Loudspeakers

While the evolution of the C20's design is recorded in some detail in our review, and on the company's website, the raw specification is limited to nominal impedance (8ohm) and sensitivity (88dB). The former accurately reflects the C20's 'easy-to-drive' status with its benign 7.0ohm/157Hz impedance minimum joined by maximum ±40° phase angles, and increase in impedance to 36ohm towards 1.9kHz as the inductance of the 180mm bass/mid takes effect. The 'harshest' load occurs at 330Hz/8ohm/+24° – this is still relatively 'amplifier friendly' and perhaps predictive of the slightly lower-than-rated 84.7dB/1kHz and 85.5dB (500Hz-8kHz) measured sensitivity.

Measured on the tweeter axis, the response trend shows a marked 'step' in output of +7dB between 3kHz-5.3kHz [grey trace, Graph 1] but this is very successfully ameliorated when tested some 3in above the top of the cabinet – a more appropriate axis for a seated listener [black/red traces, Graph 1]. Here the response errors for the pair reduce to ±4.4dB and ±4.8dB, respectively, matched to within an impressive 0.7dB up to 10kHz. The trend shows an upward tilt but the grille should be avoided as it carves out a 5.5dB notch at ~5kHz [blue trace]. The top-end rolls away to a respectable ~29kHz [–6dB re. 10kHz; pink shaded area, Graph 1], the soft dome affording a peak at 14.5kHz but no ultrasonic resonance. The 55Hz-2.3kHz bandpass (–6dB, with modes at 185Hz and 940Hz) of the 180mm woofer is lifted by the floor-firing reflex port (22Hz-90Hz, –6dB) to yield a slightly 'peaky' bass alignment and respectable LF extension of 48Hz [–6dB re. 200Hz; green shaded area, Graph 1]. PM