAUTION - turn your audio equipment o and unplug the mains power cables from the wall
during a lightning storm to prevent your gear from being damaged. If lightning strikes your
home, or very near it, damage to your audio gear is possible even if switched o.

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CAUTION - RISK OF PROPERTY DAMAGE
CAUTION - do not use the tops of your loudspeakers as a bar table, condensation forming on a
container will pool and may cause water damage to the nish, especially wood veneer nishes.
CAUTION - do not use solvents save water to clean Union. A slightly water-damp soft cloth
should be all that is needed. For dusting of the driver we recommend a can of compressed air.
CAUTION - do not use tools to tighten binding posts, hand-tight is all that is necessary.
Applying high torque on posts may damage binding post and is not covered by warranty.
CAUTION - if smoke or an electric odor is emitted by the loudspeaker or any device, turn o all
components. If you have tools and skill you may troubleshoot the problem one device at a time,
working your way to the amplier—typically the source of the problem. If you do not have the
tools or skills call the maker of the amplier for assistance.
CAUTION - screws fastening the full-range driver and connector plate need only be torqued to
26 inch-pounds [3 N-m].
CAUTION - we do not recommend storage of Union in non-climate controlled spaces. DO NOT
STORE THEM LONG TERM WRAPPED IN NON-BREATHABLE PLASTIC FILM AS THIS MAY
CAUSE DAMAGE TO THE FINISH.
PROTECT - When storing your speakers, we recommend placing a clean, thin soft fabric
such as felt or eece between speaker and packaging. Tolerable long-term storage maximum
temperature range is 20˚ F [-17˚ C] to 122˚ F [50˚ C] with a humidity average not to exceed 85%.
PROTECT - when not in use, specically when there are unsupervised animals such as cats,
dogs and kids abiding near your speakers, we recommend you snap the protective
driver covers on. This will also help safeguard from foreign materials getting in.
REMOVE - yes, please remove the mentioned protective driver covers that come installed on
your loudspeaker to let the sound out. They don’t sound good at all when covering the driver.
“This one time, at band camp, they left the driver covers on and nobody liked it.”
PROTECT - when transporting Union, wrap them with new stretch wrap lm, ne felt or eece
to protect the nish from being marred by the packaging foam. Failure to do so will result in
scung and marring of the nish.

UNION 6 OWNERS MANUAL [PRELIM V2]
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Union 6 Series speakers replace several recent models. Union is Zu’s workhorse high delity
loudspeakers, capable of revealing the best in well considered systems—modest to very high-end. They
are also at home dedicated two-channel systems or home theater. Compared to Zu’s previous similarly
priced loudspeakers Union 6 improves in the following ways:
• Raises resolution, transparency and tone across the board.
• Union are less fussy with respect to room placement and associated gear.
• Removes the confusion of having 12 and 16 ohms models in a predominately 8 ohms market.
• Eliminates the traditional Zu setup task of nding the right oor-to-speaker gap for your room.
We accomplished all of that with the Union 6. We kept the funk and fun that has always attracted people
to Zu, and eliminated the fuss that deterred some others.
Union 6 is our workhorse oorstander in the same mid format tower size as all prior Omen models, but
with resolution and tone able to leverage associated gear well above its paygrade. Union 6 Supreme
also raises prosaic amps and sources to new musical heights. Union 6 Supreme is astonishingly vivid,
transparent and toneful such that it can tap the potential of the best associated gear in any system,
without needing the same to thrive.
Union makes no eort to gild the sound. The largest driver of delity within a playback system featuring
Zu Union speakers is the quality of the recording. Great recordings and media should sound great. Flat,
lifeless and confused recordings will sound at, lifeless and confused.
UNION 6 SUPREME PITCH
There is much in common between Union and Union Supreme, but performance is noticeably elevated
with Union Supreme. Both loudspeakers are based on the Soul 6 full-range driver, and both use center-
mounted super-tweeters and both are rated for 99 dB/W/m eciency. Both have amp-friendly, 8 ohms
impedance. And both speakers have our new more sophisticated Zu/Griewe and scatter plate internals
that eliminate the fussy oor gap and instead allow the main driver to “see” the room via a rear exit. You
can place Union 6 as close as 2” from the wall behind it.
Zu’s Union 6 Supreme builds on the essential agile, bursty, toneful sound of Union 6, extending its range
and articulation and further focusing its acoustic output for even less cabinet dissipation. Harmonic
content extends out to 29k Hz and bass digs a tad deeper than Union 6, but is noticeably harder-hitting.
Locating all of the moving elements around a single axis makes for an exceedingly cohesive and unied
wavefront but in this case, we use the full Soul 6 integrated mag-ux driver with main driver and super-
tweeter fully conjoined. Union 6 Supreme is astonishingly vivid, yet nuanced and subtle when it needs
to be. It delivers salacious slam and scale in real-world spaces without forcing you to organize your
room around the speakers. Discover intricacies you’ve missed in your music until Union 6 Supreme, and
you’re likely to hear new energy in dynamic swells, too.
Union 6 Supreme taps the very best gear yet thrives with what you have (probably).
For music connoisseurs craving true high end sound at an accessible price.
UNION’S DESIGN OVERVIEW

