Soundlabs are physically dipolar and subjectively bipolar speakers - most people who listened to them will say they sound the best or miserable. In non optimum conditions they can sound aggressive, colored and even edgy, with a small central image. When optimally set, with the proper equipment, they are full bodied, seamless, and image like few other speakers, with a lifelike layering and a very large, but realistic soundstage. Fantastic transients in the bass - you fell the attack of the bass, something that most box speakers. They are so fast elsewhere that sometimes that make you close your eyes.
As all Mylar diaphragm panel speakers they have the typical rustling coloration of films, even more than the ESL63 - perhaps at the same level as the CLS or CLX, less than Maggie's. However proper choice of equipment and setup can eliminate it to non perceptible levels.
They lack the pin point imaging of many modern box speakers - they are row H, not row A speakers, as people often say. They are very clean - full bodied, but not bloated.
Curiously the most astonishing sounds I listened from Soundlabs were in unexpected very different conditions - LP with big Atmasphere's, CD with Jeff Rowlands, CD with Electrocompaniet. I have successfully used them with Atmasphere, VTL's, ARC and currently conrad johnson monoblocks. I can imagine that they would be a great match with the big DartZeel's - they sound really beautiful with the NH108b, but would need more power and slam in the bass - latest versions of Soundlab's can play loud, except in the low bass zone.
Just to end they are very, very sensitive to speaker and power cables and power quality. Probably their industrial ultrasonic high voltage box generates a lot of RF noise that goes back in the mains.