From a historical perspective the 3.5 > 3.6 transition is a watershed. The 3.5 has the more "correct" sealed box bass response. The model 2 was invented to implement the less expensive reflex bass. That introduces phase / time lag at the bottom of the spectrum, but the model 2’s reduced budget admitted that trade-off. Our pipe-dream vision of the model 3 was to develop a subwoofer that matched the second order sealed roll-off model three bass and which, by careful placement, can be made time correct and phase benign.
Around 1990 we had entered a subwoofer development project with Vifa creating a very early class D implementation. That should have become the bass foundation for a breakthrough 3.6. Another intriguing option was a transmission line bass, but at that time adequate modeling was not extant, and TL bass included tons of guess-work, trial and error and mixed results. An improved equalizer option was also floated as an intermediate step between acoustic and subwoofered bass. Through a few years of significant grief - that subwoofer didn’t materialize - it took years too long to develop. The market demanded a new model 3 offering, especially in Kathy’s opinion. Without putting too sharp a point on it, the 3.6 with its reflex bass became the result. Its bass is quite well executed, some say about as good as the form gets. But, it’s still a reflex bass system with its limitations and trade-offs.
I’m somewhat surprised that Jim continued with the reflex bass in his subsequent higher-end products rather than building on the seminal work of the sealed CS5, as well as developing transmission line and/or including subwoofer augmentation. A one-man development team can only take on so many challenges.
I second what's been said above. The 3.6 is the more mature and accurate product, plus it can be maintained with available rebuilt drivers.