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Union and Union Supreme are designed and built around the critical human voice (A1, 55 Hz, through
A6 and all the possible harmonics, to approximately 10k Hz). Serving this critical region of tone is Zu’s
10” coaxial, paper-cored nanotech sanctied, full-range driver. The coaxially located tweeter adds the
burnish and upper treble.
Union loudspeakers are high-eciency home audio loudspeaker and are precision-matched in stereo
pairs. They are able to recreate compellingly real sound in tone, dynamics and in stereophony. Union
is also oered with the Supreme performance package. There are no drawbacks save the price to this
upgrade, and the extra burn-in required. The proof of these claims we think you’ll nd in album after
album marathon listening where you nd yourself totally lost in the music.
UNION SUPREME DIFFERENCES
• Internal Cable: Zu Event Mk. II harness
[Standard uses Mission Mk. II cable]
• Full-Range Driver Assembly: ZuCX-ND-8-N151M Grade-2
[Standard Union uses the ZuCX-ND-8-APT Grade-1]
• Tweeter: Integrated Eminence N151M
[Standard Union uses the Eminence APT based tweeter]
• High-Pass Network: single element mono pole lter using Jupiter Copper capacitor
[Standard Union uses the ClarityCap MR capacitor]
The Supreme performance additions are engineered to give the Union Supreme noticeably improved
resolution and smoothness without altering its great tone and killer shove.
Union Supreme feature Grade-2 full-range drivers with integrated super tweeters. These are driver pairs
that match to an extremely tight deviation tolerance in magnitude and impulse response—the tighter the
left/right matching the more natural and satisfying the soundeld.
Union Supreme gets Event Mk. II internal cable, improving resolution over Mission Mk. II cable. Event
Mk. II internal cable features Teon insulation and silver based conductors, within a ZuB3 format. A
combination that gives a broad and uniform characteristic impedance to the cable. Conductance is on
par with Mission Mk. II but the propagation velocity is higher and the noise oor is noticeably lower.
Event Mk. II internal cable harness increases the resolution of the loudspeaker system to a point where
Jupiter Copper capacitors combine in mesmeric ways—Union Supreme features these caps.
Jupiter Copper Caps - Jupiter Copper Foil & Paper and pure silver leadout capacitors are utilized in the
tweeter high-pass network of Union Supreme. These capacitors matchup extremely well with the Event
Mk. II internal cable. The combination imparts a sense of grace and sexy magic to the whole of the
sound, and once experienced it’s hard to live without. Pair matched to 0.2% or better.
UNION / UNION SUPREME DIFFERENCES

