Zu Audio Soul Mk II Review

HiFi Guy

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It all started innocently enough. A few years ago I purchased a pair of Magnepans- I had always wanted a pair. Then I went through a few different amplifiers attempting to find the right match. Later we bought another house and moved. The square footage of the new house is nearly identical to the old, but the layout is different, so the size of my listening room (the living room) took a significant hit. The Magnepans looked positively gigantic. And as good as they sounded, I still wasn't getting the sound I was looking for. The rest of the system was pretty well set. I started entertaining the idea of another pair of speakers.

The Zu Difference

Zu Audio marches to the beat of their own drummer. Instead of designing by computer, head honcho Sean Casey uses his decades of experience and research combined with his physics background to design by ear. Casey has read all of the old speaker design books and listened to the classic designs from the golden age of hi fi. He believes that a nearly full range design with one (or two) speakers reproducing nearly the full frequency range sounds best. He adds a tweeter only to capture the highest frequencies. Additionally, he believes that crossovers are “tone killers”. Instead of a printed circuit board full of resistors, capacitors and inductors, Casey uses a single high quality capacitor. This acts to block all but the highest frequencies from the tweeter.

This means that the signal from the amplifier is connected directly to the speaker itself. Most of the time, the amplifier is connected to the crossover inside the speaker cabinet- that printed circuit board full of stuff. It's like a Guinsu knife. It slices and dices the signal sending some to the woofer and some to the tweeter. If the speaker has a midrange driver, there's some additional slicing and dicing.

Why would a speaker manufacturer want to do this? It's pretty simple actually-many speaker manufacturers buy their raw parts from outside vendors. Pick a woofer from manufacturer A and a tweeter from manufacturer B. What if they don't match in output- say the tweeter is too hot? Add a resistor. Problem solved.

The difference between using multiple drivers and a crossover versus a full range design can be compared to buying a suit. You can buy a suit off the rack and the tailor will alter it to make it fit- a nip here, a tuck there and hem the slacks. Or you could go to a high end tailor and have your measurements taken and a suit made from them. While both fit, one fits better- the custom suit without alterations. The Zu design is giving as close to an unaltered musical presentation as possible.

Zu has their drivers built to their specification by Eminence in Kentucky. Eminence happens to be the largest speaker manufacturer in the world. You've heard Eminence speakers before, most likely in live venues. Lots of guitar and bass speaker cabinets are equipped with Eminence drivers.

Zu offers all of their speakers factory direct only. This saves buyers the additional markup that a traditional distributor/dealer network would bring. It also allows consumers to communicate directly with them. You can speak with Sean Casey or another member of the team just as I did. There's no pressure to buy- the Zu crew genuinely want you to get the right speakers for you and your system. Custom finishes are available for very reasonable additional charges- they have numerous wood and automotive paint options available. Every pair is custom built for the buyer.

All are backed by a 5 year guarantee and include a 60 day in home audition period with free return shipping (if shipping was paid by the buyer).

Originally what caught my eye was a pair of their Dirty Weekends. These go on sale a few times a year starting at $999 for the pair. My idea was to try a pair and see how I liked them. These come with a 1 year trade up policy- upgrade to another pair of Zus and the entire $999 is credited towards the new pair. As cool as this is, I realized this wasn't ideal for me. Assuming I liked them, I would be wondering what I was missing by not getting the Souls that I really had my eye on. Ultimately I felt that I'd likely not give the Dirty Weekends a fair shake. After speaking with Casey, I gave it some more thought and ultimately ordered a pair of Soul Mk II in natural Maple finish ($2600 per pair base price- $2770 with the custom finish upgrade).

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Two things make the Soul the “odd” speaker in the lineup. The cabinet isn't a box, it's an obelisk- wider at the bottom that the top, with each panel tilting towards the top. It's the smallest floor standing speaker they offer and it stands a mere 31.5 inches tall, the base just over 12 inches square. This means they take up just about the same amount of space as smaller speakers on dedicated stands. The Soul is also the only model in the line that uses a coaxial driver: the tweeter is built into the center of the 10.3” driver in place of the usual dust cap. Recessing the tweeter at the mouth of the full range driver is done so that high frequencies arrive at the ear as close in time as possible as lower frequencies.

