niodari,
FWIW, from my experience of having lived with the CS6s (years ago), and now the 3.7s and 2.7s...
I agree the CS6 has more substantial bass than the 3.7s. It was denser, more punchy, and goes a bit lower. I remember the CS6s as giving the best bass I've ever had in my system and I still don't think anything has surpassed it overall. (At least going on my memory).
The 2.7s are interesting because in some respects they actually remind me more of the CS6 than they do the 3.7s. The 2.7s have that amazing dense, punchy quality like the CS6s, except it's shifted upward somewhat into the upper bass region. And they have that CS6 like density of imaging.
The 3.7s have, to my ear, the most refined midrange of all the Thiels I've owned or heard. Just really low in noise, super transparent and delicate in nuance. The midrange sounds more "complete" and lush, relative to the other models like the CS6 which have a mild reductive quality - instruments get just a bit smaller and thinner on those models, a character I tended to remain aware of when I had those speakers. (But generally speaking, instrumental timbre and density was so beautiful, it made up for it).
And the 3.7s are by far the imaging champs. They still image like nothing else I've had in my room (or heard from any speaker near it's size). And they are overall the most coherent and boxless sounding of any Thiel speaker I've had or heard. As I've mentioned before, in terms of eliminating obvious speaker colorations (e.g. hearing the box), from top to bottom, and sounding holographic and uncolored top to bottom,with no frequency response bumps or nodes sticking out, I honestly have never heard the equal in any other set up. It blows me away every time I use them.
That said, I'd love to hear the CS6s again some time, just to re-visit that wonderful sound.