UNION 6 OWNERS MANUAL [PRELIM V2]
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BURN-IN OVERVIEW
Zu Union speakers require abundant break-in and burn-in to sound their best. The changes in
performance they undergo is remarkable. While there is signicant heavy-handed factory break/burn-
in, more is required once they are in your home. The factory break-in phase is engineered to target the
full-range driver’s cone—a process that is out of reach for the vast majority of users. Breaking in the
membrane requires extreme levels of shear force to set the membrane into its performance prole,
and there’s a ne line between membrane break-in and permanent deformation. During this time other
aspects are also breaking in, the drivers’ suspension and also the dielectrics and electronics, but these,
particularly the electronic, will continue to burn-in within typical home playback levels.
Union 6 receive a minimum of 300 hours of factory burn-in.
Union 6 Supreme receive a minimum of 400 hours of factory burn-in.
We discourage the use of any special burn-in specic program material—
no special “tones” and no “demagnetizing” material.
Just play as often as you can, maybe a bit louder than normal, and selecting big
full-scale recordings. The more they play the sooner they will sound their best.
Break-in is a fairly simple, straightforward, once-and-done thing (sarcasm eyes). Not funny? Likely not.
The humor assumes you like audio-dad jokes and that this is not your rst set of new Zu loudspeakers.
Unless specied otherwise, what follows are generalizations about burn-in specically relating to home
audio direct radiating Zu loudspeakers.
Most nd Union to sound a bit harsh but promising when new. Some nd them amazing right out of the
box. Some nd them to sound strident and not so promising. In all cases users should know that they
are going to change, signicantly. The sound and enjoyment you will get from them after six weeks or so
of daily evening use is going to be night and day compared when you rst get them. Also know that the
changes are not going to be linear for the vast majority of listeners. And for reference, know with Union
Supreme there’s a very real chance that they will actually get worse for a period within the burn-in. This
has not yet been observed with Union. But either Union or Union Supreme, patience will reward and
they will snap out of any funk they might go through while burning in. If you are now thinking, “I’ve been
doing this my whole life and I have never had a speaker sound worse as it was breaking in...” we again
say, patience on your part is very likely to have a very big payout. Not always, but more than not. We too
have been doing this a hell of a long time, fully immersed most every day, with thousands of customers
as data points. If you have purchased Union, listened for a week or so and then hastily concluded that
they are not your sonic cup of tea give us a call or email, please let us help.
The majority of potential Zu owners that we talk to feel that burn-in is a thing, but that its not all that
pronounced. We agree when applied to other brands—the vast majority of loudspeakers change very
little, some so little that you wouldn’t even know burn-in was a thing. But Zu Union are not like normal
speakers and the burn/break-in changes they go through is an interesting and not subtle phenomenon.
BREAK-IN / BURN-IN

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BURN-IN MAIN POINTS
Here are some points to help inform and guide your setup, tuning and burn-in expectations. Eecting the
speaker’s transition from sounding new to sounding full and engaging include:
• The length of time played
• Power levels and program material played
• Temperatures they might have been subject to in shipping or storage
• The unknowable relationship they have with Schrödinger’s cat
• Even though Union’s sound will change with play, we still encourage you to follow our guidance on
room tuning as performance gains made there increase your enjoyment during the burn-in phase(s).
• During the burn-in phase we don’t recommend excessive juggling of components as burn-in
• is heavily impacting the sound.
• If you have amps and other components that are near-to-hand maybe give them a try. But for the
rst three weeks or so we would advise against purchasing new gear to solve problems that might
soon evaporate. New gear is going to also go through burn-in, and listening through burn-in on top
of burn-in is rarely worth anything.
• If you do change an amp and notice a change for the better, you should also switch back to conrm
that it is in fact the amp the made the dierence. It could also be that the change was coincident
with a burn-in related improvement, or some other change.
• Disconnecting and connecting gear can clean a dirty connection and improve sound. Even a clean
contact that is not snug will reduce delity.
• The act of swapping gear or feeling like you are doing work on your system has a powerful
psychoacoustic eect and is likely to allow you to hear deeper into the sound. Your brain is a
component of the playback system.
• Burn-in changes that happen after the initial ten to forty hours of play once in your home are
generally episodic and nonlinear. There is usually one very noticed transition where the day before
you were listening and your system was sounding good and you were happy, or close to happy,
say four to six weeks in with Union. Then rather unexpectedly you become aware that things are
sounding more open and involving, so compelling, so good.... This is the result of burn-in, mostly
electrically related, seemingly quantum mechanical. This change indicates that Union are now
settling into their life-long (human life) performance prole.
• Once they have made that very noticeable transition to sounding good, you may need to revisit
• how you have them placed in your room.
• If Union goes unused for three months or more, even if fully burned-in prior, they will not sound just
as they did and will go through a shorter phase of the burn-in phenomenon.