Around back are high quality binding posts in addition to a proprietary Speakon type connection socket. This is said to offer an even better connection than the usual, and makes it impossible to wire the speakers out of phase at the speaker end. I wired them with my usual Analysis Plus Oval 9 cables.

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The speakers are vented at the bottom and come with both ball ended feet for hard surfaces and spikes for carpeted floors. Because they are bottom vented, there must be a gap between the speaker and the floor to let air escape the cabinet- more on this in a bit.
 

HiFi Guy

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Why High Efficiency?

Super efficient speakers were the norm back in the 1930s and ‘40s. The transistor had yet to be invented. Even if it were possible, a high powered tube amplifier would have been cost prohibitive, far too large and heavy and would have produced tremendous amounts of heat. The tubes commonly used in today’s high powered amplifiers weren't introduced until the mid ‘50s. High efficiency speakers were the solution- they allowed room filling sound on just a handful of watts.

There's another benefit to high efficiency: reduced distortion. Look at any conventional box speaker when it's playing loudly. It's easy to see the cone pulsate. Not so with the Souls: cone movement is barely perceptible. Reduced cone movement means reduced distortion- the driver isn't working as hard at any given volume level compared to most modern designs.

High efficiency speakers also open up choices when it comes to amplifiers. While the Soul Mk II can handle up to 100 watts, it can also be driven by as little as 2 watts- yes there are a number of extremely low powered amplifiers available, both tube and solid state. As an example- speakers that are rated at 89 dB sensitivity are pretty common. Using a 50 watt per channel amplifier, a pair can generate 99.3 dB sound pressure level (SPL) at a distance of 10 feet. This scenario has the amplifier operating at its limit. For reference, a newspaper press generates 100 dB SPL.

Substitute the 99 dB sensitivity Souls and the picture changes dramatically. That same 99.3 dB SPL requires just 5 watts per channel. That 50 watt per channel amplifier isn't being taxed at all. There's plenty of power left in reserve for musical peaks. Also, one is far more likely to cause speaker damage by overdriving the amplifier than by having “too much” power. Neither the amplifier nor the speaker are being stressed. Keep in mind that 99.3 dB is LOUD and prolonged exposure to levels this high can cause permanent hearing damage.

Having lower power requirements opens up other options. The Musical Paradise MP-301 Mk III is a single ended (one output tube per channel as opposed to two or more) integrated amplifier that puts out 6.5 watts per channel. It's a simple amplifier (a good thing) and quite reasonably priced- just $430 delivered in the States. It should mate well to the Souls as well as the two lower models in the Zu lineup. I've had to talk myself off of the ledge and away from the “buy now” button more than once. Not that I think the Musical Paradise is competition for my PrimaLuna, but I'm curious. It could make a great choice for a cash strapped music lover. It will also drive headphones as well.

Setup

About 6 weeks after I placed my order, the Souls arrived. The Souls are nestled inside a block of styrofoam on all sides within a sturdy outside box. It's by far the best packaging I've ever experienced and I highly doubt shipping damage could occur with this packaging. The speakers’ fit and finish are flawless and much better than the online photos suggest.

Even though the online documentation and videos clearly state that there needs to be space between the floor and the bottom of the speaker, I have to stress that this is critical. The Souls were initially set up with space underneath, but not enough. Bass response was uneven. Midrange was as well- there were signs of promise, but overall, performance was sub par. The next night, I raised them as high as the ball end feet would allow- about a half inch. This made a profound difference: it sounded like a totally different speaker.

The only other setup issue is that the seating in the room isn't ideal. There are two leather chairs with a table between them. The table is in the perfect listening position, but having a chair there doesn't work. Setting up the Souls in a similar fashion as the Magnepans- with the front of the speakers about 3 feet out into the room and very little toe in was quite unsatisfactory. I usually sit closer to the left speaker. The left speaker was all I could hear. And the same thing happened with the right chair and speaker. The solution looks unconventional but sounds excellent: I aimed the left speaker at the right chair and the right speaker at the left chair. The stereo image snapped into place with seamless center fill between the speakers. The Souls are towed in quite a bit more than the Magnepans had been.

