@aberyclark The ODS requires the plinth because the Radian 850 used as the supertweeter makes the speaker more top-heavy than standard OD, but the upgrade is well worth it. Much more harmonic grace with the Radian 850.
@rhythmnsound If you buy Soul 6, they ship after 4 weeks in Zu's intense-abuse burn rig. It's not just the driver but also the internal wiring harness that needs it. In fact, the concentric-supertweeter FRD is so transparent it makes the need for burn-in of the dielectrics more obvious. I mention this because if you buy during cold weather shipping, that will cause some backsliding on the benefits of burn-in. If that happens, you may notice some initial stridency in a band bounded roughly by about 600 Hz - 1500 Hz. It is not the same sound as horn shout but is in the realm, and of course the supertweeter has nothing to do with it. The other thing if burn-in backslides is that the speaker will throw a low soundstage initially. I just pushed them hard for a couple of weeks. Every time we went out for a few hours I put the protective driver discs on, turned on ESPN and cranked up the volume on their bombast. In the first four days, the vertical focal point of the soundstage notched up until by the fourth day it was projecting to the same vertical point as my Definition 4s on the same music and movies. That narrow midband stridency faded day by day until it was gone after about 2 weeks. Settled in, Soul 6 is remarkable not for any horn colorations but for its objectivity, transparency, cat-like agility and sheer rhino force even with modest-power amps. The supertweeter is only a factor above 10kHz.
Quad ESLs certainly have somewhat more finesse on delicate details than any dynamic speaker, but Soul 6 gets very close and in turn the Quad cannot even remotely match the Zu's frequency extensions top and bottom, nor its dynamic elasticity and ability to project acoustic force. Soul 6 also doesn't have the Quad's single-seat beaming. You have much more flexibility for placement and the prime listening window gives you seating latitude for communal listening.
@snapsc I haven't heard an open-baffle speaker that has quite the objectivity and tone equal to the crossoverless Soul 6. The partial dipole nature of dynamic open baffles helps with live-like spaciousness along with placement complications in many rooms. The Zu has that similar spatial projection without the room placement problems, plus bass is very well controlled. Where Soul 6 and good open baffles are similarly spirited is in the openness, agility and jump factor heard from both.
Phil