Just an intermediate note here, prompted by Steve Guttenberg's evaluation on Youtube. There are some descriptive inaccuracies and setup errors, and one inadvertent error by Zu at the outset.
First, he has difficulty explaining the Soul 6 design. He refers to the supertweeter being "crossed over" and then tries to explain that the speaker doesn't have a crossover. If Steve simply and correctly noted that the supertweeter is on a high-pass filter, that whole word salad could have been avoided. He also refers to Soul 6 as a "bass reflex" design, mischaracterizing the Griewe driver-to-room acoustic impedance matching scheme.
It goes wrong in some vital ways from there, but Guttenberg does get the immediacy, speed, articulation, dynamic slam and tone factors.
I am listening to a pair of Soul 6 right now. Steve says he couldn't get satisfactory bass from his pair at the more open end of his room, claiming roll-off at 57 Hz. Not me. Even before I got into making setup adjustments, just plopped on bare floor right out of the shipping cartons, Soul 6 showed solid 35Hz bass where present in music, and useful, audible response of 32Hz content in a relatively unbounded room, verified with 1/3rd octave visualization. Further tuning of the Griewe gap to the floor improved bass response and quality further. Why was real bass easy for me and elusive for him? Hard to tell through a procedurally-light video commentary.
Guttenberg then claims the speaker sounded best if he sat on the floor, complaining of tonal shelving at his seated height. So in an effort to fix that he and a buddy got the idea to tilt back the speaker, using long spikes on the front and the stub bolts on the back. Well, now the Griewe scheme can't work quite correctly and it influences the FRD well into the midrange.
I'll post complete comments on this speaker after I put them through some further violence to complete the break-in process Zu started. I think Zu erred by shipping Steve's Soul 6 pair too soon, and mine too. Their standard 2 weeks continuous burn-in turns out not to be sufficient for this new concentric driver, and stopping there leaves a narrow-band midrange stridency that gets wrung out by doubling the burn-in regimen on Zu's rack. A week in, the resulting glare is receding for me but it's taking extra effort to apply the necessary abuse. Hence Zu is going to require 4 weeks of break-in at the plant before delivering Soul 6. Druid 6 was very much the same way initially. Zu did 2 weeks of burn-in on their rig, then it took another nine months for my pair to fully stabilize. Zu shipped Steve's speakers too soon. Steve shot and posted his review too soon. Until the new-cone stridency is wrung out, the speaker will sound too forward on lots of modern recordings.
To a Druid or Definition listener, the Soul 6 acoustic focal plane will be perceived as lower than those speakers that have FRD output above ear level, but again as the speaker opens up during break-in, that focal plane drifts higher. On my couch, my ear height, seated, is about 39" off the floor. The Soul 6 floor to centerpoint of the concentric FRD is about 27". But after the first 3 days, TV and cinema dialog accurately attached to visuals on a 60" display mounted with vertical center at 44". The speaker scales well spatially and dynamically. Depth is not lacking. Right now I have the Souls 10 feet apart and the center still holds. Dispersion in all directions is better than for any single-driver Zu speaker to date.
But you have to get a complete break-in on them, respect the Griewe gap, and preferably not choose an overdamped amp. So far I've been listening to custom tube amps 10w - 18w (p-p triode, single-ended pentode), and 180w M2tech Crosby monoblocks (meting out the flogging). My experience is that all of the Zu concentric tweeter speakers demand more careful amp selection than the non-concentric tweeter models, even going back to the original Zu Cube. Soul 6 is no exception. More later.
Phil