After extended listening, I made a couple of changes to my system. First, I changed the output tubes in my PrimaLuna amp. The EL34s that the factory supplies are fine, but the Tung-Sol 7581A is more balanced- lost is a bit of the EL34 midrange magic, replaced by a rock solid bottom end. A couple of weeks ago, I upgraded from the Grado Prestige Gold2 cartridge to the Grado Statement Platinum. It's got the classic Grado house sound, but plays noticeably deeper and with more resolution and smoothness from bottom to top.

There's little information online about the Souls- other models seem to get more attention. There is a video online that states the Souls are a bit bright- either accentuated in the treble or weak in bass response. That hasn't been my experience at all. I suspect some type of mismatch in the reviewer’s system. I'm using a warm sounding Grado cartridge, a warmish sounding Sutherland phono stage and a fairly neutral PrimaLuna integrated amp. This setup has amazing synergy with the Souls. But if I were to substitute an Ortofon 2m series cartridge for the Grado and replace my Sutherland Insight with the Sutherland KC Vibe (which doesn't have the warmth or dynamic slam of the Insight) I'm sure my findings would be quite different. Zu themselves state that the Souls will lay bare any upstream equipment mismatch. Although I have no other gear lying around at present to put this statement to the test, I have no problem believing it.
 

HiFi Guy

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Listening

I'd like to touch on a few key points regarding the Souls.

Dynamics: the Souls may be relatively small, but don't let that fool you. They sound big. Albums with wide dynamic swings are stunning- it's as if the amplifier has an endless amount of power to give. In a sense, it does with high efficiency speakers.

Sense of scale: There's a lot of room in most recordings- the room where the recording was made. The Souls give an an excellent sense of room size. Another thing that's easily noticed is the difference in how drums are recorded from one recording to another.

Bass: The Souls have incredible bass especially considering their size. They aren't a speaker that adds warmth to all recordings though: if it's in the recording, the Souls deliver. If it's not, they may come across a bit thin sounding. It's not the speakers: it's either the record or something upstream in the system.

Midrange:

Zu advertises that they get the sound of the human voice right. They do. What they do even better is delivering a sense of body- literally. One can hear the body of an acoustic guitar- the resonance of the instrument. Piano is also reproduced incredibly well. The same note played on a stand up piano compared to a grand piano sound completely different- the grand will be, well, grand sounding because it's much larger. The Souls don't homogenize. Piano isn't “just” a piano. Expensive or cheap, large or small, the Souls reveal.

Imperfections:

Strings (violins in particular) are a bit brighter via the Souls than I've experienced live in a concert hall. Not shrill by any stretch, but not perfect.

I had a very enlightening listen one night to my DCC pressing of The Beach Boys’ Pet Sounds. I knew it would be a totally fresh experience given what I'd already heard. From the first track, I was dumbfounded. “Why does this sound like Phil Spector’s “Wall of Sound” I was thinking. You see, I'm not a fan at all- I find his sound to be a wall of mud. And it doesn't matter whether we are talking The Ronettes, The Beatles (Let it Be), or solo Lennon or Harrison albums. Spector has his own sonic signature- which sounds like glass would appear if smeared with Vaseline.

So I did a bit of research. It turns out that Brian Wilson was a big Phil Spector fan and wanted that sound for Pet Sounds. Apparently he succeeded, and quite well. I've never made the connection before with any other speaker I've heard, but Spector’s influence was laid bare with the Souls. And while I may enjoy the album a bit less now, I can truly appreciate the fact that the Souls deliver music as the artist intended. A bigger compliment I cannot give.

Wrap It Up Already

Just like any fine audio component, the Souls will wow the listener when playing a great recording, and lesser recordings won't be spared- they will sound like what they are. Are the Zus a ruler flat speaker- correct on paper? Probably not. Are they among the most enjoyable speakers I've ever experienced in my home, regardless of price? Absolutely. Do they do all the hi fi tricks? Yes, but that's not their raison d’etre. If you are looking for a speaker that makes music as opposed to “hi fi” and want to forget about gear entirely, the Souls may be for you.

I hesitate to call the Souls a bargain. Yet, they are. A bargain doesn't mean they are cheap, because cheap is just that- cheap. The Souls are a bargain because they are competitive with speakers priced at twice their price. I can think of a few highly regarded speakers in the $6-7k price range that can't touch the musical magic of the Souls. Highly recommended.

