Loudspeakers

The front-facing midrange drivers in this four-way flagship segue into the two rear-facing woofers at 135Hz, the upper mid cone extending its reach to 1.15kHz before crossing to the 28mm soft-dome tweeter. There's an increase in distortion from <1% through bass and treble to ~2% at this same midband frequency, and a resonant mode too [see CSD Graph 2, below], but this is quickly dissipated. Bass is well extended down to 25Hz (–6dB re. 200Hz) but the corrected, summed nearfield measurements [green area, Graph 1] were complicated by the combined reflex ports and side-venting – the alloy woofers peak at 66Hz while the dual ports are tuned to 60Hz with a useful output down to 20Hz (–3dB). Measured on the treble axis, the forward response shows a boosted mid/presence/treble rising +5.5dB from 1kHz-20kHz, but pair matching is an impressive 0.8dB, improving to 0.6dB from 200Hz-5kHz [black/red traces, Graph 1]. Leaving the elastic grille strands in place [blue trace] reveals ±1.5dB 'ripples' appearing between 2.5-6kHz. Audible? See Ken's listening notes!

Serblin's rated 92dB sensitivity is a trifle optimistic unless a full 200Hz-20kHz range is included in the measurement, the high treble lift boosting it to 89.1dB. Otherwise, the 1kHz/2.83V/1m figure is 87.7dB and the mean from 500Hz-8kHz closer to 88.8dB. It's unlikely the Ktêma will be partnered with an asthmatic amplifier, but it remains a reasonably current hungry load to drive. Serblin's quoted minimum of 3.2ohm was proved on test at 27Hz but there's a further drop to 2.8ohm at a very high 20kHz. Phase angles are moderate at +24o/–28o but the maximum impedance is just 8.0ohm/860Hz. PM