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BURN-IN / GENERAL OBSERVATIONS
Predictive speaker qualities regarding the schedule and impact of burn-in seams to be eciency and
the extent to which speaker-level electrical ltering is employed. A speaker’s sensitivity to electric power
inputted and the resulting sound levels outputted is colloquially declared as eciency. How extensive
the use of speaker-level electrical components to achieve the desired sound is crossover complexity.
We think the combination of very low eciency combined with extensive crossover ltering are strong
indicators that the design will have little change from burn-in. Conversely, Union with its sonic design
targets of very large dynamic range and high transient and timing resolution—through the whole of the
human voice, and from as close to single-point source as practical—has resulted in a high eciency,
crossover-less design that requires extensive burn-in to sound right.
BURN-IN / TERMS AND PROFILE DETAIL
In general conversation, Zu use the terms burn-in and break-in interchangeably, to generally refer to the
changes a loudspeaker goes through on its way to reach its long-term performance prole. Technically
however there is a dierence between them. Burn-in is the domain of the electric and break-in is the
domain of the mechanical. Understanding each is interesting and might help with expectations of the
loudspeaker when new, and when returning them to service after not being used for a while.
The life of a loudspeaker can be proled in three phases: burn-in/break-in, performance, and aging-out.
Union loudspeakers are engineered to operate within the performance prole for a minimum of 100,000
hours of in-home use under normal living conditions at or less than twenty watts of nominal input power.
In the graphs to follow we zoom in on the burn-in proles of both Union and Union Supreme. The reason
for the odd burn-in prole of Union Supreme is largely the result of the near exclusive us of Teon as a
dielectric in the cable harness and leads. The Jupiter Copper capacitors also take considerable time to
sound their best and so contribute to the long burn-in schedule.

UNION 6 OWNERS MANUAL [PRELIM V2]
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0 10 100 1000
Pn
P0
[HOURS]
UNION-6 BURN/BREAK-IN PROFILE
103
Pn
P0
[HOURS]
UNION-6 LOUDSPEAKER SYSTEM FATIGUE PROFILE
104105106
Le
0
Dynamics break-in profile average (driver's suspension and membrane)
Electronic break-in profile average (capacitor, dielectric/cable harness)
Electronic variability
Performance zone
End of life (perminanet magnet fade, suspension breakdown or exessive membrane shear

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This is an overview, to get your new speakers up and running and sounding good enough. An expanded
Zu speaker placement section is further in the manual.
Start with the Union speakers placed where you’ve visualized them, likely anking that rack you have,
and hopefully symmetrical.
Union are not overly sensitive to being in just the right place—bass integration may prove otherwise.
Bass wavelengths are very large, and moving the speaker a few inches this way or that will not make a
meaningful impact in the bass region.
• From centerline, Union should be equidistant, with matching toe (horizontal splay) and lean-back.
• From the main listening chair (sweet spot) the angle formed by the speakers should be between
40° and 90°. Wider is usually better for stereo and home theater, 60˚ (equilateral triangle) is a great
starting point. Union pairs are very tightly matched which is one of the reasons you can have a wider
than normal stereo spread and not have the middle fall out. If the middle of the soundeld collapses,
scoot them in and/or mess with toe-in.
• Start with Union speakers pointing (toed in) right at the main listening chair, listen. Then splay them
out so they are pointed a few feet [0.8 m] behind. Then try wider still. Then back to right at you and
then try having them pointing (shining) in front of you. Experiment and let listening be your guide.
• Use the installed oval-end footers for whatever the ooring. Coasters or coins may be placed
between oor and footers to keep your ooring mark free. If you are on carpet or rug, consider
spikes, but after you have them positioned and sounding good, spikes make moving them around
dicult.
• Union do not require a gap between oor and speaker bottom. You can rest them directly on the
oor or you can raise them up—experiment as you please.
• Consider leaning them back, especially if you would like them to better play to very large spaces, or
sound bigger and fuller when you are standing or working about.
• Generally, Union speakers should be placed no closer than a foot or so [ ≈25 cm] to the side wall—
that is the space between speaker and wall. But they can be placed as close as a few inches [50 cm]
to the front wall (space between rear of speaker and front wall).
• If at 60º and toed so they are pointed right at you, they are still not presenting a seamless soundeld
something is wrong. The speaker cable on one of the channels might be ipped (red to black, black
to red) or one of the amp channels is going sideways—time to troubleshoot. Note, there is a small
chance of some odd room acoustic interaction and your system is ne. Troubleshooting this entails
disconnecting one of the speakers, listening to just one, making a mental map, then doing the
same to the other channel. Listening to just one speaker at a time is insightful, so much so that we
developed a whole process of placement tuning around it.
INITIAL UNION 6 PLACEMENT

UNION 6 OWNERS MANUAL [PRELIM V2]
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80°
60°
40°
128 5/8 [3]
PIVOT INSIDE FRONT CORNER
D
W6