Keep an eye on this space as @AnthonyI and @Colonel_Angus are headed here in a few days for a listen. Anthony’s system is very much like my own, while the good Colonel has a completely different setup. Hopefully, both will post impressions.
 

HiFi Guy

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Here is a follow up from @AnthonyI after his visit.

"It’s great to be able to listen to other systems, especially when the system mirrors your own closely. This was a small part of my visit with @HiFi Guy I was looking forward to, aside from always enjoying hanging out while on vacation…………meeting @Colonel_Angus, that was just the cherry on top 😉

So the Souls, when you first see them and you think back to what speaker logic you think you have, you can’t help but sit there and say “How?” Then you listen to them and well, @HiFi Guy's assessment of “They’re different” is spot on. While lacking some of the tech verbiage, when I sat down and listened to something familiar (Abbey Road) that’s the first thing I thought as well. It was hard to pinpoint a specific characteristic that you could say “Oh, X sounds better”, the sound is just different. In my opinion the Souls were more “breathy”, warmer and detailed without being analytical compared to my LSiM’s. Now I still really enjoy my Polk’s, but the Souls seemed much more “Accurately Natural” if that makes sense.

It was hard to wrap your head around these speakers, they push forward a natural dynamic space to your ears….but it isn’t your typical dynamics, instruments and vocals were in the right place at the right tone, that’s why this “they sound different” is so spot on while being no real help to anyone, lol.

If you’re in the market for a set of floor standing speakers, and I use the term lightly because these have such a small footprint, and your budget is $2-5K I would definitely consider looking into these, there are more expensive speakers out there, but you know me and my “Bang for your buck” mentality, and these have a real beautiful sound field that should appeal to most. The Souls have put me in a very precarious position, I’ve always leaned on my lack of space being the reason for straying away from towers, but honestly, the Souls take up the same amount of space my LSiM’s on their stand do… so now we ponder, but I gotta say, they’re definitely at the top of the list for consideration.

On a side note, speakers are tough, and in my opinion the $2-5/6K offerings have a lot to do with personal preference. Before jumping in the real deep end of the speaker pool, it might take some demo sessions and possibly a leap of faith as well. Over time I’ve realized that @HiFi Guy and I have similar tastes in what we like in sound, so my ears always perk up when he has something to say 😉"
 

Slimwhit33

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Thanks for the write up!

You’re discussion of the Souls on numerous fronts is like that of my Heresy III’s. First, my listening position is slightly off center, and I ended up positioning my HIII’s with the same toe in that you settled at, left speaker a hair past the right seat, etc.

Second, I experienced the exact phenomena with Pet Sounds. On the HIII’s it sounds somehow “thick”? Your glass covered in Vaseline is spot on.

Third, your descriptor of them making music not hi-fi, not flat but most enjoyable, etc is what I tell everyone about the HIII’s.

Do you feel like they could be long term speakers for you? And yes, In this hobby I feel like long term is 5 yrs. lol.
 

Slimwhit33

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Also, the finish on those is beautiful @HiFi Guy

And I’m having trouble with scale, but how big is that Breakfast in America print and where did it come from? I LOVE that album. It sounds amazing on the HIII’s, I assume the same on the Souls!
 

HiFi Guy

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Thanks for the write up!

You’re discussion of the Souls on numerous fronts is like that of my Heresy III’s. First my listening position is slightly off center, and I ended up positioning my HIII’s with the same toe in as you settled at, left speaker a hair past the right seat, etc.

I experienced the exact phenomena with Pet Sounds. On the HIII’s it sounds somehow “thick”? Your glass covered in Vaseline is spot on.

Do you feel like they could be long term speakers for you? And yes, In this hobby I feel like long term is 5 yrs. lol.
These are definitely long term for me. I can't think of any other speaker I'd rather own. And I kept my Infinity Kappa 6.1s for fifteen years, so I'm not one to change speakers often.

I'm really looking forward to @AnthonyI and @Colonel_Angus coming over on Sunday.
 

HiFi Guy

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Also, the finish on those is beautiful @HiFi Guy

And I’m having trouble with scale, but how big is that Breakfast in America print and where did it come from? I LOVE that album. It sounds amazing on the HIII’s, I assume the same on the Souls!
We had a a chain of record stores down here called Peaches, sadly long gone. They had paintings on wood of classic albums along the top of the buildings on all sides- all in a row. That's what this is- we found it while crate digging at an antique mall. It's 6 feet square.

