I reviewed KEF’s original 207 model back in Issue 26, along with the PSW5000 subwoofer, a combination that delivered a scale, transparency and musical sophistication that belied their relatively modest asking price (considering the material content of the complete system). Of course, getting a pair of large, visually imposing loudspeakers into the average domestic environment can represent something of a challenge: adding a substantial sub-woofer too could just be the straw to break the matrimonial back. Well, in a world where less is so seldom more, the good news is that KEF’s 207/2 manages to shed a drive unit compared to its predecessor, dispense with the sub-woofer and still advance its overall sound quality. They’ve also dramatically improved the finish along the way, the boat-backed cabinets now coming in a range of deeply polished lacquer or wood veneers.
Clearly, given the sonic improvements, the changes are more than just skin-deep, and they start with the new ‘Austin’ Uni-Q array contained in the speaker’s head unit. This driver was developed as part of the Project Austin development programme, widely reported on after the 2006 Munich High-End show. The experimental mules seen there were to evolve into KEFs recently launched flagship, the Muon (including their innovative bass loading), but their midrange driver, together with its centrally mounted tweeter has also become the key element in the new Reference series.
Primary design goals for the latest generation Uni-Q were improved dispersion and off axis response, creating a more natural overall tonality and balance. As the midrange cone also acts as a wave guide for the tweeter, its profile is critical to the high-frequency performance and the even transition from midrange to tweeter that characterizes the Uni-Q’s sound. Improving dispersion called for a shallower cone, which under normal circumstances would compromise the stiffness and thus the structural behaviour as a result the midrange output of the unit, losing on the swings what you were gaining on the roundabouts. But advances in computer measurement and modelling of cone behaviour have allowed the designers to optimise cone thickness and material properties to circumvent the problem. At the same time, adding a shallow roll to the previously flat surround has extended the useable output at low frequencies, allowing a lower crossover point of 350Hz and an even smoother transition to the 10” lower midrange driver.