UNION 6 OWNERS MANUAL [PRELIM V2]
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Turn o your amp to reduce the chance of shorting the connectors and damaging your amp.
Union 6 and Union Supreme 6 feature 5-way binding posts and ZuB3 via speakON NL8 connectors.
5-way binding posts are connected in parallel with the ZuB3.
Union 6 and Union Supreme 6 feature ZuB3 connection. ZuB3 via speakON NL8 connectors maintains
the functional electromagnetic characteristics of ZuB3 cable designs and lowers contact resistance.
For best results we recommend ZuB3 terminated Zu cable. ZuB3 is an electromagnetic design, Neutrik
speakON NL8 are connectors which facilitate ZuB3.
5-way binding posts used on Union and Union Supreme are machined from high copper content brass
and have the Faston male blade machined from the same billet to keep delity as high as possible. They
accept the following speaker cable ends:
bare wire
pins
banana plugs
1/4” [6.3 mm] standard spades [forks] and ring lugs
5/16” [8 mm] oversized spades and rings
3/8” [10 mm] super-oversized spades and rings
FEATURES AND BENEFITS OF ZUB3 VIA NL8
• ZuB3 via NL8 lowers contact resistance and maintains the cable’s ZuB3 electromagnetic
characteristics through the wall of the speaker, both of which can signicantly improve sound.
• Connector is clocked so ensures correct channel phase.
• Design is a single body connector, housing all contacts, and is clocked to ensure correct channel
phase: SP+ to SP+, SP– to SP–, e.g., red to red, black to black.
• Design is also locking and touchless, so no possibility of short-circuiting the amplier when making
connections, no possibility for connections to wiggle or vibrate loose, and no risk of shock or worse.
• Contacts are self cleaning, if there is a question of tarnish just unplug and plug back in.
CONNECTING YOUR AMP AND SPEAKERS

UNION 6 OWNERS MANUAL [PRELIM V2]
Page 17
PRELIMINARY
ZUB3 CONNECTOR PINOUTS
NOTE: We highly recommend factory termination or retermination of your Zu loudspeaker cable.
However, ZuB3 via Neutrik® speakON® termination convention is outlined for your DIY reference.
ZUB3 VIA SPEAKON NL8 8-POLE TERMINATION CONVENTION
Pin-outs for ZuB3 via Neutrik® speakON® 8-pole / single channel
SPEAKER ++(red)(red) SPEAKER ––(Black)(Black)
speakon 1+
speakon 2–
speakon 3–
speakon 1–
speakon 3+
speakon 4–
unused: 2+, 4+
sp+ 1+
sp+ 2–
sp+ 3–
sp– 1–
sp– 3+
sp– 4–
Neutrik 8-pole speakON cable-end connectors feature pozidriv #1 setscrews
3+
2-
4+
2+
1-
1+
4-
3-
ZuB3 CONNECTOR DETAIL

UNION 6 OWNERS MANUAL [PRELIM V2]
Page 18
PRELIMINARY
AMPLIFICATION MATCHING WITH UNION
An often asked question is which amp should I match up with the Union. This is not a simple question
as you need to factor in the rest of the system—room, the sound qualities you value and how loud you
play, or how loud would like to be able to play. Sound levels are the easy part, and for more than 90% of
Union owners ten to twenty good sounding watts is enough.
Zu loudspeakers are ecient—eciency being the conversion of electrical input from the amp to the
sound output of the speaker. For this reason much less electrical power is needed compared to the vast
majority of home audio speakers. Lets start with how loud rst:
2 - 10 watt / channel rated amps are what you need for low to moderate sound pressure levels.
10 - 50 watts for moderate to very loud sound pressure levels.
50 - 500 watts for very loud to ear damagingly loud SPLs.
WARNING - Union loudspeakers are capable of extreme sound pressure levels, play responsibly—
consider your neighbors and consider your hearing.
Another aspect of Zu Union speakers to bear in mind is their lack of dynamic compression, you can
just keep ramping up the volume and they just sound better and better, staying clean and in control to
the point the amp gives way to distortion or your ears protest. Over the years we have found that the
majority of new Zu speaker owners in our medium oor-standing range listen twice to four times louder
(3 ~ 6 dB) on average than they did with their less ecient speakers. Dynamic compression in speakers
is perceived as louder by most and less eciency speakers dynamically compress much more than high
eciency. And also consider, as you increase the volume of the speaker you disproportionately increase
the room’s contribution to the sound. If you are unhappy with the sound at loud levels it could be the
amp or it could be your room, or it could be that you are listening way louder than you realize and your
ears are pushing back. Poor loud-level listening performance is rarely due to the Union.
The amplier/loudspeaker relationship contributes signicantly to the sound of the system, we
encourage you sample some amps. Start with what you have, dust o any amps or receivers you might
have tucked away. Borrow some kit from your buddy, and his buddy, or befriend your local audiophile
society. Try stu, see what you like, and don’t be afraid to try some old gear. Don’t be too quick to judge
when you swap amps, most amps need several hours of warm-up to sound their best. Tube amps warm
up more quickly, some solid-state can take days. And if you are using stand alone amps realize that the
pre-amp feeding them can have a pretty big impact on sound as well. Oh, and what you like, in your rig,
with your room and your ears and brain might be totally dierent than others—trust yourself.
TUBES VS SOLID-STATE
We think this is just dumb. Tubes generally can sound all over the map, and the same is true with solid-
state. There are plenty of unbearable sounding tube amps and there are plenty of unbearable sounding
solid-state. Tubes is just too broad a term to have any meaning, as is solid-state in reference to how they
might sound matched up to Union.
AMPLIFICATION GUIDANCE

