Loudspeakers

Given the C 93 II's compact dimensions it was always likely that Jamo's specified 88dB sensitivity would prove optimistic, which our measurements confirmed. While our pink noise figure of 87.2dB is close, the 'music' figure of 86.1dB is more distant. This order of disparity always arises because of a non-flat frequency response [see Graph 1, below] measured here at 1m on the tweeter axis. The response trend is commendably flat to 4kHz, then begins a steep rise to 17kHz interrupted only by a deep, narrow suckout at 9.3kHz. This rise will be substantially corrected by listening sufficiently far off-axis, but then the effective sensitivity will fall further to around 85dB.

The 6ohm nominal impedance is a stretch too. Ordinarily this would mean the impedance modulus not falling below 4.8ohm but we measured a minimum of 3.4ohm, making this a 4ohm design. Quite high impedance phase angles reduce the EPDR to twin lows of 1.8ohm at 142Hz and 6.04kHz, so the C93 II is a moderately challenging load to drive, particularly bearing in mind the likely partnering amplifiers. Because of the treble rise, frequency response errors are high at ±5.4dB and ±6.0dB, respectively, but the limits to 4kHz are about ±2dB, so response flatness will be much better if the speakers are not toed-in towards the listening position. Pair matching is a little disappointing at ±1.7dB but for much of the frequency range up to 14kHz the disparity is much less, within ±0.7dB. Diffraction-corrected summed nearfield measurements show the bass response to fall off rapidly below 70Hz, reaching 56Hz (–6dB re. 200Hz). The CSD waterfall [see Graph 2] shows some HF resonances, suppressed here by the treble response rise. KH