Zu Audio Essence

This speaker has been a problem for me. I have spent countless hours figuring out how to explain what I hear, and the different ways that it sounds and performs depending on the setup and the music run through it. The flaws of this speaker have been well documented in the past by the likes of JA at Stereophile. His disregard of his own measurements saying that in fact they sound better than they measure surprised me. We will take a look at these speakers and see if that is true, discuss some of the silly things done when designing this speaker and look hard at the real sound they produce.

How about the look of these speakers? I'm not a fan, but they look pretty neat in a throwback kind of 50's appliance way. It's my understanding that hipsters eat this shit up. These particular speakers have a few options: custom finish, no grills, and Cardas speaker connectors in the back. One of my buddies who stopped by for a listen one day kept remarking on the large Zu emblem and how tacky it was. As for size, these things are massive, they tower over my other towers clocking right at 4 feet tall.

To start let's take a look at the parts of the speakers and discuss each one in detail.


Yes woofer, it's sold as a full range driver that acts as a single point source so that it seems like all of the sound is coming from it.. but that's not how it works. It needs a tweeter, and it has one on this speaker, and when listening it's obvious that it has a tweeter because the dispersion pattern's don't match. So I will call this a woofer that just happens to run without a crossover in this implementation.

Just about everything on this driver is custom, the only parts that are off of the shelf are the motors (voice coil and magnet) which are Eminence parts. The rest of the speaker, cone, basket(cast aluminum), suround, doping, phase plug are all custom parts.

As this driver is the star attraction for the brand let's spend some time looking at the details that make up this unique piece of engineering, but before we can do that we need to talk about cone breakup. Cone breakup is something that happens when a driver goes outside of its' comfort zone. Usually upon entering breakup the driver will scream letting you know it is unhappy about having to do something that physics says it should not be attempting.

The above diagram is from the spec sheet of the Delta 10B driver from Eminence that may well have been the starting point for the Zu driver. Here you can see the screaming approaching 2k as it climbs 7dB and then falls off a cliff and dies.

This type of behavior is inherent to the size of the speaker cone. You can predict with some accuracy knowing the size of the driver where it's going to break up.. so 2k for 10 inch, 4k for 6.5 inch, 7k for 4 inch, etc. Now the material properties of the cone and driver will determine how loud and drawn out the breakup sounds. Hard cones such as aluminum will have short massive spikes, where as soft materials like paper will have a more smoothed out transition.

For a speaker driver that is run without a crossover this behavior is extremely important. The obvious things that Zu does in this driver is to eliminate the spike in response normally associated with breakup is using a paper cone, accordion surround, and then doping of the speaker surround and putting lines of dope on the cone.

From my measurements they have done an alright job accomplishing this goal. The spike is about 2-5dB depending on where on the cone I measure. This will still be audible, but is reduced from what I was expecting from a prosound type driver.

Next problem with breakup is once you are in it the cone is almost a random frequency response generator. Depending on where you measure you will get wildly different results above the breakup point. This behavior causes beaming sound above the breakup point, killing off axis response as the sound waves just bounce around in the speaker cone instead of projecting out into the room. To get the sound waves out into the room Zu has slapped a whizzer cone on the front, and to counter the beaming they have a massive phase plug operates more as a way to make sure the high frequencies don't all project out and instead disperse.

I think I have all of that right, if not I'm sure someone will tell me. Anyway, the driver is pretty good at breaking the rules by making music where it should not.


This is a ribbon, I like ribbons. This ribbon is a Tangband unit with a custom face plate from Zu and the ribbon element installed by hand and tightened by Zu. This ribbon's job is to fill in the top of the spectrum where the woofer(full range driver) does not play loud enough.

I'm going to be blunt here, this ribbon should not be on this speaker. Ribbons are narrow in vertical dispersion, which draws your attention to listen on axis to the ribbon, well this ribbon is not meant to be listened to on axis and it you try your ears will be bleeding. Instead the design seems to be that you listen on the woofer axis and the ribbons vertical roll off will match up with the woofers response. This is a neat idea, but it doesn't work. The ribbon is still blasting the room with excess high frequency information and it is an audible problem making the speakers room response too bright on the top. This is the only speaker Zu ever used a ribbon on, and not using a ribbon is an understandable decision for a company that wants your ears to listen to 10 inch woofers instead of tweeters.