UNION 6 OWNERS MANUAL [PRELIM V2]
Page 19
PRELIMINARY
KEY POINTS ABOUT SPEAKER CABLE FOR YOUR UNION 6
• Start with what you have. Owned and close at hand is a good place to begin.
• Shorter speaker cables are better than longer, but don’t short yourself. Having a bit of extra cable so
you can put the speakers where they sound best within your room is a bigger factor.
• Keep the left and right speaker cable the same length. Dierent length cables of the same model will
also have dierent measures and distort the stereophonic aspects.
• Don’t use cable as tone control—a common abuse in hi-. Doing so usually leads to frustration and
further loss of delity. When cable aects timbre it usually aects timing, phase and so on. Timbre
problems are usually solved with loudspeaker placement, and burn-in time.
• The speaker cable is part of the amplier/loudspeaker relationship, and changes to the resistance,
capacitance, impedance, propagation velocity, characteristic impedance... aect the sound.
• Those that say cables do not inuence sound are wrong. They lack experience or their bias is
hindering their listening, or the systems they have used them in are lacking the resolution necessary
to notice the dierences in the stereo.
Connect up Union with whatever you have. You own it, it’s sitting there, and hopefully it’s not some
exotic hi- cable—simple cable like zip cord is known and can be really good. If you don’t have
something close, just use some home electrical wire, Romex 2/14 or 2/12, likely you have some in the
garage or stued in a cupboard. No? It’s not expensive and on the spool at the hardware store. Strip
the ends and connect it up. Don’t use the center bare ground wire, just cut it back on both ends. It
doesn’t matter if you use the white or the black insulated wire for the (+) or (–) just be consistent so both
speakers are in phase. If you want to try Zu cable, we would be happy to have you audition them.
Improvements that will be noticed from quality, well engineered speaker cables include bass depth and
resolution, reduced noise, harmonic structure and timbre, attack, stereophony, and ease of listening.
As dierent length cables of the same model will have dierent measures, we strongly recommend your
left and right cable lengths be the same. If you have one side that has a lot of extra cable just rats nest it
under the shelf—don’t coil it as that would add inductance that would not be added to the other and you
reduce the quality of the stereo. If you would like it neat instead of a nest, you can coil it in a gure-eight
pattern, that will not add inductance.
While insulation, jacket materials, pigments, conductor shape, metallurgy and structure are important,
those elements should be designed to serve the primary design of the cable, the electromagnetic. The
nal cable EM eld geometry combined with conductors determines measured attributes. Dierent
cables have dierent measures. Connections also make a dierence, usually due to contact resistance,
but characteristic impedance can also play a role, yes, even in the audible bandwidth. Try some stu,
just like amps, see what works and what doesn’t. Experiment.
LOUDSPEAKER CABLE GUIDANCE

PRELIMINARY
Page 20
ZU AUDIO | 3350 S 1500 W | OGDEN, UTAH — USA [DESIGNED AND MADE BY US]
WWW.ZUAUDIO.COM
Page 20
10 [Hz] 20 30 40 50 60 70
80
90
100
200 300 400 500 600 700
800
900
1k 2k 3k 4k 5k 6k 7k
8k
9k
10k 20k 30k 40k
TREBLEMIDRANGEBASS
VERY DEEP BASS DEEP BASS BASS POWER BASS LOWER MIDRANGE MIDRANGE UPPER MIDRANGE PRESENCE BRILLIANCE NEVE
FREQUENCY SPECTRUM TERMS
MUSICAL TERMS OVER FREQUENCY AS USED IN THIS MANUAL