KEF C10 Bookshelf speakers
The C10, the smallest of the series, and the C20, the next up, are both intended to be used against a wall or on a shelf; they have a deliberate step in their frequency response to equalize the results when so placed in what KEF have termed the 'boundary' condition. The free support at low frequencies when they are only required to radiate into a hemisphere, as opposed to 'out in the room', has given a useful overall lift to the apparent efficiency. The C10 uses a B160 bass/mid-range unit (140mm cone) with a free-air resonance of 55Hz, rising to 100Hz in the sealed box which is liberally filled with bonded acetate fibre wadding. A pressed metal frame and ceramic magnet are used. The crossover to the tweeter at around 2.8kHz is carried out by seven components on a printed circuit board (the same one is used for all models) which is anchored straight to the studs of the rear terminals. A series capacitor of 600μF provides an additional pole to the low-frequency network, and this not only improves the low-end performance but protects the unit from switching thumps or pickup mishandling; it also means that there is no DC path through the loudspeaker, which has perturbed quite a number of uninformed engineers prodding away with their test meters.
Listening tests showed most clearly that there is much to be gained by trying different positions for this junior model. Often a few centimeters made a considerable difference to the results; on stands, against a plain wall, with about 50mm spacing, seemed optimum. This done, the final sound was very satisfactory and this cheapest of the C Series must rank as one of the most desirable in the range. Critically one finds a slightly boxy character to the sound, traces of nasality in reproduced speech and an occasional exaggeration of sibilance. On the plus side, it stood up to high power very well-even in the bass, which sounds as though it goes much lower than it really does when used against a wall, in which situation it gives few clues to its small size and low price.
