Unsound - the SCSs seem fairly invisible here. My slight experience might help a little. The SCS is essentially a grown-up O2 - 6.5" ported two-way with polarity correct second order crossovers. They produce a decent step response and frequency response and can handle more power more easily than first order XOs. The SCS designation began with Thiel's first coincident / concentric driver in 1989. The specs and general performance of any generation will be similar with more modern iterations having more serious driver technologies and improved port loading, with more sophisticated performance.
I have 3 pair of O2s and a single SCS4. Side by side, the SCS4 has greater detail and nuance, but its overall musical impression is fairly similar to the O2 from 1976. As models progressed, the ports migrated from single to dual to rounded outlet to flared horn outlet which gradually reduced port air velocity and chuffing, creating better room coupling.
The ear-brain does an interesting thing with the fundamental frequencies. Any distortion there serves to slur the upper harmonics - the auditory brain interprets all sound from the bottom up. I am working with a very exciting technology, modeled on shark skin, that organizes the wave launch from the port, thereby cleaning up the entire spectrum to an unexpected degree. Not ready to show, but will upgrade any ported speaker, including Thiel O2, O4, SCS (all), CS1, 1.2, 1.6 and CS2. Stay tuned.
FYI: I picked up a single SCS4 for a couple hundred bucks and looking for another one to make a pair.
