The broad concept may be a classic one, but the detailed implementation is much more modern. Above the pulp paper cone with its soft rubber surround sits a custom-built Mundorf Air Motion Transformer. AMTs are not new, but have (at least until recently) failed to capture the public’s imagination in quite the same way as the true ribbon designs, partly for reasons of cost, but also, historically, power handling, though this aspect is no longer an issue. They still are very costly drivers however, the Mundorf range typically priced at several multiples of the cost of, say, a Scanspeak Revelator dome tweeter. The version used in the Kim has been co-developed with Mundorf to have wide horizontal dispersion but less vertical dispersion, again to manage reflections, but this time, off of the ceiling. The cabinet’s front baffle is also fairly savagely shaped to aid dispersion and directionality in the treble, a feature that gives the Kim its immediately recognisable if slightly off-beat aesthetic identity.
The AMT offers other advantages over a true ribbon. It is able to move more air and thus go loud without audible stress, to driver or amplification. Mundorf claims that they are also more linear, with far better impulse (transient) response and a more coherent phase response, especially compared to compression drivers. That might seem like an odd comparison, except that AMTs are more often than not, horn loaded. Unlike conventional dome tweeter designs, they remain well behaved right to the edge of their performance envelope while distortion levels are low and comprise almost entirely even order harmonics. Karl-Heinz Fink is happy that the implementation in the Kims, and their bigger, floorstanding siblings, the Borgs, shows this now mature technology at its best. The drivers may not go as high as the best ribbons or exotic domes (FinkTeam cites the upper roll-off as -3dB at 25kHz) but they definitely move air in a way that ribbons don’t, while offering most of the same speed of response, right through their operating range.
The ability to move all that air means that the treble, while pretty much as fast and clean as a ribbon, integrates far better with the 8” mid/bass unit than any ribbon ever has. In all my time with the Kims, I’ve never been aware of any disconnect between bass and treble. ‘Seamless’ is an over-used word, but there’s a top-to-bottom cohesiveness to the Kims’ output that just gets better as your system improves. I’m as guilty of over-using that phraseology as anyone, but more than ever, it’s relevant here. Voices, whether speaking or singing, are naturally weighted without emphasis on ‘head’ or ‘chest’ or unnatural projection; instrumental timbres are fully fleshed – double bass, for example, has weight and solidity at the bottom end, a sense of mass and volume, but with a clear sense of pitch and woody texture that comes at least as much from the upper frequency harmonics as the fundamentals. Through the Kims, it’s ‘proper’ double-bass. Piano is equally instructive: bass notes have that sonorous weight and richly resounding air, while treble has all the bell like qualities you could wish for. More importantly, you don’t actively notice these distinct qualities. Instead, the whole allows you to relax and get on with the all-important business of connecting with the music, while you don’t have to work too hard at that ‘willing suspension of disbelief’ thing.
