When Druid 6 succeeded Druid 5, some people found the leap in vividness, obvious in the latter speaker, disorienting relative to the relaxed, gear-and-material-tolerant Druid 5 and 4 before it. The jump in quickness and transparency rewarded quality recordings and upstream gear, but no longer smoothed over some sins in source material and the gear chain. For a while, Zu sold both Druids 5 & 6 side by side to ease the transition and accommodate preferences. Druid 6 was clearly the better speaker, while Druid 5 was the more forgiving one.
Soul Supreme is essentially a Druid 5 re-engineered into a compact form factor and so Soul 6 is at least as startling an advance in musical vividity over Soul Supreme as was the case between the two Druids referenced. And just as with Druids 5 & 6, where the latter's cabinet engineering was key to the differences between the two, so it is with these two Souls.
Up front, before I get into details, some quick notes about the sound of Soul 6. It has the snap, slap and quickness of a membrane speaker but with the punch and dynamic shove of dynamic Zu. Zu rates Soul 6 for +/-3db response, 38Hz - 28kHz. Believe it. On music with 35Hz content, rolloff is not detectable, and with known 32Hz content, its presence is solid. Spatial projection in width, depth and height is massive when warranted, all the more impressive when you are listening while looking at small floorstanders in front of you, where the driver centerpoint is about 27" above the floor. The scale of sound doesn't make sense while you're looking. But there it is. Tonally, Soul 6 is musically authentic top-to-bottom. You hear the full pipe of the human body in a singer, not just the throat. Bowed instruments sound loaded with real texture. You get a vivid presentation of the material resonances of wood and brass winds & horns. Drums thwack and snap, kickdrums slam, cymbals crash and shimmer at levels of realism few speakers can match. And at 100db/w/m sensitivity, those impressions are easily made with 8 to 20w of amplification, though if you throw a big amp's output into it, Soul 6 can take it. I have done my listening with a variety of custom tube amps ranging from 6w-18w per channel: PX25 SET, EL156 and F2a single-ended pentode, 300B and 2a3 triode push-pull, Williamson-circuit triode-wired EL34 push-pull, Quad II push-pull tetrode. And for good measure I lashed a pair of M2tech Crosby Class D amps as bridged monoblocks for 180w+ into the Soul 6's 8 ohms load.
There are some misconceptions floating around online about Soul 6. Among them:
1/ Soul 6 lacks bass. Wrong. Some people who already own subwoofers give them up after buying Soul 6. If you aren't getting proper bass response from this speaker, you haven't set the Griewe Gap correctly. Read the instructions on Zu's web site.
2/ Soul 6 is too "forward sounding." Not once it's burned in. This is why Zu now requires 4 weeks on their punishing burn rig before shipping. If a customer wants them shipped sooner, they waive the 60 days eval period and it's a final sale. It can still backslide a bit when shipped in cold weather, so when you get them, use them -- hard. If you want, when you're out just put the driver covers on and stream something withering and loud. If burn-in effects backslid from low temps shipping, you can get them settled in in a couple of weeks.
3/ The sound is "down there," this floorstander being only 32" tall. Again, a burn-in issue. It took just four days for the vertical acoustic focal point to rise to the level of my Definition 4 speakers. The coaxial driver behaves very close to a point source, with vertical and horizontal dispersion the same.
4/ Soul 6 is a ported speaker. Incorrect. No Zu speaker in their line is ported. The long teardrop openings along the edges of the floor-facing baseplate allow the Griewe driver-to-room acoustic impedance matching scheme to "see" the room and work, and they do not behave as ports.
5/ Soul 6 doesn't have a supertweeter. It does, right there in the center of the driver where some other Zu speakers sport a phase plug.
6/ Soul 6 has a crossover. It does not. There is no electrical dividing network between the amp and the main driver. The supertweeter is on a simple high-pass filter with its roll-in corresponding to the natural roll-off of the Zu FRD.
Some shoppers and reviewers have trouble understanding Zu speakers in general and Soul 6 in particular. The gains in transparency, sonic scale and sheer aliveness delivered by both the newest Zu driver and the talk-killing okoume ply & stiff, light skeletal structure make plain flaws, or errors-in-engineering-judgment, in source material, as well as imperfections upstream of the speakers in some systems. If you think Soul 6 is "too forward" after complete burn-in, the recording you're listening to may be the source of your irritation. Especially if you are coming from a traditional crossover speaker with also a somewhat recessed midrange, the clarity and neutrality of Soul 6 can be initially disorienting. Depending what speaker you are migrating from, you may prefer a differently-voiced phono cartridge than what you're using. You might prefer a different filter choice on your DAC if that option is present. EQ customizations in Roon may have to be reconsidered and reset.