Yep, that's the crossover. It's a Kimber Poly Cap that looks like it was hand matched to the speaker. Matching components is a nice touch for a company, but let's be honest it's not like matching one cap is that big of a deal. The crossover point advertised is 12k, but as this is a first order high pass on the tweeter it's 6dB down at 12k and 12dB down at 6k.

With the tweeter playing 6dB louder than it should because Zu wants you to listen on the woofer axis it's really only 6dB down from the woofer at 6k, and 12dB down at 3k, and 18dB down at 1.5k. Well if that was not bad enough we have two speaker drivers that are playing the same frequencies over a large area both in positive polarity. Do you want comb filtering, because that's how you get comb filtering.

Comb Filtering

Here is an extreme example of comb filtering, measuring a left and right from a very well behaved pair of speakers(not the Zu's) at the same time with a mono signal in my living room with the mic at the listening position. Two sources with the same signal in the same phase will cancel in flight creating the comb pattern.. fun thing about comb filtering is that moving the measurement position a very small amount will cause the comb filtering effect to shift frequencies up and down the audible spectrum. Although the effect is different for each ear on your head this effect is audible and very noticeable if you put pink noise on stereo speakers and move your head around, you will hear a whoosh whoosh sound as the response shifts.

Now the Zu comb filtering is not as nasty as what I have shown there but it does explain the frequency cancelation effect at 5k that you can see in the Stereophile frequency response measurement. To get around the problems with measuring a speaker that has inherent comb filtering I had to measure from lots of different angles as seen below.

The comb filtering seems to be limited between 3k and 7k where the two drivers are crossing over in a very lazy way.


Yep, Nothing on the freaking speaker is normal so yeah it's going to need an explanation as well. There is no port tube, instead we have a small gap between the bottom of the speaker and the sides. In side of this is a pipe organ like array of tubes smothered in a blanket of foam.. yeah it's odd.

The effect is a bass boost that is applied over a broad frequency range. This boost is required as the FS of the woofer is probably near 100Hz, so it needs all the help it can get to put out tactile bass. Does it work? Not to my satisfaction.. Playing this speaker out in the middle of a room like you would expect from an audiophile grade speaker will leave you wondering what the hell happened to your music. This speaker is designed for room boundary gain, and it depends on being slammed up close to a wall to produce adequate bass. I guess with modern living arrangements and the lack of dedicated listening rooms among the general populous it's probably a feature to most, but it just does not do enough it my opinion.


Yeah, you remember that neat photo of the inside of the speaker so you could see the bizarro port, well count the braces you see in there.. yep Zero.. not only that but the speaker is made from plywood instead of MDF.. so yeah, you give this thing a knuckle wrap and it sounds like a kitchen cabinet. This is a big hollow, unbraced, made of wood box... I'm not big on enclosure resonance being that big of a deal audibly, but this is retarded. I think Zu figured this out as they now have some type of multi layer damping they do to the boxes to stiffen them up.

Listening Sessions

I have two listening sessions where I made notes, one setup where the speakers sounded worst and another where they sounded best so you can get an idea of how different they can sound. I'll warn the faint of heart, I love hyperbole and expressing my opinions in the most robust way possible... so yeah this first part is going to be pretty ugly.

Setup incorrectly

I have the speakers out 3.5 feet from front wall of the room about 4.5 feet apart powered by a cheap Class D amp as I didn't feel like hauling the class A amps out into the living room (watts are watts, right?). Here we go...

First impressions are bright, stupid bright, staring at a welding torch, Burn your ear drum with sparklers bright. I've listen to plenty of shitty speakers, but these are the only ones that I actually feel like I'm damaging my hearing by just listening at 70db on the couch.

Somewhere behind that blinding sound is the hint of good bass, but its effects seem to vary with volume as it becomes choked on higher output, it also seems to have a hole in its output, I think I might be able to get that back messing with placement, but it's unknown until I pull out the measuring gear.

I'm not hearing any obvious smearing of details, but a rising response which is definitely happening will sometimes mask the inabilities of the driver.

This is a fucking joke. I have heard big box speakers sound multitudes of times better than this and play much louder and clearer as well. This can't be a matter of taste, the wife said after just 15 seconds of listening "these are awful" and she usually has nothing to say about my speakers. This is instinct level bad, no training required. If you have ears and have ever heard music before you will have a natural inherent distain for the way these sound.

