Loudspeakers

Measuring a substantial planar speaker at a standard 1m on-axis does not give a truly accurate picture of the 6x membrane’s integrated output – this only starts to become apparent at 2.5-3m distance. Tested here at 2m, and with all figures corrected for a 1m distance, the essentially flat forward response of the ESL 2912X is revealed [see Graph 1], albeit with numerous peaks and dips – amounting to errors of ±3.3dB and ±3.6dB (re. 200Hz-20kHz), respectively – along the way. However, the membrane’s impulse response is better defined than we see with most multi-way moving-coil speakers while the pair matching remains a respectable 1dB (200Hz-10kHz). Moreover, both impulse and frequency responses are smoother when toeing the ESLs inwards by 15°, trading a +3dB boost through the presence for a more obviously declining treble of –2dB/10kHz and –6dB/15kHz [blue trace, Graph 1]. Similarly, while many membrane and structural modes are revealed in the CSD waterfall [see Graph 2], harmonic distortions are very low at <0.2% through the bass (above 50Hz) and just <0.1% through the midrange (all re. 90dB SPL/1m).

Sensitivity is rated at 86dB but appears closer to 83.7dB (re. 2.83V/1m/500Hz-8kHz) while the minimum impedance modulus dips to 3.2ohm/20Hz and 3.7ohm/10kHz. In practice, the ‘drive’ is a little tougher than its 8ohm rating suggests as positive swings in phase angle cause two minima in EPDR of 1.7ohm/70Hz and 1.8ohm/13kHz. Useful nearfield bass measurements are almost impossible to achieve with a dipole so the sub-200Hz response, and 31Hz bass extension (–6dB re. 200Hz), are estimated here from a ground plane response test [dashed traces, Graph 1]. PM