The Omen series of Zu speakers, along with Soul Supreme, natively have discernibly more of what people call "warmth" built in. This, and the 12 ohms and 16 ohms loads makes them pretty much "any amp" speakers. You can keep to your preferences, but very few amps will not sound good on those speakers, including the revival of 1970s Japanese receivers via Ebay and pawnshops. Soul 6 requires more consideration in matching to amps. Its uncompromising transparency, detail portrayal and snap rule out any amp with a rough top end or slow and bloated bass. If an amp is inarticulate and prone to congestion or losing threads in complex music, there is nothing in Soul 6 to cover for it. This does not mean you need an expensive amp for Soul 6. You just need an amp that is musically-convincing, clean and pleasing to you. Questions about using Soul 6 with low power amps come up in my message box here. Sure, you can wire a 2w/ch 45 tube amp if you're willing to listen within its dynamic requirements or your room is small. I prefer the 8-25w range to really enjoy the dynamic elasticity and explosive potential in a Zu speaker. And no, Zu speakers aren't strictly for tube amps. There are lots of Zu owners rocking solid state, though high-damping amps of any kind often can sound inelastic and forced. Good Class D can be great. The speaker is very well controlled with modest-damping-factor amps. Just understand, that depending what you are migrating from, and the extent of your audiophile proclivities, dropping Soul 6 into an existing system may well drive one or more changes to the gear chain upstream.
But, take some time to work with Soul 6 and you'll experience the quickest, most responsive, Zu speaker to date, along with all the normal Zu traits in tone and musical authenticity you expect. Now these notes are for us hifi geeks here. There's another constituency for this speaker: plain music lovers who want to buy a speaker they can easily place in an apartment, get some affordable electronics and source(s), love that it's compact and looks great in all the combinations of finishes and colors Zu offers. That constituency is as interior design driven or style-conscious as they are concerned for good sound. And they love the mid-century (the last one) clean simplicity of Soul 6.
One question that often comes up regards the comparison between Soul 6 and Druid 6. When Sean Casey first told me about Soul 6, he said "This is the best speaker we've ever made." I asked, "Really; you think it's better than Druid 6? Hard to believe." His answer was to say, "OK, that I'll have to think harder about."
Soul 6 does some things a little better than Druid 6. It's somewhat but discernibly quicker on transients and other dynamic shifts. It's 1 db less efficient than Druid 6 but its speed makes it seem a tad more explosive. Its supertweeter is rated out to 28kHz whereas the Radian 850 in Druid 6 is really great to 18kHz and struggles to get to 20kHz. So there are some true phase-improving low ultrasonic effects, which are subtle and not because you're hearing the extra 10kHz of content directly. There's a little more slap and snap to bass and percussion in Soul 6 than Druid 6. BUT, Druid 6 is as a whole the better speaker. The more expensive Druid has fuller and denser tone than Soul 6, particularly vocals and strings. It conveys electric guitar more compellingly, a keynote for me. Druid 6 bass response is slightly deeper. It can dip just below 30 Hz. The Radian 850 gives Druid 6 more harmonic grace than the Soul 6 supertweeter. And as fabulously as okoume + Zu engineering slashed cabinet talk in Soul 6 over prior Souls, the complex, proprietary multi-materials, hand-laid Druid 6 cabinet ply has even less. Druid 6 sounds more planted, grounded and that may be in part because of its greater mass and thick aluminum plinth. In a correspondence with Zu I summed up Soul 6 as having "the agility of a hummingbird and the presence of a wooly mammoth." They used that in some marketing language. Well, Druid 6 adds to that menagerie some of the added sonority of a blue whale.
Soul 6 gets far closer to Druid 6 at $6000 vs. $11,500, than the price difference suggests. I had a 1st-time Zu listener visit over the weekend. He was very excited about Soul 6 but is not strictly price driven. He wanted to hear Druid 6 too. It took only seconds for him to say, "I think Druid is worth the extra cash; it sounds even more natural than the Soul." And yes, I agreed. That said, if I had one hifi system only, and didn't have room for Druids and Definitions, I could build it around Soul 6 and listen all day long for years ahead. Soul 6 is an outstanding and landmark speaker that can satisfy the broadest swath of buyer interests of any speaker Zu makes today. It fits anywhere, it costs enough to be great but not so much as to be unreachable, and it works equally well on any genre of music that's produced at least reasonably well.
One last thing I have to point out. Zu's cabinetry is impeccable and their finishes look and feel fantastic, especially the mirror gloss, for anyone who can splurge on that. But even the base finishing is beyond reproach. They are shipped with outstanding protection, unpack easily, and at just 39 lbs each and 32" tall, setup is a one-person job. If you can do it, sooner or later add Zu B3 speaker cables. Once you hear and own Soul 6, if you want to shade them for smoothness over spotlighted detail, do your cable loom in Zu Mission. If you want to fully leverage the speaker's hear-through clarity to the utmost, build your cable loom in Zu Event II. Or mix Mission and Event to taste and budget.
My listening for these notes includes vinyl, ripped CDs, CDs, Bluray Audio, SACD, movies from Bluray, Netflix, AppleTV, and music streaming via Auralic streamers and Bricasti DACs.
Note: When you buy any Zu speaker that is Griewe based, download the updated instructions from Zu to guide you through setting the Griewe Gap between the bottom of the speaker and the floor. Getting it right affects more than just bass, but bass response is your first clue you're in the zone.
I must have missed something. If so, I'll add it in the comments.
Phil