These have the resonant frequency of nails on a chalk board

If you have ever heard a speaker out of its enclosure driver laying on a table, that is the sound I'm hearing. It sounds like a phase problem, scrambling my ears. I imagine the military could mount these speakers to the front of assault vehicles and use the a some type of sonic weapon to scare off civilians.

My kid tells me he loves the looks of them, and everything about them. Also confesses that all speakers sound the same to him. I've never been more disappointed.

That good bass thing is happening again, but really it's lacking so much that it's hard to tell.

It sounds like when you go to a concert and it's the day after and your ears all fucked and ringing the next morning because you were a dumb ass and didn't wear ear plugs. That's the sound.

I'm not listening to this shit anymore, it's horrible.

Setup Correctly

Slammed as far back as my equipment rack and TV will allow, about 8 inches between the back of the speakers and front wall and 5.5 feet apart center to center powered by a Conrad Johnson MV-75 Tube amp.

Hiding details, not muffled, but instead just picking and choosing what it wants to show. Rounding off edges

This sounds a lot like an old stereo console except with less bass and more stereo separation. I don't think of this as a hi-fi sound, more like a good background music setup. It's hard to pay attention to the music because there is nothing to it. It's lacking in the dynamics midrange sounds like it has a hole in it.

White stripes - Can't hear vocals over everything else Piano sounds good. Drums are a mess, cymbals are nice, but forward.

For high efficiency speakers these have more trouble getting that satisfying level of loud than my low efficiency speakers. I think it's because the speakers lack solid bass. They are very midrange sounding.

Moody blues - Vocals smear together, making songs that have harmonies into smeared mud. More disappearing vocals, this is not good.

Strange things like picking sounds being way louder than they should be covering up the sound of notes played.

Sterile and hollow with a floppy narrow bottom.

I've got it. These sounds like a cassette tape without the hiss. Very low fi.

I think this is an amazing full range driver, and a good tweeter, but these speakers are bad.

George Thorogood's Guitar fucking smokes with these speakers

Sounds like music played in another room

It's very frustrating to hear too much bass in some songs and not enough in others. I've had this problem in the past with ported speakers and been able to pull them out or stuff ports to make it work, but these fall apart away from walls and they need the port support so badly plus I have no real way of plugging them.

Audible comb filtering from the tweeter and woofer.

Not detailed, selective.

Comfortably fucked frequency response.

Like a lab rat that has been shocked too many times I found I have been subconsciously dodging female vocals. Bird and the bee come on and while it does bloom, it does not hurt. Still pretty uncomfortable though.

These do not get loud, they get shouty. I am sorry for people thinking they are getting a party speaker out of this, it's just not much fun.

The tweeter horizontal axis is a no fly zone for your ears, its scorching sun hot.

Still sounds like its light on the 200hz range even with them just about slammed into the walls. The room is doing a good job boosting the crap out of the actual bass though.


One thing about these speakers that I can say without a doubt is that they are more concept than delivery. The whole product is based around an idea that in this iteration at least had not come to fruition. I think Stereophiles's passing grade was motivated to see if the idea could be fleshed out into a good follow up product as at the time they had all the ammunition and facts to burn down Zu as a company with that one review.

Thoughts on amplification... amps make a huge difference with speakers that play into the breakup.

A summary of this review is that these speakers sound pretty bad with some things, and interesting with other things. But at no time did the speaker sound correct. It was always colored, and by that I mean hiding information in the music with tonal aberrations, inconsistencies, and distortion. I'd love a chance to review Zu's latest offerings to see if the promise here of something unique that sounded good was ever delivered.

Give it a listen

One of the many by products of my amp testing and measuring is a few recordings of the speakers played with different amps. Now I have not level matched these, and they are more for fun than for science, but I thought it would be nice to include them.

Zu Audio Essence run on one of my Kinergetics KBA-75 Class A solid state amps

Zu Audio Essence run on Mike's Conrad Johnson MV-75 Tube Amp

For referance here is a pair of speakers that I don't have many complaints about playing the same song:
Selah Audio Galena's run on one of my Kinergetics KBA-75 Class A solid state amps

Extra Photos and Thanks

I had these speaker for a little over a month now and I've put them through the wringer, testing amps and doing research that I would never have done if not put against such a problem child of a speaker. I'd like to thank my good friend Mike for letting me review these speakers and use his Conrad Johnson amp for testing. While it may have been a little rough at times this was a great review and I learned a lot.

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