Loudspeakers

Take AVID's reflex-loaded Reference Four [HFN Feb '22], double the cabinet volume and add a further 160mm polymer-coned woofer and, broadly speaking, out pops the Reference Three. An increase in sensitivity should be possible, and although AVID rates both models at 88dB, in practice the Four's 85.5dB/1kHz sensitivity is boosted to 87.2dB/1kHz (87.9dB/500Hz-8kHz) in the Three. This worthwhile uplift in sensitivity is partially traded against bass extension and amplifier loading. The latter is tougher – though not atypically tough – than we saw in the Four, with the largest –50°/+46° swings in phase angle and minimum 3.6ohm/140Hz impedance all occurring at low frequencies and resulting in a minimum EPDR of 1.7ohm/97Hz.

Meanwhile, the dual 160mm drivers both operate over a 50Hz-630Hz/–6dB bandpass (the lower woofer is filtered >900Hz) and augmented by two downward-firing ports at 30Hz to deliver an impressive, diffraction-corrected bass extension of 35Hz (–6dB re. 200Hz). The Four achieves 30Hz, but requires more amplifier power to realise the same bass level. The forward response [Graph 1] is slightly 'U-shaped' with a rising, undulating presence/treble contributing to errors of ±2.6dB and ±3.1dB (200Hz-20kHz), but pair matching is just 1.0dB, tightening to 0.5dB from 500Hz-8kHz. The partnering 28mm doped silk dome tweeter rolls away above 19kHz to ~26kHz (–6dB re. 10kHz) and while minor mid/presence resonances are visible in the CSD waterfall [Graph 2], the lack of any ultrasonic dome break-up ensures a clean impulse response. Distortion is also consistently low at ~0.2% through mid and treble (re. 90dB SPL/1m). PM