Thanks for the comment on the finish. Natural Maple was my concession to my wife- I'd have chosen American Walnut.
 

Slimwhit33

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We had a a chain of record stores down here called Peaches, sadly long gone. They had paintings of classic albums along the top of the buildings on all sides- all in a row. That's what this is- we found it while crate digging at an antique mall. It's 6 feet square.

Thanks for the comment on the finish. Natural Maple was my concession to my wife- I'd have chosen American Walnut.
That’s an amazing find! Very cool!

FWIW my wife would want the Maple too. Lol
 

AnthonyI

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Nice write up! Now Sunday has become both exciting and scary, lol. Actually I'm really looking forward to hearing these, as @HiFi Guy mentioned, our systems are very similar so it should be interesting to hear the differences the Souls (and the Grado woody) bring to the table. I'm all about the "End Game" system, but I'm convinced that's a bit of a false statement for only two things, cart/stylus and speakers. I think those two components will forever be works in progress being the two extreme ends of the sound path......first point in, last point out ;)

3 days and counting :)
 

kvetcha

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Nice write up! Now Sunday has become both exciting and scary, lol. Actually I'm really looking forward to hearing these, as @HiFi Guy mentioned, our systems are very similar so it should be interesting to hear the differences the Souls (and the Grado woody) bring to the table. I'm all about the "End Game" system, but I'm convinced that's a bit of a false statement for only two things, cart/stylus and speakers. I think those two components will forever be works in progress being the two extreme ends of the sound path......first point in, last point out ;)

3 days and counting :)
Let's be honest with ourselves: part of the hobby is the fiddling around.
 

AnthonyI

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Let's be honest with ourselves: part of the hobby is the fiddling around.
True, but I'm trying to make an effort to spend less on equipment now a days and more on vinyl. The system truly is at it's "tweaking" stage and unless the jump is drastic I don't know if the monetary output justifies it at this point........ that diminishing return area. Better chance of me spending money on a second system than too much more on the existing one.
 

Splunders

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Great review and information! My Zu Omen Dirt Weekends arrive today. While they are different speakers, I will be referencing you're speaker setup notes @HiFi Guy I'm curious if they require similar positioning or not. They are taller, not coaxial and are traditionally shaped. I'm also nervous, since I've been waiting to get these for years. Now I wait like a dog at the door for the UPS truck to show up...
 

displayname

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Awesome write up as always @HiFi Guy! The notes about the bass are particularly interesting. I still need to find some time to get my ears on some more Zu's. Your feedback makes me feel like I need to give them a second look, maybe bring my own amp with for experimentation.

I honestly wish I could put some Zu's up against some other high efficiency designs like Devore's Orangutans. But then again, Devore's O/ line starts where Zu is almost at flagship, so that might not be a fair comparison. But those two designs have really caught my eye from a design standpoint. I need to hear them more to know if that's the sound I'm chasing, but it has me curious.

Another thing I think is important to call out about the Zu's is their tinker/upgrade factor. Most speaker companies don't make it easy or even feasible to make upgrades or mods to the design, but Zu also has a whole line of DIY and upgrades. That's not my cup of tea, but I know for some that's a huge sell point.
 

kvetcha

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Great review and information! My Zu Omen Dirt Weekends arrive today. While they are different speakers, I will be referencing you're speaker setup notes @HiFi Guy I'm curious if they require similar positioning or not. They are taller, not coaxial and are traditionally shaped. I'm also nervous, since I've been waiting to get these for years. Now I wait like a dog at the door for the UPS truck to show up...
Don't be afraid to play with the toe. Took me a lot of experimentation to get my Fortés where I wanted them.
 

HiFi Guy

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Don't be afraid to play with the toe. Took me a lot of experimentation to get my Fortés where I wanted them.
@Splunders This. I've never owned or demoed a pair of speakers that I've toed so far inward. When they are right, you'll know.

Also, bass response on the Souls improved over the first 30 days. Yours may take longer as the Souls undergo a 600 hour factory break in while the Dirty Weekends get 300 hours.
 
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